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From "Bluewater Defined"...
Jeff clarifies the issues surrounding the widely held notion that a "heavier" boat makes a better bluewater boat...
I think that it is a huge mistake to say that "the most important feature of a ship sailing in the ocean is weight." In and of itself, weight does nothing good for a boat; In and of itself weight does not add strength, it does not add seaworthiness, it does not add carrying capacity, it does not add seaworthiness, it just adds higher stresses and makes a boat harder to handle.
While it is important to have adequate displacement to be able to carry the gear, consumables, and spares to make passages,and to have adequate structural strength and adequate ballasting to stand up to its rig, any weight beyond that is detrimental to the boats prime mission which from my perspective is to sail efficiently.
Traditionally the rule of thumb has been cited as roughly 2 1/2 to 5 long tons of displacement per person. These days that number has crept up as we have become increasing dependent on more sophisticated equipment to operate our boats. Ideally, from a motion comfort, seaworthiness and motion comfort standpoint, that weight should be spread over as long a waterline length as is practical and still achieve adequate structural and ballasting capacities.
Then it comes down to hull shape.
And a further clarification...
I think these discussions often go around in circles because of the way that we come to define them. Perhaps this will clarify my point. It takes a certain amount of displacement to support the boat and crew. If we have two boats of equal dry load (meaning empty tanks, and lockers etc) displacement, generally the boat with the longer waterline will carry a larger percentage of its weight in full load capacity. Obviously there is a limit to how long an equal weight boat becomes before the boat ceases to be structurally suitable, but withing a reasonable range the longer boat of equal length will offer a gentler motion, a more easily driven hull and so a smaller sail plan making it easier to handle, and will perform better as well.
And By the same token the cost to build and the cost to maintain is larger proportionate to displacement rather than length.
So while we may rightly say that if we compare two boats of equal length, similar hull forms, rigs, and weight distributions and ballast ratios, the heavier one would be more comfortable (up to a point), when we talk about going distance cruising, I think we need to define the displacement that we need to carry of stuff, and then look for the longest boat that can safely do that (which means a lower L/D).