Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: U-33 on April 22, 2015, 08:13:33 am
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Well, here you go boys n' girls...X9 is completed, just awaiting the module from Ron Perrott, and then she can be fitted out.
(damn...just noticed I didn't attach the White Ensign...)
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Sweet :-))
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Well, thank you kindly, Oh Wise One.... ;D
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Dynamic or static diving module?
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Dynamic dive, Andy...there's so little freeboard on the X craft that you'd only have to sneeze and it will submerge.
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Just had a long chat to Ron Perrott, had a change of plan with X 9. Instead of having her as a dynamic dive boat, Ron is building a full on static dive system for the boat. If it's worth doing...it's worth doing it properly. It'll be a much better boat in the end.
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You still coming to Wicksteed Richard
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Hopefully mate...with a bit of luck and a following wind, we'll be there.
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Here we are, boys n' girls... the module for X9, custom designed and built by Ron Perrott.It's a really clever piece of work, and beautifully constructed.
610mm x 80mm diameter, with an internal ballast tank, full static dive.
Thanks Ron...much appreciated.
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Sub-Lt. E. Kearon, RNVR, has arrived, he's going to be displayed on the deck of X9 when she's on show.
He was lost with the rest of the passage crew when X9 was lost in heavy seas whilst under tow from HMS SYRTIS, on her way to Norway as part of Operation 'Source', the attack on the Tirpitz.
Some interesting reading here:
http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38204.pdf (http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38204.pdf)
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Made a start on installing the module...as you'd expect from Ron, it fits perfectly. Under the tube is a 300mm length of 15mm diameter stainless steel rod, fitted into the keel, and there's ample room either side to take some lead sheet.
(thanks to my old mate Andy (tattooed) for the s/s rod and the lead)
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Hello
Could you send me a link to Mr. Ron Perrott? I would like to get information on his WTC that he built for your X9 Static divier.
Thanks for your build log, it helps with mine.
George
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X9 update...the module is now installed, prop shaft hooked up and prop tube support made and fitted (that was interesting trying to hold everything in the right place up in the confined space in the stern)
Just waiting on a pair of smaller servos to arrive, the ones I originally fitted were a touch too big, then I can install the rudder/plane linkages, these are already made up (thanks to Andy (tattooed) for the wire)
Very nearly ready for ballasting and trimming...fingers crossed she will make her maiden voyage at the Norwich Sub Weekend.
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New linkages are now installed, still waiting on the new servos to turn up.
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And the good news is...the module is now fully fitted out and everything works as it should. It's been in the bath, weighted down with two sheets of lead for a good half hour, and when I took it out, it was as dry as a bone...not a dribble of water anywhere.
Next is to install it in the hull and get it ballasted.
With grateful thanks to Ronald Perrott (https://www.facebook.com/ronald.perrott.3) for making it for me...thanks Ron, I appreciate that tremendously.
The length of threaded rod you can see is bonded to the tube, and goes up through the deck, an M4 brass nut screws onto it and secures the deck to the hull.
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Hello U-33
Thanks for posting this and to confirm, this is a dynamic diving X Craft with Ron`s WTC built cylinder?
Also the link to Ron in your last post comes up as non working for facebook.Can you help, I would like to get in touch with him for my X Craft build.
Thanks Rich
George
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Sorry to but in but ........the link to Ron on Facebook is working from my end it may take Ron a day or two to get back to you he can be busy at times
Mark
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Thanks Mark...Ron is very busy at the minute, but give him time, George...
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You'd be well advised to build the wtc without a ballast system to start with. X-craft work very well as dynamic divers as they have very large hydroplanes, so you have plenty of control, just trim the boat a bit lower than you would for a static diver e.g. decks awash, and you'll only need a whiff of throttle to dive.
Make the tube large enough to accommodate a ballast system later on, I would say a 10-11 ounce tank would be quite sufficient for a model this size.
