[Plumper]

Originally Posted by Jeff_H

I think that this has turned into a good discussion of this complex issue. I did want to touch on a couple of Keelhaulin's discussion points. The point that I was bringing up was that there is a perception based on L/D numbers that modern performance cruisers are substantially lighter than the boats that preceded them.

As I was trying to point out a modern 35 footer is not all that much lighter than a CCA era 35 footer (perhaps 5%-10% at the most, and often the newer design is actually heavier) but they tend to have substantially longer waterline lengths and substantially lower VCG's, both of which would tend to make the boat more seaworthy, have motions that are easier on crews and increase carrying capacity as compared to an earlier era equal displacement/shorter waterline boat.

The point that I was making is that there is a problem that arises in comparing equal weight boats modern boats to older designs using these older formulas. The problem is with the expected values which were based on older style short waterline boats. When you apply these standard range of values to modern designs with their long waterlines, modern boats appear to be much lighter than they are and so also appear to be less seaworthy.

I gave a similar example above, but just for the sake of clarity if we compare say a modern 35 footer to a CCA era 35 footer, both would weight roughly 12,000 to 13,000 lbs empty and would have similar weights fully loaded, but the modern boat could easily have 5 or more feet of waterline, both static and heeled. But since the LD, CSF, and MCI use waterline length, the equal weight modern boat would appear to be extremely lighter and less seaworthy, when in fact it is the same weight, and if properly designed, more seaworthy.

Respectfully,
Jeff

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Perhaps some of those formulas should be adjusted to use length on deck instead of WL length. Maybe when comparing numbers both calculations should be used.