# New stability requirements for catamarans

Discussion in 'Stability' started by OldYachtie, Sep 25, 2006.

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### OldYachtieJunior Member

The coast guard wants passenger sailing catamarans to satisfy the following:

(b) A sailing vessel that operates on partially protected or exposed waters must be designed to satisfy the following equation:

Where—

B=the distance between hull centerlines in meters (feet).

As=the maximum sail area in square meters (square feet).

Hc=the height of the center of effort of the sail area above the deck, in meters (feet).

W=the total displacement of the vessel, in kilograms (pounds).

X=7.32 kilograms/square meter (1.5 pounds/square foot).

[CGD 79–023, 48 FR 51017, Nov. 4, 1983, as amended by CGD 83–005, 51 FR 924, Jan. 9, 1986; CGD 85–080, 61 FR 944, Jan. 10, 1996]

I can work this, as it isn't complicated, but what the heck is the outcome measuring? Apparently it's too obvious to mention. Except it's not obvious to me.

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### OldYachtieJunior Member

And here's the equation, which goes with the definition (was in a .gif and so didn't cut and paste

0.1(W)B / (As) (Hc) is greater than or equal to X

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### VegaSenior Member

The stability of the boat, considering its sail area?

This apply only to commercial boats?

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### jehardimanSenior Member

What they are measuring is the average ability to resist the moment of the wind pressure on the sail. But is seems a little low, that load would be reached at ~8m/sec stagnation pressure.

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### OldYachtieJunior Member

Yes, only commercial boats that carry paying passengers. The thing that puzzles me is that the equation contains the elements of stability, beam and displacement, and the elements of capsizing moment, sail area and mast height. So, why should the solution be anything but a coeffecient? Why would it be an outcome of force per area of something, and yes, why such a small number?

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### taniwhaSenior Member

MCA / CE and other regulations apply the International Standard ISO 12217-2 stability of sailing yachts above 6m including requirements for multihulls.

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