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Jun 11, '08 7:57 AM
by swe_1491 for everyone

Hello!!! Anybody that has a Polar for the Ballad.

Or has anyone start collecting data for a diagram? I will start collect data during summer, if anyone else is intrested perhaps we can help each other and swap data between us so we can create a polar...

Tags: racing

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5 CommentsChronological Reverse Threaded

jespermilling wrote on Jun 11, '08

Very good idea.

How should the data be specified, just windspeed, windangle, boatspeed. in a table?

may I suggest that a dataformat be specified? somehow.

Jesper Milling

msn-swe_1491 wrote on Jun 11, '08

Yes.. Windspeed . Windangle and Boatspeed is enough data. then we can do all VMG calculations.

Exampelformat like this in a simple ".TXT" file

Can u fix a file that all members can edit in some directory.. like the dictionary u have created....

TWA/TWS 2 4 8 10 12 14 (knots or m/s) knots would probaply be best...

45 BS BS BS BS BS BS

135

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jespermilling wrote on Jun 11, '08

Please have a look at the new Polar Diagram Data Capture list just below the Racing subforum in the main menu. Let me know if it works OK or not. Wind Speed may be entered in either m/s or knots. Somebody will have to take on the actual calculation of the different polar diagrams for the different wind speeds.

Would it not be better to make a spreadsheet, with a built in graph, that we could each download as many times we please, fill out and upload for others to look at (and compare with). This spreadsheet could even be made for entering windspeed in Beaufort, knots and m/s and still give the same result.

Jesper Milling

msn-swe_1491 wrote on Jun 12, '08

Data capture looks great. Now we only need to get it out in form of a text or excel file...

But i will probably fill out my own textfile during summer and have this as a public backupfile..

Now im off for swedish championship in H-boat..

See u all after the weekend!!!!

msn-s채lta wrote on Jun 15, '08

Hi!

Interesting discussion and a great initiative. I have also thought about the idea to start collect data to get an acceptable performance diagram (VPP). I have made a matlab program that can calculate and draw VPPs based on theoretically simplified models. The programming was a part of a course in Marine design at the Royal School of Technologies. The Models used are not accurate enough for producing in reality useful diagrams, but if you want I can take the collected data and plot it with a matlab script. I post an example how the results could look like.

Another tip is the company techsail http://www.techsail.com/ which is manufacturing a quite good software that you can use for calculating Polar diagrams. You can test it for free with a standard boat model but if you want to be able to modify it to a Ballad you have to buy a license for USD 49.95.

If you are seriously interested in the theory behind VPP and Yacht design, the number one book to have is then "Principles of Yacht Design" by Larsson & Eliasson. I think it costs about USD 40 by Amazon and it's really worth it.

I can also recommend you to take a look on http://www.sailonline.org/ . There you can download a client for free and take part in virtual sail competitions. The interface is not so fancy but all weather data is real and the boats performance are based on a VPP. So you can learn a lot about how to use a VPP there. The same company did also quite recently release a routing software where you can load your own VPP and then calculate the optimal route.

I'm looking forward to see the results from the data collection

Attachment: vpp.tif

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