As every rudder stock is different, we always produce them to the specific customer requirements. In general the designer of the yacht specifies the material and dimensions. We can be of assistance if a calculation for a different material is required or if the design has to be modified for a more economic production. In a lot of cases designers draw a rudder shaft with a maximum diameter rounded off to a full figure (i.e. Ø 70, Ø 80, Ø 90,etc mm). It could be that the calculated diameter is 2 mm less. This is a very costly round off that is completely unnecessary: To achieve a high tolerance surface of Ø 90 mm we would need to use a 100 mm solid bar profile. If the diameter of the rudder stock would be 88 mm, we could use a 90 mm solid bar profile. As the price of bar material goes up exponentially with the diameter, one can save a lot of money by acquiring the exact calculated diameter from the designer.