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I haven’t been very good about updating the build log lately, but I HAVE been making a lot of progress:

  1. The spar is installed, and all reinforcing layups on and around it are complete.
  2. The upper firewall is installed, and the engine mount hard point reinforcements are complete.
  3. The turtleback is installed, and most of its reinforcements are in place.
  4. The canopy is in progress. It’s in place and trimmed, and the first UNI layup around its bottom lip is installed.

Progress may start to slow down now. The shop is definitely getting very cold, and it’s getting really hard to do work. Hopefully another propane heater will help – we have one right now, but it’s just barely keeping up.

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Here you can see two reinforcements around the spar installation.

Longeron Inside

And the installation of the upper firewall. I got the tapes a little slanted. Oh well. You can also see a gap above the firewall top the turtleback – this is where I raised the turtleback. I need to fill in here.

Firewall

The fill-in turned out OK. I glassed over it after the flox cured. This was done before installing the top BID wrap over the top edge of the turtleback, so it’s all sealed under there (inside and out).

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Mounting the turtleback went fine. My new height and width made it a little awkward to do the fittings in some spots, but for the most part it turned out alright. The foam shaping is a little smaller than plans call for, and I don’t have as much overhang, but in the end the inside edges lined up exactly on top of the longerons, which means more shoulder room for the rear seat.

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Here you can see the wings mounted on the spar, and the rough-fit of the turtleback and canopy. My turtleback is 1.5″ taller than usual, so fitting the canopy is a bit odd, but it does give a lot more headroom.

Wings

Turtleback

Canopy

Like many builders, I made my turtleback 1.5″ taller to provide more room and a better fit to a slightly larger canopy. This caused me some grief, though. There wasn’t time to do the layup after installing the foam, so I left it overnight. Well, apparently the humidity and cool evening weakened the 5-min epoxy hold where I had to lengthen each piece. The joints were at the ends, where the curve is the sharpest, and they just snapped overnight. I spent all evening Thursday repairing them, and here’s hoping it will hold, because I can’t get back in there until next week!

A few things would have prevented this, and I strongly encourage other builders raising their turtlebacks to do one or more of the following:

  1. Install more slats. The plans number of support slats is just barely acceptable , and when you raise the height, it puts you over the top. I recommend at least 2 additional slats per side, more closely packed the farther you go up the curve. They’re VERY fast to install, especially if you cut their slots when you cut the rest, and could save you a lot of heartache.
  2. Make sure the flashing that supports the edges of the foam pieces is firmly attached at every spot, and especially at the top, where if you simply tape it, the tape may peel off the duct tape lining. I had used a roll of aluminum foil tape that John had lying around, and it was great at first because it was so thin, and held its position. The problem was that it didn’t stick very well, so it gave way at the top and was part of what allowed the foam pieces to buckle.
  3. Don’t do the joints at the ends. You want them even, on both sides, so you don’t get a noticeable line on one side but not the other, but that doesn’t mean they have to be at the lip. Instead, cut each foam strip in half in its middle and add the extension piece there. There’s not much flex in that section, so you don’t have stress on the j0int, and if you’re careful to use very little glue, you won’t get a joint line (it’s easily sanded, anyway).
  4. Use twice as many foam strips. This is probably annoying, but if you used 3″ strips instead of 6″ strips, they would be easier to shape for a good fit and install. You’d also need more flashing, of course, but by the time you were done you’d probably be ahead of the game.

Well, the foam is installed in the turtleback jig. It took quite some doing, but it’s good to have that out of the way. More and more I find myself getting frustrated with some of the build techniques. It’s when you see things like the masking tape to cover the remaining gaps, and you realize that you aren’t the only one who, at some point, has said “screw it, good enough.” Yup, the designer did, too.