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post #7 of Old 11-04-2007
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I did a detailed response a couple of days ago which appears to have got lost. This will be briefer.
You can ignore the polars except as general interest and to show the big difference the board down makes to windward ability vmg.
The capsize ratio is came in after the Fastnet disaster and is a rough guide. It essentially looks at beam in relation to displacement. Beam gives you initial stability ie resistance to healing from hull shape, but this then falls away. Ballast insofar as it puts the centre of gravity a distance d below the centre of buoyancy creates a righting moment. The further a mass eg keel weight is down the greater the righting moment as the two are multiplied. This righting moment as the boat goes over initially increasing then decreasing. You need to find the stability curves to see the angle of vanishing stability, which should be roughly 120-. standards vary on use, but essentially when the mast goes under you want it to self right.
The capsize ratio as a method is inadequate because it takes no account of where the weight is.

In your case I doubt that of the 3000 lb ballast it is all in the centreboard, and certainly not at the end of it. If it were then it would be impossible to retract any bulb and the draft would be deeper, secondly it would be very difficult to raise and would require some specialised hydraulic system. The whole structure would also have to be very strong to have that weight swinging around.

The ballast/displacement ratio is a little light at 29%. A blue water boat such as the Allied mk 2 would usually be around 35%.

Jeff H has argued in the past for lighter modern designs and against heavier traditional blue water boats. Certainly the former will have better light airs performance, but there remains disagreement on motion comfort in heavy weather.

However you are not seeking either a race boat, or an ocean cruiser, rather it seems a liveaboard, capable of short ocean trips where presumably you will take account of the weather ie short term as long term doesn't apply.

In that regard the displacement is some 4000 lb lighter than the Allied and 10,000 lb lighter than the Westsail of the same length. That doesn't seem excessively heavy. Further it is not always clear whether full tankage is included in the design weight. I have seen boats stated by the designer to be say 4 tons yet the owners say they are 6 and that is the registered weight which I have also seem miscalculated.

The sail area is not excessive and gives a sail area/displ of 19% which means she should be ok in light winds but is higher than the usual cruiser maximum.

For other boat comparisons and further help understanding the figures see

In essence a centreboard has the advantage of shoal draft but to get a decent righting moment has to have greater ballast as this is higher. Yours is limited. I agree it is not a blue water boat, but don't feel the overall displacement is too high.

It, on the figures, as always, is not perfect as a liveaboard, racer, or blue water cruiser. It is also likely to be quite different from the 37'. How well it suits your needs depends on the specifics of the design and build and intended use. Others can guide you on this.
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