Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: unbuiltnautilus on May 10, 2011, 07:22:53 pm
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Having had a long list of owners before me ( including me four years ago!) I have become the proud owner of a Darnell type VII u-boat, It has only been underwater once, when it sank!
I have had a large amount of helpful advice on the internals of the model from fellow forum members, for which I would like to say a hearty Thank You :-))
Now its time to look at my rebuild and see what you think so far?
(http://s4.postimage.org/hbu8xx44/Steam_open_day_etc_139.jpg) (http://postimage.org/image/hbu8xx44/)
The model had been weathered by a fellow member and camoflaged to boot! I liked the scheme but felt the camoflage was rather lost in the weathering. Then the red antifouling became an issue ( latest thinking seems to indicate red antifouling was seldom if ever used.) repaint time!
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The repainting of the sub started a couple of weeks ago, firstly I applied liquid masking film Maskol onto the model in random patches, this was left to dry and the camoflage colours were reclaimed with an airbrush.
(http://s4.postimage.org/hdv0l6uc/IMG_0778.jpg) (http://postimage.org/image/hdv0l6uc/)
(http://s4.postimage.org/hdzz78bo/IMG_0785.jpg) (http://postimage.org/image/hdzz78bo/)
(http://s4.postimage.org/he1mqktg/IMG_0787.jpg) (http://postimage.org/image/he1mqktg/)
(http://s4.postimage.org/he6lcmas/IMG_0789.jpg) (http://postimage.org/image/he6lcmas/)
(http://s4.postimage.org/he88vysk/IMG_0810.jpg) (http://postimage.org/image/he88vysk/)
The Maskol will be rubbed off of the model when the initial paint colours have been laid down, the idea being to simulate chipping of the paint, exposing layers underneath. these can then be picked out with rust effects etc at a later stage of the weathering.
(http://s4.postimage.org/hf5bmwo4/IMG_0831.jpg) (http://postimage.org/image/hf5bmwo4/)
(http://s4.postimage.org/hf6z695w/IMG_0835.jpg) (http://postimage.org/image/hf6z695w/)
(http://s4.postimage.org/hfaa8y5g/IMG_0837.jpg) (http://postimage.org/image/hfaa8y5g/)
The last three images show the waterline and black antifouling going on. The antifouling wont stay black for too long as this is just a base colour to weather down to a dark grey later.
The chipping can also be seen in the final photo, also the slightly' scuzzy' waterline. It does not warrant a pin sharp, showroom waterline, as it has been at sea long enough to chip this away as much as the other parts of the paint work. Did the dark grey antifouling always extend over the saddle tanks, as so far I have not depicted this? Mostly due to the less than distinct outline that the Darnell mold suffers from.
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The aft watertight compartment houses a couple of Pittman motors, these I am keeping, however I had to remove the beatufully done radio tray fitted by a previous owner as I needed the space.
(http://s4.postimage.org/hijpel7o/IMG_0915.jpg) (http://postimage.org/image/hijpel7o/)
The space issue was caused by my intention to be as mean as possible during this build, spending as little as possible and using up existing parts that I have laying around. This included enough D sized Nickel Cadmium 4400mAh batteries to make up two 4.8v packs, giving me 9.6v and little need for ballast. The model may sail with its bow sticking out the water at an extreme angle O0
(http://s4.postimage.org/hkajtrz8/IMG_0930.jpg) (http://postimage.org/image/hkajtrz8/)
I made a replacement radio board from 6mm acrylic to mount the two hydroplane and rudder servos, plus other, as yet undecided components.
(http://s4.postimage.org/hkxpcmw4/IMG_0931.jpg) (http://postimage.org/image/hkxpcmw4/)
(http://s4.postimage.org/hl5z1dd0/IMG_0938.jpg) (http://postimage.org/image/hl5z1dd0/)
(http://s4.postimage.org/hl7mkpus/IMG_0975.jpg) (http://postimage.org/image/hl7mkpus/)
As mentioned in the title, this model is intended for use in salt water which produces a number of limitations in operation, and forced my hand towards a 'closed' ballast system. The other problem I am likely to encounter is Depth Charge Attack! The model is going to be used in the Portsmouth Display Teams Convoy Action, where the water is suitable. Our convoy escorts are being encouraged to" make it look good, but dont mean it!" I assume the average model submarine 'reacts badly' to depth charges?!
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Lovely model, I'm just about to start building one and if mine turns out anywhere near as good I'll be very happy indeed :-))
Any chance of some pics of the insides in general?
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Lovely model, I'm just about to start building one and if mine turns out anywhere near as good I'll be very happy indeed :-))
Any chance of some pics of the insides in general?
Thanks for the complements, however, at least the last two owners had more than a small part in the tidy finish of the model. If it dives AND surfaces, however, I'm taking the credit for that!
I will post more pictures as the refit goes on...
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Looks very nice indeed!
Hope to see the display team somewhere soon!
David
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Might want to use polycarbonate for those hatch lids instead of acrylic- bit more resistant to depth charging.
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Back o the horse after the summer.
First thing to sort out is the typical Darnell 'middle age spread'! The upper hatch has already had locator pins fitted, however the fit was still a bit suspect. So, I proceeded to wax polish the upper hatch flange, while burring a rough surface on the lower main hull flange. Much fibreglass repair paste applied followed by bolting the upper and lower parts together. Then smooth the gunk that oozes out of the join and wait.....
Good news, it came apart :-)
(http://s2.postimage.org/zmp544tg/type_VII_003.jpg) (http://postimage.org/image/zmp544tg/)
(http://s2.postimage.org/zmu3q6as/type_VII_004.jpg) (http://postimage.org/image/zmu3q6as/)
The blue/green line just below the join line is the repair paste, it sticks and it works, yay!
I am fitting two 4oz trim tanks fore and aft, these will be half filled with liquid and connected to each other via a reversible pump. My plan is to use these for fore and aft trim, possibly including a 'sinking by the bow or stern' effect. So, I shaped two brass brackets to fit the 4oz tanks as shown.
(http://s2.postimage.org/zniwsdpg/type_VII_007.jpg) (http://postimage.org/image/zniwsdpg/)
(http://s2.postimage.org/znkkbq78/type_VII_008.jpg) (http://postimage.org/image/znkkbq78/)
(http://s2.postimage.org/znpixrok/type_VII_009.jpg) (http://postimage.org/image/znpixrok/)
(http://s2.postimage.org/znr6h46c/type_VII_010.jpg) (http://postimage.org/image/znr6h46c/)
The pump will be controlled, old school, by a mechanical reversing speed control. This one is a Mardave style unit available from Hunter Systems and fixes directly to a servo and can be fitted with an appropriate resister for half speed operation. I dont think I will need any sort of failsafe function on this unit, as long as I have failsafes on throttle and main pump control.
(http://s2.postimage.org/zomlopk4/type_VII_011.jpg) (http://postimage.org/image/zomlopk4/)
Finally, a quick overview of progress so far..
(http://s2.postimage.org/zoy6g50k/type_VII_013.jpg) (http://postimage.org/image/zoy6g50k/)
(http://s2.postimage.org/zp3526hw/type_VII_015.jpg) (http://postimage.org/image/zp3526hw/)
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Weathering was on the cards last night, however, first some general inside shots. This model does not claim to be at the pinnacle of technology, but is being built for the rough, salt water, depth charge riddled depths of Canoe Lake in Southsea, and is my way of saying thank you to all the airbag equipped Darnell/Metcalf/Models By Design models that have gone before :-))
(http://s3.postimage.org/9kutac78/IMG_3352.jpg) (http://postimage.org/image/9kutac78/)
(http://s3.postimage.org/9l1ffq6c/IMG_3354.jpg) (http://postimage.org/image/9l1ffq6c/)
(http://s3.postimage.org/9l4qif5w/IMG_3355.jpg) (http://postimage.org/image/9l4qif5w/)
(http://s3.postimage.org/9l9p4gn8/IMG_3356.jpg) (http://postimage.org/image/9l9p4gn8/)
(http://s3.postimage.org/9lenqi4k/IMG_3357.jpg) (http://postimage.org/image/9lenqi4k/)
(http://s3.postimage.org/9ll9vw3o/IMG_3358.jpg) (http://postimage.org/image/9ll9vw3o/)
(http://s3.postimage.org/9lq8hxl0/IMG_3359.jpg) (http://postimage.org/image/9lq8hxl0/)
Stern to bow; Rudder linkage, aft trim tank, aft compartment, centre compartment and airbag, fore compartment, fore trim tank, front hydroplane linkage. Notice the green filler along the flange line added in the last post.
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Time to empty the compartments, evacuate the bowels, so to say!
(http://s3.postimage.org/9oe5o284/IMG_3361.jpg) (http://postimage.org/image/9oe5o284/)
(http://s3.postimage.org/9omfcsp0/IMG_3362.jpg) (http://postimage.org/image/9omfcsp0/)
(http://s3.postimage.org/9p2yq9ms/IMG_3363.jpg) (http://postimage.org/image/9p2yq9ms/)
(http://s3.postimage.org/9p7xcb44/IMG_3364.jpg) (http://postimage.org/image/9p7xcb44/)
(http://s3.postimage.org/9pg711l0/IMG_3365.jpg) (http://postimage.org/image/9pg711l0/)
(http://s3.postimage.org/9pl5n32c/IMG_3368.jpg) (http://postimage.org/image/9pl5n32c/)
The aft compartment houses 2x 4.8v 4400mAh D size packs, 2x servos for hydroplane and rudder control, and 2x Pittman motors for main drive. This is all removable in about two minutes at the moment. This will soon change as I hook up wiring and linkages though.
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Fore compartment.
(http://s3.postimage.org/9rlxacsk/IMG_3360.jpg) (http://postimage.org/image/9rlxacsk/)
(http://s3.postimage.org/9rqvwe9w/IMG_3369.jpg) (http://postimage.org/image/9rqvwe9w/)
(http://s3.postimage.org/9s7f9v7o/IMG_3370.jpg) (http://postimage.org/image/9s7f9v7o/)
(http://s3.postimage.org/9saqck78/IMG_3371.jpg) (http://postimage.org/image/9saqck78/)
This contains the main air pump, which uses a single cylinder steam engine connected to a Bueller 18v motor. This is reversable and transfers air from the radio compartment to the air bag and vice versa. The smaller pump is an MFA reversable water pump and will transfer trimming water between the fore and aft 4oz fuel tanks mounted on the brass straps. Various bits of electronic trickery are still to be shoe horned into the model.
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Having only recently ruined the below waterline finish with various grades of sandpaper, grit and files, it was time to remedy the mess caused! I used Blackboard paint again, this time, however, I intended to start adding the weathering. Yesterday was stage one.
(http://s3.postimage.org/9wst0klg/IMG_3345.jpg) (http://postimage.org/image/9wst0klg/)
(http://s3.postimage.org/9x12pb2c/IMG_3349.jpg) (http://postimage.org/image/9x12pb2c/)
(http://s3.postimage.org/9xuudjyc/IMG_3408.jpg) (http://postimage.org/image/9xuudjyc/)
(http://s3.postimage.org/9y1gixxg/IMG_3409.jpg) (http://postimage.org/image/9y1gixxg/)
(http://s3.postimage.org/9y6f4zes/IMG_3410.jpg) (http://postimage.org/image/9y6f4zes/)
(http://s3.postimage.org/9ygcd2dg/IMG_3411.jpg) (http://postimage.org/image/9ygcd2dg/)
I dont like Dry Brushing as an effect, I will use it but prefer not to where I can come up with an alternative. On this model I am trying to blend two colours together at once. In the tradition of 'modern' weathering techniques, we will christen it Wet Blending. ( check out any scale mag involved in either plastic kit aircraft or military modelling, weathering is now broken down into, drybrushing, pre-shading, post shading, modulation, washes, spanish technique, blah blah blah! Its all weathering and was developed by the old masters hundreds of years ago for two dimensional painting on canvas. Now hijacked in the 21st century and labelled! Rant over...)
