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Wing sails for speed sailing, 160 km/h (100 mph)?

Old wing modified to be reefed from the back, with four areas from 4 to 8.5 sq. m

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Wing sails for speed sailing, 160 km/h (100 mph)

Current wing sails are designed for course racing and work well in a wind speed of around five meters per second (ten knots). In ten meters per second (twenty knots) of wind the speed is some 120 km/h and the ride is extremely hairy because the sail area then is far to large. To my knowledge a  speed wing skate sail has not yet been made.


 
MOV00012.MPG
MOV00012.MPG
Click on text above for short
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 manageable at speeds some 40 % faster than the 5 sq. m. wings, or some 160 km/h, 100 mph.
  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.

 

A wing sail
                built for 150 km/h, 95 mph

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 forward and the other leg backwards. In this way the body's frontal area is minimized. Then enclose the body in a torpedo shaped streamlining and the supporting 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.


Modifying wing sail no 211

The wing area of this wing is with 6 sq. m about 1 sq. m above the 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.
Stand inside wing
                skate sail

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 white extension in the picture. When it is ready the wing shall have the following four different areas in square meters, sq. m, from "fully reefed" to maximum area (in brackets is suitable speed of the wind): 4 sq. m (7 m/s, 14 knots), 5 sq. m (5 m/s, 10 knots), 6.5 sq. m (3 m/s, 6 knots), 8.5 sq. m (1.5 m/s, 3 knots)
 
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). 

Next in Skate sailing index is: Land, water and snow sailing with wing skate sails.

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