A polar diagram describes how fast a sailing boat may go at different wind speeds (TWS) and in different angles to the wind (TWA). Every type of boat has its polar diagram (or VPP, velocity prediction program), computed from hull shape, weight, rigging and a sail setup. Seapilot uses the polar diagram to compute the fastest choice of path at a given forecast for wind (and current). The polar diagram is imported to Seapilot as a polar file in text format (.txt, .csv or .pol). The name of the boat type or the specific boat is suitable to use as a name of the file (for instance J80.txt). Here at our website you can get access to polar diagrams for more than three hundred boat types. More are coming with time. You may also find polar diagrams at manufacturers, vendors, class associations and others.
If you miss any boat, please contact us at firstname.lastname@example.org
For more polars, visit jieter.github.io/orc-data/site where you can find polars for almost any boat.
Polar file formats
A polar file contains a table representation of the polar diagram. You can also get data to your polar file for instance from a measurement certificate, from the maker of the boat or from your class association.
If you don’t have the data in tabular form, but as a diagram, you can at every given TWS do readouts at a number of different TWAs (for instance 30, 45, 60, 90, 120, 150 and 180 degrees).
Choose the format (1 or 2, see below) that best corresponds to the format of the data that you have got.
- Create a new file in Excel.
- Replace blue text with your own numbers, let the black text remain.
- TWS should be true wind in knots.
- TWA should be true wind angle in degrees.
- BSP should be optimal boat speed in knots.
- TWS should be ordered from lowest to highest.
- TWA should be ordered from smallest to biggest.
- If needed, add new lines and/or columns.
In particular for format 1:
The first line should indicate the wind speeds (TWS) valid for all following lines.
Delete lines 2-3 and the two last if data for beat angle/beat VMG and gybe angle/run VMG respectively are missing.
Note that beat and run speed should be given as speed in direction of the wind (VMG), not as boat speed (BSP).
Template Format 1 (non editable)
In particular for format 2:
There must be the same number of TWA-BSP pairs in every line.
Every TWA should be directly followed by the correpsonding BSP (for the TWS valid for that line).
Template Format 2 (non editable)
When you are ready: remove unused columns and lines. Choose File/Save as; choose File format Text (tab delimited) (*.txt). Use your boat type as the name of the file.
Import polar files to your smartphone/tablet
To provide polar data for Seapilot may be simple, and it may be complicated. Choose an alternative in the following order until you find one that is working.
A. If you have a polar file (with file type .txt, .csv or .pol)
- Send the file as an e-mail attachment to yourself.
- Open the e-maíl on your seapilot unit and tap on the attachment. (On iPad/iPhone furthermore: tap the share symbol in the upper right corner and choose Seapilot as the target for the import.)
- Check to see the message ”Import saved OK” meaning that the file format and the data were correct.
- If the import did not succeed you need to reformat the file (see next section).
B. You find your boat type among more than 300 polars on seapilot.com
- Open a web browser on a PC or Mac and go to seapilot.com.
- Choose Features / Polars and Download polar files.
- Click the desired polar/boat type.
- Open an e-mail agent on the same unit.
- Send an e-mail to yourself with the downloaded polar file as an attachment (you find it in Downloads on both PC and Mac).
- Open the e-mail on your iPad/iPhone/Android unit(s) and continue as described i A 2-4.
C. If you have polar data as a table on paper
- Write these data into one of the Excel templates available om seapilot.com and follow the instructions found there.
D. If you have polar data as a table in .pdf format or similar
- Do as in case C; or copy, paste and edit the data using for instance Word or Excel into a format as described in the next section.
- Save as .txt and go on as in case A.
E. If you have polar data only as a diagram
- Use a ruler and do readings in the diagram for a number of TWSs and TWAs.
- Use for instance Excel to do scaling and save in a template as in case C.
F. If you have polar data for a closely resembling boat
- Do as in case A.
- Correct your polar using the parameters Performance upwind and Performance downwind (see the description of the Auto route menu above).
G. None of the above and cannot get data from the designer, the boat builder, a vendor or the class association
- Download iPolar from App store (at a cost of about 12 USD; Seapilot takes no responsibility for this app).
- Choose the Boat tab and give a name to the boat.
- Under Parameters, record boat’s length, displacement and sail areas.
- Check the polar data created by the program under Polars and Values.
- Tap the letter symbol and send data (will be as a .txt file) to your own e-mail address.
- If you want a spinnaker to be included in your sail setup you must use the two files Main+Jib.txt and Main+Spin.txt to create a new .txt which in every position contains the maximum of the corresponding values in the two other files.
- Continue as in case A.
Beware any error messages when you use the polar file for the first time (see section Autoroute in the manual).