Paint the screws or not

[dougweil]

I did not paint my tank screws on my RV-7. They were painted in screws on my old RV-4 and I had to remove a tank to replace the sending unit. The beautiful paint job wasn't quite so beautful after fighting to get out the screws. When my -7 was painted, I removed just about all of the tank screws except a couple to hold it in place. Those screws were backed out enough so as not to get "painted" in place. After the paint was finished, I replaced all tank screws with new AN cadmium plated #8 screws. Looks great and there will not be an issue if I have to remove a tank.

[jaradtke]

Originally Posted by Captain Avgas

Using stainless screws for the fuel tanks is very bad engineering and would not be approved by Vans. Milspec #8 stainless screws are typically 80,000 psi Ultimate Tensile Strength. Milspec cad plated steel screws as supplied by Vans are 120,000 psi.

I'd use the cad plated screws supplied by Vans for the fuel tanks and not paint them. People think that they're never going to take off their fuel tanks ...but many have to to fix leaks down the track.

Aluminum 2024-T3 - ASM Material Data Sheet -- Ultimate Tensile Strength 70000 psi

[ronschreck]

If you don't paint the tank screws you will never have to remove the tank. If you DO paint the tanks screws you can bet that you will have to remove the tank at some point and it will be a bugger!

+1 for not painting any screws!

[TCONROY]

I think they key is, paint the screws separately (if you are going to paint them). I totally agree that you don't want to paint the screws in-place otherwise you will have to cut the paint around every single one if you want to remove the tank.

[Jesse]

I would paint them on the tank. You certainly hope you don't have to remove it. If you do, you can easily use a paint cutter to cut the paint around each screw (doesn't take long). Then, you can reinstall with the messed up screws on the bottom of the wing. Or, you can reinstall with new unpainted screws. From experience, putting in all of those screws over painted dimpled holes can cause the paint to blister as you tighten, which will look much worse.

[JonJay]

Might make an interesting poll.
Going on ten years, 700 hours, tanks have never been off. Painted in assembly with wing. I don't even remember looking at options of not painting the screws but the question seems reasonable. I Replaced one sender with the tank in place. (Sounds harder than it is.)
So, I wonder how many tanks get pulled and for what reasons. (Leaks, slosh, sender, ??)
I would factor that into my thinking before making a decision. Your not going to have slosh. If you build the tank correctly there will be no leaks. The sender can be replaced without removal, not a lot else to go wrong, bird strike maybe.
I would also want to know my painters opinion.
Very good topic.

[Simon Hitchen]

Thanks for the replies guys, considering I had already painted the wing without the screws in place I decided to go ahead and give painting the screws a try..

Ill let you know how it works out.

[DGlaeser]

Originally Posted by Captain Avgas

Using stainless screws for the fuel tanks is very bad engineering and would not be approved by Vans. Milspec #8 stainless screws are typically 80,000 psi Ultimate Tensile Strength. Milspec cad plated steel screws as supplied by Vans are 120,000 psi.

I'd use the cad plated screws supplied by Vans for the fuel tanks and not paint them. People think that they're never going to take off their fuel tanks ...but many have to to fix leaks down the track.

I disagree. These screws are in shear, not tension, and lowly loaded to boot. I use SS torx head screws.