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Hi Subculture
Thanks for the reply BUT I have collected ALL the parts needed and I was hoping to build the WTC with the desire to make my XCraft a Static diver.
What I am unsure of is the overall size of the WTC and it`s compartments. Could you help me with that?
George
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In all fairness, you can buy all the parts you like, but if you haven't got a grasp of core principles, you run into difficulties when putting them together to make a working sub.
Those principles have been covered many times before. Back catalogue of SCR's, Norbert's book on sub technology, plus a few online articles.
When figuring out WTC and ballast tank size, it's really useful to have a working knowledge of Archimedes principle with regards to displacement, densities of various materials. When working with ballast systems, especially those that compress air inside rather than vent externally, you should also understand how volume alters with pressure and vice versa (Boyles law). e.g. halve the volume double the pressure.
A WTC should be large enough to provide buoyancy for the tube weight itself plus all the equipment you put inside it. In addition, allowance for ballast in the keel and remember that glassfibre hulls are denser than water by about 30-50%, dependent on the glass content in the laminate.
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Andy,
Do I see the next video you can do! How many times does the topic come up?
Peace,
Tom
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Hello Again
I would Second that video request. I learned a lot from the first one. Look forward to watching the video.
George
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it would involve quite a lot of work to make videos showing these things, and it would still only show one example.
I think perhaps I should ask some questions of those asking the questions, to test current level of knowledge.
1. What empirical method can we use to find out the ballast tank volume required for any model submarine, assuming we have an adequately sized test tank to put it in?
2. A WTC is 8cm in diameter and 20cm long. What is its displacement in litres?
3. How much weight in kilograms can that cylinder support?
4. What is the average density of fresh water, and by how much does it vary in density in percentage terms?
5. If I compress air from a 500ml ballast tank into a 1000ml reservoir, what will be the pressure in bar or psi.
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BTW, I will accept answers in imperial units for those uncomfortable with metric. It's 2.54cm to the inch, and 61 cu inches to the litre. 1 bar equals 14.5 psi.
Also I've noticed that we are getting far off topic, and the subject matter is now hijacking Richard's original thread. Perhaps the mods can shift some this to another topic, perhaps titled something like e.g. Ballast systems and WTC theory.
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Think I can hear crickets.....
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Damn...I thought it was minds ticking over I could hear.
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Smarty pants, I just read your questions.
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it would involve quite a lot of work to make videos showing these things, and it would still only show one example.I think perhaps I should ask some questions of those asking the questions, to test current level of knowledge.1. What empirical method can we use to find out the ballast tank volume required for any model submarine, assuming we have an adequately sized test tank to put it in?/quote]
Well, I have never done this my self, so all my answers are based on what I have read. So, the empirical method would to use Archimedes method of weighing it in water and air and work out the displacement. I have also read just weighing the above waterline structure. Finding it's density compared to water ( like styrene is close to water so what it weighs is what you would need to displace).
2. A WTC is 8cm in diameter and 20cm long. What is its displacement in
/quote]
I will assume you are referring to cylinder, 1 Liter
3. How much weight in kilograms can that cylinder support?
/quote]
1 Kilogram
4. What is the average density of fresh water, and by how much does it vary in density in percentage terms?
/quote]
I should remember this fromdiving, but alas I do not. So my guess is 10%. Temperature and dissolved particles can effect this, so it may be higher.
5. If I compress air from a 500ml ballast tank into a 1000ml reservoir, what will be the pressure in bar or psi.
O.k so continuing my guessing, it doubles with every half, so 2 bar?
O.k. Did I really mess this up or am I close?
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My brain hurts
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Okay. So question one- correct, although it can be tricky to accurately weigh an item like a model submarine in water and air.
The best method is to trim the boat to neutral buoyancy or just slightly negative, then use polystyrene foam to bring it to the correct waterline. Very simple, but very accurate. Skip Asay published this method many years ago, although I believe it was credited to Dave Copeland.
