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post #46 of Old 03-27-2012
keforion
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Re: Full Keel Vs. Fin or Modified Full Keel

One point that I have not seen in this discussion regarding keel hung rudders is that when close-hauled and with just the right touch of weather helm, the keel-rudder system is now an asymmetric hydro-foil giving lift to windward even if the hull is going straight ahead through the water. The modern fin-keeler with separate spade or skeg-hung rudder does not have this advantage and in order to generate lift from the fin-keel the entire boat, fin-keel and hull, has to go a bit sideways through the water.

As to performance, I sailed an IOD, with what might be the classic example of what Jeff H calls the "worst of all possible worlds," and it went to weather like a witch. I plotted courses over the ground in many passages of an upwind course and the average angle between legs was 78 degrees. Note that this is not "tacking angle" or "pointing angle" but the angle between the actual courses on successive Port and Starboard tacks made by the boat over the ground. Generally no tidal current and averaged over many different days and conditions.

Does anyone have actual data on similar performance with one of the modern designs?

Incidentally, the IOD with a 25' lwl would also overhaul Cal 40's downwind as well.
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