A Fast Offshore Cruiser - 15. VPP.

The VPP program used here is the Windesign VPP. The program was not used as a design tool during the development stages of the design work. Its has been used as a confirmation of the design brief, i.e. for the vessel to be fast.

A VPP program could be used during the development stages of a design, to help select optimum hull form etc, but due to time restrictions and design brief this was not viable. Also VPP programs are based upon data from tank testing of a series of similar models so will not be completely accurate for none similar hull form. In the present situation it would have been better to be used in conjunction with real data from tank testing of the actual hull form.

A run was completed for each of the rig configurations outlined in Appendix D.2. The internal RAW, Resistance Added due to Waves, model was activated. The keel and bulb were simplified down to only a foil with no bulb, due to the minimal distinction between the foil and the bulb. No prop etc resistance was included due to not knowing the dimensions to input. The wind speeds have been limited to produce an approximate maximum heel angle of 25° ; the lower wind speed was limited to produce a heel angle of approximately 10° . The lowest wind speed used was 6kts (3.25m/s), accuracy issues, and the maximum was 35kts (18.96m/s), program maximum. The range of the true-wind headings was set to 32° to 180° . The set-up is for a cruiser, rather than a racing yacht or experimental. Sail and rig data was entered; the windage was automatically created by the program.

The polar plots produced do indicate that the boat will be fast. 8 of the 9 plots shows that at least 9.75knots is reachable and 5 of the 9 showing speeds of 10.5+knots.

These results cannot be taken as exact but only as a guide but there is promise that the boat will satisfy the brief in that it is fast.