Effect of Canted Sails on Heeling Moment

The diagram below shows the relationship between the transverse rig position and the heeling moment. The cross section shows a proa hull configuration, but the principle applies to any hull configuration.



An MSExcel spreadsheet is available for the above formula if you wish to try a few examples.


1) The hydrodynamic force fhyd which is the net hydrodynamic lift of the hull/foil system has been shown acting horizontally, but could be at any angle e.g. in the case of canted foils (Bruce foils).

2) The line CE,ip is normal to the net sail force vector fs.

3) The reaction force is the vector sum of fhyd and fw. The weight force fw is the total weight of the boat minus lift due to bouyancy, and is equal to the vertical component of fs.

4) h is positive if CR is upwind of ip and negative if CR is downwind of ip.