Hi all,
Keep in mind that the hull speed is not the "maximum" speed that the boat will
acheive. It is the maximum speed at which the amount of energy needed to cause
the boat to go fast increases, and yes, it is a steep increase in energy input
from the sails.
That said, our C&C 27 MKIII regularly sailed above the 6.4 kts. in theoretical
hull speed. That was measured by GPS, and of course, that measures speed over
ground which can be significantly affected by current. That said, my sailing
experiences on that boat were on Lake Michigan, in all kinds of conditions.
GPS sustained recorded hull speeds (meaning more than just a surf, but lasting
more than a minute at a time) would exceed 7.0 knots multiple times in every
season. Usually this required 12 - 15 knots of speed on an apparent beam
reach.
On a couple transits between Chicago and Milwaukee, with apparent deep reaches
and sustained 15 - 20 kt winds, we had sustained 8.5 kt speeds, and on one
memorable night, we had sustained 10's, tracked by a friend's permanently
tracked GPS speeds (not just looking at the numbers). I'm not sure I can dig
up that log, but he might be able to find it. I'm not sure I've heard of a
current exceeding 2 kts on Lake Michigan, but others may know better.
And, no, even with heal, you might be increasing your waterline length by 10%,
but not much more, and considering the formula, that doesn't equate to a 10%
faster boat.
So, its a guideline, not an absolute maximum.
Hope you find this helpful (though you might find in unbelievable)
Kindest Regards,
Bruce Whitmore
(847) 404-5092 (mobile)
bwhitm...@sbcglobal.net
From: RANDY via CnC-List <cnc-list@cnc-list.com>
To: cnc-list <cnc-list@cnc-list.com>
Cc: RANDY <randy.staff...@comcast.net>
Sent: Friday, May 19, 2017 3:03 PM
Subject: Re: Stus-List Fun Race Last Night
Ok that made me laugh :D
That's why I first noticed that speed via the replay. I sure as hell am not
looking at my iPhone in the middle of that kind of chaos :) In fact this past
Wednesday night when I finally got a rail in the water, I even forgot to look
at my clinometer in all the excitement - but I suspect she was heeling around
30 degrees. I know 25 degrees isn't enough to get the rail wet.
Cheers,
Randy
From: "Gary Nylander via CnC-List" <cnc-list@cnc-list.com>
To: "cnc-list" <cnc-list@cnc-list.com>
Cc: "Gary Nylander" <gnylan...@atlanticbb.net>
Sent: Friday, May 19, 2017 12:11:53 PM
Subject: Re: Stus-List Fun Race Last Night
#yiv1219454443 #yiv1219454443 _filtered #yiv1219454443
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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:cnc-list-boun...@cnc-list.com] On
Behalf Of Gary Russell via CnC-List
Sent: Friday, May 19, 2017 2:01 PM
To: C&C List <cnc-list@cnc-list.com>
Cc: Gary Russell <captnga...@gmail.com>
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. GaryS/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 <cnc-list@cnc-list.com> 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.RonWild CheriC&C 30-1STL From: RANDY via CnC-List
<cnc-list@cnc-list.com>
To: cnc-list <cnc-list@cnc-list.com>
Cc: RANDY <randy.staff...@comcast.net>
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 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&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" <cnc-list@cnc-list.com>
To: "CnC CnC discussion list" <cnc-list@cnc-list.com>
Cc: "David Knecht" <davidakne...@gmail.com>
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
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_______________________________________________
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:
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All Contributions are greatly appreciated!
_______________________________________________
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!
_______________________________________________
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!
