J/30 Class Association Forums J/30 Forum Racing Tools and Techniques J30 Polars

I just realized that the polars that came on my boat are way different from those on the J/Boats website. For example, the one from the boat is dated 1994 and shows the optimal true wind angle in 8 kts of wind at 144.4. The one on the J/Boats website has the optimal angle at 161.

Newer: http://files.me.com/gradymorgan/gs5aww
J/Boats website: http://www.J/Boats.com/j30/j30polar.htm

Note that the newer is in apparent wind.

Anyone know where the newer came from, and if I should pay any attention to it?

Reading the legend, it looks like the newer one was obtained under the US Sailing IMS program which appears to be the Performance Products Program now on the US Sailing web site.

I made a jpg so it is easier to see the figures and compare. I also added a picture using the trial version of Expedition that includes a sample J/30 polar. I captured a screen shot and provided both the raw text file Expedition uses, and the file converted to Excel so you can play with it.

I need to get better at using these. Can others post here on how you have used the polars to help your performance?

US Sailing Polar


J/Boats Website Polar


Expedition Polar

Dacron vs Kevlar ... just how much can that factor change these?

Love those "pinch" curves on US Sailing Polar .... indicates a more sophisticated simulation???

For short 1-2mile W/L they are tricky to use and probably are a waste of time while you race. I think they are good to look at the relative angle changes as wind increases and decreases vs speed.

For distance races they are imperative because your sailing angles are so important. It is pretty easy to tell when you are beating if you are moving but when you have to crack off and sail 57deg for 4 hrs in 17knts the polars give you a good idea of what speed you should be making. This also will tell you if you are over powered (going over your polar) or under powered (not hitting your polar). Either case you want to change your sail combo to match the polars.

DB

There's a pretty big difference between the US Sailing polars and the manufacturer polars. Does anyone sail as high in light air as the US Sailing one recommends?

7kt, flat seas, NEW light 3DL sails?
and pinch happy ex j24ers?
I am impressed by the use of those pinch curls.
Next time you're out compare barely visible luff flutter to how the woolies work vs speed to two decimal places and contolled heel angle.

I can't concentrate enough to do all of this while driving, and my crew here are no sailmakers.

Using just a compass and a knot meter, we don't fool much with true or apparent wind. I figure we generally tack through a bit more than 80 degrees, which appears to be consistent with these polars.

I think the question pertains to 'off-the-wind' sailing angles. Any thoughts on optimum apparent wind angle on a light air run? 90 degrees apparent sure feels good, but how about the VMG?

Yes, I was mostly curious about down wind angles in light air. How deep downwind do you guys typically sail in light air?

On "Mmmmm" we don't have a masthead wind indicator to record windspeed and/or direction. Nevertheless, we've had the old J30 Polar chart on the boat since we bought it years ago and use it as a guide. We do try to sail to targeted speeds. After sailing for a while, you get pretty good at guessing the actual windspeeds and using that, along with our speedo, we shoot for targeted speeds. On beats, we know what that number should be on our speedo. On reaches, we simply use our Windex indicator which have the jibing angles set. Granted, it's not "data driven," but it keeps us in the ballgame.

Bob Rude