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Tank Nutplates and Spar

Brantel

Brantel

Well Known Member
I have seen that people invent at least 10 different ways to countersink the tank attach screw locations on the spar. This seems to be done because the hole gets too big and problems follow because of that.

Vans say in the instructions to use the nutplate as the pilot. And to do this, they say to rivet the nutplate on first and at the last moments, the pilot of the bit will center in the nutplate and all will be well.

Why do most people not do this and invent all these ways to countersink the spar?

I did mine the Van's way and they turned out perfect so what is all the fuss about?
 
I agree. I followed the instructions with great results.

One argument for some of the other methods is that you can't deburr the back side of the hole after the countersink enlarges it. The fact of the matter is though that anytime you countersink deeper than the full thickness of the material you are creating a knife edge. All deburring the nutplate side of the holes does is enlarge the holes further and move the burr up into the countersink where you can't feel it.

Guy
 
Brian,
I live in a very high corrosion environment. Because of where I live, I wanted to Alodine all the countersunk areas of the main spar, after exposing all that bare aluminum. (Anodizing the spar, only to create 200 flaws in it seems stupid to me). One way to Alodine the C/S holes is to use the Alodine 1132 pen (sold by SteinAir.com)
I was unaware that the Alodine pen existed. I also owned 40 gallons of Iridite 14-2 (Alodine competitor). It was easier for me to countersink all the needed holes, then dip the spar flanges in AlumiPrep and Iridite. Dipping allowed me to etch and Alodine these areas quickly, with little effort. If I had installed the nutplates first, the AlumiPrep would have caused them to start rusting.
Charlie Kuss
Boca Raton, Florida
 
I did not want to take the chance and ruin one of the plate nuts after they were installed. That would require me to drill them out. Little did I know that I would end up drilling out over half of them out anyways because my rivets kept cracking after they were squeezed. :mad:
 
No risk of damage

There is no risk of damage if you only go the correct depth for the dimple.
I did 144 of them and the primer never even got scuffed on the nutplates.
 
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