Wet Blending is a technique developed by myself, yesterday, which involves laying down more than one colour at a time, then blending or streaking it in in the general direction of the wear and tear on the vessel or vehicle. In this case, I was mixing Blackboard Paint and two shades of Tamiya acylics on the model, as well as mixing an intermediate colour on scrap card to help blend in the effect. It must not be one uniform colour as that defeats the purpose of the effect, more a streaky effect drawn across the model from the top to the bottom. The good news is that as it dried it actually worked!
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On with the weathering. The problem with any weathering effect that I find is brush marks, if you can see the brush marks, you can see how it was done. loose the brush marks by blending them in with thinners or in this case by blending them in with the other colour.
(http://s3.postimage.org/a5arfryc/IMG_3423.jpg) (http://postimage.org/image/a5arfryc/)
(http://s3.postimage.org/a5fq1tfo/IMG_3424.jpg) (http://postimage.org/image/a5fq1tfo/)
(http://s3.postimage.org/a5mc77es/IMG_3426.jpg) (http://postimage.org/image/a5mc77es/)
In this case, the brush marks were got rid of with a sludge like mix of blackboard paint and water. This was brushed over the offending area and lightly dabbed off with a bit of tissue paper. Sometimes this needs to be done more than once to obtain a satisfactory effect.
(http://s3.postimage.org/a79vjp6s/IMG_3421.jpg) (http://postimage.org/image/a79vjp6s/)
(http://s3.postimage.org/a7ghp35w/IMG_3422.jpg) (http://postimage.org/image/a7ghp35w/)
As I had some green sludge unused, I had a go at a mucky waterline, by drawing the brush along the waterline and leaving wet, watery paint where wanted, I figured it would dry to a nice finish. Fortunately this worked, if it hadn't worked, acrylic paint is a devil to remove once it dries as solvents wont touch it. Usually I would use enamel paints for this effect but I was in a hurry and did not have any with me at the time.
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With the paints drying it was time for a quick overview. Generall I am happy with the effect, there are some areas where the brush marks are showing through and they offend my eye!
(http://s3.postimage.org/acf3qkhw/IMG_3446.jpg) (http://postimage.org/image/acf3qkhw/)
(http://s3.postimage.org/acqohzyc/IMG_3438.jpg) (http://postimage.org/image/acqohzyc/)
(http://s3.postimage.org/acvn41fo/IMG_3450.jpg) (http://postimage.org/image/acvn41fo/)
(http://s3.postimage.org/acyy6qf8/IMG_3447.jpg) (http://postimage.org/image/acyy6qf8/)
(http://s3.postimage.org/ad5kc4ec/IMG_3437.jpg) (http://postimage.org/image/ad5kc4ec/)
The next stage will involve either oil paints or enamel paints, and will be washes or airbrushing...hows that for planning ahead?
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I think, Sir, that your eye is easily offended.
That has to be the best painting and weathering I've seen. Utterly convincing.
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Reply#13
HI Unbuiltnaultilus
I would like to second that and say the weathering looks very good,how do you fancy having a go at a bigger sub. I noticed that you are using a single cylinder steam engine for a air pump just a idea have you thought about using a blood pressure air pump they pull quite low current about 200ma at 6v sub looking good
All the best John
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Great job and the weathering is super!!!
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Cheers guys, truly beauty is in the eye of the beholder, however, so are those niggling little bits that you and you alone can see. We are our own worst critics.
I have a wrist mounted blood pressure thingy which will be disassembled at some time soon, however I like the look of big bits of brass chugging about, its the Steampunk in me.
Bigger subs, there lies a story. I have a nearly complete engel Typhoon which is heavier if not longer, a Sheerline Alfa at about 84", unstarted but I am looking forward to that one, and hiding in someones garage roof is a 1/32 scale WWII Group 3 T Class sub at 104"! I feel I need to get back on the submarine horse first with an easier project, hence the Type VII.
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Sheerline Alpha ???? I dont see that advertised on the sheerline webset would love to get my hands on one that big
paint job looks superb though
regards Mark
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Give the man a ring, he had the mould along with the big Los Angeles. When I bought it the Los Angeles mould was unservicable but the Alfa just needed a dust down and minor repairs. Mind you, the fate of lots of subs has befallen it. I have had it over 3 years and not started it yet!
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I think I will send Chris an e-mail thanks for the info
regards Mark
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The build is back on. Any advice on what to use in the fore and aft trim tanks as a liquid ballast. It is a closed system, transferring liquid ballast fore and aft as needed, via an MFA geared pump. I need a suitable liquid that wont rust up the pump, eat its O Rings or go stagnant and stinky over time, any ideas??
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You may not appreciate an alternative suggestion at this stage :-)) but have you considered moving one of your large battery packs with a servo?
You would get a useful angle change with a surprisingly small movement 20mm or so. (A formula in Norbert Bruggens "Technology" book will give you an estimate.
It is also much simpler than a pumped trim system and it is also proportional.
Again apologies if you have already considered and discarded this idea.
David
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All ideas are appreciated, even if I cannot apply them to this project. Space is at a premium as I am divided into three small compartments with this model. I do like the idea however, and may be able to apply it to a later project, maybe an 'unbuilt' project...soon to be an 'almost started' project, soon'ish :}
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Right oh!
Coming back to your original question. I would suggest something like car antifreeze - or a water/methanol mix. Something in there to kill the bugs but still tolerant of some water leakage.
David
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Water is really the only practical solution for a pumped system. Glycol based antifreeze lubricates as well as killing off any bugs, however i wonder if it may have an effect on the plastics used in the pumps? I have run a water cooled computer for about ten years, and that runs on normal tap water, with no antifreeze, and I've never seen a bit of algae or stagnation in the water, despite all the warnings written on the web about needing special additives etc.
Mercury is used in some fullsize vessels, and being about 13 times the density of water, you wouldn't need to move much to get the same effect. But even assuming you can find a supplier, it's nasty stuff, and you don't want it getting into the watertable if you were unlucky enough to spring a leak.
However I prefer the system David mentions. Don't forget the shiftable weight could be placed in the wet area if space is tight. You can control the weight via a watertight gland or bellows.
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Okay, could a shiftable ballast sytem be fitted either forward of the existing watertight compartments, or aft, and still be effective, or does it need to be around the mid-point of the model? Also could it be fitted above the screw down lid if it used only a small amount of weight but with a greater deflection fore and aft?
My brain stopped working about an hour ago and all the above seems totally sensible to me at the moment, I may need a lay down in a darkened room for a bit....
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Yes that isn't a problem. Generally you can get about 40mm linear shift on a standard servo. The further you can move the weight the less weight you require to get an equivalent tilt (law of moments). Mounting above he lid of the compartment is possible, but this won't help the stability of the boat, as it will reduce your metacentric height.
How many degrees of tilt do you want, and do you know the overall weight of the boat (roughly). Regarding the weight, the battery pack is often used, but could also use a lead weight, or if you have some a block of tungsten which is about 80% denser than lead, not easy stuff to work with though, so lead is probably best!
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Dont know the weight of the boat at the moment, in fact I am not sure it will float with the big D cell batteries on board. I have got back up Sub C packs in the wings just in case, its all a bit 'seat of the pants' at the moment, mind you, thats how we learn :-)
(http://s7.postimage.org/p74gt2qqv/image_php.jpg) (http://postimage.org/image/p74gt2qqv/)
This was the sort of effect I was looking for, something to integrate into our WWII Convoy Display. So the tilt angle is intended to be quite severe, or as severe as a 20" deep lake will allow anyway.
I wont be attempting anything ambitious with this model, so no mods to the installed trim system.Its just intended to get me back under water after 22 years. The next serious build will have bells AND whistles attached, and I like the idea of trimming the boat 'Ram Up'. Keep those pesky slave trading ships at bay :}
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Actually, I have been hacking away at the model structurally, which I consider fair game, but internals, dont muck about with stuff you dont understand...or have long forgotten.
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The angle of tilt in that photo looks like about 15-20 degrees.
I've not owned a Darnell boat, so I don't know what they displace. At a guess I would think somewhere between 7-10kg submerged, perhaps a little more. So if you want to go the servo route, and assuming you manage to get between 20-40mm linear movement you will be looking at somewhere between 0.7-2kg of weight to shove about. With the ballast tank system, the weight would be a lot less, because you are moving it over a greater distance.
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Well, trimming issues aside, I have started hacking again. The extended lay up time allowed me to stare at the model and be overly critical about its appearance. The main issue being the lack of slot above the saddle tanks. The problem being that I have got the lid to fit perfectly without any flexing to fit. if i start hacking it about, it may not fit so well.
But why let that stop me :-)
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Thank you Permagrit, for making a difficult job that much easier...
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The reason for the slots? So I could add just a little bit more pressure hull under the upper casing, visible through the new slots. This needed building up with something, so out with the Glass Fibre Repair Paste. Just one point, before applying, abrade the surface vigorously, I forgot and paid the price....
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Following a bit of judicious filling and sanding, I was able to apply a bit of Humbrol 87 Steel Gray to see what it looked like.
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Black over the top of the newly re-defined saddle tanks, notice the gradual loss of the original camoflage scheme <:(
New scheme to follow %%
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(http://s7.postimage.org/p74gt2qqv/image_php.jpg) (http://postimage.org/image/p74gt2qqv/)
This was the sort of effect I was looking for, something to integrate into our WWII Convoy Display. So the tilt angle is intended to be quite severe, or as severe as a 20" deep lake will allow anyway.
The angle of the bow in this photo of U-505 was due to the crew having started scuttle the boat.
http://www.history.navy.mil/faqs/faq91-1.htm (http://www.history.navy.mil/faqs/faq91-1.htm)
Were you planning on an authentic scuttling action? %%
Guy (Previously known as SUBGEEZER but had to re-register!)
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Right oh!
Coming back to your original question. I would suggest something like car antifreeze - or a water/methanol mix. Something in there to kill the bugs but still tolerant of some water leakage.
David
What about Automatic Transmission/power steering fluid? denser than water and not quite as toxic as mercury
Then again there are Marine safe Hydraulic fluids tho slightly more expensive
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How much denser than water is transmission fluid? I wouldn't have thought it was very much.
The other thing you need to be mindful of is compatibility with plastics. Water is fairly inert, although most plastics do absorb water especially if left wet over extended periods, although I would expect pumps designed for windscreen washers to be made from plastics that are very resilient in this respect (nylon and acrylic are probably the worst plastics with regard to absorbig moisture). However other fluids may cause the plastic to break down.
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Im not sure exactly... will find out and get back to you
Didn't think about the oil and plastics thing.... one for for experimenting with I guess
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How much denser than water is transmission fluid? I wouldn't have thought it was very much.
Water has a density of 1 kg/l, (salt water is around 1,020 kg/l) - ATF is around 0.85-0.86 kg/l so it's actually lighter than the water.
Your best bet if you're using a sealed system for the trim tanks, is to use either demin or de-ionised water :-))
Mark.
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Looks like de-mineralised water or its like is top of the list, possibly with some sort of winter additive type of thing to give it a nice blue tint. I will be able to see it then.
Scuttling action? Yes :-))
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My main concern with your set-up is the tanks themselves. With an unbaffled pair of tanks situated a long way past the centre of gravity, any slosh in there will I think result in some unpredictable handling.
I would think of fitting either spherical tanks (solvent weld some plastic hemispheres together from EMA's) or make some cylindrical tanks mounted end up. These will give little to no slosh.
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I will give this some thought, maybe a little bit of lateral thinking is called for.......
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whay not use the bladders instead of tanks like the TT Neptune?
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You could use balloons inside the tanks. The natural elasticity will keep the water from sloshing about Change them now and again, as they can degrade as the air gets to the rubber.
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I have spoken to my friendly neighbourhood upholsterer, who has dropped off a selection of man made fibre pillow/sofa stuffing material. Similar to cotton wool in look, but drains/dries quickly. Seems to take up about 5% volume in a cup of water and drains off in about ten seconds. As I couldn't find the stuff they put in F1 Car fuel tanks, and cannot get baffles through the neck of my fuel tanks, I will test this. It may well need a fuel filter fitted in line between it and the pump, although it does not seem to 'fray' easily.
