Potential simplifications

(not all have been implemented into the working NMBR system excel sheet, sometimes more research is required)


-1-

Replacing rated hull length by hull length overall. Simply measurements and input to the rating formula.


-2-

Replacing aspect related efficiency of sails by a much simpler to use linear regressed fitting. Replacing a expression of 4 higher order terms by an expression in the following shape : rated area = (constant + factor * aspect ratio) * sail area.


-3-

Replacing the higher order rating formula by the much simpler ti use linear regressed fittings. The regression in this case is actually quite good. The higher order Texel rating formula can be approximated within 2 % margin by the linear expression : TR rating = 148.922 -2.750 * rated sailarea -6.141 * rated length + 0.132 * rated weight


-4-

Discard the virtual weights of boats that Texel does. Example Texel specifies the F18 to weight 173 kg = 180 - weight spi gear. Just use the real weight of the platform and raise the spi hit with 1 point. This leads to the same end result as the current texel system because of the largely linear behaviour of Texel (see point 3); The 7 kg deduction Texel uses is equal to deducting 0.132 * 7 = 0.924 of the rating of every boat that has a spinnaker. Boats that are measured without spi gear need to add 5 kg's to their boatweights when fitting a spinnaker. This 5 kg is substantiated by real measurements.


-5-

Discard ISAF spi size impact for a simple fixed hit. By accident the Texel rule has create a situation where all boats of the same length share the same spi area. All spi's can be seperated into three major groups around clear concentration points. These points are 17 sq.mtr. 21 sq. mtr. and 25 sq. mtr. By coincidence a fixed hit seems to be fair to all three groups. At a later stage and after more data research some refinement in assigning the spi hit can be included, but for now the single hit seems to be effective and easy to use. There is however a need to do something with oversized spi like that on the Tornado's, Supercats and Nacra 6.0 NE. It is suggested to hit these with one extra handicap point. If smaller was faster than they would be sailing with a smaller spi so some hit must be assigned. However experience and aerodynamic limits (Theory) suggest the gains to be relatively small so 1 point seems to be enough as well.


Wouter




-4-