Hi Luiz,
It`s an interesting thread, those who are bored don`t read ..
I think the proas have a limitation in that they are super-efficient in under 20knots or thereabouts, at which point the loads on them become too high and they explode. YP, Macquarie etc suffer the same fate - 2 great days of almost-record breaking speeds, and then oops, back to the factory for 2 years to raise the millions to re-build the broken butterfly. The forces on the rig and hulls etc, from what I understand are similar to traditional sailing craft in that the load from the rig are transferred to the hulls in the form of heeling moment and in order to combat this the leeward hull must get further away from the rig as the wind gets stronger, the main beams etc must be reinforced exponentially to cope which adds weight, which adds to the forces. I`m no engineer, but I understand that the forces acting on a trimaran rig and platform are MUCH higher than on a keelboat - all the forces are the same except that a keelboat will absorb the additional force caused by a gust by simply heeling over more before it accelerates into the new windstrength, whereas the tri will have nowhere to heel when the leeward ama is fully depressed into the water and the main hull starts to lift - the forces are way higher, and to compound this the drag is at maximum.
This is why the windsurfer design is far more speed-friendly, it may be less efficient at lower windspeeds although debatable : http://www.fanatic.com/cgi-bin/news/news.cgi?id=1130756729&sprache=e&navi_sprache=e
(Doing 29.7knots in 12-14knots cannot be called inefficient).
The fact that as windspeed increases the rig is used to support the sailor`s weight and causes LESS drag on the hull with no heeling moment due to the flexible mast base means that the board stays flat, the main challenge is keeping it from becoming airborne and maintaining good contact between skeg and waterflow, a spin-out at that speed will most likely end up in a few bruises at least.
Yes the windsurfers are using really high windspeeds to get their records but as can be seen from the link I gave this will start to change, although efficiency will always drop exponentially as the conditions get stronger whichever craft you use. If you use the efficiency ratio of the windsurfer in the link posted above, you would expect the windsurfers to break 50knots in 24,07knots of wind, we know this to be impossible or they would have run at 100knots in 50knot winds.
If the proa`s and other strange craft want to be the first to 50 they will have to either increase their efficiency in light winds (sub-20knots) or increase their maximum wind-range while maintaining their efficiency ratio.
Good luck to all who make the effort. I remember it wasn`t too long ago when the critics said the boards would NEVER break 40knots, and a while before that they would NEVER break Crossbow`s record (36knots).