This is me being stubborn :} as I have already made my nice brass frames for the tanks. However, notes are being taken for the next project, so thank you for the ongoing input, greatly appreciated as always, and hopefully helpful to others along the way :-))
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stuff they use in motorsport fuel tanks is available from MERLIN MOTORSPORT , based at castle coombe racing circuit , wiltshire !
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They use it in aeroplane fuel tanks too I believe. I've not seen or heard of it being used in a submarine before. Unnecessary if you use a ballast system which doesn't employ an exposed water surface.
It must reduce the volume of the tank by a fair bit, and I'd be a bit conserned by the risk of bits breaking off and possibly clogging the pump.
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wouldnt wire wool do the job?
Grendel
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It looks like it could easily be 'over stuffed' into the tank if not careful, so I will see what is the minimum amount neccessary to reduce sloshing. As I said, if took up only a small volume in a cup of water, stick in fibres-add water to the top-remove fibres carefully, which left about 95% of the water in situ. My main concern is how easily the pump will be able to deal with the last 20% of the water, if an amount of it is still suspended in the fibre.
just cos its not been tried before doesn't mean it wont work..if it doesn't work I will hold my hand up and admit being wrong, once a year every year can't do me any harm %)
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wouldnt wire wool do the job?
Grendel
I guess it would depend on what I was using as a liquid, water may well be a problem due to the possible development of rust. Thinking along your lines, how about stainless pan scourers, shredded up a bit to reduce their volume?
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Scotchbrite pads are effectively synthetic wire wool. I notice you can get the fuel tank foam easily on ebay.
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I would think that might work.
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Looks like we might have an interesting option developing here, must go and play in the bath....
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Well, to paraphrase ( badly ) a world famous gentleman..
"Two steps forward, one giant leap backwards."
However, i am getting ahead of myself, the U-Boat has been on hold over the winter as other projects have taken precedent. With my promise to myself to complete four of my own models by the end of the year, I have had to pull my finger out. Tug finished, back to the sub.
Aft compartment fitted with three servos, auto leveller, speed control, two Pittman motors and a Futaba 7ch Rx hiding away behind the servos.
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Front compartment fitted with two Action Twin Relay Switchers, Mtroniks Failsafe, and old USE Steam Engine/Bueller Motor air pump combo and and MFA reversable water pump.
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Centre compartment fitted with a bright orange SHG Marine air bag, covered by lots of holes wrapped up with grey plasticard. Old school.
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Futaba 4 Channel Radio Control, with a fifth channel added and groovy submarine graphic, to indicate up and down when my brain cells fail me ( most days, night time, Wednesdays, November 5th, the smell of gunpowder, whats not to like? ).
This specific set by Futaba is easy to add a fifth channel to, i can reveal all, it does involve a soldering iron though.
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my views on the " it doesn't work, its the manufacturers fault!" syndrome were confirmed while I was setting up the two Action Twin Relay Switchers. no matter what I did, I couldn't get one of them to work in both directions. Much swearing, dismantling, checking of solder joints resulted in nothing obvious. Walk away, contemplate ordering another one.
Then a moment of clarity, I was using the fifth channel, recently added by yours truly, for the control of the 'faulty' switcher. there are three adjustable pots to control end points and mid point on the conversion. My mid point pot was set fine for a servo, but way of 'mid point' for the switcher, a quick tweak with the screwdriver and all was well.
Lesson learned, stuff you can buy is usually tested alot, stuff you do yourself isn't %)
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So far so good, the internals were ready for final fitting. thats lots of plumbing and electric string to fit in a small place. Still, not too much of a challenge, what could go wrong..?
The sub being dwarfed by a Mk1 Tank, look at the sub, look at the sub....
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The last week consisted of fitting cables and plumbing, shortening silicone hose where needed, cable tying cables up and out of the way. The antenna wire was first re-routed inside the model, run to a 2mm gold socket connector, then up to an unfeasably long salt water antenna ( which is removable for either static display or fresh water runs ). Not forgetting some blocks to restrict the movement of the batteries when in the water.
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The trim tanks were topped up with distilled water and the electronics flashed up and set up.
The trim tanks have no baffles or previously discussed wadding at the moment as this was going to be a fresh water test tank run only. However, the stainless scourer i tested back in October was still in one of the tanks, still damp and showing signs of corrosion, so thats off the list as a suitabletank filler.
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Have you thought about using pond filter/aquarium foam?
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Test tank Sunday came around. The sub had only been bolted airtight the first time the night before. I had my feelings something was wrong when I pumped about three pumps of air into the model with a bicycle pump, then tested the bike valve for the expected hiss as I let the air back out..nothing.
So I had a leak, I knew not where.
I am at least the fifth owner of the model, at least two of the previous owners should not be allowed near sub models again, while at least one and a half of them have done a great job so far ( not sure if I am included in that list one way or the other??). I have previously been chasing leaks in the wall between the hull and bulkheads, caused where very early bonding problems have been cured with successive applications of epoxy, silicone or some thick paint, hopefully this was not one of them leaks.
In the test tank, with the air bag deflated and a pile of EPO foam and lead ballast beside me, we launched the model. With the bicycle pump attached so I could find this pesky leak, the model plunged to the bottom of the tank stern heavy. that can be fixed. The problem was the large amount of bubbles escaping from at least eight places UNDER the bolt down plate. Multiple failures in difficult to access places, under many layers of glue, gunge and muck.
PANIC!
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Have you thought about using pond filter/aquarium foam?
No, but I like your thinking, and may know someone who could help with that. Cheers.
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The long and the short of the problem being the flange around the top of the watertight compartment is 1/8" aluminium plate, bonded down a long time ago with epoxy, and probably leaking and failing.
The build quality is great, the aluminium is 33" long and has been bonded UNDER the Darnell return flange, so may have been the first thing fitted to the model. Problem being the best fix looks like replacing it with something not aluminium, but more suitable for sticking with epoxy or similar. Such as fibreglass sheet, got some of that :-))
Problem being removing the aluminium. At points like this you know what has to be done, but if you dont talk about it you can pretend it isn't an issue...
So, about an hour after the first run in the test tank ( everything else worked faultlessly <:( ), it was out with the angle grinder, off with the flange, and out with the hammer and chisel...
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So thats where I am today, all the bits now removed from the sub, locator pins in the spares box, upper to lower hull join now missing 4mm of material over two thirds of the sub, £10 worth of stainless bolts purchased for the new hatch, an aluminium hatch bent, buckled and fit for scrap, and weirdly filled with confidence that this was the best move I could have made :-)
Lets get the latex gloves on and start hacking up fibreglass....more to follow.....
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Looks like some nice trays you've made for the equipment. They would slide very nicely into two cylinders either side of the bag, not that trying to influence you into abandoning the boxes you understand.....
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That thick black paint reminds me of underseal for cars
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That thick black paint reminds me of underseal for cars
It does look like the bottom of an old Ford, do they use it on submarines?!
Looks like some nice trays you've made for the equipment. They would slide very nicely into two cylinders either side of the bag, not that trying to influence you into abandoning the boxes you understand.....
As I believe you mentioned way back in the thread, old school submarine technology.
I am aiming for a three sub fleet, believe me the other two will use clear cylinder WTCs, the idea that you can see all, leaks included, kind of appeals to me more than chasing leaks hiding under inaccessible flanges. The Darnell U-Boat though, nuts, bolts and vaseline, old school :-))
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Fibreglass work, out with the latex gloves and facemask, I think I am becoming sensible in my old age.
The first job being to replicate the aluminium flange removed last Sunday. The M5 bolts were still attached in places, with both epoxy and an 'anti-spin' wire bonded into their slotted heads. A good idea that prevents the bolt working itself loose once all assembled into the model. Still had to go though, this was the point I realised the aluminium was actually bonded to polyester resin, not epoxy. Explains its apparent brittleness, and probably its not sticking to metalness also!
The old flange was cut to size, the scrap centre parts being disgarded. Then bent back into shape to fit the sub ( the removal process was pretty brutal, the aluminium was less than flat when it finally let go of the sub last Sunday!). I checked that the metal was the correct shape by fitting the acrylic lids back on top and dry fitting the whole shebang back onto the sub.
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My stock of fibreglass sheet dates back about ten years and was laid up for a sailing ship, still in service. It is a bit like the South Downs, lumpy in places, not so much in others, still needs must ok2 .
The aluminium was laid on top and drawn around as accurately as possible, once I had remembered to ensure the aluminium plate was up the correct way, yes, I did it upside down. Noticed the error before cutting it all out though.
This was then cut out on a band saw. The acrylic top hatch was then placed in position and the bolt holes marked as accurately as possible.
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These were then drilled out to 3.5mm, allowing me to tap out to M5 later. Todays deliberate mistake being to assume that being a less tough material than metal, I could tap through with a smaller tapping hole than usual (4.2mm as opposed to 3.5mm ), wrong. I will be opening them out to 4mm later!
Countersunk partially to fit the CSK bolts. Then I marked roughly, the position of the inner hatch access. Drilled 8mm dia holes into the corners of the hatch, allowing me to get a jigsaw with a tunsten carbide blade in to start cutting.
And that is where I am today, so time for a bit of forward planning for the weekends building, a trip to Halfords for some fibreglass repair paste to bond the whole lot down ( when it cools down a bit, dont want the job going off too quickly ), and a bit of grinding with the hobby drill to remove any remaining flappy bits of sub-standard waterproofing. :-))
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tapping size for m5 is a 4.5mm hole ! best wait until the sun has gone down a little before any grp / bridging filler this weekend , dont want to set fire to the clubhouse when it all cures too quickly .
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M5 csk bolts now fitted, along with the upper soft seals.
The copper wire in the slots of the bolts helps to prevent the bolts spinning loose in the future when tightening down the hatches, a common submariner trick. mind you, epoxy in the thread as you wind them in plus more on top afterwards, should hold them in...
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As the hatches start to look better, the watertight compartments are looking a little worse for wear. A bit of controlled chisel action has resulted in a large amount of poor quality epoxy and paint flakes coming off. Also, I have managed to remove what looks like white Sikaflex from some of the leak points. to be replaced with epoxy re-enforced with fibre filler powder, once all hull to bulkhead joints have been ground with a drill and burr.
Removing the old flange will also allow me to remove some of the now surplus plumbing parts that litter the model. One visible alongside a pushrod outlet tube.
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Bulkheads now re-enforced with an epoxy/Glass Fibre Strands mix. Applied, warmed up with a hot air gun, run round the bulkhead and left to set. The new upper hatches are bonded on with Glass Fibre Repair Paste, trimmed while 'green' and finally sanded back to a clean edge 24 hours after first bonding.
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And concerned about the uncontrolled decent to the bottom of the test tank on its first float, I have added EPO foam bouyancy in strategic locations around the model. I dont think I have enough aft yet and am considering fitting an arm band around the outer hull if all else fails :} .
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Now I have to show some level of patience unknown for me. We have a display this weekend, so I cannot set up the test tank till Sunday week, fine, I will think of something to do in the mean time. Maybe get some filler out and make good the damage caused by the angle grinder, sounds like fun....all that dust....whats not to like?
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Sounds like a very dry and dusty job.
After all the sanding you would deserve
a pint and a juicy pie.
Still and West springs to mind.
Ned
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Their 1980s pork pies will live on in my memory forever.
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A month and a half on. Dusty work complete, paint on, almost ready for the test tank again.
First the making good the damage caused by the angle grinder. I prepped the hull with a drill and dental burr, after first degreasing with acetone.
A balsa strip was bonded between the outer hull and the soft seal and acrylic of the removable lid. This was sacrificial and kept the fibreglass repair paste away from the shiney posh bits! Once sanded, it could be chiselled out. the upper hull was treated to some hand cream as a release agent and it was time to slap on the paste..
