


Lets say I gain 0.1 knots, going from 25 knots with HG to 25.1 with C0.
It takes 75 seconds with no speed for sail change... (or is it 75 seconds with reduced speed, like half the speed?).
Anyway, how many hours do I need to go with C0 with this gain of 0.1 for it to be worth while? Let's assume constant TWA and constant windspeed.
So I made the following formula
NS = New speed after sail change
CS = Current speed (before sail change)
75/3600 = 0,020833h = penalty in hours for sail change.
T = time (hours)
Formula is derived from NS x (T-0,020833) = CS x T
which give
T = NS x 0.020833/(NS-CS)
So in the above example
25.1 X 0,020833/0.1 = 5.229 hours = 5h 15 min


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