Now that everything in the tailcone is primed and the tailspring mount is painted, I clecoed the tailcone together.

The tailspring mount fits between F-711 and F-712.  I shot and bucked the keeper rivets the hold the mount to F-712 (you can see them on the right side of the mount here.  These just keep the mount from shifting until the bolts that tie this and the vertical stabilizer spar together are installed.

I flipped the tailcone upside down to make it more stable for riveting and shimmed it until there was no twist.

It was too late to run the rivet gun, but I squeezed all of the rivets in F-712 and all I could reach on F-711.

I didn’t have a lot of time tonight, but I primed the stringers that I forgot to prime last night.

I also put a couple of coats of gloss black paint on the tailwheel spring mount to give it a little extra protection beyond the primer.

I received my Grove Aircraft master cylinders in the mail today.  I decided to upgrade from the stock Matco master cylinders because people have had issues with them sticking.  It appears that the issue can be addressed with external springs, but I don’t really like the way those look.  Also, I heard such good things about the Grove cylinders that they seemed like the better choice.  These have internal springs, so there should be no issue with them not extending fully when brake pressure is released.

Before reassembling the tailcone, I took care of one additional task that would be tough if I waited until later.  I drilled the holes next to the rudder cable exit holes out to #19 and dimpled for a #8 screw.  This will be used to attach an adel clamp to hold the rudder cable guide.

I primed all of the bulkhead and stringer seams since these got somewhat scratched up during the drilling.

I also primed the rest of the components for the tailcone.

Since these are the lowest seams in the fuselage, I wanted to prime the overlap areas in case any water gets trapped there.  I also primed the entire inside of the tail skin.

The top angle can now be riveted to the F-710 bulkhead.

And F-712 can be riveted to the tail skin.  These rivets were a little tricky to set, and I ended up drilling out two of them and replacing them.  Since these flanges have an acute angle to the web, using the 4″ no-hole yoke with its thin nose made these easier.

Here are the rivets on the other side of F-712 (remember that it is a double bulkhead).  The only ones that couldn’t be squeezed were the two lowest ones just next to the mouse hole.  It’s too late to fire up the rivet gun tonight, so this will have to wait.  I’m not ready to rivet the tail spring mount in place yet anyway since I want to give it a top coat of paint and the primer needs to dry for 24 hours.

I went ahead and riveted the autopilot pitch servo mounting bracket to the rib using some AN470AD4-5 rivets.  Apparently, I had forgotten to dimple the holes in the bottom of this rib, so I did that now as well.

Finally, I got started clecoing the tailcone together.  It was at this point that I noticed that I forgot to prime the stringers, so I had to stop for the night.  I’ll do those tomorrow and then the tailcone can be fully clecoed together and riveting can begin.

When I drilled my tailwheel spring mount, somehow one of the holes came out lower than it should (this picture is upside down, so the right hole looks too high).  Van’s confirmed the reduced edge distance wasn’t an issue, but I wanted to make sure the misplaced hole wasn’t causing the mount to be cocked to one side.  I clecoed the two rear bulkheads back to the tail skin with the mount between them and took a bunch of measurements.

Despite my best effort at positioning the mount, the tailwheel was cocked to one side about 2º.  I don’t know if that is significant enough that it would affect the handling, but it would be virtually impossible to change later, and it would bug me knowing that it’s not correct, so I ordered a new one from Van’s.  It came in today, so I wanted to get it drilled to the fuselage tonight.

Unfortunately, the new mount didn’t have the hole drilled in it that attaches the mount to the spring (the one under the drill bit).  I needed to figure out how to drill a hole in the mount that would somehow line up with the hole in the spring inside.  What I ended up doing was positioning my v-block so that the hole would be the right distance from the right end when the flange was butted up against the v-block.  I then took a reading with my digital level of the angle of the flange top edge when the drill bit was pushed all the way through the old mount.  I then positioned the new mount so the flange top edge was at the same angle and clamped it down.  I drilled through the top wall of the tube and then put the spring in place and lined up the holes.  I then used that as a guide to drill the bottom wall of the tube.  This resulted in perfect alignment of the holes.