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Following this, the latest sand down of the by now ruined camouflage and paint job, I decided to start again. New bottom colour, which turned out to be just a little too glossy for my liking, then abused with my favourite Scotchbrite pad. This time I was not happy with the look so some subtle work was required with a can of Humbrol Matt Varnish, all over the lower hull..
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Then I proceeded to cut in the above waterline colour. As the model was going to represent a U-Boat returning from patrol, it could look a bit scruffy. This started with my cutting in of the mid-grey colour. This was applied in a strictly patchy nature, just covering any obviously sanded down areas, not anywhere else, where the already patchy look would add to the final finish.
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Painted the '88'.
Then pencilled in the new camouflage pattern, followed by a stipple of Maskol masking solution, latex based pink liquid, to represent chipping on the camouflage. You paint over it, then peel it away revealing a random pattern showing the base colour through the chipping.
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Rust. I love my rust. This time I was going to try Humbrols new weathering powders. These are available in a number of colours and are eminently unsuitable for use on a model that goes under the water, washing all the powders off again, so, fine then :-) .
Making them useable for the marine environment entailed a 50:50 mix of Humbrol Mattcote and a suitable thinner, once mixed and shaken up, I then added small amounts of powder to the mix, till I had a colour somewhere between seaweed and rust. testing it showed that i had to work fairly fast as it tended to dry quicker than I expected once applied to the model.
An unexpected bonus from using different colours from the range, when left overnight, the colours partially seperated in the pot. This gave me more than one colour to use, depending on how deep the paintbrush went into the mix, excellent!
On the conning tower I placed some of BECCs U-Boat insignias, more for the little bit of colour than anything else. My mixing of U-37 with the 10th U-Boat Flotilla and Erich Topps boat would surely go unoticed? Except by the first person to see the model...so all change!
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The problem with rust, if you dont deal with it, it just gets worse...
The rust is either streaked down the hull wet, with a very fine brush, or applied a little more broadly and dabbed off with a tissue. The end result shouldn't look too much like a 'brush job' or a 'spray job'. It should be at least a little difficult to tell how it was accomplished.
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The last few photos show the new 9th U-Boat Flotilla emblem of the Laughing Sawfish and a Stag on a plaque on the front of the conning tower. I knew this would be useful when I bought if from Games Workshop 20 years ago, and I was right.
It also shows where I overdid the rust on the front of the conning tower, this was remedied in the last photo by dry brushing the original grey colour over the rust, not just on the conning tower but elsewhere where it was a 'bit too much', blending in any obvious bits that offend my eye.
All that remains is a little bit of Humbrol Chocolate Brown to darken small 'edges' of rust, to give them that deeper corrosion look. Its also about time to get it wet again, RC is re-installed and its almost ready to dive :-))
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so when are you going to do my barge for me then
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so when are you going to do my barge for me then
You're big enough and ugly enough to do a good job of it on your own :-))
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:P :P :P <:( <:( <:( <:(
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Sunday was test tank day. However, following re-installation of the equipment I found the Action Switcher was not switching tha air bag pump. Through a process of elimination I found that the Tx mod I had carried out was causing the problem. Without a clean 'mid-stick position' signal the switcher got the hump and wouldn't play. upon checking the Tx I found I had cut corners fitting the buttons for dive and surface, neglecting to fit any resistors in line, but tapping straight off the board...naughty.
So in went a 10k potentiometer in line and everything was fine.
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At the test tank the good news was that the seals were 95% good with just two small leaks to address, also the front of the sub floated nicely, however the back of the sub sunk :o . Still better than a poke in the eye with a sharp stick!
Much tea in evidence at the test tank, good for thinking is tea...
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Never one to miss an opportunity. Back in April 2011 when I started this project ( No rush :-) ), I took a photo before the work began. It seemed right to take a second photo as she is today, from the same position, resplendant in rust..
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That looks nice, love the weathering job! Just don't show Ben, whatever you do...
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Cheers :-)) . First leak now sealed, second one identified. Next job, cutting up more foam for the upper structure. It will float on an even keel, whatever it takes.
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Pressure tested the model out of the water. lost most of it over about 60 minutes. I checked it this morning using soapy water ( if it works on my bike tyre, it should work on a U-Boat..), air was escaping from round the bolts through the perspex. I am currently using fibre washers under M5 nuts, have just purchased 50 off M5 x15mm Stainless Steel washers as an alternative to the fibre washers, thoughts??
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Use both
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Miniature O rings, maybe?
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Hi.
I use stainless washers under mine, lot more durable than fibre which will break up.
notice you have some oversize holes in the perspex lid for the bolts to pass through.
Mine are a lot tighter tolerance plus a
silicone gasket so deformes around the bolt filling the gap. You might try o rings under the stainless washers to fill the gap as it were.
hope its of use........keep the faith nearly there.
regards sub.
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I ask as some of the bolts seemed to leak more as I tightwened them, possibly pointing to the washers deforming as I tightened down on them. I will try both the fibre washers under the stainless ones, and the stainless on their own. I am using hand cream as a hatch seal at the moment, purely experimental and easier to clean up afterwards than vaseline. However it might be back to vaseline as well.
My perspex lid 'tolerances', shall we call them? I blame the fitter who opened them out to 5.5mm and some to 6mm. You would expect better after doing this for thirty years. We learn by our mistakes but I think I have been 'round the clock' once already and am now making all the old mistakes again :-)
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And two suggestions for o-rings that I read and didn't sink in. Will factor that option in also, cheers :-))
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how often does the perspex lid need to be removed ? ( i prefer my models to stay above the water ) ive a couple of yachts with hatches that are occasionally immersed , im using roof and gutter sealant ( bought from toolstation ) to form the " gasket " the hatch is kept in place with m4 stainless bolts with washers under the heads . jon
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Simply stunning work.. :-))
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Thank You :-)) .
Best result so far, 15mm washer first, fibre washer second, M5 nut last. Pressure tested to fifteen pumps with a bicycle pump ( a bit over the top, I know, but its a good test. ), now only leaking the smallest amount UNDER the neoprene soft seal. Hopefully at more 'operational' pressure this wont be an issue.
Next job, get it to float......
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Yay, It Floats!!!
Yay, No Leaks!!!
Air pump wont work once the sub is pressure tight, Stuff A Bucket!!!
Anyway.. it appears that the little piston pump is unable to reduce or increase the pressure in the main two compartments in any way. Once the screw top is released an audible hiss can be heard as the compartment re-pressurises to atmosphere, so thats a bust {:-{ .
Plan B, water tank. I have a redundant trim tank for a surface boat, now cut in half. Baffles under construction and three alternative geared water pumps tested for suitability. The sweetest is also the slowest at over 70 secs, the noisiest is also the fastest at about 25 secs. I have repaired a Norbert Bruggen Ballast Tank Switcher, water sensor now working. all that remains is buttoning up the tank and making more holes in the sub bulkhead. Dimensions of said tank 75mm dia x 195mm long, rough estimate is 800 grams of lift, I think...
I am planning to vent the tank into the RC compartments, I assume a pinch valve would be recommended for the water feed? The pumps seem to suffer from a little 'blow back', however a water sensor turning the pump off is of little use if water still seeps through the pump when submerged, despite not running!
Anyway, photos show the model floating in the pouring rain, in our team test tank. Now with excessive amounts of foam in place ( Trimmable as needed ), also the placement of the EPO foam blocks along the length of the model. I can highly recommend EPO Foam, just dont know where to get it. The blocks I am using were purchased from an RC Aircraft stand at Hop Farm about 3 years ago as cheap offcuts.
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Please note giant 'Salt Water' antenna. This will be trimmed a bit and is entirely removable for static display or that holy grail of coastal dwelling submariners, fresh water :}
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the basin is not bulky in exhibition? %)
beautiful underwater :-)) :-)) :-))
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Unless you are using a peristaltic pump, then you will need some way to block the flow of water back through the pump to maintain trim.
You can purchase diaphragm air pumps very cheaply that will work much better than the old USE pump.
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Before you junk everything again, I would just check on the original Darnell air pump - it should work better than you describe.
I'm puzzled about its inability to pump anything and it was such a simple system. Have you got the original air reservoir in the bow?
I'm refurbishing a Darnell Type XXI here:
http://www.theassociationofmodelsubmariners.com/t1092-darnell-type-xx1-graham-s-dad-s-boat-for-refurbishment (http://www.theassociationofmodelsubmariners.com/t1092-darnell-type-xx1-graham-s-dad-s-boat-for-refurbishment)
The first post shows the original boat "as received" and you can see the original air reservoir. I checked the pump over and after fixing a few leaks I thought that the air pump was serviceable and that the original Darnell dive system could be made to work.
So I would have a look at the original system before going to more time and trouble.
David
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For such a basic, simple idea, that little USE/Darnell set up always worked well...once you could get the boat trimmed up properly. The late Bernie Wood had a twin pump/twin air bag system in his famous Darnell U boat, and it always worked perfectly...lovely level static dives, and it looked so realistic when diving under way (I expect you've seen it at some of the shows we did back in the day, Alan?)
If I can find it in my archive collection, I have some video footage of Bernie's boat in action at the Plumpton Show back in the early 90's, I'll have a hunt for it and post it up here if anyone would like to see it.
Rich
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If you're referring to the boat that was built by Jim Ward, that was converted to a modular system by Nick Burge in 1991, the boat was a test bed for the system which was later commercially produced by Craycraft.
It featured a single hard ballast tank with a custom made twin cylinder compressor. The two cylinders were to prevent the pump loading up against itself, as the compressed air was stored in the forward compartment with the compressor. You can also circumvent this by placing the compressor in another compartment, or by making a small discrete enclosure for the pump to sit in.
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No Andy, I was talking about Bernie's original Darnell U boat.
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I do remember those days, Hat, Badges, Beard, Bernie Woods :-) .
The piston unit is not one of the cast units by USE but a brass affair with flywheel. It works perfectly well with all the lids open, taking about 70 seconds to inflate the bag, however, once buttoned up, nothing. Once the twist caps were released, there was a rush of air in or out, depending on how I tested the setup, then it would work.
I am proceeding with a water tank, but making no alterations to the model just yet. If I can get the air system working, great, if not, everything is removable anyway and I have more than enough bouyancy to accomodate weight variations in the internal layout.
When I started this project, the aim was to get back into the underwater mind set. I am glad I didn't start with a tube system, which would probably have been relatively trouble free. This project, setbacks, chaos, leaks, tech problems, loving it. Must be mad %%
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How have you got this air system set-up?
Do you fill/prime the bag with the boat out of the water, then use the pump to suck air out of the bag, and store under pressure, or do you use the pump to pull a vacuum in the chamber to fill the bag?
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I have tried both, so far with the same result. I am wondering if the pump is running too fast to 'bite' the air, similar to an over revving impellor pump/fan. Seems unlikely, but anything is possible. The fore and aft compartments are interconnected, so its a big reserve of air.
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No don't think so- positive displacment design. My money would be the valves are probably leaky. Is your pump an oscillating model?
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Single Cylinder oscillating.
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Do you have a check valve inline with the pump and bag?
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Hi.
try some one way valves in the system, I use windsceen washer non return valves....work a treat. Available from most auto suppliers.
Regards
Sub.
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Hope this helps show the original Darnell setup. (I connected it up and photographed it 30 seconds ago!)
Dead simple:
- No need for one way valves - you need flow in both directions.
- No pressurisation of your WTC - unless you have a very worn, leaky steam engine.
Hope this helps your setup.
David
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Looks like it might be a drain on the system.
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I had that setup, it was quite power hungry.....
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I was referring more to the backdrop of the picture. ;)
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Looks like it might be a drain on the system.
Oh Andy, please...is that the best you can do? Mind you, it is early in the day... ;D
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What function does the third hose on the left do? I have an 'in' and an 'out' only, reversing depending on motor direction. Substitute the air reservoir shown for my RC compartment and it is pretty much the same system.
Drain jokes, shame on you ok2
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I think that must be for initially priming the system.
