Bottom Wing Skins 20-4-2 to 20-4-6, Priming

While I had time in-between getting help with riveting, I decided to tackle a small part of the bottom wing skins section, and work on the flap and aileron gap fairings. These are riveted to the top wing skin and rear spar, and can be installed as soon as the top skins are riveted on (assuming you will be going with an alternative to Van's suggested pitot tube).

Flap and aileron gap fairings, and flap gap stiffener ready to be worked on

I started by marking the flap gap stiffener for cutting into left and right parts. The were cut on the band saw, and then sanded and deburred to the correct size.

Flap gap stiffener marked for cutting

I then deburred the edges and holes of each of the fairing, and proceeded to dimple them where needed using the pneumatic squeezer.

Here is where I got a little trigger happy with the squeezer on the left aileron gap fairing, and accidentally squeezed before the dimple die pilot was in the hole. This resulted in an additional hole being punched through the fairing, and additional income for Van's Aircraft as I will be ordering a replacement fairing.

Unwanted hole in the left aileron gap fairing after accidentally squeezing the dimple dies too early

Instead of waiting for a replacement left aileron gap fairing, I decided to continue working on the remaining fairings as they are installed separately, and I can complete the replacement fairing at a later time.

I continued dimpling (more carefully) the holes in the fairings, and then dimpled the fairing attachment holes in the top skins. These are actually easier to dimple while the skins are not riveted to the wing spars/ribs, as the flap and aileron hinge brackets tend to interfere with the pneumatic squeezer, which then results in needing to flip the dimple dies around and dimple from the opposite sides in those areas.

I also countersunk the 6 holes for #30 dimples called for in the rear spar doubler. These were easy to countersink with the wing assembled, but could just as easily have been done prior to wing assembly.

Fairing and flap gap stiffeners ready for priming

Fairing attach holes dimpled in the right top wing skin

Fairing attach holes countersunk in the right rear spar doubler

Next I primed the gap fairings and flap gap stiffeners.

Priming the right flap gap fairing while the other parts dry

All fairings and stiffeners primed and left to cure for a couple of days

Once the primer had cured I riveted the flap gap stiffeners to the ends of the flap gap fairings, and then proceeded to start riveting the fairings to the right wing assembly. Most rivets were handled easily with the pneumatic squeezer, with a few exceptions

1. The rivets that attach through the fairings into the main wing ribs require the squeezer to be held upside down for riveting due to limited clearance. These are fairly easy to set, but holding the squeezer upside down can be a little awkward.
2. The AN470 4-5 rivet between the outboard most flap hinge bracket and the inboard most aileron hinge bracket needs to be bucked because there is no room to fit the pneumatic squeezer between the brackets
3. There are two locations where the AN470 manufactured head or shop head cannot be squeezed due to proximity to other parts. In those holes, I instead pulled MSP-42 rivets which is an allowed alternative to solid rivets here.

Flap gap stiffener riveted to the end of the flap gap fairing

Flap gap stiffener rivets were easily squeezed with the pneumatic squeezer

An MSP-42 blind rivet was used here where the fairing hole is right next to the rear spar doubler, and a normal rivet set would not fit over the domed head of an AN470 rivet without interference

Turning the pneumatic squeezer upside-down (due to limited clearance) to set the inboard fairing rivets. I used some tape over the rivet set against the manufactured heads to help prevent sliding while squeezing.

Another MSP-42 rivet pulled near the inboard aileron hinge bracket. This is necessary because the hole lies right next to the reinforcement bracket riveted under the rear spar

With the fairings riveted to the rear spar, I continued with setting the remaining rivets through the top skin. These were all done with the squeezer, with most of them easily set from the bottom side of the wing. For those rivets close to the hinge brackets, I had to rivet from the top side of the skin which was a little awkward, especially with the wing already placed in the cradle, but I was able to get them all set within spec.

Right wing fairings completely attached to the right wing

Right aileron gap fairing fully riveted

Right flap gap fairing fully riveted

Build Hints

• For final drilled kits, it is easier to dimple the top skin fairing attachment holes while the skins are not installed. The same can be said for countersinking the fairing attachment holes in the inboard rear spar doubler.
• Use masking tape over the squeezer sets to help prevent the set from sliding over the countersunk rivet head while squeezing
• Use MSP-42 rivets in place of AN470 rivets on the fairings where holes do not have enough clearance from adjacent parts
• It is probably easier to rivet the fairings to the wing (while having easy access to both side of the wing) prior to putting the wing in the cradle. I'll be doing this with the left wing fairings.

Primer used:              ~75g + 7g distilled water.

Primer Time Taken: 1.7 hours

Time Taken:     6.4 hours 

Dates:                May 25 - May 31 2024

Bottom Wing Skins Total Time:        6.4 hours

RV-10 Build Total Time:                704.2 hours

Priming Total Time:                     83.6 hours (not included in build time totals)