Frequently Asked Questions:
|Q: "Self Trimming" - Has it
been used before. If so, is it a successful way of controlling a wingsail?
A: Yes, they date back to the 1940s
when one was constructed in Norway by a man name Utne.
Another more recent use was on the "Greenbird" - a landsailing craft which is the current record holder for the fastest wind-powered vehicle on Earth at over 126mph (Click Here).
These examples indicate that the principle is a well-established and successful concept.
Q: How Do the "Windthrusters" with the automatic system work?
A: The tail is adjusted by the angle the whole rig makes to the boat. You can think of the wing and tail assembly working as a weathervane with the counterweight always facing the wind. The tail pivots a few degrees either way, adjusting itself by the angle the "weathervane" makes with the boat, and thereby setting the main wing to provide thrust. This is what makes control automatic.
The idea came about as a result of
practical experiment you can see in the video below, not theory.
In the video you can see that the boat is never blown downwind, even when head to wind, because the tail is making very small adjustments to the main wing, causing it to provide enough thrust to keep the boat on station. The (patent applied for) windthruster system works the same as that shown in the video, but has the added option of being able to be adjusted at will, between the three positions, forward, neutral and reverse.
These tests, along with my full-size wingsail tests which you can find here prove the effectiveness of the system.
Q: How about reefing them if the wind gets up?
A: When the tail is a zero angle and perfectly aligned with the angle of the main wing. The rig presents a perfectly streamlined section to the wind and the drag is less even than a normal rig with "bare poles" - (with no sails up).
All builders of self-trimming wingsails like this have found that reefing or taking them down is not needed no matter what the conditions. They are perfectly safe to leave up when in "neutral" and will not drive the boat in any direction.
Q: How much would they cost?
A: Not much. There are a variety of ways of building wings, none of them very expensive, and they can be built lighter than aircraft wings, without such a large safety factor. There are no electronics or batteries to add to the cost. Simplicity is a keynote of the design. (Click here for further information about this.)
Q: Who would want one?
A: Due to their simple operation they could be attractive to the following groups:
This way the boat would be using the most appropriate form of power. If enough wind, using windpower and saving battery. If not enough wind, using electric power for drive.
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|Construction Method||Windthrusters||Rotary Sailing|
P. Worsley 2010