March 11, 2008

Pressure Testing the Tank - 1.0 hr.

Last night I put the tank in my warm office and left it all night, to speed up the curing of the proseal. I'm anxious to finish the pressure testing today and make sure I don' t have any leaks.

A short piece of aluminum tubing has been flared and cut off to make a plug to seal off the tank. Kind of hard to see in this photo, but the plug has been filled with proseal. Put together with standard AN fittings, it gives you a plug to seal off the fuel pickup tube. Not only will this be useful for pressure testing, but it will keep bugs, spider webs, and other unwanted critters out of your fuel tanks while they are in storage for the long months ahead while I'm building the rest of the plane. This is not a trivial issue. I read a story recently about an airplane that had to make an emergency landing when the engine quit. The problem was traced to fuel starvation caused by a wad of spider webbing and eggs from a small spider that made its nest in the fuel tubing. You've seen 'em... almost like a little cotton ball. Gotta keep these parts clean and sealed up!

I used another short flared piece of tubing with some AN fittings to make this contraption to hold the balloon. The balloon is simply duct-taped on. This fitting will be attached to the vent line on the tank for the pressure test. When I'm done, I will remove the ballon and fill this tube with proseal for storage.

This is the fuel tank pressure-testing kit from Vans. This is a bicycle-type inflator valve that's threaded on the other end. This part goes into the fuel drain flange on the bottom of the tank for pressure testing. It's function should be obvious. Pump up that balloon.

The fuel cap needs to be sealed off airtight, since air leakage here can obviously cause you some stress during the pressure test.

Duct tape does the trick just fine. Simple and cheap.

Here's the pump-up valve installed in the fuel drain flange. The spring drain assembly is removed and this installed temporarily in its place.

Here you can see the plugged fuel pickup tube and the balloon, waiting to be inflated.

Ta Da!! Now all we have to do is wait...

... and wait...

... and wait some more...

Stay tuned...

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