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gorgesailor said..fpw9082 said..WhiteofHeart said..
Yeah it always made me wonder aswell, especially once you start riding 3.0's and 2.5's and the clew doesnt even reach the mast hahahah. I asked the same question to a friend of mine who's a nautical designer of racing yaghts. He said he didnt know, but it had to be balanced otherwise it doesnt work.
It is funny thing that even windsurfing desingers dont have explain..(but this is first thing you have learn in wsurf-school,"board go in straight line
only if COE and CLR is in same line")
It seems in windsurifng nobody knows anything but evertyhing works in practice.This is miracle.
Our sport evolution is based on trial and error method..:) :)
(i have my half-explain,when board is heel to windward than front wing handled lots side force,so CLR is just in front of back feet,
,BUT there is lots of situation where board is flat and still going in stragiht line so this is still unclear...)
None of the diagrams have legs... Seriously... This is what you are missing & what Dietrich Hanke & White of Heart were saying. Think of the kite example. As much as we might not like it we are more like Kite foilers than Sailboats.
Just imagine you could take a Windfoiler in perfect trim & remove the pilot. Just fix the mast & boom position, & for a second imagine the sailor weight is not affecting the longitudinal trim. Without the forces being directed through the sailors legs will the craft still go straight? NO the sailor is balancing the forces & moments though his legs.
Like snowboarding; gravity is the COE of the sail, your boards rail is the foil. Depending on how you adjust your weight over the front / backleg you can change your direction from completely downhill to almost perpendicular to the mountainside. Backleg preassure is uphill / upwind, frontleg preassure is downhill / downwind. The steering works because you load for example the frontfoot, making the front of the board heavier than the back and steering it downhill, and vice versa for uphill. You need to balance the two to not end up going straight down the mountain, or end up pointing too high up the mountain and loosing speed. Same goes for windsurfing.
Ofcourse the sail (and foil) is a little different from gravity in that it doesnt only generate a force sideways but a little bit more forward than sideways, bluntly meaning for windsurfing, to put it in the snowboarding example, our "gravity" doesnt come from right below but a little bit angled relative to the slope so we can go "uphill".
In practice, for windsurfing by moving your hands forward on the boom, changing the position of your harnesslines, or changing the position of your hips slightly, you can push the sails power more through for example the backleg, making the backleg "heavier" and thus pushing the back of the board downwind / front of the board upwind. The opposite should hold for steering downwind, although personally I think in practice I lift my frontfoot, changing the boards angle and thus moving my rotational axis back from the frontwing more towards the mast. (Because less angle would mean the front wing provides less of the counter-drift force and the mast provides relatively more, movin the sum back)
In the end for going upwind I suppose its a balance game like the snowboard example, if you have too much power on either leg you're suboptimal. In all honesty I feel this on the water aswell, for me having both legs straight is the fastest way of going upwind, but to manage that my footstraps, mastbase and most importantly harnesslines have to be in the right place. You often see people who are sailing with a bent frontleg upwind have their sail tilted farther back, and people who have 2 straight legs have their sail more upright/forward. Logical if you follow my reasoning, since bending the frontleg means you have more weight / power on the front of the board and have to compensate by angling the sail back. In the end the balance is delicate, since your weightdistribution determines both your angle and your height, I suppose thats why its so hard (and important) to get the trim exactly right.
The fact that you're not on the centerline is indeed of importance, but I'm gonna have to keep breaking my head on that for the moment. Keep in mind that upwind on a wide board, the biggest part of your weight is not on your feet but in the harness, especially if you look at the angle of the rider and board relative to the water, I think only a small portion of your weight is pushing the windward side of your board down (Y-Axis). I think most of it is more of a combination of the sail lifting your weight, being at an angle, and since its fixed at the mastfoot, part of your weight ends up pushing the board through the X-axis through your legs to counter being pulled over the board (Which basically returns us to the snowboarding example), and part of it goes down through the mastfoot because of physics which I find hard to explain, other than to refer people to armwrestling in reverse (try lifting someones hand with your arm at a 45 degree angle), and the fact that your elbow (mastfoot) takes the load.
fpw9082
> 9 months ago, 9 Apr 2020
