top end/low end speed...?

[schakleton]

Could somebody explain these concepts to me?

[spyder]

Hi, Im not a sail designer or anything, but generally this refers to the low end power and the high end speed of the sail.

sail design is tricky, and there are a few things to consider when talking about sails, one is the aspect of the sail. The sail can be high aspect or low aspect, generally low aspect sails are more powerful, but lack high end speed, whereas the high aspect sails are generally faster but less low end power.

Another thing is the draft pocket. This is what keeps the sail stable over its power range. The draft pocket is designed to provide stability so the pull of the sail feels centered and consistent. Sails with more battens and camber inducers tend to provide a more stable draft pocket.

The low end power of the sail comes mainly from the bottom of the sail, how the foot of the sail is cut and how wide it is. The top end speed of the sail comes from the top portion of the sail, and how aerodynamic it becomes when going fast. Again, battens and cambers help create an aerodynamic efficiency that allows the sail to have more top end. It is similar to an airplane wing, that provides lift from the high/low pressure differential over the airfoil created by the draft pocket.

if anyone has any other ideas to add go ahead.

hope this helps.

The leech twist off is another feature that allows the sail to dump wind gusts that would overpower the sail and make it unstable.

[isobars]

Spyder said it eloquently.

Lets me add a grass roots perspective:

Top end refers to the sails stability in huge gusts. A sail with great top end will not only remain stable (no draft drift) but will also accelerate in gusts (presuming we stay sheeted in) rather than merely tolerate them well. This is the Miata end of their useful spectrum. Its vital for people who usually deliberately sail overpowered (relative to the sail size eveyone else is planing with) so they never hit any lulls and who sail at pretty constant speeds.

Bottom end refers to the power they generate at the light-wind end of their performance range. This is the geared-down, 4-wheel-drive, stump-pulling end. Its vital in B&J and wave sailing where one is constantly slamming on the brakes (i.e., swerving; any time we disturb the water were robbing speed) and reaccelerating.

The range of compromises is huge. I find plenty of stability with no cams in my whole quiver, and have plenty of low end power for my sailing style -- following imaginary ant trails totally-to-over-powered and sheeted in.

Mike \m/

[schakleton]

Thank you Mike and Spyder.

For a beginner, what should be more important: to have a good top end performance sail (more stable= easier to practice harness in a gust situation ) or bottom end ( beginners = light wind)

Thanks again.

[schakleton]

Thank you Mike and Spyder.

For a beginner, what should be more important: to have a good top end performance sail (more stable= easier to practice harness in a gust situation ) or bottom end ( beginners = light wind)

Thanks again.

[schakleton]

Thank you Mike and Spyder.

For a beginner, what should be more important: to have a good top end performance sail (more stable= easier to practice harness in a gust situation ) or bottom end ( beginners = light wind)

Thanks again.

[isobars]

Bottom end, definitely. The top end we refer to means out at the upper limits of a sails wind range. Beginners and intermediates wont even see that range (for more than a millisecond), because its out there in the You were on a WHAT size sail in that??!! range for that sail. A sail designed to emphasize top end, usually a race sail (primarily for people who race upwind for money and are willing to put up with its distinct disadvantages to gain its top-end upwind ability) or maybe a three-cammed slalom sail still intended to be used really powered up), is meant to be run big -- meaning when people are planing on 5.0s, the people on top-end-oriented sails will be on a 6.0-7.5. This means they are on heavier, harder to waterstart, more cumbersome sails to ensure they are never underpowered. Beginners and intermediates just dont normally sail in that wind range of their sail. Experts who are maneneuvering extensively want lots of power, but theyre going to get it from more powerful, low-end, deeper-draft sails so theyre throwing around less weight. Ive been blasting around fully powered on a sinker in the Gorge on my 3.7 while the racerheads were on their 6.0s, because if I hit a lull I just slow down for a minute; if they hit a lull the guy who is still fully powered wins the race. Id sure rather manhandle a 3.7 than a 6.0 when maneuvering extensively.

The reason a beginner/ intermediate wants a low-end-power sail (a B&J or slalom sail with just 1 or 2 cams -- if any) is at least three-fold:
1. Hes not pushing the stability envelope yet. Hes going to hit lulls and drop off a plane.
2. Hes making mistakes and dropping off a plane. Hes going to need low-end power to get planing again.
3. Its likely to rig easier, be lighter, be smaller, and water start (or uphaul) more easily.

Realize were just talking matters of degree here. Its a continuum, not the flat sails lined up on one side of the dance floor and the deeper sails lined up against the far wall. Any bump & jump or single- or double-cammed sail should be fine. You just dont want a sail intended to be rigged flat or with a wide luff sleeve, because the former has limited bottom end power and the latter (usually a race sail or a racy slalom sail) is a BEAR to waterstart once the luff sleeve is flooded.

Mike \m/

[schakleton]

Thank you, Mike

Think i got the idea now.