I then used some scrap 1/8″ angle to make sure the tailwheel fork tube was exactly perpendicular to the tail skin.  This picture shows how the angle is clamped to the tailwheel fork tube and rests on the tail skin.

And here you can see that this is perfectly perpendicular.  I clamped the angle to both sides of the tailwheel fork tube to make sure the measurements agreed.

This shows that the tailspring bolt is perfectly centered in the hole in the tail skin (with the old mount, the bolt was cocked noticeably to one side).  After everything was clamped in place, I drilled the mount to the F-711 and F-712 bulkheads.  I double checked that the tailwheel fork tube was straight, and it was perfect (easily within 0.1º of vertical); I feel much better now.

I did a little further trimming on the mousehole so that the tail skin also cleared the welds on either side of the tail spring mount.  I haven’t decided if I’m going to paint the mount or have it powder coated yet.  I’m going to call around tomorrow and see how much it would cost to have it powder coated.

With my buddy Andre’s help, I finished prepping all of the tailcone components for priming.  It’s a bit late tonight to start the priming, but it should be fairly easy to knock it out in the next day or two.  Here is the bottom skin and all of the bulkheads behind it.

And here are the side skins.  The skins got a little scratched up inserting and removing the stringers, so I scuffed up the rivet lines and will prime those.

No pictures again tonight since it’s still just a pile of parts, but I made a good dent in deburring and dimpling the parts.  Tomorrow will be a long build day, so I’m hoping to finish these up and start riveting the tailcone together.

I had a couple of tasks to take care of before disassembling the aft fuselage.  First up is to mount the autopilot pitch servo mounting bracket.  The forward edge of this has to be 3.43″ from the center of the 1/4″ pivot hole for the elevator bellcrank.  This required drilling out three rivets so the mounting plate could sit flush.  If you’re installing a dynon autopilot, just leave these rivets out from the beginning and save yourself the time.

Here’s how the bracket sits against the rib.  The flange on the bottom can be cut off or drilled to the skin (which I’m doing).

After match drilling the bracket to the rib, I laid out for rivet holes aligned with the ones in the rib (as if aesthetics matter on the bottom of the aircraft).

After clecoing the structure back to the bottom skin (and using a clamp to keep the bracket tight against the rib), I match drilled the skin to the bracket.

The F-710 bulkhead needs a piece of 1/8″x1″x1″ angle fabricated to sit at the top edge.  The ends have to be tapered and shaped to nest into the longerons.

The F-711 bulkhead also needs a piece of 1/8″x3/4″x3/4″ angle, also with tapered and shaped ends.  This won’t get riveted on until the side skins are riveted to the longerons.

Here you can see why.  The longerons rivet to this flange on the bulkhead which is covered by the angle I just fabricated.  In fact, I had to notch the ends of the angle here to clear the future shop head for this rivet.

The tailcone is now fully disassembled so I can begin deburring, dimpling, and priming.

The bracket is 0.048″ thick, so it can’t be dimpled.  Instead, I machine countersunk the holes here to receive the skin dimples.

I started deburring parts, but ran out of steam.  I’d like to finish this up this weekend so I can get the tailcone riveted together before the holidays.

No pictures tonight as it would look just like last night.  I drilled all of the holes in the tailcone that needed to be drilled right now.  This included the stringers and bulkheads (except for the frontmost one (F-706) and the top row of holes where the longerons are attached.  Drilling the bottom was a pain because I had to lie on a creeper and was absolutely covered with aluminum shavings by the time I was done (wear a full face mask if you want to keep them out of your eyes).

Jenn helped me raise the tail so that the plumb bobs would be more accurate and then I reshimmed the tailcone so that there was no twist.  I then drilled every fourth hole down the stringers (the horizontal rows of clecos in this picture).  The tailcone is pretty stiff now though it can still be flexed a little bit until the aft top deck is riveted on.