Re: [PSUBS-MAILIST] A Solution

["Sean T. Stevenson" <cast55@telus.net>]

Stability is not that complicated.  Fully submerged, it just means CB must be
above CG.  On the surface, or at any degree of partial submersion, CG can be
above CB, provided that as your vessel rolls, CB shifts outboard so as to create
a moment arm about the center of roll which counteracts the moment arm created
by CG.  Imagine your vessel as having a plane amidships, which rolls with the
vessel.  The vertical distance between the instantaneous CB (which changes due
to hull geometry, angle of roll and how far the vessel is submerged) and this
plane is the metacentric height, which is a measure of stability for that
particular angle of roll.  Large metacentric heights indicate a "stiff" vessel,
which has lots of stability but may not be quite as comfortable in a sea as a
"soft" vessel with less (but still sufficient) stability.  A cylinder lying in
the water has exactly zero stability since CB and CG are always in a vertical line.

-Sean


Quoting Joseph Perkel <joeperkel@hotmail.com>:

> 
> Gentlemen,
>  
> I seem to keep coming back to this particular solution, probably because as a
> mechanical guy...I can figure out how to build this. As a pilot, I can
> visualize CG, W&B and forces at work, but what I am not......is an engineer.
>  
> That lack of knowledge and my desire to build a successful and uniquely
> spectacular project, is partly the impetus to pursue Naval Architecture,....
> but I am not there yet. I do not yet know how to calculate for surface
> stability of floating bodies, but I do have an idea of what's required.
>  
> the link below is in case the photo won't load
>  
> http://www.frappr.com/?a=viewphoto&id=269116&pid=3198712&myphotos=1
>  
> My post to Rick about width is what it is.....a guess. Would this be unstable
> at 8.5' ???, the key is in the math. Somewhere in here is the answer to this
> particular option. I'll let Jay speak to the sea sled option as it's beyond
> my ability to envision it.
>  
> Thanks to everyone for the participation, the results are self evident.
>  
> Joe





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