Top Wing Skins 16-3-1 to 16-3-3

With the skeletons of both wings assembled, I was now ready to begin attaching the top skins. 

Starting with the right spar, I placed it across 4 saw horses that I had modified to ensure they were all roughly the same height. Using a laser level, I put shims under the spar along the sawhorses until the spar was uniformly straight along its entire length (zero bow).

I then used a box level to ensure that there was no twist in the spar, and finally clamped the spar securely to the sawhorses at both ends.

Using a laser level to ensure that the main spar is straight, not bowed, and supported well across each saw horse

Main spar clamped at inboard end...

...and at outboard end to prevent any movement

Spar was also checked for level between each pair of ribs to ensure that it was not twisted

Main spar leveled, clamped and ready for attaching top skins

Next I positioned the skin stiffeners in place, and then clecoed the inboard top skin and wing walk doublers onto the ribs. I wasn't happy with the fit because I found that rivets would not fit easily through the holes aligning the 3 parts. Clecos are great at holding pieces together, but not so great when you need accurate alignment because they are slightly smaller than the holes they are designed to go through.

I ended up disassembling the skin and doublers from the ribs, and ordered some skin pins which are similar to clecos but more accurate with alignment (and also more expensive!). Once I receive these I will return to the top skins.

[a short time later...] 

The skin pins arrived quickly and I was able to get back to work aligning the top skins to the ribs and spars. Starting with clecoing the skins to the rear spar in the region where they overlap I was able to align the skins perfectly so that there was no oil canning in any of the sections between ribs. 

The skin pins definitely helped to keep parts in alignment, but I also found that pushing a 3/32" pin punch through the holes also helped to fully align the parts prior to inserting the clecos. 

One thing to be aware of with the skin pins is that because they have such a tight tolerance, if the holes in the parts are not already almost aligned prior to inserting the skin pin, it just won't go through. 

I did find that inserting rivets into some of the countersunk holes over the inboard wing walk doublers was somewhat tight due to very minor misalignments (possibly due to primer thickness). I reamed these holes with a #40 reamer and then had no issues after that.

Now it was finally time to start riveting the top skin to the wing structure. With my daughter's help on the rivet gun, and myself with the bucking bar, we started riveting outward from the center of the outboard top wing skin. 

I chose to avoid backriveting as suggested in the plans due to the need to use a long double offset backrivet set. I don't have one of those sets, but also don't like using double offset sets unless absolutely necessary due to the higher air pressures required and greater possibility for mistakes. I have been very happy using the Boeing flush rivet set with a tungsten bucking bar and anticipate great results on the wings as well with these.

Tungsten bucking bars that I use. The one on the left works for the majority of the top skin rivets, especially with its slightly angled end. The middle bar is useful in narrower spaces, especially along the ribs right under the rear spar. The tungsten bar on the right has a 45 deg. angle and a notch which are extremely useful for bucking rivets under the J-channels 

Riveting started in the center of the outboard top skin, moving out radially

Shop heads looking good!

After a couple of short riveting sessions the clecos are starting to disappear and we are making progress. My daughter picked up using the rivet gun very quickly and is doing a great job!

Rear spar rivets were also bucked. Those around the inboard aileron hinge bracket are a little trickier due to space limitations, but I was able to get them all with my angled tungsten bucking bars

Very happy with how the skin looks after setting about 350 rivets so far... progressing slowly but surely...

Build Hints

• Skin pins are useful to have when tight tolerance is needed to align parts. A handful of 3/32" and 1/8" skin pins (with 1/2" throw) are adequate for the top wing skins.
• Boeing flush sets and tungsten bucking bars make quick work of setting rivets in the top skins. These are my go to items for bucking rivets, and result in a beautiful skin finish that rivals backriveting.
• I would definitely recommend having a riveting partner to help rivet the top wing skins due to their size. Makes riveting the top skins a far more enjoyable process, and my daughter is doing an amazing job handling the rivet gun!  

Time Taken:     10.7 hours

Dates:                April 6 - April 22 2024

Top Wing Skins Total Time:       32.7 hours

RV-10 Build Total Time:           643.8 hours

Priming Total Time:                     73.4 hours (not included in build time totals)

I lost a little footage clecoing the outboard top skin to the spars and ribs so this video is a little shorter. I'm also not recording every riveting session as that would become somewhat boring to watch, however the techniques used are the same across the entire top skins