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I have looked up the USE engines, they are designed to be stacked, making two, three or even four cylinder engines. I assume this is a take off for that connection. Fitted with a one way valve here they could indeed be primed through this pipe.
How about stacking a couple of these units to increase volume of air to the bag? As long as the motor could drive the twin cylinders?
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I was referring more to the backdrop of the picture. ;)
Thats a system on a drain though!
Grendel
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Thats a system on a drain though!
Grendel
Good point, well made.
Bad joke, well ruined :-))
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Personally I wouldn't persist with this pump, becuase you can get something much better for under a score. They were considered superceded decades ago, back then modellers replaced them with the tyre inflator pumps- not that great either, but considered a step-up from the USE, and the best you could do unless you had the tools and ability to make a pump yourself or adapt an old glowplug or diesel engine. I've only ever seen one working Darnell boat with a USE, and that had been heavily reworked by the owner because in his words" it had a bore like a map of the Himalayas!"
I appreciate you are trying to make a bit of a working time capsule, but in some instances, I think nostalgia is a little overrated. Your call.
http://www.technobotsonline.com/12v-vacuum-pump.html (http://www.technobotsonline.com/12v-vacuum-pump.html)
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Nostalgia is giving me a 120 sec dive time, as long as I leave the hatches open to atmosphere, I want a crash dive!
I assume these are one way pumps, I have some tiny diaphram pumps with servo motors driving them, very effective but slow, also not reversible. Those suggested certainly look more suitable. May consider two, one up, one down, with suitable one way valves if needed.
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Well you know what they say...'If in doubt, order it.'
Two on the way from Technobots. Thank you :-))
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Good stuff. They're excellent pumps, and move a lot of air for their size, I think you'll be impressed when you try one out. They also make pretty good pressure, certainly much better than smaller models of diaphragm pumps.
You won't need any check/one way valves with these, they have the valves already built in, but you are quite correct, you can only pump in one direction with these.
The best way to set up the bag system is to inflate the bag before putting the boat in the water, then use the pump to collapse the bag, by sucking the air out, and storing it in either the box, or a separate bottle/tank. Do mind the pressure if you go for the former, as the forces ratchet up very quickly, and boxes are rather 'soft' when it comes to that kind of thing.
To come up just release a servo controlled valve or a solenoid air valve- a fail safe system (well as near as you can get).
The main snag with a compressed air system like this, is that it is impossible to trim for different water densities unless you leave some air in the bag, which of course is squishy, and will compress as you dive deeper. I think this is one of the main reasons modellers moved away from this system.
Some modellers in Germany use compressed air systems for the main ballast tank with smaller piston tanks for trim usually amounting to about 1-2% of the boats overall displacement. These boats offer the advantages of compressed air (e.g. minimal effort to surface and fast evacuation of ballast tank) with the benefits of fine trimming from the piston tanks.
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Good to know about the installed one way valves. I have just had a very interesting and infuriating brainstorming session with one of the Display teams Johns. Between us ( mostly him! ) we have two systems to look at. Bearing in mind that we did not know about the non-return valves fitted in the pump at the time :-) . A system as described above, roughly (!), using one pinch valve and one pump, and a system using two pinch valves, one pump, but using the pump to both dive and surface.
My brain will be exploding very soon now.
This does leave me with one spare vacuum pump, good for experimenting with, and two SEL Steam Launch engines. Which seem to be at least a bit collectable, so tart em up and flog em both, pays for the vacuum pumps methinks :-))
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To answer an earlier question, I don't actually know what all the ports do on the USE engines. I simply blocked the ones off that stopped it working! Interesting what you say about the ability to connect them all together.
I am still puzzled about the problems you have had with the engine pressurising the WTC. I can only conclude that your engine is the "worse for wear" and hence best binned!
The example I have seems OK and I will try to get the original Darnell system working. "Grahams's Dad's Darnell is that kind of project.
However any problems with it and I confess that I will revert to my current "norm" ballast system. A home made piston tank proportionally controlled by AMS software. I can knock these out very easily and cheaply now and those of you who went to Norwich this year will have seen these systems in my R class and Resurgam.
So best to scrap your USE engine , I was hoping to save you some time and trouble but I can see that like any good Model Submariner you thrive on challenges! It is probably worth pointing out that Internet advice is very cheap but the reality can be expensive.
Good luck with developing your system.
David
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Oscillating steam engines are very simple with just two ports, an inlet and exhaust. The conrod is fixed to the piston, and the cylinder oscillates on a pivot. You will have a single inlet to the cylinder, and as the cylinder moves back and forth that hole aligns with the inlet or exhaust port. As this is a sliding fit, you do get some leakage past the ports, and this will get worse as the engine wears.
You can lap the surfaces to improve this, but in all fairness as far as using these things for a compressor, it's putting lipstick on a pig.
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but in all fairness as far as using these things for a compressor, it's putting lipstick on a pig.
Surely you could just put a bag over its head?
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You could indeed.
As an aside, the pump Brian Cornelius incorporated in the craycraft modules back in the day were oscillating, however they featured miniature plate valves located in the top of the cylinder heads. You could do a similar thing by plugging up the original ports, drilling a hole in the top of the cylinder, and plumbing in a pair of one way valves, but it won't be terribly efficient. The diaphragm pumps you can get now just weren't available until a few years ago, and their introduction made life a lot easier, as they're largely maintenance free, low reciprocating mass, meaning less vibration and thus fairly quiet in operation.
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Surely you could just put a bag over its head?
We don't need to know about your other "interests", Alan, thank you very much.... 8)
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Surely you could just put a bag over its head?
We don't need to know about your other "interests", Alan, thank you very much.... 8)
Everyone should have a hobby, sometimes more than one....
Anyway, I assume these vacuum pumps would be equally capable of vacating the air from an acrylic tube, allowing water in from below, as well as inflating a bladder system?
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Yes, they would work fine in that application, also unlike piston designs, they can quite happily live with ingesting a bit of water
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Hi Subculture
Do you have any personal experience of using these vacuum pumps in a working model submarine?
Many thanks Andy,
David
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I've used a virtually identical model in my Seehund. Was more than a match for the original piston compressor, and much smoother. Could have got away with a much smaller model of pump actually, but you can always slow the pump down.
The version I have is made by Smart products called the SP8000. They're not readily available (I got mine for a special price for trialling) and quite expensive if purchased at list price- the ones I linked to at technobots are much better value, and pretty much identical in terms of spec.
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Bag or tank, this is my conundrum...or something like that anyway. The acrylic tank has a lower volume than the bag, so will support less. However it can be used with a reversable water pump or the vacuum pump, either blowing or sucking. The air bag can use one or two vacuum pumps, either reversable in and out, or transferred into a rigid tank and vented back to surface. The reversable option could burst the bag and will no doubt need a pressure switch in the system, them vacuum pumps are most excellent, cheers for the recommendation :-)) .
Nothing like having too many options....
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If you're going to have the tank completely empty or completely full, why not use the hull itself as the tank, and glass in a top cover. this will make full use of the boats beam, giving you oddles of volume.
It wouldn't suit a pressurized tank as the tank wouldn't be rigid enough, but fine for the sort of system you have in mind.
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A case of a 'can't see the wood for the trees' moment. The centre compartment was originally a sealed tank, I took it out!
Good plan :-))
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If you're going to have a fixed tank, with a recirculating air system, you will need to ensure there is no, or at least minimal chance of sucking water into the pump. That's probably the sole advantage of using a bag, you don't need that additional complication.
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Quick question? What should I expect to be an approximate ratio of volumes between air receiver tank and either air bag or water tank? I have tried fairly small reservoirs and the vacuum pump is giving up at about half deflation. am I looking at a reservoir of similar size to the ballast tank? I am hoping not to use the RC compartment as an air reservoir at the moment.
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That's an easy one to answer- for every halving of volume you must double the pressure.
If you have say a 1 litre ballast tank/bag and you have a 1 litre reservoir, then your pump will need to compress the air to one atmosphere (14.7psi) above ambient pressure. If you wanted to squeeze the same volume into a 500ml pot, then you would need two atmospheres (29.6 psi), and so on.
In the case of the diaphragm pumps, they make about 1 atmosphere, beyond that you're pushing your luck, and they're inefficient at pumping higher pressures anyway unless you series pumps up.
One of the problems with older submarines, and indeed some newer ones is high freeboard, and the need for large volume tanks. If you're using a recirculating system then you need fairly high volume reservoirs or you have to run at higher pressures, which comes with its own set of issues.
If it's difficult to find the space for a reservoir, then I wouldn't rule out a partially vented tank system, perhaps to get the boat to decks awash, then take the tower under with a recirculating system based on any system of your choice. The diaphragm pumps work well with this system unlike piston based pumps, which can't afford to ingest any water.
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You know, I waded through three model submarine books and a fairly useless submarine special and couldn't find that sort of info, much appreciated :-)) .
That gives me all I need to know. The vacuum pumps are good up to 32psi at 12v, I am running at 9.6v so will assume a little less output, I will now look at either air or water based pumping, with or without an auxiliary reservoir, at no greater a ratio than 2:1 volume. If I cannot use my newly silver soldered pressure tanks for reservoirs, I can always use it to fire torpedoes!!
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It's Boyle's law. http://en.wikipedia.org/wiki/Boyle%27s_law (http://en.wikipedia.org/wiki/Boyle%27s_law)
There are online calculators for this sort of thing, but it's pretty easy to work out in your head.
32psi sounds high. Is that through testing, or are you going by the pumps datasheet (which is a bit optimistic IMO).
Silver soldered pressure tanks sound complete overkill. I've hydraulically tested plastic coca-cola bottles to over 100psi (don't be doing this unless you know what you are doing please), so they happily can take the pressures likely in your submarine, without the weight penalty.
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I hope that you already have "Model Submarine Technology" by Norbert Bruggen on you bookshelf.
If not it is well worth getting (second hand only now, I think.) since it really is the "bible" of model submarines. Very good if "in depth" theory (sorry!) which is still very sound. The electronics is rather dated. But all the dive and construction systems are there, many of which you have already looked at in your build log.
The theory is extensive but it is also very practical since he has actually done it, unlike some experts.
David
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32psi sounds high. Is that through testing, or are you going by the pumps datasheet (which is a bit optimistic IMO).
Silver soldered pressure tanks sound complete overkill.
I am a slave to the data sheet, but will test thoroughly first. Silver soldering is kind of second nature to me, mostly working cannons in sailing ships etc, rather than subs. I am aware of the remarkable capabilities of the humble fizzy drink bottle, but they do look like fizzy drink bottles from the outside!!
I hope that you already have "Model Submarine Technology" by Norbert Bruggen on you bookshelf.
If not it is well worth getting (second hand only now, I think.) since it really is the "bible" of model submarines.
David
Yes, I have Model Submarine Technology in my collection, It may be too in depth in places though, and I did not find the last valuable nugget of info in the book, regarding relative tank volumes.
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There is a formula on page 57 of that book that allows you to calculate the volume of the reservoir. Norbert doesn't spend much time discussing systems outside of the ones common in Germany (not surprising), so systems very common in the UK like recirculating compressed air and sealed tank water ballast systems get little mention.
It is a book quite heavy on math and formulas, and a lot of modelmakers get somewhat bamboozled I think.
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I do bamboozled better than anybody I know!
Norberts book makes for an interesting read, I particularily like his distinction between torpedos ( being warlike and 'beligerent' ) and submarines ( underwater buses, no harm to anyone ), different cultures I guess..
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I guess, in Norbert's book, I'm a bit of a savage then. Oh, well. Another sleepless night.
(http://www.vabiz.com/d&e/alligator/images/scan15d-sm.jpg)
Here, my little 1/72 ALFA is busy making the local pool safe for Communism.
David
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I guess, in Norbert's book, I'm a bit of a savage then. Oh, well. Another sleepless night.
(http://www.vabiz.com/d&e/alligator/images/scan15d-sm.jpg)
Here, my little 1/72 ALFA is busy making the local pool safe for Communism.
David
Is that just compressed air ?..
