High-Speed Sailing

I am going to back-track a bit and discuss Bernard Smith. His book "The 40-Knot Sailboat" inspired much of what is being done in speed-sailing today.

The most important concept that Smith taught is that by proper positioning of the airfoil (sail) with respect to the leeway resisting hydrofoil (keel, centerboard, etc) the forces that drive the boat could be brought into alignment; properly done, this results in a craft that the wind cannot heel or flip. This is a major advance in the evolution of sailboat design, and I'm certain it will become the design standard. Smith used the analogy of a kite towing the boat in discussing this concept, and today kite-boarding is big.

A look at Smith's sailboat patents shows an interesting progression as he designs toward a 40-knot sailboat. His first patent (1963) shows a design that still needs weight to balance it. In his next (1967) he no longer needs weight for balance but his windward foils are vertical and would get overpowered in high wind situations, the craft would be stable but speed would be limited. His next patent (1972) corrects this with curved windward hydrofoils. Skipping the next two patents (hardware & design variations) we come to his 1980 patent. In this, Smith takes a huge step backwards in terms of fast sailboat design. He puts the leeway resisting (steering foils) to leeward; this eliminates roll (overturning) stability and violates what I said above to be the most important point Smith taught.

I'm not criticizing Smith for doing so; I'm just trying to convey an understanding of some key points that have to be understood if you want to achieve roll stability optimally. I suspect Smith did this in an attempt to improve low wind-speed performance.

Following Smith, we have Ned Snead, who designed a variation on Smith's 1980 patent, in which he used three slender hulls that were all steer-able. This again put leeway resistance to leeward which destabilizes the craft in high wind conditions. A version of this craft was built and sailed in a speed competition. Well they got a good breeze and managed to put on a good show with a spectacular flip. Go to the address below for more info. I would like to get a clip of the video from that run if any of you know how.

http://www.geocities.com/aerohydro/othercraftframeset.htm

I have been told that "An inclined rig is inherently unstable." (I had already proven otherwise when I first heard this.) I do not know where that statement originated or who first said it, but it's false and will cramp your thinking. The flip of Ned Snead's craft may have contributed to that idea.

Sailrocket appears to have its origins with Ned Snead, but I'll have to chat with designer Malcolm Barnsley to find out more.

Bob