Up to a point, a sail develops more power when trimmed with a greater max camber. Power is work per time, and in this context it means more force is generated for acceleration following a tack or when busting through heavy chop. Speed on the other hand requires only a balance of forces and not necessarily the largest raw amount of force (and if you are thinking speed made good to windward optimum course issues come into play as well). This usually means a flatter sail. If you are one who thinks about such things, how do you go about continuously or periodically adjusting trim for conditions requiring power or speed? I'd be very curious to read your thoughts on the theory of why these adjustments work the way do (being such a wintry day, with Spring so far off and all).
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LOL ... 
Below 6 knots true = trim with lots of twist and semi flat sails (the low energy air will detach from full sails) Above 6 knots true = trim for power up to 75% of hull speed. Above 75% of hull speed, trim to reduce heel (flatten sails, reef) without loosing speed. The wind speed that a boat will reach 75% of it's "hull speed" will depend on the sail area, bigger sails will reach that boat speed in less breeze. Those same larger sail can be flattened at lower wind speeds to improve windward performance. The best windward performance will be at the high end of the wind range where the sails are flattest, because the ratio of lift to drag is best. The 6 knot true wind trim change is due to the nature of air moving over water. Below about 6 knots, the air flow over the water is smooth (laminar) and has little energy (no or few ripples in the sea surface). The wind speed is 0 at the surface and increases up the mast (classic wind shear). This requires lots of twist in the sails because the wind shear causes the apparent wind speed and angle to change dramatically from the deck to the masthead. Above 6 knots true, the flow over the water is turbulent and has much more energy. Sail can be trimmed to their full power shape. We have all noticed the big change in the power of the wind when it goes from mirror smooth water to just tiny ripples. The huge change is due to the layer of air next to the water going from laminar to turbulent flow. The change in boat speed from when the wind speed goes from 4 knots to 6 is large. The change in boat speed when the breeze changes from 6 to 10 is small by comparison.
Below 6 knots true = trim with lots of twist and semi flat sails (the low energy air will detach from full sails) Above 6 knots true = trim for power up to 75% of hull speed. Above 75% of hull speed, trim to reduce heel (flatten sails, reef) without loosing speed. The wind speed that a boat will reach 75% of it's "hull speed" will depend on the sail area, bigger sails will reach that boat speed in less breeze. Those same larger sail can be flattened at lower wind speeds to improve windward performance. The best windward performance will be at the high end of the wind range where the sails are flattest, because the ratio of lift to drag is best. The 6 knot true wind trim change is due to the nature of air moving over water. Below about 6 knots, the air flow over the water is smooth (laminar) and has little energy (no or few ripples in the sea surface). The wind speed is 0 at the surface and increases up the mast (classic wind shear). This requires lots of twist in the sails because the wind shear causes the apparent wind speed and angle to change dramatically from the deck to the masthead. Above 6 knots true, the flow over the water is turbulent and has much more energy. Sail can be trimmed to their full power shape. We have all noticed the big change in the power of the wind when it goes from mirror smooth water to just tiny ripples. The huge change is due to the layer of air next to the water going from laminar to turbulent flow. The change in boat speed from when the wind speed goes from 4 knots to 6 is large. The change in boat speed when the breeze changes from 6 to 10 is small by comparison.
Outhaul
What a timely subject, Had to have my mainsail recut, because it had streched and was starting to rub on the top of the bimini. So I had it recut to be loose footed, as well as releasing the bolt rope. Now hopefully I can have more control over the draft position. Memories of when I had a Supercat. Now I have to think of a way to make the outhaul adjustment easy to use. At the moment my outhaul exits the boom at the mast. Suggestions?
What a timely subject, Had to have my mainsail recut, because it had streched and was starting to rub on the top of the bimini. So I had it recut to be loose footed, as well as releasing the bolt rope. Now hopefully I can have more control over the draft position. Memories of when I had a Supercat. Now I have to think of a way to make the outhaul adjustment easy to use. At the moment my outhaul exits the boom at the mast. Suggestions?
I would opt for...
...outhaul and leach lines being moved near to the goose-neck. That way when the boom is out over the water as on a broad reach or run the adjustments can still be made. Putting those adjustments at or near the back of the boom precludes you being able to do this. I find that most outhauls are grossly under sized. I upgraded mine to a 6:1 purchase which makes adjusting very easy in all conditions.
...outhaul and leach lines being moved near to the goose-neck. That way when the boom is out over the water as on a broad reach or run the adjustments can still be made. Putting those adjustments at or near the back of the boom precludes you being able to do this. I find that most outhauls are grossly under sized. I upgraded mine to a 6:1 purchase which makes adjusting very easy in all conditions.
Catalogue
Check out the Harken catalogue. They have some pretty good diagrams of outhauls that may give you some ideas.
Check out the Harken catalogue. They have some pretty good diagrams of outhauls that may give you some ideas.
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