RV-10 Inboard Wing Prep

Was wondering if anyone had some photos they could possibly share of the inboard edge of the right or left wing. I'm having a slight challenge understanding Page 16-2, Step 3. In particular I'm trying to figure out the 2nd sub-step that talks about machine countersinking for a #8 flush head screw dimple. I think I've gotten everything else figured out.

I'm countersinking the skin for a dimple? Not sure how the works exactly.

Thanks
Charlie

Yeah, not the greatest wording. You are CSKing to accept the flush #8 screw vice dimpling like you do for that most aft hole. I guess they should have said CSK to accept the #8 flush head or something to that effect.

Actually, it is worded correctly, and means exactly what it says. You need to machine countersink deeper than for a screw head. Find a piece of scrap the thickness of the panel that screws on there and drill it number 19, debut and dimple it. The machine countersink needs to be deep enough for that dimple (#8 flush head screw dimple) to sit flat. Two dimpled pieces will nest correctly with the same dimple, but a machine countersink hole will need to be deeper to hold a dimple and a fastener than just a fastener.

Jesse said:

Actually, it is worded correctly, and means exactly what it says. You need to machine countersink deeper than for a screw head. Find a piece of scrap the thickness of the panel that screws on there and drill it number 19, debut and dimple it. The machine countersink needs to be deep enough for that dimple (#8 flush head screw dimple) to sit flat. Two dimpled pieces will nest correctly with the same dimple, but a machine countersink hole will need to be deeper to hold a dimple and a fastener than just a fastener.

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I guess that is what I'm struggling with. Its a skin that needs the countersinking for a large dimple. To me, it seems like its just going to be a very large hole...

cderk said:

I guess that is what I'm struggling with. Its a skin that needs the countersinking for a large dimple. To me, it seems like its just going to be a very large hole...

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In the top skin, yes, but the stack up of parts there *should* provide the necessary thickness to contain the full countersink. I just recently did this section and chose to dimple instead of countersink. I'll have to swap the nutplates with K1100 ones...

What I did was take a scrap of aluminum the thickness of the root fairing and drilled and dimpled it for the screw. Not a big scrap, say 1" x 2". Now I countersink the wing root. To check the depth of the countersink, I lay the scrap with the dimple in place. I prefer it to be just slightly proud of flush due to the radius at the top of the dimple; otherwise it won't be properly supported once the screw is tightened. What you don't want is so deep that the scrap is flat on the skin but there is a gap between the dimple and the countersunk hole. I made dimple gauges like this for all the screw sizes used in the -10 as the same technique is used for the slow-build spars and other areas.

Dimple instead of counterskin

I never liked the Van's countersink in the skin deal for the wing root fairing. The countersink is huge and is easy to get out of round.

For an RV-10 and a set of RV-14 wings I dimpled the skins, the wing doubler and the associate rib for the #8 screw dimple in the wing root aluminum. If you dimple, you can then take a deburring tool and open up the dimple just a little to make sure the wing root fairing dimple fits inside.

A lot less material is removed and I find this a much easier way to get the wing root fairing to lay flat on the wing.

Note - this follows the wing root treatment per Van's instructions when I built the RV-8A.

Carl

Thanks for the feedback. I'll probably give it a try and see what happens. Looks like I can dimple as well, but then will have to use a different nut plate.