If I understand this correctly you take your DP-N number and subtract any modifications from it to create a lower number, is that correct? I ask to correctly classify and rate my boat for future race events. I have looked at every spec for each Hobie 18 class and feel the inactive TheMightyHobie18 Formula is closest to what I sail. I would take the penalty for taller mast(SX) and non-standard main ( of equal or lesser size). And a separate penalty of .995 for my jib set-up(which isn't standard). If I'm calculating correctly ( 71.2(H18F) - .995(mast) - .995(main) - .995(jib) = 68.2 )
After several races with the boat I feel certain it will never sail to the 62.0 of the Tiger. I wish I could say differently but the F18s eat me for lunch. My boat is faster than the H18s even without the spin in most situations, which I am very pleased about.
If I'm wrong please tell me so, if I should calculate the numbers differently tell me. I'm trying to learn and be fair with myself and others. Thanks!
You need to multiply the ratings by the modification factors. Not subtract. Also keep in mind that the rating is intended to grade the potential of the boat without consideration for the sailor. Getting this deep into the modification factors with a modified boat is a grey area when using a handicap system that is established based on performance data.
The HobieSX rating you are suggesting has an antiquated deep-downwind spinnaker, 40 lbs of wings, and only rates .2 different than a standard Hobie 18 without a spinnaker. In my opinion, it's not fair to use the Hobie 18sx rating to run a modern F18 spinnaker on a Hobie 18 without the wings. You should start with the Hobie 18 rating and take a hit for a taller mast, non-class legal mainsail, and spinnaker. The jib is smaller than the standard jib so I wouldn't necessarily start with taking a deduction for that.
Also understand that while you can argue for a particular rating, at the end of the day, the rating and the handicaps applied is ultimately the responsibility of the PRO.
Using DPN numbers (not wind correctors)
Hobie 18 = 71.4
Spin hit = .96
main hit = .995 (assuming of equal sail area)
Mast hit = .995
DPN = 71.4*.96*.995*.995 = 67.86
Given that the only difference between your boat and an F18 that rates 62.8 is the hull shape and the board aspect ratio (maybe weight?), I believe this is a very generous rating but a reasonable place to start.
