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Glenn, how does it feel to have a fish hook in your mouth?
the marketing people done did snag you. 170# at 5 knots is 85# at 2.5 knots is 42# a 1.25 knots. For a fixed ***three*** blade prop. In other words, zip. In fact, a two blade at 5 knots was IIRC about 75# and a two blade behind the keel wwas about 45#. In other words, "You how the f*&*% much to gain 0.05 knots speed??" And, that damned feathering three blade cost you HOW much in forward speed because the blades are flat? Folding props are for race boat boats, and boat owners who like to brag how much *they* spent on their boat. Sorta like the suburban home owner bragging about spending $400/week to have his LARGE swimming pool cleaned. btw, glenn, Dave Gerr rehashes other people's writings without all that much verification. glenn, just where is it you found you "facts" that "a medium displacement boat" has 2,866.66666666 pounds of drag? From the VPP diagrams and backup data on my boat, the VPP for a Beneteau First 47, C.A. Marchaj's "Sail Performance" and working backwards from Dave Gerr's figures. The VPPs were run with standard and Gori folding 3 bladed props and showed from 12 to 15% increased speeds with the folding props up to about 80% of the first reef point. 20 miles a day is a 15% improvement on a base 5.6 knot cruising speed and you are correct that folding props make the most difference in light air. Reducing drag has the advantage over adding sail area in that it does not add to heeling moment. BTW, Gori, Martec, Brunton/Varifold and others make 3 blade folders. Volvo even makes a 4 bladed folder. Now, you can continue to rant and make an ass of yourself as usual but that is all I have to say about it. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
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