threaded inserts
 

What are everyones thoughts on threaded brass inserts on bolt on wing planes as opposed to threads cut into balsa? I already have my wing holes drilled and tapped but ran across these at my LHS and thought that they looked more durable in the long run and more resistant to being worn down. Any opinions or experiences?

Thanks,
Rob

RE: threaded inserts
 

I use them to mount cowl with nylon bolts. They work OK. You can also use blind nuts for your wing bolts.

RE: threaded inserts
 

Actually, most builders don't thread into balsa. Most every wing that uses bolts will have bolts that go into T-nuts. And since the object is to hold the wing to the airplane, the T-nuts are behind hard wood that's attached securely to the fuselage framework. So what we do is thread the hardwood and it works like gangbusters.

For most 40-60-90 size airplanes, two 14/-20 nylon bolts are strong enough. And if the wood is at least as thick as the bolt is wide, the bolts will hold great. Thread the wood. Run the bolts to check the angle and tightness. Pull the bolts and strengthen the threaded hole by soaking in some thing CA. Let it cure. Thread it again. You're good to go.

If the hardwood isn't very thick, then back it with either another piece of hardwood. Any kind will do. Even plywood works.

If the airplane wasn't designed to use bolts, then supply your own hardwood. Any will do.

RE: threaded inserts
 

Those brass inserts need to be epoxied into wherever you plan to use them. But they do add useless weight.

The only sensible use is to hold heavy objects with small bolts. If you're going to use large nylon bolts, they're going to be big. If they're big, CA hardened wood will hold whatever the nylon can hold. If they're small, CA hardened wood (if it's thick enough) will still probably hold whatever the nylon bolts can hold.

RE: threaded inserts
 

Rob,

For very light planes, wing bolts can be secured with threads cut into balsa. You would probably want to "harden" the threads with CA, or use hard balsa.

Heavier planes that use steel blind nuts usually use nylon bolts, because steel bolts would be prone to loosen. There is more friction between the nylon bolt and the steel threads than with a steel bolt on steel threads.

My 25 lb Meister Corsair has threaded brass inserts epoxied into the wooden framework, to hold the wing on. I use long steel Allen screws, and the bolt pocket in the wing is wood. The wooden pocket seems to have enough friction to keep the bolts from backing out. If they wanted to back out, I'd put an O-ring or section of tubing beneath the bolt head, to intruduce some friction.

Good luck,
Dave Olson

RE: threaded inserts
 

I've used both "T" nuts and inserts....

Don't worry about the wing coming off with them instead of CA hardened wood... ;)