Why are sails tall instead of wide?

[Jamie Kennedy 108]

It is to reduce wetted surface. Downwind the aspect ratio makes no difference. However, a tall sail will have a stronger wind due to the velocity gradient.

I agree that it is primarily to reduce wetted surface. In very light air you can heel to more extreme angles, at least in the Laser Full Rig. The others I have sailed but very little.

It is also to balance the helm, but it light air you will often go beyond that to reduce wetted surface more, at least temporarily.

But there is more to it. When sailing By-The-Lee, which is generally faster in those boats for a variety of reasons, when you go up to a more extreme angle in a lull or to accelerate or to get up into more wind… you get into territory where a lower aspect ratio does give you more thrust, and then take that speed down with you.

But there is more to it than that also. When you are heeled over more, and sailing by the lee say 150 degrees off of true; if you let off your mainsheet past 90 degrees at that point because you are heeled over so far letting the boom out is partially increasing rake. Something happens at that point, like a controlled death roll where the boat definitely gets a boost and the boat wants to heel further and round up (to leeward but more upwind) and so you pull on the tiller extension to keep the rudder straight and you move your weight to the upwind boom side of the boat to flatten it some and sheet in some and drive the boat downwind more as it accelerates.

I’m not sure all that’s going on with it since I started doing I’d 45 years ago but it definitely has to do with vortices, and pulling more wind down from aloft if that makes any sense. Love to hear your thoughts on this.

why is rake so fast downwind? I think that is part of it also. Cheers.

 

[jehardiman]

But there is more to it than that also. When you are heeled over more, and sailing by the lee say 150 degrees off of true; if you let off your mainsheet past 90 degrees at that point because you are heeled over so far letting the boom out is partially increasing rake. Something happens at that point, like a controlled death roll where the boat definitely gets a boost and the boat wants to heel further and round up (to leeward but more upwind) and so you pull on the tiller extension to keep the rudder straight and you move your weight to the upwind boom side of the boat to flatten it some and sheet in some and drive the boat downwind more as it accelerates.
I’m not sure all that’s going on with it since I started doing I’d 45 years ago but it definitely has to do with vortices, and pulling more wind down from aloft if that makes any sense. Love to hear your thoughts on this.

If you are racing be very careful what you are doing. Yes, I can get a 5-10 ton sailboat moving at a fair clip in DFC by sheeting in and sallying her; trading off the forces between keel and sail. But some of that is prohibited by The Sailing Rules. Specifically Rule 42.

https://www.sailing.org/tools/documents/42interpretations2010final-[8881].pdf

 

[Jamie Kennedy 108]

If you are racing be very careful what you are doing. Yes, I can get a 5-10 ton sailboat moving at a fair clip in DFC by sheeting in and sallying her; trading off the forces between keel and sail. But some of that is prohibited by The Sailing Rules. Specifically Rule 42.

https://www.sailing.org/tools/documents/42interpretations2010final-[8881].pdf

Fortunately now that I am older and not racing I am no longer restricted my rule 42. This year I am only restricted by rule 64. Next year it will be rule 65.