Is it correct that the people who engage in this discussion on seakindlyness have an interest in ocean-crossing yachts? Is it also true that most cruisers are not sailing 50-60 foot yachts with a crew but single-handing or couples cruising on boats in the 30-45 ft. range?
Given those caveats, I would presume to define "seakindly" as a boat whose lines and form allow her to give to the stresses of sea and wind with a motion that is smooth, without jerkiness and remains somewhat predictable in a given set of conditions.
The biggest and most significant variable is the condition of the sea, as it is the waves that affect the kind of motion I'm discussing. How the waves hammer a boat's hull
and create turbulence against the rudder
, whether she lifts to a following sea, or surges into a trough, these are all design issues that affect the motion in the cockpit, on deck
and while your'e trying to get some sleep below.
On a smooth bay, seakindliness isn't an issue. I don't think I would ever consider a boat that couldn't heave to in a gale to be "sea kindly." As to what makes one boat behave well when others are behaving badly, ask the naval architects. I know that I can look at a boat out of the water
and "see" where her problems will lie. Beautiful curves present a surface that disperses the force of the waves.
Bob Perry could speak to the physics of drag, water
weight, righting moment and so many of the variables that affect a design--the equations that allow him to see how a boat will behave. Any one who's interested can read books
on the subject and see how their boat measures up to the criteria.
If you spend time in the cruising crossroads: Panama
, Durban or Capetown, you can take your own survey
of which boats are rough on their crews and on which boats the seas have been rough. There are boats you will never see in South Africa
because they sea won the bet long before they got that far. Lots of wives and crew jump ship in Panama
. Boats get shipped back from Tahiti
. There's a lot of atrition. But there are other boats you see again and again with happy crews who sail safely and with reasonable comfortable. I think they would
call they boats "seakindly."