I made two layups for the heat duct and seat back brace parts. This was pretty easy - cut the foam to shape then put the parts next to one another on the table while you do the layup. Due to the timing for these parts, I was able to knife trim them. If you don't knife trim, start. Saves tons of time and actually makes your next steps easier. I leave what little rough edges I get from the knife trim on until the part gets assembled. You can then sand it to exactly the size needed.

There's a ton of discussion in the archives about the fuel valve mount. Made of 2024 T3 aluminum, most people make about three of them after getting cracks in the bends of the first two. One builder said he'd made one out of fiberglass - what a great idea! This is a non-structural, not a flight control, not an airfoil surface so I thought it'd be okay to make the materials change. I started with a piece of 2x4, cut it to size, rounded the corners and covered it with packing tape for easy release of the fiberglass. Then, I made a 6 layer BID layup inside two layers of waxed paper (like tapes are made), trimmed it oversize, then removed the waxed paper and squeegeed it onto the form/jig. I then let this cure.

After the fiberglass "blank" was cured, I used double-sided tape to stick on a paper copy of its dimensions/shape/holes from the plans. This was then cut and sanded and drilled to final dimensions. The jig I made came in very handy for drilling the holes that were needed as well - the wood served as backup to prevent too much fraying as the holes were drilled and the jig, since it was square and true, held the part nicely for drilling vertical holes.

Here's the final part. The rivets even went in nice since they're brass. Given I've just spent 300 or so hours making fiberglass parts (and not working aluminum) this thing turned out pretty nice! I'm actually a little more comfortable that it will "stick" when floxed into the seatback brace as compared to the aluminum. No cracked aluminum either!

After scribing a line on the seatback foam where the plywood inserts go, I used a chisel to chisel off the foam from the fiberglass.

Here's the front seatback brace, plywood doubler in place, floxed and ready for assembly.

Here's the seatback brace, map pockets spaces and etc. floxed in, with the fuel valve mount I made floxed in. I am not sure why the plans say to flox the mount in place with the valve mounted to it - they even have you put saran wrap on the valve to keep the flox off. Why not just leave the valve off? I have done (as of the writing of this) all the downstream steps to install the seatback brace in the fuselage and still don't see why this is necessary.

I assembled my heat duct parts together on a jig of sorts I built. Kept it square and straight. Used a lot of clamps, too!

Don't do your heat duct this way. When I did the fiberglass layups, the sides of the heat duct moved together in between where I had the little wood pieces. I'll be able to heat the distortion back out again, but, if I did this again I'd have used a piece of wood full length and avoided that problem.

Here's the heat duct, after carving out the slot for the seatbelt tube and fuel line and applying the UNI layup that reinforces the seat belt tube. I used a lot of strips of peel ply, taped down to help keep them in place, to keep the UNI held down in front of and in back of the seat belt tube.

Here's a shot of the front seatback brace and heat duct after being assembled with BID tape. A few weights, clamps, some peel ply, a square, a level being used to hold the brace against the square... wow it took a lot to get this all held together properly!

I worked really hard to get the brace and heat duct installed square and true into the fuselage. This shot shows the front end of the heat duct, a couple of plywood pieces being used to ensure the heat duct is flush with the bottom of the IP.