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 [...]

Proof is observable or useless

17 December 2008
At this time I want to remind you not to accept anyone's statement as being true until you understand the statement and you have been able to observe that things work in the manner stated. A theory is useful if it correctly describes how something works and if it correctly predicts how something will work. A theory does not prove nor disprove anything; likewise a mathematical formula does not prove nor disprove anything. Proof is accomplished by observation; did it work as predicted or not.

When I was a child in school, I was told that according to aerodynamic theory a bumblebee can't fly. Well I saw lots of bumblebees fly, so I knew that either the theory was wrong or that someone didn't understand or properly use the theory. Bumblebees and other insects have thin flat wings and they fly just fine as we all know. The funny thing about this is that if insects had "proper" airfoils for wings (curved upper surface, flat lower surface) they couldn't fly. Anyone that might be interested in this, a good simple fluid dynamics text will explain why.

For those of you that would like to verify the force diagrams I posted and my statements about them, it can be easily done. You don't need to build a model of Sailien to test this; all you need is a kite. While you could use the classic child's kite, you would have to move the bridle to make these tests, so a basic steer-able kite is what you want. Kite-boarders demonstrate everything I diagramed and discussed, every time they sail, but many may not have realized this.

Fly your kite and hold it steady, note that the kite will stay in one position in the sky; this is an accurate demonstration of one half of my force diagram #1. The resultant force on the kite "lift" is exactly in line with the kite string. You, holding the string, represent the anti-drift hydrofoil. Now use the kite controls so the upper edge of the kite is moved toward the wind and the lower edge is moved away from the wind; the kite will rise in the air or "roll to windward". Kite-boarders do this to de-power the kite and "park" it overhead. This is the situation described by diagram #2. Next move the upper edge of the kite away from the wind and the lower edge toward the wind; the kite will descend or "roll to leeward" as shown in diagram #3. Finally, with your kite flying steady, move the right edge of the kite so it is closer to the wind and the left edge is farther from the wind. The kite will move to the right, this would be a "starboard tack" on a sailboat. Now move the left edge closer to the wind and the right edge farther away. The kite will move to the left, a "port tack". This is the situation described by diagram #4 (which shows a starboard tack).

The anti-drift hydrofoil (keel, dagger-board, centerboard, paravane, etc) works in exactly he same way, except this time we "fly" our kite in the water. Probably the easiest way to demonstrate this is to fill a bathtub with water and take something like a credit card and move it through the water. The water will force the card down, up, left, or right, depending on which way you angle the card.

By doing these simple kite and credit card experiments you will have demonstrated everything about basic sailing theory; it is that simple, there is nothing else to it and it applies to any sailboat. The structure of a sailboat is simply an exercise of how to make a platform we can ride, to which we can attach and control our sail (airfoil) and keel (anti-drift hydrofoil). Now if you want to go fast, you have to start learning about fluid dynamic drag, structural engineering, etc. and optimize your craft to get the greatest possible lift/drag ratio (a description of how much force your airfoil and hydrofoil are generating compared to how much drag is generated sailing the craft). However, if you want to go fast, you first have to gain total control of the craft. We have had some great demonstrations of what happens if you have less than total control.

Bob
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