Hi J
Closest thing we catsailors have readily available is a handheld GPS on board , often distance racing good crews will check vmg directly from the GPS -
distance traveled vs speed to the finish -VELOCITY MADE GOOD ,-A boat may travel at higher speed by heating it up w spin set but sail a longer distance and longer time than a boat sailing more directly towards the finish point at a slightly slower speed , that often a surprised crew finds have finished in front.--tHE KICKER IS THERE ARE TIMES YOU MAY NOT WANT THE BEST vmg --if you know your setting yourself up to take advantage of an offshore current sooner ,-expected shift ,or other course factor ,--this is where distance racing varies greatly from short term gain oriented buoys racing .
--Beyond playing ocilating shifts as noted in the article Variables of tides and current ,-wave size and pattern effect on speed and angle sailed ,-wind speed variables ,-gusts , persistant shifts ,-ocilating wind directions that play such an important part of racing , then add crew and skippers inconsistancies along with tactics ,-other boats partially blanketing or effecting wind ,-being washed off the side temporarily by large waves taking out your feet ,-recovery time ,-gybing time , often very difficult to get a boat going full speed again in large seas after a 6 hour straight high speed spin run .
All the intangable aspects make any polar diagram that can not factor these almost infinate variables in combination just a basic guideline for settings and angle of that particular design.
If you are going at full max theoretical speed ,--but in the wrong direction into a persistent shift ,-or away from better wind velocity near shoreline ,-or ignoring major ocilating shifts , or heading into adverse current offshore or one that may be very favorable like the Gulf Stream . the end result and latter finish time will be very confusing .
A good basic guideline with spin rigged cats in higher winds is once you get beyond 20 degrees course heading it is time to take down the chute and begin to reach .In lighter winds you can often reach typically 90 -some to 75 best vmg without spin ,--from wind direction .
A GPS can be used effectively by for instance placing two on the wire w spin up sailing at higher speed but higher angle to maintain it ,--or one on the wire at lower angle and speed sometimes as mentioned with a better speed to distance traveled ratio.
Direct comparison with other boats in the area ,--their settings and angles chosen is sometimes best source of info on the race course , each is different in each condition .
There in the extreme difficulty of rating different boats fairly or with any consistancy .
It may be best to group boats into similar max -Length beam weight ,sail area catagories , allow crews to modify each for the conditions as they choose , just race in the truer ideal of sport .
The one wind condition that gets many catsailors is the slight persistant shift where the inside cat on a beat gets lifted up inside the outer boats often making them feel they have no boat speed , -but this occurs mainly from the wind shift and the ability of a crew to recognize it and place themselves relative to the fleet to take advantage of it .
Only looking at theory or finish times without the comprehension of all the other factors involved is misleading ,
We always see catsailors after racing asking questions about wind speed near shore , shifts ,-wave size and pattern further out etc . Very honestly I,m very fortunate to race each year around some of the best catsailors that I often ask these types of questions from ,--This is the best way to learn your particular type of cat design raced .
It is a wonderfull complex interesting sport we play ,-never completely mastered by any .
