Tail Cone 10-7-1 to 10-7-7

Now it was time to begin initial assembly of the tailcone. I started by raising my adjustable saw horses to their maximum height of 39", and I then pulled out the bottom skin, removed the blue plastic from the inside, and laid it upside-down over the saw horses. 

After clecoing the bulkheads in place as directed, I slid the -F stiffeners through the notches and in-between the F-1008 bulkhead tabs and the bottom skin. They fit perfectly! I also clamped one of the longerons along the top (bottom) skin surface to minimize any sagging for the upcoming match drilling.

Tail cone assembly started!

Next I aligned both F stiffeners so that the marks lined up with the forward holes and proceeded to match drill #40 the skin holes into the stiffeners. To keep the stiffeners lines up correctly, I first drilled every 5th hole, then each hole in the middle of those, and finally the remaining holes from the forward end of the tail cone to the aft. I clecoed each hole as it was drilled, and adjusted the stiffeners slightly as I went to ensure that the marked rivet center line remained aligned with the center of the holes.

Stiffener lined up with the first hole for drilling

After match drilling both F stiffeners I repeated the procedure with the G stiffener down the middle of the bottom skin.

F and G stiffeners match drilled to the bottom skin

Next I clecoed the bell crank ribs in place and reamed #30 the 6 holes common to those and the F-1007 bulkhead.

Bell crank ribs clecoed in place and final drilled.

The whole assembly was then taken apart for deburring of all edges and holes drilled so far. Once that was done the parts were reassembled ready for the next steps.

I placed 1 each of the -C, -D and -E J-channels on the right side of the tailcone (placing the narrower  part of the -C J-channel I had questioned earlier towards the back of the tailcone)

Right side J-channels inserted into the bulkheads

I then removed the blue vinyl from the inside of the right skin and clecoed it to the bottom skin. As I was clecoing the right skin to the bulkheads I noticed a fair bit of pressure in the area where the bulkhead tabs pushed against the curve of the skin. Worried that this would cause outward dimples in the skin as I placed clecoes, I decided to once again disassemble the whole structure so that I could facet the bulkhead tabs further to reduce this pressure. I faceted the tabs around the curves of all 3 bulkheads using the bench grinder wheels, being careful not to remove too much material.

Bulkhead tabs faceted around the curves to prevent dimples in the skin

I then reassembled the tailcone, and this time after attaching the right skin to the bulkheads, the tabs sat well against the skin and the clecoes went in much more easily. I will still need to push those tabs firmly against the skin when I rivet, but faceting definitely helps. 

Next I proceeded to match drill the holes in the skin to the stiffeners in the same way I did on the bottom skin. The first round of holes (every 5th hole) took the longest as I had to make small adjustments to keep the rivet center line in view as I drilled. This was made slightly easier by using small magnets on each side to help clamp the stiffener against the skin near where I was drilling.

Tail cone reassembled with faceted bulkhead tabs and J-channels in place

Initial match drilling into the right side J-channels complete

With the initial holes match drilled, I was then able to "quickly" drill the remaining 183 holes.

All holes match drilled into right side J-channel stiffeners

Once match drilling on this skin was complete, I removed the right skin and stiffeners so that I could debur the edges and drilled holes before moving on.

Build Hints

• Make sure that tabs around curved parts are faceted as described in the Van's General instructions. Even somewhat gentle curves can cause the edges of the tabs to dig in to the skin when clecoed if the tabs are not faceted enough.

Time Taken:     15.1 hours

Dates:                February 5 - February 7, February 11 - February 15 2023

Tail Cone Total Time:           38.4 hours

RV-10 Build Total Time:      294.4 hours

Priming Total Time:                     26.4 hours (not included in build time totals)