Update 10-May-18: If I were to build another set of wings, I would dimple the skins, doublers and associated rib flanges. It would come out nicer and I suspect have no meaningful change in joint strength (probably would be stronger).
Got the inboard skins countersunk over the wing walk doublers. Using my new microstop countersink cage, I set it on some scrap angle, then moved over to the skins. I was terrified of making an error since replacement skins wouldn't be cheap. I checked each and every countersink to make sure the rivet sat flush, so it was time consuming, but all turned out well. The only mistake I made was I accidentally countersunk a hole that the J-stiffener attaches to (despite my labeling it as a non-drill hole, d'oh!). That hole should be dimpled. The countersink chattered (which is how I knew I made a mistake), so the hole is enlarged. I'll up it to a -4 rivet with the #30 cutter. Then I'll just press out the dimple in the J-stiffener, up the hole to a #30 and call it good. No big deal.
There is a remarkable strength difference in the wing walk area versus the places between wider spaced ribs without the doublers. That's how it's supposed to be of course, but experimenting with these things is part of the learning and exploration process.
Got the inboard skins countersunk over the wing walk doublers. Using my new microstop countersink cage, I set it on some scrap angle, then moved over to the skins. I was terrified of making an error since replacement skins wouldn't be cheap. I checked each and every countersink to make sure the rivet sat flush, so it was time consuming, but all turned out well. The only mistake I made was I accidentally countersunk a hole that the J-stiffener attaches to (despite my labeling it as a non-drill hole, d'oh!). That hole should be dimpled. The countersink chattered (which is how I knew I made a mistake), so the hole is enlarged. I'll up it to a -4 rivet with the #30 cutter. Then I'll just press out the dimple in the J-stiffener, up the hole to a #30 and call it good. No big deal.
There is a remarkable strength difference in the wing walk area versus the places between wider spaced ribs without the doublers. That's how it's supposed to be of course, but experimenting with these things is part of the learning and exploration process.
Things to watch out for:
- Make sure to get those two extra holes over the flap bracket doubler.
- Be sure to sit the microstop cage flush to the surface. It's a wing, so it's curved.
- Be sure to final drill #19 the correct holes on the nut plate screw holes. Mark them properly and cleco the holes around them to block those off.
- Go slowly. Better to work from shallow to proper depth then find yourself with a c'sink too deep.
- Test each countersink with a rivet after cutting. Now's the time to make adjustments.
- Tape off the VA-146 bearing on the torque tube support bracket so shavings don't get into it.
Here's the right side, all c'sinked.
And here it was prior to the c'sinking, all cleco'd in, nice and cozy.
Following the placement of the rear spars, I was surprised how wobbly the whole wing assembly was at that point. A simple push on any part of the assembly parallel to the length of the spar saw quite a bit of deflection with little force. That should be expected really, since there's nothing rigid preventing that kind of shear. So when I cleco'd in the inboard skins for all that c'sinking, the whole assembly was very stiff. Cool.
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