Answers to two and three, correct. Converting volume to weight is so much easier when working with the metric system.
Answer four- not quite. Water actually varies very little, just 1% depending on temperature and mineral content.
Question five. You are compressing 500ml into 1000ml, pressure will need to increase by 50% above atmospheric about 0.5 bar or 7 psi (rounded down to simple figures).
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Regarding question five, how did I arrive at that answer?
Well Boyle's law says that our initial pressure multiplied by our initial volume should equal our final pressure multiplied by our final volume. Now we knew three of those answers.
Initial pressure is normal atmospheric pressure, which tends to be about 1 bar- this varies a bit depending on your location, but for example we'll leave it that figure.
Our initial volume is 1500ml, adding both the ballast tank and the reservoir, so 1x1500= 1500.
Our final volume is 1000ml, so in order to have that reach the 1500 magic number, then we get a pressure figure of 1.5 bar. of course on a pressure gauge that would read 0.5 bar, because our gauge will be at atmospheric pressure like the rest of the kit.
Hope that makes sense.
All these questions were asked for a purpose. If you are building a WTC, then you really should know how much it will displace, and how much weight it will support.
If you are designing a ballast system, you might want to know how much extra to add on if you want to be able to trim your boat for different water conditions.
If the ballast system recirculates air, then you will want to know what pressure it will reach, to see if your pump can make pressure.
You can of course use solely empirical methods, but a few minutes spent with a pocket calculator can save hours and wasted material.
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So, Andy, are you going to do a three part video? Oh please oh please oh please (said in my best whiny voice). I like your piston video and think this would be a great starting place for many, seasoned and beginners. Show the math and show the practical ways to use the information.
Skip Asay is one of the greats in the hobby. The foam will relate to the volume needed for the cylinder, I remember reading that.
I have not dealt with using a pressure tank, either by bag or water, but I will someday. So, understanding this aspect better will help. I am surprised by 1% variance in water, I would have bet it was more (And I am not a gambling type). I need to look that up just to retrain my mind.
Thank you for the testing and challenge. I can only learn more when I do not know what I do not know.
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And I haven't got a clue what you're both on about...this is a perfect illustration of why the dinosaurs died out. :embarrassed:
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Good link on water physics-
http://www.marietta.edu/~biol/biomes/water_physics.htm
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Before you posted that last link, I went looking.
I found this sight, [size=78%]http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html (http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html)[/size]
From this site it would appear a 5% variance, but most of this information goes way over my head. No matter what the answer is, it is not 10%. Thank you for the exercise!
Now back to that video......
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I should have added within the type of temperatures you will operate a sub at your local puddle.
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Richard, you better post something about your sub or I will keep harassing Andy to make a video!
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Tom, I know Andy would have kittens over the way I go about building, trimming and ballasting my boats. It's much easier with a box to start with, but once the box or the cylinder is installed in the boat, it's a case of putting it in the bath...if it sinks I either remove a piece of lead, or add foam.. If it floats too high, I add lead...and that's about it really.
I don't understand all the technicalities of volume, displacement, water temperatures, etc...if the boat floats when I want it to and sinks when I want it to, and is level on or under the water, that's good enough for me. If it comes back up when I want it to...then that's a bonus.
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Truly a Zen Master of the principles of 'suck it and see'! I salute your approach to technology and envy you..."Respect to the Man... :-))
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Skip, I've been called a lot of things over the years, but never before have I been called a Zen Master...I thank you for that from the heart of my bottom. ;D
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As I said in an earlier post, nothing wrong with taking an empircal approach.
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i will have to agree with andy that using metric to convert between mass and volume is so much easier than using imperial units... especially when i buy the majority of my gadgets and toys from the germans.
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What did I learn from this ??? well for starters I need a bit of foam in my type VIIc to bring it back to its correct water line the instruction contained in those well written lines were so simple to understand thanks for taking the time to put that out here Andy.
Mark.