REFLECTOR:fuel tank leak testing

[reflector@tvbf.org]

If you're at a few PSI, you may have caused the leak blowing the skin off 
the spar.  At a few psi you have thousands of pounds of peel force.  As one 
of the other posters said, you shouldn't pressurize it more than by mouth - 
less than a PSI.

You can get a gas detector cheaply at an RV supply place.  Drip some 
propane in the tank, cover the fuel port with duct tape, run the detector 
around the area and play with the sensitivity, you'll get it isolated.

For sealing it, you can put a slight vacuum on the tank with a shop vac 
(don't tape the hose in, you want the connection leaky) use a heat gun to 
get your epoxy very thin (it will exotherm, be careful) and dab it into the 
leak.  Or use a syringe - good ones can be gotten from the Veterinary 
supply store.

At 12:01 PM 7/5/03 -0500, you wrote:
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>I'm still having difficulty finding and eliminating my fuel tank 
>leaks.  Let me review what I have done.
>
>My two small bulkheads between the large rear bulkhead and the main spar 
>have already been installed, but I can get my hand through the opening.
>
>I reduce the pressure on my air tank/pump to a few psi (so I can easily 
>stop the flow with my finger) so as to not damage the tank.  I can hear 
>the air escaping from behind the large bulkhead.  When I first began 
>working on it, I could feel air coming from that area just by reaching my 
>hand in there.  I have used a soapy solution, but cannot see any 
>bubbles.  I have used this technique with tires  before with good 
>results.  However, the pressure in those cases were over 30psi.
>
>I then tried using the tubing as some of you suggested.  The sound is not 
>localized and seems to be very steady all along the rear bulkhead.
>
>I have applied sealant all along the seam using a paint brush attached to 
>a pair of sticks so that I can adjust the paint brush after getting it 
>through the small bulkheads.
>
>It is hard to tell without quantitative measurement, but I think it is 
>improving some.
>
>I also tried to spray epoxy in the cavity using a water sprayer.  The 
>epoxy and cabasil were too think to really spray.
>
>Any help would be appreciated.