When I was in Houston (Galveston Bay) I had a Soverel 33 that by one design standards had a highly modified keel. The former owner (a boat yard owner and world class sailor) has a buddy that is a NASA engineer (also a world class sailor). This guy did some "foil work" on the NASA computers. What he came up with was a "laminar flow" design that incorporated a "drag bucket". The keel shape was narrow and had the "high point" much further aft than the original design. It also had a hollow area in the aft 1/4 of the cord (the "drag bucket").
The end result was, coming out of a tack you had to keep the "nose down" 'till the speed came up then, when you hit the "sweet spot", the boat would climb the breeze on it's own. Down wind in medium air you could sail dead down (where there is no angle of attack on the keel) with little or no (foil induced) drag. The "groove" was about a 1/2 inch wide and when I was out, I knew it immediately 'cause the boats from "B" class were passing me! The A/C programs, when developing foils, not only take into account the wind and sea state of the venue but also the salinity of the water (among many other factors) as well. Mark, Gratis (6115) Want to keep your WHOLE PAYCHECK? PLEASE VISIT http://www.fairtax.org ----- Original Message ----- From: [EMAIL PROTECTED] To: [email protected] Sent: Monday, March 17, 2008 10:54 AM Subject: Re: catalina27-talk: Keel Fairing One might think, that because a keel is like an symmetrical wing, which can only produce lift by altering the angle of attack, (as in a sport, aerobatic plane) that the shape of the foil would be irrelevant, aside from possibly reducing drag, which will make your boat faster.....But there is no "high" or "low" lift with a symmetrical wing....just angle of attack. Tommy, One might think... In a message dated 3/17/2008 11:30:33 A.M. Eastern Standard Time, [EMAIL PROTECTED] writes: For example, there is a concept called the lift/drag bucket--a high-lift keel profile provides a lot of drag, but might be a worthwhile price to pay if you're trying to achieve the best VMG in light air, because at low speeds the drag doesn't hurt as much and adding lift while minimizing leeward slippage pays off. For higher speeds, a lower-lift profile works better because when the boat is moving faster through the water, you'll get a resultant increase in the actual lift windward and have less drag to worry about--but overall you'll see more leeward slippage. ------------------------------------------------------------------------------ It's Tax Time! Get tips, forms and advice on AOL Money & Finance. ------------------------------------------------------------------------------ Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.19.16/1251 - Release Date: 1/30/2008 9:29 AM
