I was reading the article for Velocity Prediction Programs in the November Mainsheet this weekend with some interest. Is a polar diagram available for the C36 (I'm sure it must be)? The second part of my questions is, have others been able to put it to practical use? I think it might be interesting to compare actual performance against the predicted speeds.
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Dave Motter
Sweet Sue II
Hull #177
Everett, WA.
Yes, we have them in the C36IA Technical Reference library.
Larry Brandt
S/V High Flight #2109
Pacific Northwest, PDX-based
2002 C-36 mkII SR/FK M35B
I have seen a lot of computer generated polars for a lot of boats, both racer and cruiser/racer. The only ones worth a damn are the ones that have been heavily refined with actual collected data on raceboats. The polars for a Farr 40 for example, which have full instruments running from the moment they leave the dock, are very good. The polars for most boats like ours, are really more like guidelines.
The most useful way for the average joe to use Polars is not to have the polar graph or the full polar chart at hand, but to get the best VMG numbers, ie. a chart of TWS, TWA, and BSpd, arranged by TWS, that gives the best VMG upwind and downwind. This will help you determine if you are pinching or footing too much for optimal performance upwind, and whether you are too high or too low downwind.
Don't forget that downwind polars will be significantly different for a symmetrical or asymmetrical spinnaker also.
Jason V
Vancouver, BC, Canada
I admit that my boat is not equipped with all the instrumentation found on some of the high-tech racing boats. As a matter of fact, I really only have the windex at the top of the mast, boat speed and hand-held wind speed. That said, I still think it might be interesting to experiment with the polar speed diagram in a very narrow downwind range. I think my boat sails very well downwind with the jib in the whisker pole and sailing slightly by the lee. It would be interesting to take some measurements to see if the numbers actually bear that out.
Dave Motter
Sweet Sue II
Hull #177
Everett, WA.