John,

As I mentioned in my earlier post on the subject, this simple formula does
not totally rationalize a very complex problem. It is probably pretty much
useless trying to compare a 126' schooner and a 46' powerboat.  Just
guessing at waterline length and beam I get about 75 for the Alden.  It will
be more comfortable than the DD.

There is nothing specific in Ted's formula that will differentiate sail or
power boats.  The key is, as he says, it's useful to compare boats of
similar types.  In my mind that would go for size as well.  The concept has
limited value, as you found trying to compare two very different vessels.
But the formula does indicate they both will be reasonably comfortable in
many offshore situations, which would hold with common sense.

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Tad,

I think you make a good point i.e. "similar type"
is very important.  My experience would suggest that a similar vessel length
width and draft of a sailboat and a power boat are still VERY different.

I conclude that comparing one or the other by the formula would be
interesting but not one WITH the other.  The sailboat - given the sails are
up and the mast is in place - has a very different axial frequency and
damping that a power boat unless you at least add stabilizers or paravanes
to the power boat.  Maybe then they can be compared.

New item . . . .

My observation is that a Nordhavn 57 or larger with "modern" variable gain
stabilizers set for flattest performance is VERY much flatter than any
similar sized power boat equipped with paravanes in flat to moderately heavy
seas but not necessarily more comfortable - because it is so stiff as to be
a little jumpy, and produce significant horizontal motion instead of a soft
roll.

Other observations ??

John Harris
World Odd @ Sea

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