Are you the same D. Merriman, " Stop using my air Merriman "(or similar) ?.. Love to have your SeaView build on here ..
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I guess, in Norbert's book, I'm a bit of a savage then. Oh, well. Another sleepless night.
David
I am fairly sure you are big enough and ugly enough not to be too bothered...
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LOL! Right you are, sir.
David
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OK, enough. We're high-jacking this thread. Bad form.
David
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I have been in a secure panic room over the weekend, Hijackers you know!
Anyway, this is the system going in U37, its a water pumping system, isolated from the main RC compartments, avoiding damp sea water air entering where it shouldn't. The tank will fill to the probes with the auxiliary tanks fitted. Only my higher pressure water pump has the guts to fill this, so heres hoping it doesn't fail me as I dont have a spare. When left with the pinch valve open, the pressure in the system is enough to two thirds empty the tank without the pump engaged. The tank took on 730 grams of water from empty, hopefully enough for the job.
And it looks really cool too ok2 .
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That's a bit like a mix between the systems used on the sheerline and OTW units.
I have no idea what the displacement of a Darnell Type VII is, I would hazard a guess it's more than 750ml though, so you may have to live with a lower than scale waterline.
Will your pump cope well with the salt water.
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The pump has nylon gears and is not directly driven from the motor shaft, so shouldn't suffer from the creep of water that the MFA pump suffers from below waterline. Much though I would have loved to use the vacuum pump(s) on this model, the air reservoir available, unless I was willing to use the main RC compartments, was just too low. No problem, I have two Craycraft tubes which would love a new vacuum pump each.
I would scale down the submerged and surfaced displacement of the Type VII, however the Darnell moldings are six months pregnant, so the figures probably wouldn't help me greatly :}
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Have been busy over the last couple of weeks, re-setting a Set Top Box, Throwing a Set Top Box out the window, avoiding being re-elected Secretary ( failed, nuts! )and sorting out a re-design of the pump compartment etc..
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The old upper acrylic tray was replaced with a shorter, wider one, onto which went the servo for the pinch valve, one only Action Switcher now, a snazzy voltage indicator from Component Shop ( £3.95 from Warwick, bought two :-)) ) and nothing else yet. The Bruggen/Engel Ballast Tank Controller is going under the top tray, in a splash proof box not yet built.
Salt water being an ever present risk to the electrics, I purchased an Acrylic Circuit Board Protective Spray from Maplins...fairly sure its just acrylic varnish, but three coats later the various lumps of electronics were a little less vulnerable.
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Pinch Valve..having built a plunging rod in a bit of acrylic for a fellow Mayhemmer, no names, no pack drill :} , I decided I dont like them...so tried this option. I am sure its as old as the hills but it seems to work. Two ballraces on the servo arm, a right angle of aluminium, and a shim of plasticard to get the 'pinch' just right. Works so far.
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Yes, I line up my screw heads, not mad at all, just a little %% or maybe a little :(( . Dont care, criticise if you will...you will all be doing it by the weekend....
Ballast tank, a reworked, shortened unit from my CHANT Tanker, baffled, like me, and epoxied shut. Along with the two 22mm copper 'overflow' reservoirs for the pressurised air. The ballast tank is currently designed to clip onto another 22mm pipe running between the fore and aft compartments. It does end up a little high, which will affect the waterline when on the surface, but it works. If I can find a neat solution to fix it in place a bit lower, while allowing easy removal, I will incorporate it, but for now..
Not sure how the copper pipes are going to be secured yet, but thats half the fun, surely.
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And finally, I have re-worked the through bulkhead tank feed, last time it was pumping air, now its water, under a fair bit of pressure. So, I replaced the old tube, 5/32" Dia brass, with a longer bit of the same. At the same time, epoxying a right angle bend to the 'free flood' side of the tube, to provide feed to the pump from the central free flood compartment. I may fit some sort of Klunk Tank Filter to the end of it, maybe..
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the screw heads havnt had the locking wire fitted yet !
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That's a clever bit of work, skip..have you thought about using Velcro to secure your tank? I'm using it to secure the cylinder in the X craft, the Dragonfish and the Skipjack...it's cheap, holds like concrete, but it removes easily.
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almost a year....good grief..when the call came to help the Display Team finish off our Fort and Harbour complex, who would have known what a pain in the arts it was going to be..and how it would delay ( more! ) my projects. Anyway, it floats, it explodes when asked, and it looks great, so lets get on with something else..
I have started to work on U37 again. The Engel/Bruggen Dive Controller is now neatly fitted..no photos, and the ballast tank is bonded in, silicone for the ply to copper and ply to acrylic joints, then secured into the model via nylon spring clips, as long as I dont swing it round my head it should all be secure.
So thats how it stands at the moment..back on the Red October, got to finish that, I have sold it!
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Another season nearly over and I can get on with some of my stuff again :-) . Just replaced the locator pins for upper to lower hull locating. Not sure why they were too skinny at 2.5mm dia, but replaced them with 1/8" dia instead...much more imperial! Lid fits with little wobble now. However, the joins are ugly again. So last night was out with the green filler again and make the joint good again and ruin the paint job again!
So I have just been re-reading the thread, trying to figure out why Humbrol 31 Slate Gray has a satin finish on the model, while the paint patch applied yesterday is flat matt? Simple answer..dumb luck. Its the same pot of paint, only now over a year and a half older, and half full only. Following a stir all is matt. Only problem, the sub is satin.
Tonight I shall be buffing my U-Boat..they can't lock you up for it, surely?
:-))
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Some say I am a slow builder...to them I say "Tune in next year for my stinging rebuke of your accusation!"
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Some say I am a slow builder...to them I say "Tune in next year for my stinging rebuke of your accusation!"
Why so soon, ignore them and take your time replying :-)) :-)) %) %)
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I tried buffing up the sub..all that happened was a Genie appeared and granted me three wishes!
None of my wishes came true..so it was out with the paint brush again :-)
But first..more photos of filler and a ruined paint job. Plus a half built SS Ohio and a partly Unbuilt Nautilus!
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So with big matt patches all over the sub, none of which I could buff up to a suitable match..som lateral thinking was required. I decided to put MORE matt paint on the model!
I have seen some stunning examples of static Type VIIs based on the Revell kits, I decided to shamelessly copy one of these and claim it as my own interpretation..
So here is my interpretation!!!!
I roughly dry brushed ( Damp Brushed!) lighter matt panels in, fore and aft, in an 'up down' pattern, roughly where plating breaks are on the real subs. These seem to be closer spaced towards the extremities of the sub than midships. Probably something to do with the saddle tanks being in the way. This was, admittedly, a bit rough in application. the intention being to fix it further down the line.
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Then I got the airbrush out. Couldn't resist it!
Mixing up a Chromate Yellow/Burnt Umber/Lamp Black mix of oil paints, thoroughly thinned to almost nothing with spray thinners, I started to apply it between the newly applied Matt Slate Grey panels..and anywhere else took my fancy.
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Then that ran out so I added lots of Raw Umber to this to give me a rust colour. This was oversprayed onto the existing stippled rust along the waterline plus some vertical streaks extending below the waterline ( I once watched a bit of rusty muck roll down the side of an Oberon Class Submarine, and keep going below the waterline..I lead an exciting life :-)) ).
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As a happy person now..I have little excuse..must get on with the electrics %)
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Now that looks damn good to me, skip...now leave it alone, don't touch it again, or else I'll bring my Akula down and let you loose on that with your air brush thing.
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In the pics of reply 179, it shows a spiral to the deck gun barrel.
Is that correct and if so do you know the purpose of the 'spiral'?
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I believe it is a rope that holds the barrel plug from getting lost.
Look at the 4th photo down on this page http://www.subpirates.com/showthread.php?288-Type-VII-U-boats-reference-photos
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And there is an off cut of cocktail stick as a barrel bung jammed in the end of the barrel.
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Spiral on deck gun?
I think it is more likely to be a fixed item on the barrel to break up the wake and make it less visible.
Without checking any photos and from memory - don't you see the same arrangements on some of the periscopes??
David
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I thought the same until fairly recently, when I found photographic evidence of the barrel plug and securing cable hanging loose.
When you think it through it makes sense having some sort of 'wake dispersal device' on the periscope, not so much on the gun barrel of an '88'. Behind which is the rest of an '88' plus a stuffing great big conning tower. BIG spirals needed to disperse that lot :}
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Great pics.
Looks like it is a rope. found this one on google
http://www.bing.com/images/search?q=u+boat+deck+gun&view=detailv2&id=B11F331FE79EF78A435F7CB7B03ED8206B6DAA6E&selectedindex=32&ccid=i%2FnqPWVR&simid=607996056430775241&thid=OIP.M8bf9ea3d6551096f7e20a70468522e1bo0&mode=overlay&first=1
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Very good - so it is!
David
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Right. That's it. This sub is getting wet. Maybe not today, maybe not tomorrow, but soon!
Other stuff can wait.
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Last week I cleared the decks and started the final fit out with the intention of being in the test tank by last Sunday. First job was to beef up the pinch valve servo. Despite using a heavy duty servo arm, it was still bending out of position, causing a loss of pressure in the rest position. Luckily i know someone with a 3D printer, so could order a heavy duty servo arm beefer upper, cheers Helen!
Fitting this required a bit of fettling as it ended up slightly higher than the original, due mostly to me making a bit of a bodge of the order..
Also while testing over the weekend the Futaba S3003 servo proved to be borderline for the job. Wandering out of position after a few minutes, plus getting warmer than I would like a servo to get in normal use. This has now been replaced with a high torque metal geared servo, all seems to be well at present.
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With the Pump Deck out of the sub, I could hook it up to a watt meter and test it, just to see really. Amps were good, voltage held steady. All working well so far.
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With all looking good I decided to bolt everything shut and go for a pressure test. Over pressuring everything with five pumps from a bicycle pump ( Yup, five!), then releasing the valve to see what hissed out. Nothing! Tried again, nothing!
It turns out that the twist lock caps I fitted are much better with the O-Ring fitted than with the O-Ring under the Workmate!
Second test held good pressure for thirty seconds, but lost everything over five minutes. This would need a test tank to look for the leaks.
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So, with no access to the club test tank till Sunday, it was out with the rust paint, fit the crew and install the salt water antenna.
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Following Sundays leak trials much was discovered;
1) Tighten the nuts up more, it will be fine.
2) One pump of a bicycle pump results in much less leaking than five pumps of a bicycle pump, who'da thunk it %)
3)The water ballast tank is still under lots of pressure when full of water, and slightly soft epoxy wont keep the air in, avoid old epoxy for crucial joints.
4) Everything gets wet testing submarines!!
So, no maiden voyage on Monday then >:-o
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I must say though, the dive system worked, even if it dumped all its pressurized air to atmosphere. The reversible pump still vented the tank and the sub surfaced and dived, very stern heavy though. Such is life.
So, I have spent the last couple of days improving the pipe seals, replacing T-Connectors with better ones, and re-enforcing the end of my ballast tank. This I have done with a mix of 50 year old US of A medical gauze, Z-Poxy and epoxy thickener, rather like plastering a broken leg, only this hopefully wont be coming off in six weeks!
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And while waiting for the epoxy to cure, I trimmed the upper foam block so I could actually see the voltage meter fitted inside the watertight compartment.
That's where we stand today. Should I go back to the test tank on Sunday and trim everything proper like, or risk all with a dash to the local lake, while the sun shines, and have a quick blast around the pond? We shall see :-))
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Following Sundays test tank visit an interesting problem occurred. Using the reversible water pump to submerge, all went well. Upon surfacing, many bubbles could be seen coming out of the vent pipe. Being closed off to thinking this would be a fault, 'brain' here kept surfacing and submerging, looking for air leaks out of the plumbing. After about five dive and surface tests, I could see 'raindrops' along the inside edge of the foam sealing tape. What was happening was that as the pump emptied the water tank, it was also drawing air out of the radio compartment and dumping it into the test tank. After five ups and downs, it had produced a considerable vacuum inside the RC compartment, drawing water IN to the model wherever it could!
