Polar Chart

[Bisquit]

Does anyone have a polar chart for the Commander or the Ariel?
Phil

[ebb]

Delft Systematic Yacht Hull Series (?)

possible lead:
altendorff.co.uk

sorry, don't believe anybody's done this.
can't find the chart...

[Bisquit]

Thanks I'll start there. I already use IRegatta and IPolar interfaces with it. Once I have it sorted I'll share. I think I can get one from US Sailing -just costs money. Also if there are any floating around they have probably already been tuned.

[Bisquit]

Here you go folks. Looks a little slow. I'll tune them this summer and post some revised numbers in the fall.

Main Jib & Symmetrical Spinnaker

10035

[ebb]

For a possible intro to these game, check out:

VPP Graph Generation

http://forums.sailinganarchy.com/index.php?showtopic=153695

[Bisquit]

I have Expedition for a couple of boats I navigate on. I'v used it before to tune designer generated polars. 'll run it and trim the polars over time when I am confident that I have consistent conditions and am well trimmed. I think the chart generated by Ipolar is a good start. I don't anticipate any drastic changes.

[joeniver]

what is a polar chart?

[Bisquit]

It is a chart that shows the predicted speed of a boat at a given wind speed and wind angle. The values in the left column of the chart are true wind angles and the values across the top are true wind speeds. When you plug these values into a routing program it will take grib files (Gridded Binary Files used in weather forecasting) and calculate the optimal course to get from point A to point B for a given forecast. They can also be used to help when sailing by providing a reference point for speed vs trim. For example based on the attached chart for a Pearson Commander if you are sailing at a true wind angle of 90 degrees in 18 knots of breeze the boat should be able to reach 5.9 knots. If you can't achieve this speed check your trim, or buy some new sails. The values in the chart I posted earlier were created by entering just a few values into a program and are probably not super accurate although then seem to be generally in the ballpark. This summer I will make observations using software I have and update the values using actual observations.

[ebb]

In the not so distant past

we had a couple skippers

who always came in first

in every race they started

by the seat of their pants.
.
.
.

[Ed Ekers]

Who you calling an "OLD " ???

[Bisquit]

There is no substitute for a good seat of the pants.

[joeniver]

thanks for the great explanation--though over my head. Are you allowed to use this during a race?

[Bisquit]

Using polars is allowed. On distance races they are used with routing programs and routes are updated when fresh forecasts are released. Most boats with sophisticated instruments can display polar target speeds or alternatively a percentage of the polar target speed. If your polars are accurate, you have good sails and a good helmsman you should sail at 100% of your polar speed or close to it. If you want to get really tricky you can display a polar % for the routed course. In this case if you start to sail at a speed higher than your polars then you are probably sailing too low if heading upwind or too high if heading downwind. I realize for our little boats this is overkill. I'm planning on doing some distance sailing this summer and I like to look at potential route scenarios. I need polars for that.

[SkipperJer]

Polars are not overkill if you are racing PHRF against bigger boats with lower ratings that are using polars. It's how you keep up.

[Bisquit]

Here are the polar diagrams - speed and VMG

10062

10063