I’ve been spending lots of time recently researching shapes to use for rudders and leeboards. While I never used to think this was a big deal, I found out differently when testing the first boat I made. I had two excellent Sabot sailors out testing with the new boat and a Brian Thomas (Corsair). The results showed a bit of an advantage to the BT upwind. “Ugh!”, I thought, “what did I do wrong?” Then I said, “Let’s swap leeboards.” Well, that made all the difference. Suddenly my new boat was beating the BT upwind.
I realize you can spend lots of money on new blades, and to be honest, some are really a work of art. It would take me a long time to get to produce the same quality of finished product as some of these (See Gresham Boards), but I decided to experiment on shape. I phoned a couple of marine architects who have spent plenty of time sailing and thinking about the Sabot and they agreed that a “4 digit NACA” design would be my best bet. You can google this and find lots of background if you’d like to read more but basically it is a symmetrical aerodynamic shape (verses what you’d see on a wing where the top has more curve than the bottom to induce lift – not good for a boat that tacks!) So, I built some templates and have been having good success re-shaping wood boards; they don’t look as pretty as the “pro” versions but they do cost me less.
Next time you get out tuning your Sabot, try swapping leeboards / rudders with your buddy and see if it helps (or hurts) your performance.