We can move this conversation over to the other thread if you prefer. I will briefly answer some questions here.

1) LTM = is length of the top of the mainsail as you state, so it does factor in and my apologies on misspeaking on that front.

2) I'm not sure the sinking hull correction applies only to H14's and H16's. I would have to dig into that more. Will probably knows the answer off the top of his head.

3) So I used the same VLB. I would have to look at the formulas directly but I don't believe SCHRS distinguishes between short stubby Tornado-like centerboards and narrow, high aspect ratio F18 like daggerboards beyond this number, i.e you could build a boat with very high VLB but super big chord and be slow.

4) I was quoting the Isotope class website, NOT the F16 class website when making that statement. I'm not arguing your point that 45 years of technology hasn't made a significant impact on boat speed, because it has, but the Isotope manufacturer is claiming the boat as a fantastic trainer for the Tornado (same statement made by the F16 class) and they are the ones claiming the boat performs as good or better than an F16!!!!

5) When looking at the SCHRS numbers, one big thing sticks out to me in general, and that is platform and sailing weight matter a healthy amount to the final number. I would weigh your actual platform if at all possible, as I suspect it is heavier than the 113 kg you have quoted (even the Blade F16's aren't really there). That could drive you back to a more 'fair' number.

6) SCHRS may not be creating a perfect number for your boat in a long downwind race, but take a look at the Taipan 4.9 numbers. I'm referencing that as I believe it is pretty similar to the Isotope in many ways (including design age). The big thing is they race without the jib in solo mode. Add the jib in and you drive the number from 1.097 to almost half, or 0.980. That may need some looking into on the SCHRS side as I doubt the boat is actually twice as fast with a jib as without.

Hopefully we can resolve your issue, and I'm okay with it being public because it is important for others to see the process and become familiar with it.

Last edited by samc99us; 02/12/18 05:03 PM.

Scorpion F18