Static heel Angle Aproximations

Hi was hoping some1 could help me in regards to static heel angle aproximations. I have worked out the static heel angle for an existing boat but i want to transpose the wind speeds onto the gz curve, however i cant create a line for representing the wind speed because i have only worked out 1 point for it. thats is where the heel angle interects the GZ curve. I hope some1 out there can help me and i know its very basic but have forgotten and have been racking my brains so much i know that i am over complicating it. .

Thanks for any help in advance.

Peter

 

I think if You multiply heeling moment to cos of heel angle, You will get result for worst case. Some experts claim this should be cos squared. More details on this matter You can find at Marchai's "Sail performance", where more detailed approach is presented.

 

Multiplying by cosine of heel angle is correct for any applied moment. The formula is GZangle = GZzero cos(angle). However, the use of cos-squared is a refinement that considers the reduction of sail area when heeling, whereby the area is also reduced by cos(angle).

 

Heeling arm curve

Use Excel and solve wind heeling moment for angles of heel, beginning at zero degrees, and up to about 40 degrees. Then use the Excel chart function to draw the graph. The equation to use can be found at comment #2 by TANSL at:

http://www.boatdesign.net/forums/stability/wind-speed-vs-angle-heel-45588.html

The above uses metric units.
Then, divide wind heeling moment by displacement to get a derived wind heeling arm in units of meters.

The curve will diminish with increasing angel of heel. If you superimpose that curve on the Stability Curve, using righting arm in meters, and 'virtual' wind heeling arm calculated as wind heeling moment/displacement (kg), then the wind heeling arm is referenced in the same units as the righting arm, i.e., meters.

 

Another current thread which is directly relevant to this one.
http://www.boatdesign.net/forums/stability/wind-speed-vs-angle-heel-45588.html

ISO 12217-2 uses the cosine to the 1.3 power. As the convenor of the ISO12217 committee explains in a post in that thread: