High-Speed Sailing

Vessel Name: Sailien
Vessel Make/Model: Experimental/custom
Recent Blog Posts
28 September 2013

The America’s Cup

I watched, with interest, the videos of the 34th America’s Cup. At last we have fast sailboats engaged in a competition that is fun to watch. The virtual images (such as course boundaries, distance grid lines, separation between boats, etc.) overlaid on the real images really helps to keep the race [...]

31 August 2013

100 Knots for Hydroptere?

The latest news from Hydroptere is that they have plans for a 100 knot sailboat. This was posted on 26 Aug 2013, so look for that date at this address. http://hydroptere.com/en/the-news/last-news/

17 November 2012

Aptly named Sailrocket, blasts off!

While yet to be ratified, Sailrocket posted an average speed over 500 meters of 59 knots. I will not be surprised if they increase their record into the 60 knot range during this record attempt.

02 January 2012

More drag for VSR2?

I want to start by pointing out that the whole VSR2 team has done a stellar job and has demonstrated conclusively that the forces that drive a sailboat can be aligned for roll stability without using ballast and without using any down-force. (Trifoiler achieved roll stability by using down-force, but [...]

18 December 2011

My analysis of Sailrocket

I copied a diagram of VSR2 (wing doesn’t show well) and added in the major force arrows that apply. Be aware that these arrows are not correct in terms of scale (length) and some of their locations are guesses, however I believe I’m correct enough for us to learn something about what VSR2 has been [...]

23 October 2011

60 is within reach, what’s next?

I have been watching Sailrocket’s progress with great interest and there’s no question they have a winner. I fully expect to see them reach 60kt in the near future. Sailrocket has now demonstrated what I first learned with my models and again with my full-sized prototypes, that if you get the forces [...]

Sailien windward foil

04 January 2009
Van asked for a clarification of the pivot point I recommended for the anti-drift (windward) hydrofoil on Sailien. Foil shapes are said to have an aero- or hydro-dynamic center. This is the point at which the lift (resultant) is acting on the foil. On normal foil shapes this dynamic center is about 25% back from the leading edge of the foil.

On the drawing, the rounded end is the leading edge and the tapered (sharp) end is the trailing edge. The black arrow represents the flow coming toward the foil and the blue arrow represents the resultant "lift". The blue dot represents the hydro-dynamic center, note that it is about 25% of the distance from the leading to the trailing edge. The red dot represents the center of the foil (50% of the distance from the leading to the trailing edge). If you put the pivot point (rudder post) at the center of the foil (red dot) the lift force (blue arrow) will try to rotate the foil counterclockwise, until the foil is "sideways" to the flow. By putting the pivot point where the blue dot is located, the lift force will not try to rotate the foil - it will be neutral. If the pivot point is forward of the blue dot (at or near the leading edge) the foil will "weather vane" and try to rotate clockwise until it lines up with the flow (zero lift). By placing the pivot point at the hydro-dynamic center, there will be no rotational force on the foil and the servos on an R/C model will not get overpowered.

Bob
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