Hatz Biplane Association

Hey folks. After 2 years of getting a new business up and running I'm actually finding a little time here and there to get back into my Hatz.

So.... I am working on the trim tab. I've heard from many builders how important it is to use bushings for bolt holes. But the trim tab hinges bolt on with 1/8" bolts through a 3/8" tube, leaving essentially no room for a bushing. I'm concerned about vibration causing the bolt hole to crack and fail without a bushing. Does anyone have thoughts on this? Your advice appreciated.

Nick

Don't know if this would apply to your trim tab assembly, but I used piano hinge on my trim tab. Made the tab out of a slab of thin (3/8 or 1/2") pine then painted.

I used 1/8" pins with no bushing and have had no problems.

Jeff Moore

Oh I see. Cotter pins? Stainless? How did you protect the inside of the tube?

Nick

Cotter pins, yes. Stainless, no. Nothing special on the inside of the tube.

Jeff Moore

Just an annual lube...?

That's all.

Jeff

It's my limited understanding that smaller diameter 4130 steel tubing with heavy walls is bushing stock. If I recall correctly only my aileron bell crank has oilite bronze bushings. All other bushings are made from heavy wall 4130 steel reamed to fit AN3, AN4 etc. bolts.

My two cents.

Bushing stock is not usually made out of 4130 .