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2559Re: WetaWest on efficient sailing and mainsheet trim.

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  • George
    Aug 3, 2011
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      Thanks for the tips, Dave, but I query some of the hydrodynamics. With a Weta heeled at an angle of ten degrees the vertical component of daggerboard lift would be tiny. Furthermore, by sitting forward and squeezing the bow down you are reducing the angle of attack of the board relative to the horizontal so you get even less lift. The lift in the photo is coming from the leeward ama which is almost completely submerged and therefore (by Archimedes rather than Bernoulli)has a bit of spare buouyancy to lift the rest of the boat. That the bow is well out of the water is a result of wave jumping and your athletic style of sailing, I would have thought.

      For interest - sailors of planing dinghies always want to get their boats to plane because it reduces wave drag and wetted area. Sailors of displacement boats usually want to immerse the maximum length of boat because that delays the critical rise in wave drag as maximum hull speed is approached. For trimarans the best combination is probably with the leeward ama completely submerged (there is very little wave drag on a submerged submarine due to the 'orange pip effect'), and the main hull planing. Whether you can achieve this upwind in a Weta I am not sure - I would think 6 or 7 knots would be enough to plane, but you might have to sit further back to get the boat up on the plane by using the flatter parts of the hull to generate lift.

      As for sitting on the ama - I have yet to try this for fear of not being able to get back in! I suppose I should try it 'dual' before doing it 'solo',then the other person could pull me back in if I got stuck! For what it is worth I have just ordered a small mainsail so that I can sail in 25knots WITHOUT having to sit on the ama.


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