Does the Code-0 calculation include setting the (downwind) spi area to 0? This would suggest an enourmous speed potential in the "useable" wind ranges.
Yes and no.
These rating systems were developped to accurately rate optimized sloop rigs, this assumes an optimal interaction between jib and mainsail. However you can't maintain the latter when adding a code-0. Sure the performance will increase some by adding the code-0 but it is really doubtful whether it will be by the amount these rating system predict.
Compare it to this. I can also add a 40 sq. mtr. spinnaker to a Tornado (old worrell 1000 style) and the rating systems will duly predict a proportional performance increase. However, we have all learned since then that a 25 sq. mtr spinnaker is faster then this monster spi even though it is significantly smaller. The same can be said for replacing the current jibs by a monster jib called a code-0.
Wouter
