Stability Curve and CE Rating

matt1

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Hi

Some builders reference a number immediately after the rating and in some cases provide 2 ratings for the same boat eg A10/B16 is this as simple as the boat being rated category A with upto 10 people on board, but diminishing to category B if you have between 10-16 people on board??

Similarly the stability curves for the same boat show three lines on the graph; "MOC" which has the best stability, then a curve for "LDC 10" and "LDC 16" (presumably related to the above) which show less stability.

Lastly, my current 31' boat (with healthy (bulbed) ballast ratio) has an AVS of circa 125 degrees with peak righting arm being nearly 0.6m. I'm comparing with the stability curve for a 42' boat that is nearly identical eg peaks at around 0.6m despite being 6 tons heavier and clearly having more form stability and 1 ton more ballast. Would this seem right? The only difference being my boat has 37% ballast ratio and the 42' has 28%

Thoughts?
 
'Form Stability' simply affects the steepness of the Stability curve between 0 and about 30 degrees.

The righting arms might well be similar but the Righting Moment will be very different as that is the righting arm multiplied by the displacement. Therefore the bigger boat will be more stable.
 
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