• For boats fitted with a rudder, the torque of the rudder or rudders is calculated according to following formula and corrections.
It must be known that the torque necessary to manoeuvre a boat depends on :
- the speed of the water flowing on the surface of the rudder at a certain angle,
- the rudder size,
- the total sweep of the rudder (and part of the boat), if the rudder shaft is not perpendicular,
- the compensating surface of the rudder (balance).

C = S x [ (0,4 Lg) – Lc ] x V² x K

Start the calculation

C = Torque in kpm
S = Total surface of rudder (H x Lg) in sq. m
H = Height of rudder in m
Lg = Width of rudder in m
Lc = Compensation width in m
V = Maximum speed of the boat in knots
K = Coefficient according to total angle of rudder