So when the boat is up on the foils, it doesn't go upwind very well? I was wondering about how well it could point if most of the boat is out of the water, and most of the boards/rudders too. Not much left in the water to keep it from side-slipping. Now that leads to the next issue, if a foiling cat were to be developed, would it need a new type of race course? Instead of upwind, downwind, maybe reach back and forth over a longer course?
I'm sure Dave can correct me if I'm wrong, but the difficulty with foiling up wind is an available power issue. As the boat gets faster, the apparent wind comes more forward. As the apparent wind comes forward, less power is available. Except in the case of the uber-efficient moth (with very low windage and extreme lightness) most cats and tri's are going to exhibit a pretty high aero drag profile and find it difficult to take full advantage of foils completely around the race course.
