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RE: Information on the San Juan 23






Hello SJ23 trimmers,
Does anyone have polar diagrams for the San Juan 23 sailboat?
Are there any other boats that might have similar performance with polars
available?
If the manufacturer did not make any polars, is it feasible to make one?
How do you make a polar?
I would imagine it takes a fair amount of instrumentation.
knotmeter
windvane
anemometer
external windvane (true)
external anemometer (true)
Real-time data acquisition computer
GPS
For added precision all the junk should be connected to some type of computer.
I believe polar diagrams existed before laptop computers,
so maybe there is a low dollar way we can create polars for the boat.

Assuming no no current. I would imagane the procedure would be similar to this:
o wait for a day when the wind blows 5kt consistently
o stall the boat record windspeed
o sail directly downwind as fast as you can.
o record the knotmeter
o jibe starboard run at 225 degrees off the wind record knotmeter
o reach 270 off wind and write down the reading from the knotmeter
o close haul 315 record the knot meter
o repeat data collection for port tack
o stall the boat and wait for wind to build to 10 kt then start data collection
again

How is sail trim factored into the creation of polar diagrams?

Does anyone have a VPP program?




San Juan 23 Internet Fleet:  http://www.geocities.com/Yosemite/Trails/5492/
San Juan 23 Tech Tips:  http://www.geocities.com/Yosemite/2358/index.html


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