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post #6 of Old 11-14-2001
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Expert advice needed

I really liked the Dehler 36. I had seen at the show and at Annapolis Yacht Sales. I thought it sounded like a good deal for the quality involved. Another boat that I thought looked like a really nice boat is the Farr designed Beneteau 36.7 which is quite agood deal for a lot of boat.

As I have said here before "the motion comfort formula" is totally useless in that it was developed at a time when boat design was very different than it is today or was even when the Farr 38 was designed.

The so called Motion Comfort Index is a surogate formula that does not look at a single factor that effects the actual motion of the boat. It does not look at the center of gravity, the distribution of the boats weights and waterline plane, the hull sections, or even the waterline beam. These are very real factors that shape the comfort of motion in a boat. To try to interprolate a comfort level using only length, max beam and displacement is useless. These parameters do not look at the canoe body, so, for an equal length, beam and displacement you can have a boat with a wide waterline beam carried for a large percent of the length of the boat which would result in a shallow canoe body and a snappy motion or whether then boat has some flare, a fine bow and so a deeper canoe body and a gentler motion. Or for an equal length, beam and displacement, it does not look at whether a large percentage of the boats weight is in a ballast keel that is low below the boat and therefore acts to slow the roll rate while also dampening roll to a small angle or whether its displacement is in heavy teak trimmings held high above the waterline where it can incite wider roll angles.

Beyond that the constants were based on the IOR type form model of a light boat. These were boats that were tortured to meet a rule, a rule that by its nature created boats with a high center of gravity and a snappy motion.

I researched and weighed this issue very heavily before deciding on the Farr 38 because I saw this as a boat that I expect to own for the next 15 or more years and plan to do distance cruising in. I sailed on a lot of boats of this era and it was from that experience that I made my decision. What I have found in many of the more recent IMS generated modern light designs and in the designs that lead up to the IMS type form is that hull shape and weight distribution go further toward creating a more comfortable motion than these surrogate formulas can begin to predict.

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