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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/25/2011 : 07:55:21

I've hit over 8 knots before (measured with knotmeter and somewhat verifed by GPS) and have seen sustained speeds in the upper 6's lower 7's (knots). Makes me giddy when I see the beginings of a roostertail forming at the stern.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 05/25/2011 : 08:42:19

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JohnP
 Current or tide, indeed! With info from both a knotmeter to give speed relative to the water, and a gps to give speed relative to the stationary satellites, the question would likely be moot.

But what kind of currents are on your lake, Chris?
<hr height="1" noshade id="quote"></blockquote id="quote">

You know I am sitting here laughing as I read through all the reasons it isn't possible. I used to post the same sort of thing until I figured out how to beat hull speed.

We sail on a bay with neither inlet nor outlet nearby. No currents to speak of. Here is the googlemap of our location:

http://maps.google.ca/maps?f=q&source=s_q&hl=en&geocode=&q=Jacksons+Point,+Ontario&aq=0&sll=44.463555,-79.33529&sspn=0.667455,1.686401&ie=UTF8&hq=&hnear=Jacksons+Point,+York+Regional+Municipality,+Ontario&t=h&z=15

pan a little north for the area where our race marks are - nestled between Jackson's Point and Georgina Island.

Edited by - on

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 05/25/2011 : 08:49:15

Wind moves water. Even on a lake if you've got a good wind it will create localized current. Also with a reasonable amount of heel you have a longer piece of hull in the water which allows for more speed. Hull speed is real, it's proven, it's a rule. BUT there are always exceptions to the rule and logical forces and circumstances that create these exceptions. I've exceeded 10 knots in a current and hit at least 7.2 sailing with the wave flow.

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GaryB
Master Marine Consultant

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USA
4303 Posts

Response Posted - 05/25/2011 : 09:21:07

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Joe Diver
 Peter,

I haven't been out to the marina to check on the boat, but my Mom lives in the neighborhood not even a mile from it, and my brother has a house on the hill overlooking the marina. I checked on my Mom and she was fine, no damage and little to no hail. I haven't heard from my brother but he'd call me if there was a problem. I'll go out there tomorrow over lunch and check on the boat. It was interesting here in NRH. The rotation and wall cloud passed right over my house. I heard there is some possible damage around 820 and Rufe Snow, and some in Watauga....both locations directly west of my house. We got rain, wind and hail, but nothing like they got in Irving. At one point, I was standing in my back yard looking up as the wall cloud passed over, the sirens wailing, and the rotation quite evident as the base lowered and spun...but, no funnel ever formed. One of my Brothers in Irving got some severe damage. He claims softball sized hail, says his and his old lady's cars are badly damaged, roof of the house is pitted all over, and many windows are broken. He says it looks like someone took a baseball bat to his car. They have no power, but are okay and that's all that really matters anyway. I hope everyone else out there is okay. Did you guys out on Ray Hubbard come through okay?

Prospector....old lady is just a term quite commonly used in my world...doesn't mean anything bad and nobody takes it that way. But if they do and things get ugly, thats cool too. We like ugly. Hell, most of them call us their old man....just the way it is.
<hr height="1" noshade id="quote"></blockquote id="quote">
Sorry to hear about your brothers damages but glad eveyone is OK.

I saw a picture last night of some apple size hail that fell around the Irving area. That has to be hard on your roof and cars.

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Joe Diver
Master Marine Consultant

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USA
1218 Posts

Response Posted - 05/25/2011 : 12:22:58

Just got back from the marina....all's well out there. Must have been mostly missed.

Thanks Gary...I talked to him today and he's off from work to deal with the insurance adjusters, cleanup and make emergency repairs.

Back on topic....I sure hope someday I can reach these speeds. There have been a couple times when I'm beating that I was heeled over a bit and splashing through the waves, very exciting!

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/25/2011 : 13:05:57

From Wiki..

Hull speed, sometimes referred to as displacement speed, is the speed of a boat at which the bow and stern waves interfere constructively, creating relatively large waves, and thus a relatively large value of wave drag. Though the term "hull speed" seems to suggest that it is some sort of "speed limit" for a boat, in fact drag for a displacement hull increases smoothly and at an increasing rate with speed as hull speed is approached and exceeded, with no noticeable inflection at hull speed. Heavy boats with hulls designed for planing generally cannot exceed hull speed without planing. Light, narrow boats with hulls not designed for planing can easily exceed hull speed without planing; indeed, the unfavorable amplification of wave height due to constructive interference diminishes as speed increases above hull speed. For example, world-class racing kayaks can exceed hull speed by 70%, even though they do not plane. Semi-displacement hulls are intermediate between these two extremes.

Edited by - on

JohnP
Master Marine Consultant

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1520 Posts

Response Posted - 05/25/2011 : 19:42:44

That's interesting. Thanks, Don! Let's all do it now!

Edited by - on

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 05/26/2011 : 06:13:46

Another article explaining displacement hulls and hull speed.
[url="http://www.boatdesign.net/forums/boat-design/hull-speed-displacement-hulls-7785.html"]Hull speed for Displacement hulls [/url]

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hillerji
1st Mate

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USA
37 Posts

Response Posted - 05/26/2011 : 07:57:00

Joe Diver,

I like your philosophical outlook on sailing vs golfing. I too can make her go but some much of the finer points are hard to grasp. It makes sense but like you said it's putting it to use and applying the technique that is the challenge.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 05/26/2011 : 15:10:56

Interesting discussion in the Potter link from that page about Gerr's formula. I like th etable at teh top that gives speeds relative to cargo weight.

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 05/26/2011 : 17:00:28

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Hull speed, sometimes referred to as displacement speed, is the speed of a boat at which the bow and stern waves interfere constructively, creating relatively large waves, and thus a relatively large value of wave drag.<hr height="1" noshade id="quote"></blockquote id="quote">

Complex way to say wave length equals waterline length, but more precise. We frequently got our Clipper 21 with 17' of waterline in the 6.5 - 7 range. It has a very fine entry that effectively split the wave without enough buoyancy to try to ride over it in a plane. Pearl has never gone that fast, but that doesn't mean that she can't in the right hands and conditions.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 05/29/2011 : 07:10:38

Well I took the camera out yesterday, but never got into reportable speeds.Maybe next time.

Also, I forgot to hit record...

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