Stability at low heel angles?

Given the RM at 1 degree of heel, how do I calculate the RM at 10 degrees please. I'm aware that for the first 10 degrees of heel the stability curve is pretty much a straight line and is straight forward to calculate.
Thanks and enjoy your sailing, RedAtNight.

 

I assume you're talking about a monohull, since the rm of a cat starts to level off at about 5 degs. 1 deg out to 10 degs sounds like a long ways to extrapolate, it might be more accurate to make a separate measurement or calculation. Of course, if it were exactly straight, you would just multiply by 10, or to be more accurate, sin(10 degs) / sin(1 deg) = 9.95.

 

Thanks Skippy. Yes, she is a mono and your approximation is fine for my calcs at this stage.
Cheers.

 

Be aware its pretty innacurate. Works if the section is close to a circle but can be out a fair bit if the hullform tends towards an extreme. Its easy to get a fairly non linear COB shift by the time you get to 10 degrees so be careful.

 

If you are using Maxsurf academic, try selecting all control points and then rotate them about any point you select. With the rotate menu, you can heel or trim the hull in any way that you want (roll, pitch and yaw), then see what you get for stability. Just don’t save the changes.
Robert Gainer