I took the pump apart and have now silicone sealed every possible route through the pump from atmosphere inside the RC compartment ( except the motor shaft, couldn't silicone that together!). Tested it yesterday with a bowl of water, no air being drawn through the pump. although the hose did spray me down with water as it went into 'surface' mode :embarrassed: .
As fortune favours the bold, and its quicker to just drop it in the pond than fill up the test tank again, AND the sun is shining....I shall report back tomorrow,
:-))
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Good news :} ...it didn't leak (any water in...although I still have a small pressure leak to find.). Following about fifteen minutes removing foam bouyancy and testing the main pump, it was time to button the model up and let her go...
There was a small problem with surface targets!
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Trim was pretty good, a little stern heavy still but nothing to worry about on a first run. I tried 10, 20 and 30 second fills on the tank. Having forgotten to time how long it takes to fill up the ballast tank, this seemed the best option. Speed was good on the Pittman motors, turning circle was as expected..pants!
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With a good forty second fill on the tank the model was almost decks awash. Despite this, it was not keen on submerging. I have an auto-leveller on the aft planes, set to completely automatic mode at present, with active bow planes. I will try making both fore and aft planes RC with auto-leveller providing levelling inputs when the stick is in neutral, see how that works.
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Then the rudder linkage worked itself loose and that was that for the evening. Last shot shows the sub on its bespoke trolley with its 'hydrophone on a stick', just in case!
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The shots of her on the water are realy good, she looks very sinister indeed :-))
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She does look very good on the water indeed!
Hopefully she'll have her crew reunited with her soon(tm).
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Cheers guys :-))
It will be back to the test tank on Sunday, for final trimming and searching out the last of the air pressure leaks. Rudder is now re-connected, all I need to change is the set up of the Auto-Leveller plus see how many amps I sucked out of the battery on its maiden run.
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Great photos and congratulations on a good run! Sitting in the water it looks like it has been on patrol for awhile! It tells a story without words. Nice.
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In its own way it is a story. The model has passed through three people that I know of before me, plus a murky past before that. It is pleasing to bring an old model back for a new life. It will be joining our U-Boat arm as part of the PMBDTs World War II Convoy Display during the summer...once I have polished out one or two little issues that is............ ok2
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I built a darnell u boat in the early 90s and i liked the look of the boat more so than everything that came afterwards , a lovely boat ,regards pete
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On the second run it submerged, after a bit of a fight though! I am still drawing air out of the RC compartments when running the pump to surface, not as bad as before but still an issue.
So, the following mods are planned; I shall replace the 4oz fore and aft trim tanks with bigger, bespoke tanks with acrylic tube, they did help with diving the boat by re-trimming slightly bow down. Doubling the size should prove more useful.
I will modify the Tx to give me a two position surfacing function, one, moving the servo just off of the pinch valve, utilizing the pressure held inside the dive tanks to vent and surface slowly. Two, full deflection of the servo plus activation of the pump to surface, in case of emergencies only.
I may consider hacking off some of the lead keel at the aft end of the boat. This is mounted externally and should not cause any damage to the water tight integrity of the boat.
Back in the test tank for a re-trim :-)
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With the display season behind us (mostly!), it was back to the test tank on Sunday. All the external keel lead was hacked off with chisel, hammer and crowbar. Then sanded flat with a big Black and Decker hand held belt sander, nice!
With the lead removed it promptly turned turtle in the test tank as expected...then Colin arrived. From now on he shall be referred to as 'The Sub Whisperer'!
Following a couple of hours of subtle trimming, removal of foam, more trimming, the model sat upright, but a little deeper in the water.
Following some suggested mods, including cutting a 5" long by 3/4" wide slot through the keel at the front of the free flood compartment, into which a hammered lump of 250g of lead was fitted, the model is now ready for a final test tank test next Sunday.
Once again, thank you to The Sub Whisperer :-))
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Great stuff, can't wait to see it, roll on Sunday :-))
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Well, it was one step forward and two steps back on that Sunday. I added some more ballast in the form of lead bullets, drilled into the keel. Probably .38s or 9mm, not a bullet expert, however, I know they are heavy, and 9mm across. So a series of 9mm holes were drilled in the keel areas adjacent to free flood areas within the model. did not want to be putting 9mm holes into water tight compartments!
The bullets were tapped in and then epoxied into place..
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To explain the next part, I need to give you a brief history lesson.
The Portsmouth model Boat Display Team have occupied the Weigh Bridge Offices at the site of the Pump House museum at Eastney for the last nineteen and a lot years. Unfortunately, due to issues beyond our control, we will be losing this building in the next few months. This has resulted in a bit of a fire sale on some of our assets, including our much loved used test tank ( two baths glued together for the un-initiated!). So cutting a potentially long story short, Colin The Sub Whisperer offered to buy it from us. Unfortunately, Colin was in a bit of a rush to acquire this asset, forcing me into a bit of a rushed series of tests.
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The trimming, foaming and ballasting was going mostly to plan, except for a problem with the acrylic water tank, which has sprung another leak. A crack has appeared again, at the join with the turned nylon end cap. This, I think, is due to the end caps being fractionally too big, putting strain on the 3mm acrylic tube. Not helped when the tube is pressurized when full of water. This is an issue, as I rely on not losing any air pressure from within this tube for surfacing actions. I epoxied and bandaged this joint as a quick fix, knowing the test tank would be gone by the end of the day.
Back to the water and the sub settled slowly down as the compartments filled up with water. The latest foam placement had cured the trim issues, with the boat settling on an even keel. Suddenly, the model started to settle rapidly, with many bubbles emerging from the rear compartment. It took about three seconds to comprehend the model was sinking!
Out of the water and back inside double quick, I already knew what had happened, I had left the aft screw cap off the model. The screw cap being directly over my Microgyros Auto Leveller, 7 Channel Futaba Receiver, Microgyros Speed Control, three Futaba Servos, two Pitmann Motors and a 9.6v NiMh pack, so no panic then!!!
Its funny, when in a workshop environment, as opposed to a salt water lake based environment, I had 30 seconds of 'what do I do'! Unscrew the big lid, got to be three minutes to do that. Nope, grab the sub, turn it upside down and pour the water down my leg!
With the test tank due to be gone within a couple of hours, I had to make a decision. So, once the water had been removed from everything, bolt it shut again and continue with the ballasting.
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So, sub now successfully ballasted, but ballast tank not reliable under pressure, it was time to rip everything out of the model again.
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Fast forward four days...following a bit of the old magic Graupner Wet Protect, and much drying out, I powered everything up.
:-))
All electrical items working, thank you fresh water!
So, this leaves the pressure vessel. It will need to be replaced, I cannot trust it under pressure. This week I have looked at 68mm down pipe. 110mm soil pipe, plus I have some 86mm black tube of dubious origin. But probably best option, I have some 5mm wall thickness acrylic tube which is a sliding fit over the current tank. This will require a bit of a midships refit, plus new end caps, but promises to be the best way forward.
Still, the model looks good with its big lead lump removed.
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i would not recommend using acrylic for your ballast tank. as you witnessed with the past one, acrylic cracks relatively easily when under pressure. by replacing the original acrylic tube with another acrylic tube, you are just setting yourself up for doing this all over again when the new one cracks.
call these guys and see if 1) they will ship to europe, or 2) the have a european warehouse... http://www.mcmaster.com/#polycarbonate-hollow-rods/=14ha1pg
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Advice Taken, just spoken to Mike at Microgyros also. Its either polycarbonate or PVC. Watch this space.
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Plastic pressure vessels are not very easy to arrange. (Presumably you are going up to 2 or 3 Bars?) Polycarb would certainly be better than Acrylic but is expensive in the UK or US, I believe.
I have had success in the past by making up the tank in PVC (even thin walled drain pipe is OK for this) to be leakproof and then sheathing it in 2 or 3 layers of glass and polyester resin.
However I never liked these pressure tanks much and so moved on to (home made) piston tanks using aluminium tubing.
David
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Well, this model is a test bed for all and sundry, a bit of a crash course in every option for a model sub within practical limits. I don't want to tear the RC compartments out and fit a tube as I have spent much effort improving the model structurally ( all except the most important dive system! ). I have a couple of subs waiting in the wings, both with Craycraft modules waiting for a 21st century spit and polish, however this one is staying bolt down. Space is at a premium, as is usual with subs, which focuses the mind!
The Red October had pistons, which were great, but being Engel units were pretty big bits of kit. I have idly toyed with the idea of piston tanks in the past, however the precision engineering side has frightened me off. Aluminium and salt water certainly don't get on, so that is out. Other materials, I discount nothing %)
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Have you considered going for a vented system?
It would allow you to use all your existing stuff, and you would just need to modify the tank slightly. Because the tank is no longer under pressure it doesn't need to be particularly strong, and the pump will have an easier life.
Chief snag, you have to trim your boat so it remains slightly positively buoyant. Also you can't produce a big slug of upthrust if you get caught in weeds etc.
You could add a smaller dive tank inside the main tank for going negative or for adjustments to different water densities.
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Sorry to read of your trials and tribulations in getting this boat sorted, amazing how quick we can react sometimes when prized model gear is at stake!! One important thing to make sure of with acrylic tubing is to make sure that the ends are radiused both around the inner and outer edges and then polished to remove any saw and file marks, ideally to the same level of finish as the tube surfaces. This is quite important in preventing crack propagation. Polycarbonate tube though stronger, should receive the same level of care and finish after cutting the ends.
I buy my polycarb. tube from http://www.theplasticshop.co.uk they are a good supplier.
Trevor
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I mentioned pvc for the replacement of a pressure vessel and polycarb tube for a complete cylinder. But that was after hearing about the high pressure windscreen pump and pinch valve to add to the desire to retain the existing layout and system.
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Have you considered going for a vented system?
It would allow you to use all your existing stuff, and you would just need to modify the tank slightly. Because the tank is no longer under pressure it doesn't need to be particularly strong, and the pump will have an easier life.
Chief snag, you have to trim your boat so it remains slightly positively buoyant. Also you can't produce a big slug of upthrust if you get caught in weeds etc.
You could add a smaller dive tank inside the main tank for going negative or for adjustments to different water densities.
Sorry about not responding sooner, not paying proper attention to my own thread!
By a vented system I assume you mean one that relies on outside air to pump dry and surface? I am not keen on this option in a salt water pond. If I loose signal or bouyancy, its going to be difficult for the model to recover back to the surface, or near to it, to pump out water, it just plain makes me nervous {:-{ .
I have a smaller 65mm x200mm tank to go in the model now, PVC etc, do I mount high as before or low as I now can, with the smaller diameter pipe? High, I assume will aid stability, while low will sit the model deeper in the water?
I have been doing too much thinking lately, so I am sub-contracting any thinking out to others....
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Provided the tank sits below the waterline, its height will make no difference to the overall displacement.
I understand the requirement for reserve buoyancy. unfortunately subs are like all forms of engineering- a compromise.
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Thank you, food for though as always. This may call for another, slightly left field, solution. Its in my head, lets not let it out just yet. Must size up the space that I have first...
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Your external tank lends itself perfectly to what I think Andy means. Just chuck out the pressure rated cylinder tanks, probes and pinch valve and replace with a pop bottle.
If that sounds like a joke then look carefully at the wafer thin vented ballast tank in the middle picture. http://www.jotika-ltd.com/Pages/1024768/Krick_4.htm
The two bottom ports in the mostly submerged tank are connect to by a t-piece to the pump. The bubble canopy, capillary holes and fore/aft feed from the gear pump ensure there is no trapped air. The feed from the gear type pump possibly has an inverted u-bend if the water feed to the pump is below the water line, giving a couple of inches depth of water pressure. I've been assured otherwise on the last speculative detail.
Remember the Modelboats small ads for a cylinder system by David Evans? The designed-in trapped air bubble in that wtc was meant to expand under the vacuum created by two Lucas washer pumps. The air bubble method would not suit a vacformed or pop bottle tank where the only stress is from two inches of water. The bubble would also contract on diving to reduce the smallpositive buoyancy.
