Hatz Biplane Association

Hey folks,

The fuel tank calls for 5 holes in the bottom, 4 for fuel feeds and 1 for fuel gauge. The 4 holes take an aluminum welding flange AN867-3 which is 1-7/8" in diameter. So I can punch a 1-3/4" hole and flare it to size with an automotive flare tool that adds 1/8" to hole dia. Should fit perfectly.

The problem is the fifth hole for the fuel guage. Plans call for an AN867-6 aluminum welding flange with has a diameter of 2-1/4". I'll need a 2-1/8" hole punch and flare tool, but I don't think anyone makes one. I could go up one hole size which would leave a 1/16" gap around the flange. Is it OK to gap fill this while welding?

Would like to hear your thoughts and experiences. Thanks

NIck

Hi Nick. Looks like you've had no response yet to your post. For some reason the forum has been preventing me from logging on for a couple months. Just logged on this AM.
Since I can't yet weld aluminum, I pro sealed and riveted my tank flanges ala the RV series of planes. I don't know if my method would also work when welding instead of pro seal and rivets. The openings I made in the bottom pan of the tank were maybe an inch dia. Then I pro sealed and riveted through the flange into the skin. Would not welding be possible the same way? That way, you end up drilling the large diameter hole in the wooden floor of the C section instead of the tank. The depth of the flange below the bottom of the tank skin pretty much matches the thickness of the C section floor (my floor is made from Finnish birch and is either 3 or 5 mm which ever is closest to 1/4".
But then, by now you've probably figured something out and welded her up. Good luck!

I think the plans call for a Stearman fuel gauge. We used a PA-12 fuel gauge (Wag-Aero) which uses the same flanges as the outlets.
John Hanson

Thanks guys.
John...useful as always.

Nick