Righting moment

[Paul Davenport]

Guys,

What exactly is 'righting moment' as applied to yachts?

Grateful for any response...as usual the virtual beer awaits, and awaits
and...

[Umi_Ryuzuki]

A sailboat works because the heeling moment and righting moment balance. The heeling moment is the amount of pressure against the sails measured in pounds of pressure. The righting moment is displacement of the hull pressing down as the boat heels. As the boats heels farther over, the righting moment is increased because more of the boat's displacement sits on the windward side of the center of buoncy of the boat (the part the boat seems to be balanced on as it sails with heel). Once you know these forces, you can measure the required sail area to move the boat at a specific heeling angle and how much heeling will occur for a given wind condition and sail area.

Heeling Moment

The heeling moment (HM) is defined as the pounds of wind pressure per foot squared multiplied by the sail area (SA) in square feet multiplied by the heeling arm. The heeling arm is the distance from the center of effort (CE) to one half of the draft of the boat.

Righting Moment

The righting moment is the distance from the center of gravity (CG) to the center of buoncy (CB) multiplied times the displacement.




reprinted from
http://www.geocities.com/mithrys/u_sailplan.htm