Wednesday, December 26, 2012

Sail Speed Records

New speed records for sail powered water craft are being set constantly. The latest by the Vestas sailrocket is 65.45 knots.  Of course these are records set under ideal conditions.  One should not expect cargo carrying sail boats to reach these kinds of speeds.  Still, regardless of limitations these records are impressive and raise the question, what makes these speeds possible and why weren't they achieved in the past? In other words, what has changed?
I suspect the answer to the question is multifaceted.  Perhaps the biggest impediment to new boat designs was tradition.  It took a while to apply airplane technology to sail design.  It also took a while to bring the weight of a sailing craft down enough so a sail could generate enough power to make the sailing craft rise on a hydrofoil.  Speed in a watercraft seems to be limited by friction between the craft and the water and minimizing that makes new records possible.
But in the past, new, faster sail boats evolved from working craft that had to operate under all conditions and not just special race course conditions.  One thing that is apparent from watching the videos of sail records being set is that the wind seems to be off shore with the craft racing alongshore, thereby avoiding waves. 
And there are any number of other things that a useful work boat has to be able to do that a racing craft cannot do.  Still, new ideas are always welcome.  I am looking forward to seeing recreational versions of these craft.  Who knows, perhaps a skin on frame model that does 20 knots would be a fun experiment.  Planing hull, no hydrofoils. 
The little experimenting that I have done with putting sails on skin on frame kayaks has taught me that the inherent flexibility of skin on frame hull limits how much sail one can carry.  The faster the boat is expected to go, the stiffer it needs to be, or in any case, stiffer than a boat that travels at 4 knots.

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