September 2013 Archives

More Empennage Work

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I drilled out one of the rivets on the horizontal stabilizer and installed an adel clamp to secure the aft end of the antenna.  I also wrapped a bit of silicone wrap around the antenna where is passes over the forward spar of the horizontal stabilizer so that it can't touch.

I drilled a hole for the tail strobe wiring.  The material here is so thick that a single snap bushing won't go all the way through, so I glued a snap bushing in from each side.

I also drilled a hole in the aft deck to bring the ELT antenna wire and trim cable through.

The ELT antenna cable crosses the deck and goes through the existing hole in the forward spar of the horizontal stabilizer.

From there, it crosses back across the deck and connects to the antenna.

The trim cable is zip tied to the rear spar of the horizontal stabilizer and then follows the torque tube out to the left elevator.

It's also zip tied to the torque tube and then goes through a grommet in the left elevator spar.

I installed some d-sub pins and sockets on the cable and trim motor to make it easy to disconnect the motor if it ever needs repair.  I added some heat shrink to each side so that there will be no electrical contact between the wires.  If the elevator ever needs to be removed, it's fairly easy to fish the cable out through the hole in the spar.

By doubling the wires back on themselves and zip-tying them together, the d-sub pins can't pull out of the sockets.  This bundle can easily be tucked along side the trim motor.

Finally, I adjusted the length of the pushrod to give me 25º of down movement (up elevator) and 20º of up movement (down elevator).

Afterward, I started fitting the rudder bottom fairing.  This is going to have to move up a bit more, but it's been a long day and I'm exhausted.

I did the initial fitting of the empennage fairing tonight.  These are from Fairings Etc. and the initial fit right out of the box was quite good (much better than the fairings from Van's from what I've heard).  I first used a heat gun on the leading edge to get it to lay down more smoothly on the fuselage.

These flanges were also different in length by about 1/2", so I marked and trimmed the right one to match the left.  It's pretty tough to make this symmetrical since everything is curved, but I'm happy with how it turned out.  I then drilled out one of the rivets on each side and tapped it for a #6 screw.  I may end up installing nutplates here since I'd otherwise have to use thread locking compound to keep these from backing out.

I also drilled one hole on each side at the aft end of the horizontal stabilizer and installed a couple of #6 nutplates.  The fit around the fuselage and horizontal stabilizer is great.  I still need to do a little work to get the fit around the vertical stabilizer as nice, but I think this is going to turn out great.

I added a couple more nutplates at the aft end of the empennage fairing.

The lower one is through the fuselage side aft of the vertical stabilizer rear spar.  The screw just barely clears the spar flange and setting these rivets was a little tricky.  I double checked, and this easily clears the rudder in all positions.  The plans specify MS24693C28, but they're clearly too long for most positions.  I'll probably replace most of them with MS24693C27 or even MS24693C26.

Finally, I trimmed the aft end of the fairing so that it's flush with the vertical stabilizer and fuselage.  I may end up having to trim the vertical stabilizer and fuselage a bit for rudder clearance, so this may need to be trimmed further.

I drilled an additional hole on each side of the aft flange so that both the forward and aft ends are secure.  This hole also goes through the cover plates on each side.

I also drilled an additional hole at the forward end of the fairing.  I originally tapped the holes here through the longeron, but that will require thread locking compound to prevent these screws from backing out.  I don't like having to mess with that, so I drilled out the holes to #27 and installed nutplates here.

I used the longeron bending template to mark some additional curves on the empennage fairing.  These will bring the flanges in closer to the screw holes which will help them lay flatter.

I spent a little time with the heat gun to reshape a few spots on the fairing that weren't sitting tight against the aluminum.

The fairing now fits pretty tight all around.  There's no more than 1/32" gap  all the way around.  Here's the right side of the vertical stabilizer which was one of the worst fitting spots.

And here's the fit along the right horizontal stabilizer which was also not great.  It now fits pretty well.

To get the fit perfect, I mixed up some epoxy/flox and applied a bead under all of edges.  I'll have a little more filling to do underneath each flange after the epoxy sets up.

There were also some minor gaps along the leading edge of the fairing.  This should fit really nicely after I'm done.

Sanded Empennage Fairing

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I spent about an hour sanding the empennage fairing and cleaning up the filler I put under all of the edges a couple of days ago.  I need to add a little more filler underneath and some final trimming, and then It'll be ready for paint.

Installed Data Plate

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I drilled the data plate to the fuselage.

I also drilled the rudder cable fairings to the fuselage.  Dimpling and riveting the lower rivets is going to be a little tricky because of the J-channel just below it.

I shot a bit of primer on the fuselage and riveted on the data plate.

I drilled some holes through both pieces of the lower hinge bracket so that I could mount the rudder stop between them.  I fabricated a little drilling template that let me get the holes in the right spot since the stop slides farther back when between the brackets than it does when above or below them.

There's just enough room to use an AN960-10 washer above and below the stop to center the stop between the brackets.  This should evenly transfer any load into the brackets, spar and aft bulkheads.

I removed the vertical stabilizer because I just couldn't get my arms in comfortably to work on the rudder cable fairings.

I used the pop-rivet dimple dies to dimply the fuselage and then clecoed the fairings on.  I've pulled the tubing out of the way for now to make it possible to buck the rivets.

I also countersunk these two holes that are normally used to hold on the external rudder stop.  It's too late to rivet these on now, so I'll do it tomorrow.

I didn't like how the middle of the ELT antenna could flop around, do I adhered a zip-tie base to the forward spar of the horizontal stabilizer and anchored the antenna there.

With the vertical stabilizer out of the way, it was easy to rivet on the rudder cable fairings.  After installing the lower rivets, I slid the plastic tube back in place and then installed the upper rivets.

The upper fairing on the rudder was about 1/4" too short and didn't go all the way back to the trailing edge.  I mixed up some epoxy/flox and extended the fairing.

The control surfaces will have to come off for paint (and will likely have to come off at other times), so I decided to add a connector to the trim cable so that I don't have to fish the cable back out of the elevator each time.

Worked on Rudder

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I drilled the rudder bottom fairing to the rudder and then riveted it on with some epoxy/flox.

I'm going to need to trim the forward end of the fairing to clear the tail wheel spring, but I left it long so that the bottom edge will roughly align with the bottom of the fuselage.  This should look better than shortening the whole fairing and making it not align with the bottom of the fuselage.

I laid in some fiberglass to fill in the gap around the control horn.  I scarfed the fairing along the line on the left side and laid in four layers of 9oz glass.  I also drilled a hole in the upper right that I'll drill out and install another CS4-4 rivet through the fiberglass to prevent it from separating from the aluminum flange underneath.

Finally, I filed and sanded the fairing flush with the metal and laid a strip of 1.5oz cloth over the joint and glassed it in place.  I only did this on one side; I'll have to do the other side tomorrow.

I also did the same thing at the top of the rudder.  I'll fair these in with some filler so that you can't see the joint between the rudder and the fairings.

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