Tuesday, July 9, 2013

Fuel tank leak test - Sat

For the last couple of days I have been doing leak checks on the left fuel tank.  The first iteration included a balloon sealed over the vent line.  This looked like it was going well until Monday morning when I came out and the balloon was pretty much flat.  I was a little disappointed thinking I had a very small (and hard to detect) leak in the tank somewhere.  After coming home on Monday night I decided to use the manometer method to check for leaks thinking the balloon may have a pin hole in it.  So, I hooked everything up, filled the hose up with water, pressurized the tank up to 1 psi and started spraying the tank down with soapy water to see if I could find the bubbles.  Well, it took a while but I finally found them.  They were on the test fittings that I had installed for the test!!!  Woo hoo, I tightened up the two fittings and started the test again.  Here it is 24 hours or more later and the tank is still sitting where it was last night at this same temperature!  I am calling this tank sealed.

While all of this was going on I have been busy with the left wing skins, deburring, dimpling, re-dimpling, and prepping for final riveting.  As of tonight all I have left to do is the leading edge skin dimples and I can start the process of riveting the left wing together.  Finally.

Oh, one more thing.  The instructions call for me to "bevel" the joint where the two upper wing skins overlap at the point where they butt up against the fuel tank.  I kept looking at this wondering how I was going to get this to look decent using a hand file.  So I decided to see how other builders had done it and I found a few people who had actually trimmed the inner skin a little and then beveled the aft part of the rest of the overlap area.  I did that and you can see the result in the pictures below.

Leak test number 1 with the balloon.

The trimmed overlap area on the inner skin.

The pencil marks are last nights marks for the same temperature.  Tonight when I made the call that the test was completed with no leaks the temperature was 81 degrees and the level in my manometer was at the 81 degree mark from last night.

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