How does the stability of the Pearl compare to a stock boat?
The design goal was to have the same righting moment without water ballast that a stock boat has with the ballast full. We haven't done any actual righting moment tests on the Pearl, but the math is pretty straight forward and by feel we hit the target right on. Unballasted, the boat seems to sail a little more upright than a stock boat as the breeze picks up, but I suspect that difference is mostly from the huge improvement in sails. It's really important to be able to control the draft in the sails as the wind picks up.
With the ballast tank full and the keel down, the boat has double the stock amount of ballast induced righting moment. She doesn't have quite double the total righting moment, as hull form stability only increases slightly by adding weight, but she gets REALLY stiff with the tank full. The boat certainly is faster if you ballast when the wind picks up rather than reefing the main.
One option that we loose is the ability to pull the daggerboard up when sailing downwind to reduce drag. With the ballast on the end of the board, righting moment goes way down with the board up.
We do have even more stability than a stock boat when motoring unballasted, the 500# keel is both heavier and a little lower (even retracted) than the 300# fixed ballast inside the hull of a stock boat.
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