Wing Rear Spar 15-5-2 to 15-5-3, Priming

I completed a few more steps on the rear spar by deburring the reinforcement forks and doubler plates and countersinking the bottom row of each double plate as directed. I'll leave the steps that countersink and dimple the rear spars themselves until I have the wing ribs in place to make sure that I don't miss anything.

Reinforcement forks and doubler plates countersunk and deburred

With the rear spar parts prepared and deburred, I started the process of priming them. 

Rear spar small parts cleaned with EkoEtch and ready to be primed

Getting ready to prime the rear spar parts

EkoPrime Smoke Gray left to cure for a couple of days

Next I assembled and riveted the aileron bellcrank brackets. This involves inserting a bearing into the slots at the aft end of the parts. These were easier to insert than I thought, still tight enough to stay in place but I didn't need to use the sockets as suggested in the plans.

I was able to squeeze the majority of the rivets in a random pattern switching between universal and flush sets.

Outboard aileron bracket rivet shop heads

Outboard aileron brackets assembled with a combination of flush and universal head rivets

For the AN426 4-11 rivets, however, I couldn't use the squeezer because those rivets are too long to fit within the yoke. The two choices I had here were to buck those or try to back rivet them, and I went with back riveting as I felt I could get a better result.

After setting up the back rivet plate with proper support for the bracket so that it lay completely flat, and using stubby clecos to hold the short angle in place, I back riveted a couple of the rivets. They set fairly well, however, I would prefer the shop head height to be a little taller as they were barely to spec. I think longer 4-11.5 rivets would be better suited here, so I will trim some 4-12 rivets down by 1/32" using a new rivet cutter that I have on the way, and then try setting the remainder of the rivets with those.

Back riveting the 4-11 rivets. I used some hardwood beneath the back rivet plate to raise it, and made a 1/8" support piece (covered in tape) to place beneath the aft end of the aileron bracket so that the bracket lays flat during riveting

With a new 04-501S rivet cutter I found on EBay in hand, it was easy to snip 1/32" off the length of a 4-12 rivet, and that length of rivet was a perfect replacement for the AN426 AD4-11 rivets called out in the plans. I used the same back riveting technique to quickly finish setting all the remaining rivets in the inboard aileron brackets.

Inboard aileron bracket rivets all set with the squeezer and by back riveting

Inboard aileron bracket rivet shop heads

Build Hints

• When countersinking the bottom row of holes in the reinforcement fork doublers, ensure that the correct sides are countersunk. I test fit the forks and doublers, and then marked the holes and sides that needed to be countersunk to avoid any mistakes
• A rivet cutter is very useful for trimming rivets by 1/32" where needed to ensure the length of the rivet tail prior to riveting is adequate for the material thickness

Primer used:  ~30g + 3g distilled water

Time Taken:     3.8 hours

Dates:                September 5 - September 17 2023

Wing Rear Spar Total Time:      14.3 hours

RV-10 Build Total Time:           472.6 hours

Priming Total Time:                     50.1 hours (not included in build time totals)