Laser 28 - Excellent example of this great design Hamble le rice |
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Rossiter Pintail Mortagne sur Gironde, near Bordeaux |
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Laser 140101 Tynemouth |
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![]() ![]() ![]() ![]() Posted: 06 Sep 13 at 1:46pm |
Hi Graeme, I generated that one for the 100. To create theoretical polars you need three things: 1. The drag of the hull 2. The power from the rig 3. Other stuff The drag of a dinghy hull is severly impacted by incorrect trim, waves etc. I used the measured values from a towed 59er and tweaked it by crude judgement to suit the shorter, lighter 100. The power from the rig can be estimated using standard aero calcs, provided you have reasonable lift and drag coefficent estimates. There are a number of ways of getting these, but getting accurate numbers requires money. The other stuff covers things like crew weight, mast height, sail roach, daggerboard length etc, which affect the righting moment and hence power available. So there are quite a few inputs, which you can either guess, estimate, measure or calculate. The more precise these numbers, the better the answer. To get numbers good enough to calculate a PY (becasue yes, you could, in theory use polars to calculate PY) would require a decent level of accuracy. Nice job though! Having said that, PYs to 4 decimal places is overkill anyway. |
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i tick ![]() Groupie ![]() Joined: 15 Jul 13 Location: Tunstead Milton Online Status: Offline Posts: 93 |
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Hell, did I start all this? I am so glad I am stupid now. I fail to understand the relevance of any of this because there are so many variables. The only instrument I would like is one that told me when to tack for the mark. This would prevent me from going backwards or not making the mark at all. This instrument could also tell me when to harden up after going low and make said mark.
No set of calculations could allow for that patch of Water Bistort growing near number three and different every week.
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iGRF ![]() Really should get out more ![]() ![]() Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499 |
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Holman? You're not from Poland I hope. ![]() |
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Rupert ![]() Really should get out more ![]() Joined: 11 Aug 04 Location: Whitefriars sc Online Status: Offline Posts: 8956 |
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I know many successful sailors who write down settings, angles sailed, all sorts of things for races sailed, and one Firefly sailor who has been winning in them for 50 years who does this, still, for every race. However, my mind doesn't work like that either, but I do find having an understanding of the concept of such ideas that a straight line isn't always quickest really helps with my sailing. What some forget is that sometimes a straight line is quickest, even when the maths might tell you otherwise. As for the weed... hate, hate, hate ,hate, hate. Somehow I can never see it. And maths has proved no help at all... |
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Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686
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iGRF ![]() Really should get out more ![]() ![]() Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499 |
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You haven't been smoking it have you? ![]() |
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