Now for the sanding. :shock:
First, the taper is sanded into the fin, using the spars as a how-much-more guide and measuring every few strokes to verify. If you end up slightly thinner on one side than the other on the front and back ends of the fin, it's okay you only need the center to be correct, since the sides will be sanded down into tapers anyways. I used 220 grit.
Once the tapers are sanded to satisfaction, masking tape is laid with one edge along the plywood spar as a sanding mask. The uncovered side is then sanded into a bevel reaching the center ply of the plywood, or more or less depending on preferance. (once again with 220 grit)
There was an issue that arose while sanding, however, and it was that the fin became thin enough that it flexed (this was accentuated by the lack of plywood in that area, the tab should probably be further back in similarly shaped fins) and too much balsa was taken off, which created a concave shape instead of a flat one. Our troubleshooting team is working on the issue and will be back later with a solution. Fortunately, despite the poor sanding, the fin slot slot was still intact.
Anyways, after the bevels are sanded, the masking tape is removed and another piece is applied to the other side and the process repeats. Chances are that if you're anything like me, the sanding is lopsided and you're not satisfied. So next, the fin is shaped further until satisfaction.
The edges get squared up if needed and the fin can be sealed, filled, and finished to preferance. After that, the tab gets glued into its slot.
That's all, folks!
Well, for the bulk of this post anyways. More pictures and stuff later.