Abstract:
The Effective Angle Theory (EAT) has been articulated in 2001 [1] in order to predict the performance of a yacht when heeled over. Although this theory is often used by Velocity Prediction Programs (VPP), it has been found in past project that the theory does not match perfectly the reality as the actual aerodynamic forces are lower than those predicted. Because the gap is not fully explained, this project has looked at the particular effect of the heel on the foot of the sail as a possible reason for the difference between the EAT and the reality. To achieve this objective, pressure measurement sails have been used with denser measurement over their foot. A number of tests have been performed: the first aimed at looking at the influence of heel. The second investigated the use of end plates on the boom as tool to improve the forces over the foot of the sail and to see if the results could reduce the gap with the EAT. The last set of test looked at a variation in deck size in order to amplify the effect of heel. From these tests described in the present report, one may conclude that the heel does not affect enough the pressure over the sails to explain the gap. However new and more accurate data have been obtained thanks to this unique testing method. The loss in force due to heel can now be quantified in terms of drive and side forces and the height of the sail the most affected by the heel can now be seen.