Actually aspect ratio is luff squared / sailarea. Higher aspect ratio and longer luff are good upwind. Low aspect ratio is good downwind. Aspect ratio 3 is said to be good compromise if I remember Marchaj correctly. Marchaj tested up to aspect ratio 6 with improving upwind performance. Downwind aspect ratio 1 was very effective. You make your compromise.   Of course those figures are only wind tunnel test results. Once we add structural issues, heeling moment, weight distribution etc. we end up in compromise with very many variables. Handling all those variables is difficult enough for professional designers and marine engineers so there is still enough challenge to make boats better. No perfect boat for all conditions with such amount of variables.   Arto --- On Thu, 12/11/08, Gardner Pomper <gardner@networknow.org> wrote: From: Gardner Pomper <gardner@networknow.org> Subject: [harryproa] Aspect ratio? To: harryproa@yahoogroups.com.au Date: Thursday, December 11, 2008, 5:52 PM Hi, I know what a sail's aspect ratio is (Luff/Foot), and I see mentions that a high aspect ratio is more efficient than a low aspect ratio, but I cant find any real description of how high it needs to be to be considered "high aspect ratio" and how much more efficient it is. The containerizable design I have been playing with is limited to a 34' maximum luff. I started with a 10' boom, then increased to a 12'. In an extreme case, I could increase to boom to a max of 20'. What foot length is "reasonable" for a 34' luff? Is 34:12 low aspect or high aspect. My sail area is about 550 sq ft (for both sails combined) with a 10' luff, 650 sq ft with a 12' luff and 750 with a 14' luff; all calculated with an 80% roach. I assume the 80% figure is harder to maintain as the aspect ratio goes down. Thanks for any feedback, - Gardner Pomper

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