Fuel tank fabrication issues

[MarkM]

Hi All!

After a long hiatus, I'm finally back!
I have a build log website started on EAA's website. I'll link to it here once I get it updated.

My top wings are finished and in the hangar, while my bottom wings and center section are in my workshop. With the bottom wings, I only have the wing walks and leading edge plywood to go. Not too many issues there, fortunately.

I'm also working on the center section. I decided to outsource the fuel tank to a professional, but even he is a bit stumped on the top skin. When trying to weld the .090 top skin to the rest of the tank, the welding distortion left the first effort looking like a large, very expensive metal potato chip.

I realize most people are going rogue when it comes to the tank, using rivets and pro-seal, or fiberglass, and just about anything other than the welding the tank per the Makelan plans. Most everyone who does have a stock to-the-plans tank were those fortunate enough to buy one from Makelan when Jeff was still in business. I know I'm grasping at straws here: have any of you here actually welded your tank per the plans? If not, does anyone have some insight as to just what secrets Jeff Shoemake had to get his tanks coming out so nicely? I've seen photos of the Makelan tanks, and it's clear to me that the weld bead does not penetrate completely through the skin.

[painless]

Hi Mark. Welding aluminum is an art form. I became comfortable with welding 4130, but like you, I farmed out aluminum welds.

I had a pro from Enstrom Helicopters, located in Menominee Mi close to where I live do mine. I prosealed and riveted my tanks, using my experience building tanks for my RV6A, so I just had fittings welded for me. Craig made sure he had some moist towels near where he was welding to suck up any excess heat, and did each weld in increments, letting heat dissipate in between welding runs. Still had some distortion. One thing you can try is prior to closing up the top skin, rivet and proseal aluminum angle as stiffeners. Can’t be too close to the weld line due to heat possibly degrading the proseal, but even being within a couple inches should help. Just my two cents worth, and that’s probably all it’s worth…..