Big thanks to NickVanBruggin and Neira for the great dimensions. I took a little liberty in the fins, as I like my twins to have a lot of base… Look closely at the stringers and you can see where I made a continuity boo-boo. In laying up my deck skin, I forgot that on the bottom the quarter-inch “stringer” went in the center, and the 3/8" ones to the outside. Got them reversed on the deck. Oh well, this one is for me to ride anyway.
Did the fins out of 3/8" birch ply (actually three layers of 1/8"), for that nice thick foil, then finished them off with two layers of 4 oz to either side and a bead of glass rope on the leading/trailing edges. It was my first set of glassons (only my 3rd and 4th hand-foiled fins) so I went overkill on glassing them on, with four layers of glass covering the entire inside surface. Also, since they were so thick as the bases, I ground the cant into the bases, so they would sit “flat” when I was tacking them down. Didn’t actually measure cant, but I’m going to guess 5-7 degrees. I’m still not a big fan of making fins, though.
For the stringers, I used my $90 Lowes tablesaw to mill down a rough-cut 2"x6"x8’ cedar board into strips. Spent about 30 min at Lowes going through all the wood to find that one clear, straight-grained, red-colored board, then about two hours sweating over the tablesaw, annoying the neighbors and ruining my hearing. Since the “stringers” were a bit rough after my “milling”, I cut them to about 3/16" thickness, and then just used a handplane to bring them flush and smooth to the balsa after vaccuing. Tip:when cutting a 3/16 strip from a 2"x1/4" board, if you cut about six inches into one end, then turn it around to make your long cut from the other end, it keeps the tablesaw from chewing up (as bad) the last foot of that delicate 3/16x1/4x8ft stick. And those cedar fenceboards don’t work worth a damn. They looked like corkscrews after I cut from them, big lumber is the way to go.
The hotcoat isn’t sanded yet, hence the drips on the fins, but it looked so good I had to share right away.
MR-style twinnie, 6’3" 20 3/4 x 2 3/4
Flat rocker, just a hair of vee out the tail. BIG (7.25"x6.25") twins, no trailer.
Thanks again to all for all the help and inspiration!