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Has anyone run into a slight bow (1/2") lengthwise across the bottom center of the skin after fitting the top and wrapping / re-attaching to the spar for bottom rib pilot drilling?

Were you able to work the skin down from the spar forward while pilot drilling / clecoing from the center forward and outward?

I haven't mustered the nerve to start pilot drilling yet, since it feels like there is quite a bit of pressure needed on the last two forward rivet holes of the rib while trying to work the skin down by hand.

I seem to recall something similar on one of my wings, with most of the pressure focused on the forward tip of 1 or 2 wing ribs. I rounded the tips of those ribs slightly to keep them from poking into the skin too much, then just made sure the skin was pulled snug before pilot drilling. End result seems good.

If you are using the kit skins then yes this is a common problem. The leading edge radius is too big. I remember trying to split the difference between the upper and lower sides. If possible try to have the bigger dimples on the underside if possible. Look at most leading edges at Oshkosh next time and you will see a common fit. Don't think its possible to change the radius.

Nice to know I'm not the only one experiencing this! Thanks for the suggestions.

Rynoth wrote:I seem to recall something similar on one of my wings, with most of the pressure focused on the forward tip of 1 or 2 wing ribs. I rounded the tips of those ribs slightly to keep them from poking into the skin too much, then just made sure the skin was pulled snug before pilot drilling.

Rynoth - Mine was all the way across inboard to outboard on all the rib tips with a gap at the very tip when I get the skin down to the last two rivets.

rk2436 wrote:If you are using the kit skins then yes this is a common problem. The leading edge radius is too big. I remember trying to split the difference between the upper and lower sides. If possible try to have the bigger dimples on the underside if possible.

rk2436 - Good thing I started with the top of the wing, I took a leap of faith (along with a recommendation from Sonex) to re-attach the padded board and work it down that way. So far it has worked well, just need to get the last two rivet holes piloted. We'll have to see how it comes out.

A few pictures of the frankenstein setup to get it worked down to this point.

The issue I see is the skin is not very tight on the two most forward holes on the bottom of the leading edge. I think I will have dimples there. I suppose better on the bottom than the top.

Bryan Cotton wrote:The issue I see is the skin is not very tight on the two most forward holes on the bottom of the leading edge. I think I will have dimples there. I suppose better on the bottom than the top.

Bryan, yea, I had the same thing, it seems the pre-bend in the leading edge could be a bit tighter. Since you're working from the spar forwards, it tends to increase the gap between the ribs and skin as you get to the front. It's a bane for us polishers but I've made my peace with it.