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Subject: Re: leeway
From: Buck Godwin (bgodwin@XXX.XXX)
Date: Thu Dec 06 2001 - 21:44:42 EST
Ross Garrett wrote that leeway is proportional to the sine of the heel
angle and inversely to the square of the boat speed. He cites a
proportionality constant of 464 based on model tests of for a
particular 12.2 meter boat when using leeway in degrees and boat speed
in knots. In section 3.5.3 he presents a graph that shows good
agreement between the model test data of the actual leeway and the
leeway calculated from full-scale trial data. He recommends the
proper constant be determined for each boat from trials. It is fairly
independent of sail area, unless heavily reefed. I believe the
constant would depend on the hull bottom condition.
Rather than measure leeway by your wake, steer a steady course from a
floating marker dropped overboard and take a bearing on that marker.
Leeway is taken as the difference in the relative bearing and 180
degrees. Don't use a tethered buoy, unless there is no current.
Measure heel angle and boat speed as well, to determine your boat's
constant of proportionality.
I am quoting from "The Symmetry of Sailing" by Ross Garrett, Adlard
Coles Limited, 1987
Buck Godwin
> -- --from Ocean Navigator #45 p. 72
>
>58.5*heel/boatspeed^3
>
>Is an approximation of leeway.
>
>Steve Tripp
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