RE: what fin size for a 6.8m on a S type104
Thank you for your feedback.
You correctly pointed out my inappropriate tone. I let my frustration come out that these formulas, while simple, represented a huge amount of work in years of gathering data, analyzing the data to find the relationships, and then distilling them to make user friendly formulas (the focus was for my wife). I think that my objectives are not clearly understood by the team and I feel dismissed with data that is on a tangent and gut feel. I have further found it difficult that Starboard does not have sufficient support for the average sailor in terms of a simple "research" section on their website and my previous suggestions seem to have fallen on deaf ears. I had to learn too much the hard way. My motivator for my work was to make the learning curve for my wife a lot easier than it was for me and it grew from there. But that is arrogant on my part and it is all no excuse. I have taken a deep breath, put this in perspective, and I will chill out. I appologize if I have offended anyone. Thanks for your heads up.
As regards your data, I am stumped. You are indeed the base that the formula was derived from. I checked your calculations which seem right on. I even checked the conversions to knots as I never use them and could find no errors there. My experience is specifically that cambered sails or not and different tail shapes made no difference in the formula, so I can not see that as an explanation. And yet I have too much consistent data to not believe that I can somehow rationalize this. If you are willing to help me out, do you have any other information that relates and could shed some light on this? How did you measure wind speed? (That was one of my most difficult obstacles as even iwindsurf uses algorithms). I assume when you say planning, you mean your normal planning speed, not just planning. Any other relevant data would be appreciated. If this is going too far off the topic of this thread please feel free to e-mail me.
Re your comment "You said yourself everybody can adjust the coefficient to their needs, so what's the point of a formula, when it's always different?" Until your data, I had not come across any need to vary the coefficient for a wide variety of sailors in a wide variety of conditions. But if someone, for whatever reason, needed a different coefficient it should still be a valuable formula as it should be consistent, even if unique, for that person. But your data on fin sizing is even raising a question on linearity there.
Thanks again for commenting in a very positive and constructive manner and I look forward to possibly hearing from you.