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Any sub with a high waterline is tricky when you are using a system that compresses the air inside. It becomes worse when the hull is moulded thickly, as it ratchets up displacement. Some hulls are better than others in this respect. On u-boats the use of etched metal decks can help a lot, as the metal although heavy, can be made very thin and therefore the tanks can be kept as small as possible.
Full size subs use very high pressure to store air for blowing the tanks underwater, but it's not terribly practical for modellers to replicate, plus the use of higher pressures tends to create an additional hazard best avoided.
The sealed tank water pump system is simple and pretty reliable if everything is built well enough to deal with the forces involved, which shouldn't be underestimated. You're generally looking at pressures of around 40 psi, which when spread over the area of the tank amounts to a lot of stress on the walls. Some of the later Sheerline boats used metal ballast tanks (they looked like brazed stainless steel, but not inspected one up close to confirm).
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Although I have not used one for a submarine tank, nor have I any experience of sea water submarines, a pop bottles, I used the well known brown, tooth rotting, beverage containers, will certainly stand way more than the pressure generated by screen wash gear pumps, some years ago I made water powered rockets to amuse my children ( not myself of course O0 ) and they were pumped up to my operating pressure of 110psi after burst tests burst tests were always over 150psi.
I've tested the Kavan 12volt pump at 48psi some time ago, that was fresh water though I cannot see why sea water would be different, suspended sediment might be an issue for the pump but a filter can deal with that, placing two pumps in series would yield an increase in pressure.
The 'emergency surface' system, triggered by a fail-safe, that I am building into my T Class Thrasher will use Robart r/c aircraft retraction system tanks, valves and lines. This equipment has an operating pressure of 110psi, so can well deal with the pressures of the water depth that model r/c gear can penetrate.
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Okay, I surrender ok2
Vented system is now on the radar. As I never intended to go negative buoyant in salt water, for fear of dropping the antenna below the surface and loosing signal. Therefore, remaining slightly positive buoyant lends itself to a vented system. Also as previously mentioned, everything is on board the model now, excluding a vertical vent pipe. Would 1/8" I/D be an acceptable size, or could I get away with 3/32" I/D instead?
I wish we had not sold the test tank two weeks ago now!!
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Only need a small pipe- it's for air not water to go through.
A further advantage is you will have no exposed water surface to slosh, so stability of the model should improve slightly.
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Breather pipe flush with the top of the tank, or down a few mm to retain a small bubble at the top of the tank?
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I would run it completely empty or completely full with an aspirated system. So flush.
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Breather pipe flush with the top of the tank, or down a few mm to retain a small bubble at the top of the tank?
A simple tilt of a cylinder tank may not be as effective as the canopy, ring of holes, and twin drain on the vac formed tank of the Krick VII. You'd be better constructing a new tank made of plasticard.
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A simple tilt of a cylinder tank may not be as effective as the canopy, ring of holes, and twin drain on the vac formed tank of the Krick VII. You'd be better constructing a new tank made of plasticard.
I shall stick with the tube that is fitted for now, it's built and secured in the model. i still don't quite understand the ring of holes on the top of the Krick Type VII. to replicate that on my bigger boat, would I not need either many pipes rising up from the tank, or as you suggest, a plasticard version of the Krick tank, that fits my sub, with many holes?
I like the idea of the single breather pipe being as high as possible, maybe a 'voicepipe' in the top of the conning tower, rather than above the water line,but not necessarily visible when surfacing.
Of course, the only concern, which I cannot check until the sub is re-assembled, is will the high power pump be happy sucking air through a 3/32" dia tube, but not then start sucking air from the radio compartment also, as it did when the sub was bolted shut. My hunch is that it wont be an issue, but it is a powerful pump.
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What pump is it you have again? I'm assuming it's a geared pump.
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If the holes are the correct size they should vent any air trapped above the lowest end of the pipe but not negate the pipe's drawing of air when it just breaks the surface. There is no air vented to the water tight compartments, just hose connections to the pump. One from the pump terminates in the free flood, the other to both ends of the tank base, via a T-piece. Don't ask me how the tank doesn't just fill from the small pressure of a few cm depth. I don't know.
I've recognised the occasional model using the system with a three-compartment cylinder wtc, one with a row of holes in the centre section, one with a dome, one with external water tubes. At least one other had made the vent and drain points in the bulkheads when the tube was white pvc.
However I have not spoken to this kit developer or producer. Tugmad George has the kit instructions.
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The Krick ballast tank
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Larger view
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The other half
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The actual tank
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What pump is it you have again? I'm assuming it's a geared pump.
It is a Darke Horse 20 (something) litre 12v to 20v geared pump. Fully reversible.
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Tugmad, thanks for posting images of the Krick system. I think its the lateness of the hour, but I am more confused now than I was before!!
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Yes it does seem a bit weird but as far as I can make out from the very sparse instructions, the idea is that the boat is ballasted to a surfaced waterline with the tank empty, then to get it to the diving decks awash state the tank is filled,it holds 375Ml .the boat is then dived using the forward planes only,I am looking at making the after planes work,but have not got to that stage yet.
On the good side is that the boat has positive buoyancy at all times. ( possibly? )
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Not familiar with that pump, but it looks like a gear based unit, so no worries. If you find the tank is now too large, then you can either reduce the tank, or add some foam in the conning tower, which will increase displacement and improve submerged stability.
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Yes it does seem a bit weird but as far as I can make out from the very sparse instructions, the idea is that the boat is ballasted to a surfaced waterline with the tank empty, then to get it to the diving decks awash state the tank is filled,it holds 375Ml .the boat is then dived using the forward planes only,I am looking at making the after planes work,but have not got to that stage yet.
On the good side is that the boat has positive buoyancy at all times. ( possibly? )
For my sub I am building a very similar system, the boat is a wet hull with wtc and is ballasted to waterline, a Kavan gear-pump fills a pair of saddle tanks to decks awash, a small piston tank will then get the boat to 'periscope depth' or varying with temperature/density the boat is then in the top few cms of water where it can be visible and it is dived dynamically being held level by commercially available electronic gubbins. As mentioned in a previous post, failsafe triggers an air release system to blow the 'pumped tanks' and up she comes if something goes really wrong, battery fail, signal loss(timed),safe depth exceeded, a separate timer system will blow a buoyancy bag and float.
Well all that is the theory of the system, of which the component parts have been thoroughly tested and I'm happy with, but because of the poor quality of the molding, particularly the top heavy piece, I have had great difficulties getting the boat to balance which has meant lots of rebuilding of that half of the hull, and so I've not done a full out of sight pond test- -maybe next year?
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Patience is a virtue when it comes to subs. Take your time and get it right. One of the advantages of most sub models is that they are too big to throw out of a window :}
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Patience ? :} Perhaps we are patients to endure building working model submarines, and with an unknown neurological quirk %% %%
Yes Sir! Difficult through a window sideways maybe, but sometimes tempting to throw it, or parts of, just like a spear through the same opening into the scrap skip outside the workshop <:(
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You can make a very simple bu effective trim tank using a peristaltic pump, with a balloon flexible tank running inside a small tube to constrain its proportions. This only has to be volumed to about 1% of the overall displacement to giev you the ability to trim the boat for all water conditions.
Pumps are very inexpensive e.g. http://tinyurl.com/jrg2tm8
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You can make a very simple bu effective trim tank using a peristaltic pump, with a balloon flexible tank running inside a small tube to constrain its proportions. This only has to be volumed to about 1% of the overall displacement to giev you the ability to trim the boat for all water conditions.
Pumps are very inexpensive e.g. http://tinyurl.com/jrg2tm8 (http://tinyurl.com/jrg2tm8)
They are nice little units, the 12v ones at the bottom of the page look useful too.
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I haven't tried the 12 volt units, only the type I linked to. They all work on similar principles and are very good value.
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Today I played about with the model. However, first things first. Upon turning on the model, nothing happened....no lights, no twitching, nothing. Did the flood damage of a couple of weeks ago cause a problem only becoming apparent now?
Turns out the only thing to fail was a two quid on/off switch. Once bodged with a rat tail file, all sprung into life..result.
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Now on to serious stuff, ballast tanks. Following this weeks online discussions, I have decided to fit a vented system, i.e. one that pumps water in to a tank and vents the air above the water, to atmosphere. This is arranged via a thin pipe run up to a high point on the model.
Loosing the high pressure system should sort out problems encountered so far. Options, options, options...
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The first picture shows the high pressure system with the two saddle tanks, which reduced the pressure on the acrylic tank, allowing more water into it than would be the case otherwise.
The second picture shows the same tank without the saddles. This would be vented to air instead, solving the pressure related issues.
Picture three is a PVC tank, slightly smaller diameter, but better assembled than my old tube. This would lower the height of the tank in the model slightly, for better or for worse.
The fourth picture shows a 32oz Ripmax fuel tank, which I happened to have, and which by some quirk of nature, fits between the existing plumbing nicely. Also, being florescent yellow it looks like an old school Darnell with the hatch on. Bright colours visible through the free flood holes!
So, I have three options, today I just wanted to test everything with a vented system, trialling how small a vent pipe I could use etc. This is where the trouble started...
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Previously, with the high pressure system, I was having a problem with the pump when venting the tank. It was drawing air from within the main pressure hull and dumping that into the lake, along with the ballast water. This was resulting in a vacuum being created inside the RC compartment. This, in turn, encouraged water to find its way into the model through all the seals. I assumed this had something to do with the pressures involved when venting the tank. No, it still does it, with no pressure in the tank, and with the sub open to atmosphere, I could see bubbles being pumped into my pot of water as the sub pumped itself dry. Nothing to do with the system being sealed up, as it is now under no pressure whatsoever.
So, I swapped the pipes over on the pump, 'in' becoming 'out' and vice versa. Now the air bubbles were only visible INSIDE the ballast tank as the model filled with water. It turns out this only happens in one direction of rotation of the pump..most puzzling. So as a pump in/pressure out system, with the pump running in its 'good' direction, this unit is fine. However, pumping both in and out, a problem is occurring. With the new plan for a vented system, whatever I do, air escapes, one way or the other.
As a pressurised system with the pump only running one way, Sheerline style, all would be good. If I want to pump up and pump down however, this pump is problematic. Whatever happens, it's got to come out. I will strip it down and have a proper look at it, while considering options..
Most annoying >:-o
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Previously, with the high pressure system, I was having a problem with the pump when venting the tank. It was drawing air from within the main pressure hull and dumping that into the lake, along with the ballast water. This was resulting in a vacuum being created inside the RC compartment. This, in turn, encouraged water to find its way into the model through all the seals. I assumed this had something to do with the pressures involved when venting the tank. No, it still does it, with no pressure in the tank, and with the sub open to atmosphere, I could see bubbles being pumped into my pot of water as the sub pumped itself dry. Nothing to do with the system being sealed up, as it is now under no pressure whatsoever.
So, I swapped the pipes over on the pump, 'in' becoming 'out' and vice versa. Now the air bubbles were only visible INSIDE the ballast tank as the model filled with water. It turns out this only happens in one direction of rotation of the pump..most puzzling. So as a pump in/pressure out system, with the pump running in its 'good' direction, this unit is fine. However, pumping both in and out, a problem is occurring. With the new plan for a vented system, whatever I do, air escapes, one way or the other.
As a pressurised system with the pump only running one way, Sheerline style, all would be good. If I want to pump up and pump down however, this pump is problematic. Whatever happens, it's got to come out. I will strip it down and have a proper look at it, while considering options..
Most annoying >:-o
me made um vacuum prevention doodah and no understand all dat!
The tank choice may come down to material. It is easy to bond to pvc, acrylic but not polypropylene.
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Have you got a leak in the seals on the pump I wonder. Sounds very peculiar to me. A gear pump shouldn't really care which way it pumps.
One thing to bear in mind, is that the water is likely to be colder than the air, so the air inside the compartments will pull a slight vacuum, so that's a potential source of leaks. I test small enclosures for leaks by putting them in hot and cold water.