Where is the Fulcrum for a Boat Hit by a Wave?

[Ilan]

Hi,

I'm making an animation of how a boat behaves when hit by a wave. This is how it looks like after the wave:

(see attachment)

At this point there should be a righting moment that tries to balance the boat by turning it clockwise.

Which point does the boat rotate around?

I'm not sure because the forces act on the C of B and the C of G and so I was thinking it would be the black dot, but shouldn't the C of B not move since it is a circular bottom?

What do you guys think?

Thanks!

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EDIT:

Ok so I tried to animate it:

http://www.ironwhisk.com/wordpress/wp-content/uploads/2012/12/test.swf

If this motion is correct, then does that mean that the fulcrum moves? Why?

 

[springwave]

Yeah, the centre of buoyancy remains stationary. (its, basically just the centre of geometry of the part inside the liquid, and hence as shown in the animation remains unaffected as boat moves).

So the motion of the boat can be considered as pure rotation about its C of B. (like rotation about a pivot)

 

[CWatters]

Some hull shapes are designed so that the CoB moves outboard when the boat heels over. Consider a catamaran. With the mast vertical the CoB is mid way between the two hulls. With one hull "flying" the CoB has moved to the hull still in the water.

 

[Naty1]

You might find this article of interest:

http://en.wikipedia.org/wiki/Metacentric_height

Such factors are rountinly calculated when loading cargo ships.

 

[russ_watters]

Most boats, including this one, will have a center of buoyancy that moves. The circular hull would only enable a stationary center of buoyancy if it was at the center of the circle. The wiki link explains it well.