High-Speed Sailing

On thinking a bit more about Bernard Smith's sailloon, I realized that if we pumped it up with a little extra helium, achieving zero weight, we could easily beat the parachute/water-skier I mentioned in my post of 1 May 08. In this case we would be imbedded in a mass of air moving at 70 knots, feeling not the slightest breeze (ignoring turbulence) and would beat the skier by 20 knots. (But that doesn't fit my definition of sailing.)

I was looking at the Wing-Borne Hydrofoil a bit more and noticed that it is described as being "self-righting". If you look at the image, you will notice a torpedo shaped appendage under water, I suspect this is ballast that provides for the self-righting properties.

At this point in my discussion on weight, I will define some terms to ensure we're all in agreement on those terms. Ballast: which my dictionaries define as heavy material placed in the hold of a ship to enhance stability -- thought to derive from Old Danish "barlast" (bare load - cargo carried only for its weight). Payload: which is described as the cargo you are getting paid to transport. Of course, in recreational sailing, we're not getting paid money to sail, but we are getting paid in fun (vastly more valuable than any amount of money). So our payload is our self, friend, picnic lunch, etc.

The overall weight of our craft can be seen to come from three sources; the materials the craft is made of, our payload, and (if needed) ballast. Since we have already seen that weight sets our craft lower in the water, slowing it, it is to our advantage to get rid of any weight we don't need if we want to go faster. It is true that in many designs ballast is needed and helps that design to go faster, but that is a dead-end which ultimately limits speed.

Our options for trimming the weight are to optimize those three sources of weight. By using the best in modern materials and structural engineering, we can trim the weight of the craft. By reducing the number of crew needed, we can trim our payload weight (this may only be a benefit if we want to run a small, less expensive craft - note Hydroptere's success with a large, fully crewed craft). But by redesigning the craft so we can eliminate all ballast, we have the potential for the most gain.

The real key however, is not light weight, it is stability. It is essential that we have the stability needed to sail in the conditions we wish to sail in and if we want to go really fast, we will find ourselves sailing in some fairly strong winds.

From what I have been able to learn, the following is how weight is being used by the various contenders. Note that I have not verified this and if any of you know more, please correct/update me. I should point out that using the crew for any needed balance is an efficient use of the payload.

-Hydroptere puts most of the crew on the windward arm to help improve their stability. I thought I had read that they have water ballast tanks but do not see mention of this on their web site. Anyone know about this?
-Macquarie Innovation uses the crew in a long lever arm to balance the craft.
-Wotrocket also places the crew in a long lever arm to balance the craft.
-Wiebel uses the crew for balance.
-Windsurfers and Kite-boarders use their body weight for balance and I understand they have also been wearing weight-belts for ballast. The next significant advance for them would be to tie a paravane to their backside, eliminate any ballast and join the following projects.
The projects below do not use weight for stability (neither ballast nor payload).
-Le Projet Dared
-Paravane
-Trifoiler
-Sailrocket
-Windjet (water-craft version)
-Sailien

Bob