Wing platenuts for tank

Guys,

The holes that allow for the screw to attach the tank to the wing are enlarged when I countersink for the screw. I am using a .032" test skin(thickness of tank skin) to test fit and when it is flush with the spar, the hole in the spar flange is large (close to .370). I searched this web page and that seems to be okay. I called Vans support and they said to not use a .032 skin as a guide to establish the depth of the countersink into the spar, but to countersink the spar until the screw is flush with maybe a slight halo. I have only done one hole and woulod appreciate some help.

Countersinks

I would stop where Vans suggests and if necessary, work them by hand when you fit the tank.

If I understand you right, you are countersinking the spar to accept the dimple from the tank skin? I would either use what vans suggested or use a piece of scrap as colse to the thickness of the tank skin, with the correct diameter hole drilled for the screw and dimple it and use that as a guide to figure out the depth needed to get it to fit against the spar without it moving around in the countersink. Hope that helps.

Jimmy
Im building a 7 and the tank attach nut-plates use #8 screws. I used .370 as my outside diameter as referenced in an earlier RVater publication. I am very happy with the results. As an earlier post mentioned, if I install the screw without the outer skin I have a slight halo around the screw head. I did a bunch of test coupons and got the dimensions perfect and then went to town on my spars. Go slow with the drill, use boelub and have the nutplates installed as a guide for the countersink cutter. Now get back out to the garage and get to work.

Perfect....thanks guys.