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We had to buy the minimum carbon fiber which was 5 yards. I put one layer on each side of the seat and back. The edges are done by gouging out a groove of foam next to the top and bottom, filling the groove with flox and covering the edges with 1 layer of carbon. To save material and to align the cloth with the stress, I laid it on the weave, not on the bias.
I think I used about half of it. As you can see, I used ribs cut out of the KR skin plywood. Ie got some 2" pink foam and using one of the ribs, layed out the shape of as many sections of foam as I needed. I then cut the foam, over sized, and sandwiched the pieces between the ribs, attaching it with hot glue. On each piece of foam, you must have a flat bottom that will allign with the flat bottom of the ribs, for alignment. It will take two of you to put it together.
If you plan ahead for your rib placement, it will help for cutouts around stick and seat belt attachment clearance. On the pilot seat, the second I made, I have no support between the spars. Each end of the seat laps over the spar. That seat also has the tunnel for the elevator push tube protection.
The seat back is made of 1/4 Last-o-Foam and attached only at the shelf with Velcro. To aid with radio reception, you can probably get away with making the seat back out of regular glass if that little bit of extra weight won't be a problem for you.
I can stand in the middle of either seat and it gives no indication of wanting to break down.
For a full size view, click on the pic.