exposed tube on wing support frames

[Chewie]

Did you drill a hole through your end brackets on your flap/aileron support frames and poke the 3/4" tube through the other side to make the welding easier? If so, this question is for you:
How did you deal with protecting the inside of the tube, since it is now exposed? Bob suggested treating the inside of the tube or welding a disk onto the end of the tube at each end to seal it. I'm curious what you guys did. I was pondering a fender washer with a rosette weld in the middle, easier than trimming out a bunch of 4130 disks.

[S Lathrop]

I have the tube into the hole into the bracket but not extending past the surface of the bracket. The weld is then done largely inside the tube and hole.

[nichzimmerman]

Polyfiber has a product that coats the inside of steel tubing. It's designed for fuselages, and I also used it on the flap torque tubes and aileron/flap drives.

[Chewie]

Thanks for the responses. What is that product called... And what makes it different from traditional top coat?

[rodsmith]

Thanks for the responses. What is that perfect called... And what makes it different from traditional top coat?

Its called tube seal. It is not a paint it is a liquid coating that helps seal small holes and prevents corrosion. People still use linseed oil for the same purpose.

[Chewie]

I'm intrigued. This seems to be great for closed-in structures but is it still appropriate for a tube with the ends open to the outside? I may try their customer support.
Thanks for the referrals! I may just use this stuff regardless for treating the fuse.

[geraldmorrissey]

I checked a factory support frame weldment (inboard with flap torque tube fitting) and there is no hole for the tube in the end support fittings. All the welding was done inside the end support channels. If I did have open ends I'd probably treat the tube like a shotgun barrel. Gun cleaning tools might be useful. Clean REALLY well with a scothbright patch, then swab with primer.
Cheers
Gerry
Patrol #30 wings

[Chewie]

Those guys welding the kits are good...
I found a large pipe cleaner in the wedding aisle of our local Ace that fits well in 3/4 tubing. Thanks for the tips!