Anyone know about where the center of rotation is on a full keel power cruiser or sailboat?
 

Does anyone know about where from bow to stern the center of rotation
is on a full keel power cruiser or sailboat?

I've heard it's as far forward as 1/3 from the bow....my boat behaves
differently. I'm interested in what the architects think, particularly.
Thanks in advance.....

On 1 Feb 2005 18:51:58 -0800, "rascalfair"
wrote:
Does anyone know about where from bow to stern the center of rotation
is on a full keel power cruiser or sailboat?

I've heard it's as far forward as 1/3 from the bow....my boat behaves
differently. I'm interested in what the architects think, particularly.
Thanks in advance.....

=============================================

It depends of course. As the proud owner of a full keel power cruiser
which has an incredibly large turning radius, I'd say the center of
rotation must be at least 200 feet forward of the bow.

All kidding aside though, it will turn in its own length with the
engines reversed so its hard to say where the center of rotation
really is. The largest turning radius I've ever seen was on an older
12 meter racing sloop (with a full keel of course). It was actually
necessary to start your turn well before the bow reached the windward
mark.

On Tue, 01 Feb 2005 18:51:58 -0800, rascalfair wrote:

Does anyone know about where from bow to stern the center of rotation
is on a full keel power cruiser or sailboat?

I've heard it's as far forward as 1/3 from the bow....my boat behaves
differently. I'm interested in what the architects think, particularly.
Thanks in advance.....

I'm not an architect. But for foils which are not stalled, the center of
pressure is usually about 25% of the way back from the leading edge of the
foil.

When you are barely moving, the foil is probably stalled, and the center
of pressure is then at about the 50% mark.

If the keel leading edge is swept back (I'm sure it is) then use the
middle (vertically speaking) point as your reference for the leading edge,
I guess.

I don't know what a full-keel power cruiser is. If it has a keel in the
water, the above should hold more or less true.

HTH!

--Mac

rascalfair wrote:
Does anyone know about where from bow to stern the center of rotation
is on a full keel power cruiser or sailboat?

I've heard it's as far forward as 1/3 from the bow....my boat behaves
differently. I'm interested in what the architects think, particularly.


At first I thought you meant the center of rotation when rolling or
pitching, but you probably mean turning.

Sailboats rotate around their Center of Lateral Resistance (CLR), an
imaginary point which the boat would balance on if shoved directly
sideways thru the water. Generally figured to be the geometrical center
of lateral plane.

Motorboats are a bit more complicated. Because of the directed thrust of
the prop wash coming off the rudder, motorboats rotate around a point
well forward of their CLR. It's usually figured at between 1/4 and 1/3
of the way from the stem. Light or fast boats tend to rotate around a
point more forward. It gets even more complicated when maneuvering in a
crosswind, because the boat's rudder will try to turn the boat around a
different point that it would rotate around if pivoting due to windage.

So, how does your boat behave differently?

Fresh Breezes- Doug King