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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction
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  #1  
Old 02-25-2010
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Rolling Rolling.....

ain't gonna worry no more.....ah I digress yet again...

In a discussion off forum the comment was made about a certain boat potentially being a "roller".

What aspects of a boat's design would cause her to be a roller ?
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Old 02-26-2010
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I don't know but i do know that some are.

In the marina I used to be in, a big wake would come by and all the boats would roll - some would still be rolling looooong after others had stopped.
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Old 02-26-2010
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I imagine that a flatter bottom, or v shaped hull would tend to roll less than a round hull. Hard chines probably roll less than soft one. It probably also depends on the size and shape of the keel. I also imagine that a beamier boat would roll less, while a narrow boat would roll more. Deadrise at the waterline would probably also make a difference. Vertical topsides at the waterline would encourage rolling as compared to ones at an angle to the waterline.
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Old 02-26-2010
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just think water resistance. It all becomes clear, at some point, grasshopper.


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Old 02-26-2010
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Wide flat bottomed hulls will tend to have greater form stability... and roll less.
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Old 02-26-2010
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Another possibillity, is a round bottom as mentioned, along with a shallower keel and lower % of ballast to disp, and/or along with a taller mast.

A deeper heavier keel will counter the above water movement potential a bit better with the longer pivot arm to stop the rolling. A taller mast/shorter keel, the keel does not have the potential to stop the rolling as easy.

my 01 to the mess.

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Old 02-26-2010
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I probably should have limited the discussion to round bilge.

Anywho..it would seem intuitive that beam coupled with ballast down low give less roll but I'm not 100% certain that this is the case or that it is all of the case and that other factors also come into play.

Thinking of moored boats at our marina I've noticed quite beamy boats that seem to move around a lot more than narrower ones while our multi chined hull does not seem to be inherently more stable than a friends round bilge version of the same boat.

I'm thinking that the curve of the bilge (is that the correct expression ?) and buoyancy fore and aft may also have an impact, so that a wider stern might limit rolling while a very fine stern encourage it.

To that end would it follow that a typical IOR hull (fine bow, pinched in stern) be more of a roller than say a modern wide arsed jobby ?







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Last edited by tdw; 02-26-2010 at 04:11 PM.
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Old 02-26-2010
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I don't think ballast to displacement ratio matters much. A ballasted poly drum still rolls. An unballasted raft does not.
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Old 02-26-2010
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I don't think ballast to displacement ratio matters much. A ballasted poly drum still rolls. An unballasted raft does not.
aye...but which one would be preferable going to windward ?
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Old 03-22-2010
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Quote:
Originally Posted by tdw View Post
What aspects of a boat's design would cause her to be a roller ?
Centre board is raised?
Heavy mast?
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