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movie with sound (170 kb, 8 sec) of Speed sail testing in light wind.
|I am now, 2000/2001 finishing a 2.5 sq. m. sail. It may be
at speeds some 40 % faster than the 5 sq. m. wings, or some
160 km/h, 100
I found out last season that the wing was too cramped inside. This season the wing has been modified to a greater width. Since then it has been tested in a wind gusting 10 m/s, 20 knots, and proven unstable even at low speeds.
It is known that thick foils have a switching behavior: when you change the angle of attack from zero the force first comes from the wrong side, the switches to the right side.
It is also know that this can be cured by giving the foil a cut off rear edge. This modification has been done.
The wing has a stabilizer behind the main wing. The instability may also come from the thick wake hitting the stabilizer.
We'll see what future tests will give.
|Here is a around 1995 all metal high speed sail. The rear cloth has been added in an effort to make it stable at high speeds. Not yet successful.|
For still higher speeds the wing skate sail probably has to be modified some way to get the sail area down. You can not just make the wing shorter because then it becomes relatively too thick to be a reasonable airfoil.
One way may be to stand the sailor on one leg, with body bent
and the other leg backwards. In this way the body's frontal area
Then enclose the body in a torpedo shaped streamlining and the
leg in a wing. On top of the streamlining is placed a wing.
Finally a stabilizer
is put at the end of the body streamlining.
With this design you can get the sail area down to .5 sq. m., which I think would give you quite smooth sailing at 150 km/h, 95 mph, and a top speed maybe over 200 km/h, 125 mph.
The winter 1996/97 I tried a kneel down very small wing, which technically can be sailed up to some 150 km/h (94 mph) before you start to become over rigged. But first tries revealed that you don't have the same skate control as when standing up.
|The wing area of this wing is with 6 sq. m about 1 sq. m
average. Is was unbeatable in light air but uncontrollable
in winds above
5 m/s, 10 knots, probably because of a weak structure.
I am now making the structure stiffer and also reshaping the forward, red, ribs to make it wider inside. The latter could no be done on e.g. GRP wing, on this wing the red forward ribs are taken out, reshaped and then put back, giving the wing its new shape.
I am going to make a reef in the trailing edge. When reefing the cloth is folded forward inwards, shorter batten are put in the pockets.
I am also planning a tip extension with a reef, instead of the
extension in the picture. When it is ready the wing shall have the
four different areas in square meters, sq. m, from "fully reefed"
area (in brackets is suitable speed of the wind): 4 sq. m (7 m/s,
5 sq. m (5 m/s, 10 knots), 6.5 sq. m (3 m/s, 6 knots), 8.5 sq. m
|Here the different sail areas ae shown: 4,
5, 6.5 and 8.5
sq. m, with a flap. The leading edges are facing left.
When racing the right sail area is very important. I sailed a Stockholm district championship in very light wind with a 6 sq. m which was 3 m tall. My competitors had wing areas of 5 sq. m and sails 2.5 m tall. When I finished I was just about to lap number two. It was a three lap course making my wing almost 50 % faster!
Guinness Book of Records doesn't yet have a skate sail speed record. So build yourself a wing, sharpen the skates and sail into the record book!
|The best tactical compass for sail boats? You see the wind shifts directly on the compass! No figures to read, write or compare. Can it get simpler?||The position of the white pointer directly shows where the direction of the wind is between best lift and worst header, in oscillating wind shifts. Picture on to the right is an animation (you must have animation activated in your browser to get the message).|
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