ec12-1582
Posts: 41
Score: 100
Joined: 11/20/2002
Last Login: 9/3/2010
From: Enterprise,
AL, USA
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Hi Disco,
The rigid sail, or wing for sailing has many technology issues that really apply to boats only. On an airplane, a non-symmetrical foil is used in most aircraft, with a symmetrical foil used for hi-performance aerobatics.
Problem with sailing is, you just about have to go with a symmetrical, as the sail does not have a constant angle of attack that can be controlled through the vertical plane(elevator-elevon). The angle of attack is never consistent for a vertical foil that moves horizontally through a variable direction and velocity (Wind). Wind provides your thrust in sailing, and is not overcome as in flying by the use of a prop. Wind provides your 'thrust', and you must be much more aware of it's effects than in flying. In flying wind is a consideration to take into effect, in sailing, it is your source of power, and everything else is a consideration.
This is why sailors constantly need to sheet and trim the sails to the 'apparent wind' and why 'flexible' sail material is still used.
On a rigid vertical wing, as the "sail" cannot form to the apparent wind, but must be tilted to it. (i.e. rotating Mast, adjusting foil, etc) This creates a weight and complexity problem that the racer making a course would just as soon not deal with.
Wing sails work great in one direction and at limited apparent wind angles, but their perfomance envolope is relatively narrow, and the controls cumbersome. This is why they are not used for course or match racing, but primarly for speed trials in one direction, and perhaps the reverse course. They have the potential to be much faster in a straight line over a "sailed" boat, but they give up almost all their manuevering ability to do so. Kind of like racing a rail dragster against a BMW. The dragster will win if the race is 1/4 mile long and straight, but the BMW will eat it for lunch once a turn or two is introduced, especially over a distance. with multiple turns.
As to your specific question why wings are canted leewards (away from wind) this is due to the wings inherint stability. In a 'puff', the loading force on a rigid wing can increase more rapidly than any sail trimmer could adjust for. This is a saftey issue. By canting the wing, the loading is delayed, and less force driven to the hull. This improves the stability of the boat. Without the delay, the chance of being dunked and turning turtle becomes extreme.
Just a word or caution. You are a novice to sailing, and you are about to undertake the two most challenging sailing issues there are. First, control of a multi-hull(catarmaran) which is much harder to sail, especially in R/C, and then adding a rigid wing sail that quadruples the complexity.
This is not beginning sailing!!!!.
I'm not trying to squash you here, but, this is like going from a 40 size trainer with an instuctor, to going to a twin turbine powered R/C F-15 on your second outing to the airfield. You are bound to pitch-pole, or capsize this boat, find it un-controllable, and decide that R/C sailing sucks.
I would suggest you learn sailing from a keel boat type, I.E. Victoria, Seawind, Victor, Northwind, or what ever else they happen to sail in your area. Learn the rules, and learn to race and control a boat.
Then move to a multi-hull; then decide about rigid sail wings.
This will save you a lot of money, let alone heartache.
Chris
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Angles of lean - 
