I remember that Randy is on a lake in Colorado. More than likely his burst of speed is the hull settling into the water as it goes faster and thus increasing the waterline – and/or being heeled over which also increases the waterline. When my 30-1 gets the rail in the water in 20-30 knots of wind, I am generally too busy to look at the speed.
I’m sure all of you nautical types remember the war stories about clipper ships going so fast they literally bury themselves as the make a bigger and bigger hole in the water. I am not interested in trying that. Oh well. Gary From: CnC-List [mailto:[email protected]] On Behalf Of Gary Russell via CnC-List Sent: Friday, May 19, 2017 2:01 PM To: C&C List <[email protected]> Cc: Gary Russell <[email protected]> Subject: Re: Stus-List Fun Race Last Night Remember your GPS gives you speed over ground, while Hull Speed is speed over the water. A one knot favorable current can easily explain the difference. Gary S/V Kaylarah '90 C&C 37+ East Greenwich, RI, USA ~~~~~~~_/)~~~~~~ On Fri, May 19, 2017 at 1:16 PM, Ronald B. Frerker via CnC-List <[email protected] <mailto:[email protected]> > wrote: GPS is usually in miles per hour IIRC. Knots is faster by about 15%, so 6.7kt times 1.15 would be about 7.7mph. Unless your GPS is set in kt in which case this is all wrong. Ron Wild Cheri C&C 30-1 STL _____ From: RANDY via CnC-List <[email protected] <mailto:[email protected]> > To: cnc-list <[email protected] <mailto:[email protected]> > Cc: RANDY <[email protected] <mailto:[email protected]> > Sent: Thursday, May 18, 2017 3:52 PM Subject: Re: Stus-List Fun Race Last Night I'm just as surprised as anyone. I know that 1.34 times the square root of 24.75 (Grenadine's waterline in feet) is 6.67 knots. But apparently that's only a very general rule - see http://www.boats.com/reviews/crunching-numbers-hull-speed-boat-length <http://www.boats.com/reviews/crunching-numbers-hull-speed-boat-length/#.WR4GQccnuq0> and https://en.wikipedia.org/wiki/Hull_speed. At 9,000 pounds displacement I guarantee I'm not planing :) But I assume GPS doesn't lie. On June 22nd last year I was using RaceQs during a race. I forgot to switch it off after finishing, so it recorded Grenadine sailing for fun in the 25-33mph gusts that piped up after the race, under full main and 150% genoa (which tore that night, before I could get a rail in the water). If you watch this replay from 19:42:50-19:43:00 local time, you'll see Grenadine going 7.5 knots over ground according to RaceQs GPS-based iPhone app: http://raceqs.com/tv-beta/tv.htm#userId=1032518 <http://raceqs.com/tv-beta/tv.htm#userId=1032518&divisionId=41508&updatedAt=2016-06-23T03:05:38Z&dt=2016-06-22T18:08:05-06:00..2016-06-22T21:05:54-06:00&boat=Grenadine> &divisionId=41508&updatedAt=2016-06-23T03:05:38Z&dt=2016-06-22T18:08:05-06:00..2016-06-22T21:05:54-06:00&boat=Grenadine I'm not one to look a gift horse in the mouth :) Maybe at 25 degrees of heel my waterline length is appreciably longer than 24.75 feet. Or maybe I just have to give credit to George Cassian, George Cuthbertson, and Rob Ball for designing a faster-than-predicted hull form. Cheers, Randy _____ From: "David Knecht via CnC-List" <[email protected] <mailto:[email protected]> > To: "CnC CnC discussion list" <[email protected] <mailto:[email protected]> > Cc: "David Knecht" <[email protected] <mailto:[email protected]> > Sent: Thursday, May 18, 2017 1:25:19 PM Subject: Re: Stus-List Fun Race Last Night Theoretical hull speed of a C&C 30 is 6.7 knots (based on 25’ water line). How are you hitting 7.6-8? Foils? Dave _______________________________________________ This list is supported by the generous donations of our members. If you wish to make a contribution to offset our costs, please go to: https://www.paypal.me/stumurray All Contributions are greatly appreciated!
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