Actually Grob, there is a very clear counter example to your thesis and as such it disproofs it.
At low speeds (below roughtly 6 knots) the wave system around any 16-20 hull is such that wave-making drag is negligiable. In effect any energy lost in the bow wave is won back at the rear of the hull. This is the scientifically correct intepretation of the Froude law, from which the (errornous) max hull speed law is derived. So at these low speeds the drag from the hulls is almost entirely created by wetted surface drag. In effect relatively long hulls are more draggy in this speed spectrum then shorter hull, that is under the assumption of equal displacement.
So to say that an F16 is optimized at 5m is saying that it is optimized for a speed of between 20-25knots.
The F16's aren't optimized for any particular speed. They were developped with the idea of optimizing the average speeds over a wide range of (wind) speed conditions. In effect some speed in specialized conditions was traded of to improve speed under some other conditions. We know of ways to improve F16 speeds under special conditions but decided against doing that as it would have required accepting less speed in other conditions. The F16's were always intended to be good alround boats and not to be single gear race cars. This is also one of the reasons why the jib was included in the design. It allows the boat to be better over a wide range of conditions, especially races where the course is not pure upwind/downwind.
The other very important point is buoyancy distribution to enable the boat to carry the sail power. Here again longer is better.
You can't look at boat design through a set of independent rules of thumb. All these factors are interacting with eachother and so for a truly good design one must look at the interactions as well. I think the Taipans and F16's have shown that less sailpower can be faster as well. Afterall the F16 upwind sailarea is LESS then that carried on a Hobie 16, still some excellent results agains F18's, I-20's and A-cats were scored on elasped time lately.
Sometimes the interaction between these factors opens up a new pathway to higher performance, one that may well go against gutt feelings and rules of thumb.
But lets forget about the F16's, this thread is not about them. We should be focussing on a 20x10 ultimate beach cat of 105 kg. The F16's aren't 20x10.
Wouter
