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Old 25-11-2012, 20:23   #1
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Displacement Per Person Rule of thumb?

I swear I've searched for an hour but haven't found an answer I like yet.

I've spent a lot of time living on various small boats but always with a car/truck stash for stuff I still needed longterm but not needed on the boat everyday...fishing/dive gear/cold weather clothing, tools ... stuff.

Somewhere I read there was a loose R of T that applied to being fairly comfortable in a more of less minimalist way with x tons of disp per person. Searching, I found a number of 3-5 long tons (~2240#) per as a R of T. My thinking is that it was a little less. Anyone care to opine?

I'm talking coastal cruising so added supplies would be available.
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Old 25-11-2012, 21:10   #2
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Re: Displacement Per Person Rule of thumb?

I am most comfortable on any boat over 1,000 tons.
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Old 25-11-2012, 21:21   #3
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Re: Displacement Per Person Rule of thumb?

Quote:
Originally Posted by Blue Crab View Post
Searching, I found a number of 3-5 long tons (~2240#) per as a R of T. My thinking is that it was a little less. Anyone care to opine?

I'm talking coastal cruising so added supplies would be available.
I guess that would depend on what material the boat was made of.

But really it's the facilities within the boat that make it comfortable or not and that depends on the person as well. So, I don't think there is a firm answer to your question. But it is known that one person can sail the average boat up 14 to 20k# w/o needing another person aboard, unless it's set up for single handing. Now power boating is a different story but one still needs someone to help dock larger boats.
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Old 25-11-2012, 21:46   #4
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Re: Displacement Per Person Rule of thumb?

I think that this particular rule of thumb won't work anymore. Composite hulls, fin keels with bulbs, etc compared to wood hulls or overbuilt 40 year old fiberglass design is going to make a hash of any RofT
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Old 26-11-2012, 05:54   #5
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Re: Displacement Per Person Rule of thumb?

This reminds me of the Comfort Formula by Ted Brewer that is used on Carls Sail Calculator in comparison of monohull sailboats, result is listed as Motion Comfort

SailCalculatorPro

This may not be what you are asking exactly but may help with comparing Brewer's ideas of Motion Comfort.
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Old 26-11-2012, 07:55   #6
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Re: Displacement Per Person Rule of thumb?

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Originally Posted by Pat Ross View Post
This reminds me of the Comfort Formula by Ted Brewer that is used on Carls Sail Calculator in comparison of monohull sailboats, result is listed as Motion Comfort

SailCalculatorPro

This may not be what you are asking exactly but may help with comparing Brewer's ideas of Motion Comfort.
This calculator has an error, you should use his new one.

Link SailCalculatorPro New

CeesH
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Old 26-11-2012, 08:12   #7
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Re: Displacement Per Person Rule of thumb?

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I am most comfortable on any boat over 1,000 tons.
Hey, Mark, when did you resurface? Welcome back!
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Old 26-11-2012, 09:09   #8
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Re: Displacement Per Person Rule of thumb?

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Hey, Mark, when did you resurface? Welcome back!
Thanks Sean

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Old 26-11-2012, 09:38   #9
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Re: Displacement Per Person Rule of thumb?

Thanks folks. Exactly what I was looking for. I get the point about the older style heavy boats and motion comfort. Gonna hold off any serious research for a couple of days in case I win the lottery.
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Old 26-11-2012, 10:30   #10
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Re: Displacement Per Person Rule of thumb?

The figure stuck in my mind is 4 long tons per man, but that's from an old RN source and meant for long distance oversea transport. Still, might have something to it....
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Old 26-11-2012, 15:18   #11
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Re: Displacement Per Person Rule of thumb?

Welcome back Mark.
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Old 26-11-2012, 17:11   #12
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Re: Displacement Per Person Rule of thumb?

Approx. 4 tonnes per person, for an ocean-going ballasted monohull, sounds familiar. For an unballasted multihull it's closer to 2-2.5 tonnes / person. A small dog counts as half a man, a large dog counts as one man, and a horse counts as five men. Or something like that. Not that it really matters these days; I think most folks just look at the intersection of "comfortable with" and "can afford" and see where that leaves them.
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