I think one of the first poster said it best :

Windsurf record rely on gale force winds for their records. (1 to smaller then 1 times the windspeed)

Yellow Page achieved its record by doing 3 times the windspeed.


First is brute force with huge refinements in control.

Second is elegant with huge refinements in efficiency.

Both records are equally important and interesting. Especially interesting is to see how close both approaches are in their final result.

Wouter

It finally came to me. I think the name of the Roque 16-footer(or maybe 18?) that raced at Sailfest was Planecat.
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By the way, another planing cat that Randy sailed in the Worrell 1000 was a Holder design. Didn't sail it very long, though, because the mast broke right after the start of the first leg. He replaced the mast with a Supercat tall-rig mast, and then the beam broke right after he started off again. That was a beautiful boat, and I am wondering if that is the one that somebody said is still sailing in the Miami area.

The Roque boat that Randy sailed in one of the Worrells looked like it was upside down on the beach and as though somebody had mounted the mast on the bottom instead of the top. As I recall, he won the race with that boat, but it was not a comfortable ride. Also -- and, again, this is distant recall, because it was more than 15 years ago -- I think that boat capsized on the first or second leg of the race and he and crew were not able to right it until they finally drifted almost to shore and were in shallow enough water to stand up.

The reason those planing-hull boats were designed for the Worrell 1000 is because it had traditionally been primarily a downwind race, which would be more favorable to a planing hull.

I wish more attempts would be made to develop a catamaran that planes. I think one of the problems has been the difficulty of making such a boat both light enough and strong enough with a flatter profile. (That probably explains Roque's upside-down-boat design.)

I have always had this weird theory that a Shark catamaran could plane if the boat could be made light enough. But same problem -- fat hulls need more interior reinforcement and probably stronger crossbeams, all of which adds too much weight.

In the ideal world, if you had two cats of identical size, with identical sail area and identical weight, which would be faster, the displacement cat or the planing cat? It is a question that has nagged me for many years.

On a Windsurfer the canting rig is a major factor in performance, but not because it lifts the board out of the water. If you look at the pictures of the boards sailing the speed course the rig is nearly vertical.

The canting rig allows the force vectors of the sail and the fin to be aligned in the horizontal plane. Since the vectors are aligned there is no yawing moment and only one wing (a fin) is required in the water. That fin can operate at the minimum lift coefficient to balance the force in the sail. Since the fin is operating at the minimum lift coefficient its induced drag is minimized. More importantly, the additional wetted surface of a second wing is eliminated.

Reduced wetted surface is the real key to the windsurfer’s remarkable speed. As speed increases the induced drag on the planing surface becomes nearly constant since it is a function of the weight it must support. The induced drag of the fin becomes nearly constant (slowly decreases) since the required lift depends on the available righting moment. It is the reduction of wetted surface area that allows the board to keep accelerating. The viscous drag, which increases at nearly the square of the speed through the water, actually begins to drop above a certain speed as the wetted surface is reduced.

The design of a windsurfer allows the center of gravity to be kept behind the center of lift of the planing surface as the rider moves back on the board. This allows the board to maintain pitch stability with a very small wetted length. The smooth water surface allows the boards to maintain their most efficient trim angle (typically 3-4 degrees) for minimum planing induced drag while still keeping more of the bottom of the board clear of the chop (less wetted surface than in rough water).

Most of the other technology that goes into the speed boards revolves around maintaining control. The rigs have very effective gust response just like the production sailboard rigs but are set up stiffer. For added stability of the rig center of effort the booms are stiffened with a compression member on the upwind side. The rails are more parallel and the tail rocker is flat to reduce foot steering sensitivity. The nose is very short to minimize wind induced pitching moment that makes the nose “blow up” in high wind. Not many people can sail a board at 50 miles per hour, and if these folks lose control they might break more than equipment.

Windsurfers are fast in real world conditions as well as on a speed course. Competent sailors can reach at over 30 knots on open water. Formula windsurfers can approach twice the true wind speed.



A am not sure that windsurfers are the brute force approach to raising the speed record and Yellow Pages is elegant efficiency. Look at the available righting moment of Yellow Pages compared to that of the windsurfers. I would say the opposite is the case. The triscaphs exemplify BRUTE force. Her successor is even more extreme (and pretty): http://www.macquarie.com.au/speedsailing/gallery.htm

I would never trade my cat for a sailboard. I would never trade my sailboards for a cat either. That is like Sophie’s Choice.

-colin

http://www.windjet.co.uk/water/competitors.php

Yea, but who would want to go to france anyhow?

Good discussion though

I was surprised nobody mentioned the wind-jet (not to be confused with windjet) - a French production planing catamaran: http://wind-jet.com/uk/technologie.html

I think the 16 foot planing catamaran folks keep mentioning was called a Hardcore 16.

To plane efficiently a catamaran's hulls must have a lower load coefficient than displacement hulled cats have. Since load coefficient is proportional to 1/beam^3 it pays to make the hulls wider. Narrow hulls have higher induced drag when planing.

-colin

That's it!! Hardcore!

Hi, regarding the wind-jet: Having watched the videos on the website, it doesn't seem to be travelling that fast considering it's planing. In fact, I'm pretty sure I could take it on a broad reach . Does anyone have any experience racing one of these things downwind? Maybe with a wider beam and more sail and an asymmetric chute . . .
Al

oops, meant to change my associated picture rather than post an attachment.