J/30 Class Association

J30 Polars

Posted By: gmo

J30 Polars - 01/23/10 06:14 AM

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
JBoats website: http://www.jboats.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?
Posted By: Rhapsody #348

Re: J30 Polars - 01/23/10 12:50 PM

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
[Linked Image]

J/Boats Website Polar

[Linked Image]

Expedition Polar
[Linked Image]
[Linked Image]

Description: J/30 US Sailing Polars
Attached File
J30-Polars-USSailing.jpg  (16921 downloads)

Description: Expedition J/30 Sample Polar
Attached File

Description: Expedition Sample Polar Data
Attached File
J30_Polars-Expedition.txt  (488 downloads)

Description: J/30 Polars from Expedition - Excel Format
Attached File
J30_Polars-Expedition.xls  (2136 downloads)

Description: Expedition data as a graphic
Attached File
Expedition-data-as-graphic.png  (5390 downloads)
Attached File
J30 Polars-from UK-Website.xls  (2254 downloads)
Posted By: Cap'n Vic

Re: J30 Polars - 01/23/10 02:22 PM

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

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

Re: J30 Polars - 01/23/10 04:31 PM

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.

Posted By: gmo

Re: J30 Polars - 01/25/10 06:39 AM

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?
Posted By: Cap'n Vic

Re: J30 Polars - 01/25/10 01:25 PM

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.
Posted By: Bob Rutsch

Re: J30 Polars - 01/25/10 06:29 PM

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.
Posted By: R II

Re: J30 Polars - 01/26/10 07:32 AM

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?
Posted By: gmo

Re: J30 Polars - 02/09/10 07:21 PM

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

Re: J30 Polars - 02/10/10 04:08 PM

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

Posted By: Rhapsody #348

J30 Polars from UK Website - 04/20/10 06:46 PM

This file was added to the post with the other polars. Looks very similar to the Expedition file.

J/30 Polars from UK Website in Excel Format
Posted By: Cap'n Vic

Digging into Polars - 01/15/13 04:26 AM

so ok ... i am missing something here?

1. do we assume that the polars going up to 22 kts wind are only using the 163? if not where do they change?

2. if at true wind speed of 6 ... true wind angle of 47.5 ... are we thinking that the tack is 95 degrees.

and then at 14 true, the tack is 86 degrees?

3. and then what is OPT VMG? to waypoint?

Also there seems to be a broken link re J boats

[Linked Image]
Posted By: Rhapsody #348

Re: Digging into Polars - 01/15/13 04:58 AM

Originally Posted by Cap'n Vic
so ok ... i am missing something here?

Also there seems to be a broken link re J boats

Vic - It appears that J/Boats has revised their website. I just sent a message to them asking if we can get the J/30 content restored.
Posted By: Rhapsody #348

Re: Digging into Polars - 01/15/13 02:06 PM

A follow up to the post above about the J/30 content on the J/Boats site. J/Boats updated their site over the weekend to a new format. The portion for older boats did not yet get updated, but is in process and will be back online shortly. If any of the links have changed (e.g. the polars referenced by Vic above), we'll search the J/30 class site and update accordingly.
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