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Help leaking water

R/C Submarine modelers

Help leaking water

Postby xxl » Mon Jul 27, 2009 4:32 pm

whats the best way to find a leak in a wtc
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Postby subdude » Mon Jul 27, 2009 4:47 pm

Remove sensitive electronics
Fill with paper towels and lead weights so it will stay submerged
Put it in your test tank
Watch for bubbles
If the bubbles are inconclusive, check the paper towels for the wet spot.
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Postby Skip Asay » Mon Jul 27, 2009 5:00 pm

Drill a 1/8" hole in the pressure hull/wtc and glue a piece of brass tubing into this hole. Attach one end of a piece of hose to this brass tube and the other end in your mouth. Submerge the pressure hull/wtc and then blow. Look for bubbles. Fix leak. But DON'T FORGET to plug the brass tube BEFORE the boat goes back in the water!

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Postby Rogue Sub » Mon Jul 27, 2009 5:07 pm

I use skips method. Its simple and WORKS.
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Postby Davinci » Mon Jul 27, 2009 7:33 pm

On my larger WTCs that have O-ring-seal type end-caps, I tap a hole in end-cap and install a Schrader-valve (tire-valve). Pressurize it a little, check for bubbles. Going to higher pressure will remove the end-cap and it's attached assembly, which is handy if it's very tight.
Schrader-valve is at very bottom of this pic, with chrome cap on it.
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Postby Carcharadon » Tue Jul 28, 2009 7:52 am

If it holds a vacuum for an extended period it’s sealed. A vacuum better approximates the real life situation more so than pressure. But bubbles are easy to spot.
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Postby Ramius-II » Tue Jul 28, 2009 12:10 pm

One other mix of techniques is to use a fish tank air pump feeding a brass tube installed in the WTC. Then a mixture of soap and water "painted" on the outside of the WTC. Much like when you look for a natural gas leak. The advantage of the fish tank air pump is that you will not "colapse a lung" if it takes time to find the leak. :shock:

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Postby Skip Asay » Tue Jul 28, 2009 1:05 pm

Note that none of the methods described above is 100% fool proof. I recall many years ago testing my boat in the test tank, getting zero bubbles, and then finding a couple of cups of water inside once I got home. Proceeded to go back to the test tank only to find zero bubbles. Time to start pulling the hair out! To cut to the chase, it turns out that a silicone fillet inside one of the bulkheads must have been applied over epoxy which hadn't been prepared properly and this resulted in a one way valve. High internal pressure would seal it off while high external pressure would open it up. Since I wasn't using plex/lexan lids at the time, it took some doing to find that one!

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Postby junglelord » Tue Jul 28, 2009 2:14 pm

Very informative thread. Thanks for all the replies.
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Postby tsenecal » Tue Jul 28, 2009 5:52 pm

I also had a situation where the temperature of the bathtub was 15 degrees higher than the temperature in the pond.

the difference caused enough shrinkage of the cast endcap to allow a tiny dribble of water to get past the o-ring when it was in the pond, but not in the bathtub.

I now include a 30 minute sit in the fridge for my WTC prior to it going in the bathtub for testing.
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Postby SteveNeill » Tue Jul 28, 2009 6:08 pm

What I do is use the tire valve in the end cap. Attach a filler to it and blow a bit of pressure through the tubing connected to the filler and release.

Then using some dish soap in water solution I coat the surfaces that can leak. End caps, seals, etc. The slightest leak will produce and nice foam of bubbles.

I have found leaks this way when the submerging method did not or it was so small I failed to see it. And you never have to submerge it in water. All on the bench.


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Test for leaks

Postby Art Broder » Tue Jul 28, 2009 7:56 pm

RCABS equipped models can easily be tested for leaks using the aforementioned pressure or vacuum methods. For RCABS WTC's there is already a brass tube through an end cap going from the air pump to the external bladder. Remove the bladder hose and the air pump hose from each end of the brass tube, reinsert the end cap and blow into the brass tube through an externally attached rubber hose as described in the above posts. Pinch the rubber hose, and look for soap bubbles or underwater bubbles depending on your chosen technique. That is a pressure test.
For a vacuum test, keep the fully assembled WTC and attached bladder underwater (or slather the end cap/cylinder sealed areas and penetrations with the soapy solution) and signal the pump to inflate the bladder, causing a partial vacuum in the WTC. Look closely for either water or soap bubble penetration into the WTC. That would be the vacuum test.
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