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post #1 of 5 Old 01-02-2011 Thread Starter
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Boat Displacement

I have a question regarding boat weight maybe someone can answer. On the site below, its shows displacement and ballast. My question is, do you add those two figures to get the total weight of the boat?

On the other hand, I am wondering is displacement the total weight and ballast is simply showing that amount of the displacement is ballast?

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post #2 of 5 Old 01-02-2011
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The other hand is the right one! Displacement is technically the weight of water that the boat displaces when floating... equal to the actual weight of the boat. (Archimede's law) Anything that weighs more than it displaces will sink.. (a chunk of lead, for instance)

The ballast is the portion of the overall weight that is in pure ballast form (a bolt on keel, or ballast loaded into a hull cavity) Ballast ratio is a general term that implies how tender or 'stiff' a boat may be. Ballast ratios generally range from .25 to .50 in production boats, running around .3 - .35 or less in more modern designs, whereas boats built 20 - 30 years ago often had ballast ratios in the .45-.50 range.

The actual characteristics will depend on keel design and hull form in combination with whatever the ballast ratio might be.

Ron

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post #3 of 5 Old 01-03-2011
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Just beware that the data on there isn't necessarily accurate! My boat is listed at over 33ft long and weighing 10000lbs

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post #4 of 5 Old 01-03-2011
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Yes.. a short list and some inaccuracies.. here's a couple of better ones:

Types of Sailboats - Sail Boat Database - Sailboat information - Jibslist Sailboats
(click on boat type once found for more detailed info)

SailboatData.com - sailboat database with specifications, drawings and photos, more than 8000 listings
(This one often has pictures or drawings too)

And for Canadian built boats:

Used Sailboats in central Canada
(suggested prices are somewhat out of date)

Ron

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post #5 of 5 Old 01-03-2011
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Quote:
Originally Posted by Faster View Post
Yes.. a short list and some inaccuracies..
The 'brochure' displacement figures are
invariably reported lower than actual
boat weights. In some cases the discrepancy
is a substantial amount, 10% or more of the
'as designed' displacement.

Islander 30 II 'COOL'
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