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Author Topic: Salt Water Darnell U37  (Read 54910 times)

unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #50 on: October 31, 2012, 05:55:32 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #51 on: October 31, 2012, 05:57:49 pm »

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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Subculture

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Re: Salt Water Darnell U37
« Reply #52 on: October 31, 2012, 06:00:34 pm »

Scotchbrite pads are effectively synthetic wire wool. I notice you can get the fuel tank foam easily on ebay.

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Re: Salt Water Darnell U37
« Reply #53 on: October 31, 2012, 06:04:23 pm »

I would think that might work.
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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #54 on: October 31, 2012, 06:09:00 pm »

Looks like we might have an interesting option developing here, must go and play in the bath....
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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #55 on: July 03, 2013, 05:49:08 pm »

 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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #56 on: July 03, 2013, 05:52:13 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #57 on: July 03, 2013, 05:54:42 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #58 on: July 03, 2013, 05:58:55 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #59 on: July 03, 2013, 06:06:30 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #60 on: July 03, 2013, 06:10:32 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #61 on: July 04, 2013, 06:10:34 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #62 on: July 04, 2013, 06:15:28 pm »

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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essex2visuvesi

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Re: Salt Water Darnell U37
« Reply #63 on: July 04, 2013, 06:20:31 pm »

Have you thought about using pond filter/aquarium foam?
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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #64 on: July 04, 2013, 06:27:56 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #65 on: July 04, 2013, 06:29:22 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #66 on: July 04, 2013, 06:39:06 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #67 on: July 04, 2013, 06:45:31 pm »

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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Subculture

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Re: Salt Water Darnell U37
« Reply #68 on: July 04, 2013, 07:24:45 pm »

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.....

essex2visuvesi

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Re: Salt Water Darnell U37
« Reply #69 on: July 04, 2013, 09:31:28 pm »

That thick black paint reminds me of underseal for cars
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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #70 on: July 05, 2013, 05:19:30 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #71 on: July 05, 2013, 05:50:35 pm »

 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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #72 on: July 05, 2013, 05:55:51 pm »

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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unbuiltnautilus

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Re: Salt Water Darnell U37
« Reply #73 on: July 05, 2013, 06:07:13 pm »

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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Re: Salt Water Darnell U37
« Reply #74 on: July 05, 2013, 09:50:46 pm »

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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