Jump to content

Solve This One Then

Biggles

By Biggles
in Boat Building & Maintenance

 Share

Featured Posts

Biggles Veteran

Biggles

Posted
Posted

I have been working on my integral water tank. I welded the side that faces the interior in today, then I sealed it all down. I hadn't painted any of the welds I had done but I have painted the rest of the tank as this was already welded when I got the shell.

 

I then blew it up to 4psi and with soapy water went round to find any leaks. There were a few pinpricks which I soon sealed.

 

The real problem in in the front wall of the tank. This forms a bulkhead in which the bow tube is fitted. I could distinctly hear the hiss of escaping air, but heres the thing. I can't get it to bubble, I just can't find the leaks!

 

Anyone got any suggestions.

 

Biggles

Link to comment
Share on other sites
paulcatchpole Rising Star

paulcatchpole

Posted
Posted

Not many... Put water in it, with or without food colouring or UV dye, and see where it comes out, aided with some blue roll or similar to act as blotting paper. Try some gas leak detection spray, instead of soapy water? I take it you're hearing the hiss where you think you're hearing it, not reflected from your air fittings, around the surfaces, and tricking you?

 

PC

 

Reminds me of a favourite phrase, 'I can hear the sound of escaping vacuum...' - can you? Really? :lol:

Link to comment
Share on other sites
Biggles Veteran

Biggles

Posted
  • Author
Posted

Will gas spray work with air?

 

I did consider it could be a reflected sound, and still haven't ruled it out. Before I came in this evening I managed to work out a way of getting in and out of the space. I would have tried earlier but there was no one at home so didn't want to be stuck without help at hand.

 

When I do get to putting water in I won't need dye. The space is not yet painted so any seepage will make the light rust darker.

 

This has got me puzzled for sure.

 

Biggles

Link to comment
Share on other sites
paulcatchpole Rising Star

paulcatchpole

Posted
Posted
Will gas spray work with air?

 

Aye, it's just a low-tension bubbly film, that shows leaks as bubbles a bit better than fairy... :lol:

 

Now there's a thought, having become enamoured of our BSS examiner's gas sniffer, you could pressurise it with LPG vapour, to 37mbar, and go round with a sniffer... :lol: (Not a totally serious suggestion, sorry...) Or perhaps the UV dye would be better - do you have an access hole in the top, you could paint the penetrating dye around the inside of the welds? UV light on the outside - that'd nail it?

 

I did consider it could be a reflected sound, and still haven't ruled it out. Before I came in this evening I managed to work out a way of getting in and out of the space. I would have tried earlier but there was no one at home so didn't want to be stuck without help at hand.

 

When I do get to putting water in I won't need dye. The space is not yet painted so any seepage will make the light rust darker.

 

This has got me puzzled for sure.

 

Biggles

 

It's an interesting one for sure - not sure I've got any brilliant ideas, sorry! :lol:

 

PC

Link to comment
Share on other sites
Radiomariner Rising Star

Radiomariner

Posted
Posted (edited)
Aye, it's just a low-tension bubbly film, that shows leaks as bubbles a bit better than fairy... :lol:

 

Now there's a thought, having become enamoured of our BSS examiner's gas sniffer, you could pressurise it with LPG vapour, to 37mbar, and go round with a sniffer... :lol: (Not a totally serious suggestion, sorry...) Or perhaps the UV dye would be better - do you have an access hole in the top, you could paint the penetrating dye around the inside of the welds? UV light on the outside - that'd nail it?

 

 

 

It's an interesting one for sure - not sure I've got any brilliant ideas, sorry! :lol:

 

PC

 

Gawd Paul, you very nearly gave me a heart attack there!

Can I suggest filling with water and using water detecting paste smeared along outside of the welds

Edited by Radiomariner
Link to comment
Share on other sites
Biggles Veteran

Biggles

Posted
  • Author
Posted
Use a piece of tube as a stethoscope to probe round for the hiss.

 

m@

 

Thats an idea.

 

I will have another bash tomorrow. Let you know how I get on.

 

Just can't figure why something so straight forward should be such a mystery. Puncture... air leaking, soapy water, should be the answer.

 

Biggles

Link to comment
Share on other sites
RobinJ Experienced

RobinJ

Posted
Posted
I then blew it up to 4psi and with soapy water went round to find any leaks. There were a few pinpricks which I soon sealed.

 

The real problem in in the front wall of the tank. This forms a bulkhead in which the bow tube is fitted. I could distinctly hear the hiss of escaping air, but heres the thing. I can't get it to bubble, I just can't find the leaks!

Does this not suggest the leak is at the top where there is an air pocket, probably on the opposite side to which you are laying!

Link to comment
Share on other sites
Biggles Veteran

Biggles

Posted
  • Author
Posted
Does this not suggest the leak is at the top where there is an air pocket, probably on the opposite side to which you are laying!

 

 

No. The whole tank is full of air. No water in it yet. The air is the test before I am happy to put water. If its air tight at 4psi it sure as hell will be water tight too.

Link to comment
Share on other sites
RobinJ Experienced

RobinJ

Posted
Posted
No. The whole tank is full of air. No water in it yet. The air is the test before I am happy to put water. If its air tight at 4psi it sure as hell will be water tight too.

Oops, dyslexic eyesight!

 

Well it either has to be becuase the hole is too big to support a soap bubble, or its like a crack and a bubble cannot form.

How about something a bit thicker? Can you feel the breeze?

If you are using a compressor, is it still running or have you left the tank at a pressure and turned off. Would knowing how much air over what time help?

Link to comment
Share on other sites
Biggles Veteran

Biggles

Posted
  • Author
Posted
Oops, dyslexic eyesight!

 

Well it either has to be becuase the hole is too big to support a soap bubble, or its like a crack and a bubble cannot form.

How about something a bit thicker? Can you feel the breeze?

If you are using a compressor, is it still running or have you left the tank at a pressure and turned off. Would knowing how much air over what time help?

 

 

Its losing it quite fast which is all the more puzzeling as you would think this would make it easier to trace. I agree a bubble might not form but it would show some tell tail. I'm going in!

 

Biggles

Link to comment
Share on other sites
Biggles Veteran

Biggles

Posted
  • Author
Posted

Mystery solved.

 

I got in the compartment where the hiss is coming from.

 

The problem is the 2 x 1 C section thats used under the deck floor as reinforcing is continuous from the water tank to the front of the bow tube bulkhead. This channel is only tack welded to the floor so it leaks air from the tank to the bow tube locker.

 

I had put seam sealer on these prior to painting with potable blacking, so I am hoping some more coats of blacking on these seams will eventually seal it all up with some seam sealer on the parts in the tube locker. Thats gonna be fun.

 

The good news is this area is right at the top of the tank and is unlikely to get water that high.

Biggles

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.