How to measure your boats best points of sail

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Mike16388

Mike16388

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Jun 7, 2004
13
Beneteau 343 South Padre Island, TX
Don, My boat manufacturer, Beneteau, doesn't seem to have done polars on my model (393) and I wonder if you have a method for developing one. I'd like to know specifically how my boat performs on all points, so I can make good decisions to optimize speed and VMG. Any suggestions?
 
Don Guillette

Don Guillette

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May 17, 2004
2,110
Other Catalina 30 Tucson, AZ
Mike: Most manufactures do have the polars on their boats. That's how they determine the effectiveness of their design but most don't publish the numbers. Most boat owner organizations have compiled these numbers - I know the Catalina groups have them for their boats. Additionally, there are web sites that tell you how to calculate polars. The last time I looked at one of those site (the polar question came up on the last forum I ran), I got confused very fast by all the calculations. I'll bet one of the Benny owners that are on the sailboatowners.com network can help you out.
 
Don Guillette

Don Guillette

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May 17, 2004
2,110
Other Catalina 30 Tucson, AZ
What are polars?

Kevin: It is probably easier to show you one than try to describe it. Do a google search for "boat polars". Briefly, a polar is a diagram that looks like a number of concentric circles radiating out from the center. Each circle represents a wind speed. There are also lines radiating out from the center which represent degrees. So, for example, someone figured out that your boat sails best downwind in 5 knots of wind at 150 degress and they plotted it on the chart. They also plotted other points of sail to. Racers use this stuff a lot because they want to know their 'tasrget boat speed" for all points of sail to determine if they are fast or slow. Whew, I'm glad that's over as Polars is a subject who's explanation could go on forever.
 
B

Bruce

Why not do it yourself?

Mike- How about finding a fixed buoy, placing a marker in your GPS, sailing upwind to a point where your Windex is pointing directly back at the buoy (ie, it is DDW)- and note the compass reading to the same. Then sail for max VMG to the buoy, according to GPS, noting the compass heading again. Calculate the difference. You should be able to find the optimum number of degrees to sail off DDW for that particular set of wind conditions. On most boats, polars change a LOT as wind strength is altered, so you may want to do this several times under various conditions. In general, better VMG is made heading up under light conditions. The harder the wind, the closer to hull speed you are anyways, so better sailing closer to DDW. Bruce
 
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