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 [...]

Getting Air

20 May 2008
I've run across an interesting sailing idea (thanks Gj) I'd like to comment on. This has to do with getting a sailing craft airborne. Wing Systems mentions this, you can find them at

http://www.wingsystems.com/Development.htm

I have run across this idea before, from some project aimed at sailing fast and claiming they could reduce hydrodynamic drag by "flying" the craft, at least briefly.

Well the windsurfers and kite sailors have been getting "air" for some time now, so there's no reason it can't be done by a larger craft. Getting air is done by a launch off a wave and also for kite sailors by getting the kite more vertical. However as soon as you get airborne, you loose power and you will slow down and fall back to the surface. Any attempt to sail fast by getting airborne is impossible since the water provides the power almost as much as the wind, except for straight down wind. (See my earlier analogy with the bar of soap.) In order to sail, you have to use the wind's force against the water's force. You can get everything out of the water except your leeway resisting device (see earlier posts). This describes a kite sailor with the board in the water. I believe Wind Jet will be attempting to do this as well.

Wing Systems talks about the possibility of "dynamic soaring". Is this possible? Depending on what they mean by that, yes it is. We look to the albatross for our model.

The albatross rarely flaps its wings, but glides instead. It uses two techniques; in one it heads into the wind, swoops down next to the surface (where the wind is slower) gaining speed, then climbs higher. The wind blows it backwards but it swoops down again regaining the speed needed to stay airborne. It glides in continuous vertical circles and its net motion is backwards. It's using the wind speed differential between the surface and higher up to stay aloft. Could we do this? In theory yes, however it would be much slower than turning around and sailing conventionally. Also it takes a very efficient glider to do this; the albatross glides at about a 22:1 glide ratio.

The other technique the albatross uses is essentially surfing the ocean waves. It does this by riding the wind which is blowing up the surface of a wave. (This is the same as flying a glider in the updraft along the edge of a ridge.) The albatross is being propelled forward against the wind by the wave. I watch pelicans surf the waves at the beach on the west coast of the USA all the time. So I have a good understanding of this. For sailing this also fits into the realm of theoretically possible but probably impractical and again it takes a very efficient flyer to do this.

Bob
Comments

About & Links