ISAF Rating for small cats
http://www.schrs.com/The approach taken by ISAF RATING - schrs differing from Texel is basically to take base standard sail area calc. for non-spin and apply the following for spin.
-basically plus 10%* max.spin area - minus- max. jib area
which reads { +10% * CSPI -CJ } -
Note; -interesting that jib area is subtracted-but is a correcting factor on average, jib efficiency with spin is negated to a large extent, this also eliminates the need to rate non-jib types separately.
Roller furling jibs are often used effectively with spin rigged cats increasing their efficiency in many conditions.
The ISAF RATING provides very similar end rating numbers with Texel ,-but has this variation in spin rating -and other minor variation in calc .
Average comparison --rough estimate, --Texel uses 4 points -
ISAF uses 10% factored into S A -
On average spin area is just over area of main and jib in the majority of classes. -This brings it to 5% on average after calc - then subtract jib area per ISAF Calc and we end up with an approx. 4-point average, which Texel uses.
Texel then uses targeted spin area, which further simplifies the process by standardizing sizes per Length. Then penalizes spin area over max. targeted size by 11 % added to rated SA .
Before spin. were widely used a simple method needed to be applied and a uniform point of beginning to further simplify spin adaptation to existing cat design was applied as then needed.
Spin sizes are now established with numerous classes based on Texel size target areas. Most Formula Classes use max per L catagory.
The need for variation is developing particularly in lightweight F Classes and the larger size range up to 22 ft often with more beam and sail carrying capacity. Designers should decide ideal spin area per L- B
. The Texel rating is ideal but may update periodically along with the developments in our sailing craft oriented sport.
The ideal update to the rating may be to substitute the targeted spin areas per L category ,---AV 4 POINT application,---and penalty over calc .
Replace this with a similar ISAF rating approach, --adding a 10% spin area {the CSPI number}}on to the base equation that factors in W ;L- SA- and Spin Area
Texel lists all non spin and with added spin categories,
Many classes now are spin dedicated classes, -those few that are not can be listed twice w spin and non-spin.
This application allows variation in spin area as per design criteria per designer, -or per modification per N A sailor without penalty added. Again most spin sizes per class are now established.
Future and current potential HT Classes like HT F18s will benefit from such a spin rating revision update, --but also conversely be corrected with the jib subtraction aspect of this proposed N A rating system having no jib as several future spin classes may opt.
Also the foreseeable need for future H T Formula 20 or Formula 22 Classes to emerge capable with added beam and sail carrying ability to require larger spin sizes than per current category max .
Summery
1- Wind Speed mod factor as proposed ;per previous outline
2- Update ;revision of spin rating --per outline;
3 ;needed;handicap added factor
Would like to work on this aspect handicap added factor based on DPN rating ,-applied to older design in handicap classification with fellow interested catsailors that see the need for this refined and improved combination rating system .
Taking the best elements from each of the current catamaran rating systems in use and formulating a future universally accepted international catamaran rating system.
Carl
