Righting Moment

[Stevens47]

In the process of ordering a new mast for my boat. I have supplied the mast builder with the sail plans that I obtained from Sparkman & Stephens. The builder has asked me for the RM. I am going to make a call to S&S to ask what the RM is for my particular design. I have only a rudimentary understanding of RM.

My question how is RM expressed. I have seen charts giving examples of Disp lb, Hull lb, Ballast lb, Mast & Rig lb, Roll Period sec.

As a example a Cruising Mono with Disp lb=24000, Hull lb=13900, Ballast lb=9600, Mast & Rig lb=500, Roll Period sec=5.7

Static Stability=

Righting Arm ft 1.6
Max RM ft lb 38399
Heel at Max Moment deg 64.5

Would the above example be considered a example of RM that the mast builder will be looking for. If not what is the format the RM is expressed in.

Jack

[Olav]

Jack,

yes, the 38400 ft-lb (RM = Displ. * GZ = 24000 lb * 1.6 ft = 38400 ft-lb) is what your mast builder wants to know.

[Stevens47]

Many thanks Olav for the clarification.

Jack