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Generate your own polars

Discussion in 'Ask All Sailors' started by Jackdaw, Mar 26, 2018. Add this thread to a FAQ

  1. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    It's out of beta now. An on-line VPP system Avalon Navigation (a French Company) will do a very decent job of creating polars for your boat, IF you can provide the detailed measurements required for hull, crew, and sails. Hull is by far the most critical and hardest.

    Avalon - input.png
    They DO provide over 250 example boats as maybe close fits to start, but note that small differences make for big errors.
    They are still tuning the results but as an on-line tool every week it gets better. It tends to under-speed boats that can plane. Like for BlueJ, who its does not believe will pop up in 20 knots.
    avalon - output.png

    The two lines are typical; one is jib and main, the other is main and spi. BlueJs official polars look like this/ They get the upwind pretty much right.

    VPP 260.png

    The free version gets limited wind speeds and plotted points. For 35 bucks you can buy their REAL product, a weather/wave/current router nav app, which is amazing and an amazing deal.

    The VPP is here:

    http://www.avalon-routing.com/en/polars/
     


  2. BobbyFunn

    BobbyFunn

    Joined Apr 16, 2017
    447 posts, 186 likes
    Federation NCC-1701
    US Riverside
    Thats pretty cool, especially for smaller boats without navigation systems.

    As a data guy my first thought would be to record the wind speed, record apparent wind direction, heading, and speed over ground, etc.

    With this use regression to report polars with observed data, seems easy for larger boats with electronic installed. The report would be specific to the boat measured, versus an ideal boat.
     


  3. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Yes, if you are interested in polars that show what you actually do in your boat vs what it SHOULD be able to do, then generating polars based on observed performance is a good idea. And maybe the best idea if careful measuring is not possible!

    iRegatta Pro, interfaced with wind and speed instruments via WiFi, can collect, trim, and reflect this data automatically to generate polars.
    iRegatta.png
     


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  4. Davidasailor26

    Davidasailor26

    Joined May 17, 2004
    1,615 posts, 387 likes
    Beneteau Oceanis 37 LE
    US Havre de Grace
    Very nice. Glad it came out before our boat launches so I can take the underwater measurements. I have the iRegatta numbers so I'm curious as to how they compare.
     


  5. tfox2069

    tfox2069

    Joined Apr 8, 2011
    29 posts, 5 likes
    Hunter 36
    Intrepid US Deale, MD
    Am going to work on this over the season. Thanks for the pointer!
     


  6. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,502 posts, 1,144 likes
    Catalina 36 MK1
    US Everett, WA
    The yacht devices N2K data logger will also generate polars based on data collected from instruments connected to NMEA 2000 (or SeaTalkNG)
     


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  7. Apex

    Apex

    Joined Jun 19, 2013
    837 posts, 116 likes
    Oday 28
    US Traverse City
    ^^^wait WHAT!?!^^^
    now that is awesome. :thumbup:
    (nothing to really contribute, but had to point that out here.)
     


    Jackdaw likes this.
  8. JRacer

    JRacer

    Joined Aug 9, 2011
    869 posts, 306 likes
    Beneteau 310
    US Cheney KS (Wichita)
    This looks like an after tax season project, I think. :laugh:
     


  9. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,489 posts, 2,440 likes
    O'Day 19
    US Littleton, NH
    I find this post very interesting, but I'm curious about the data contributed by sog? Wouldn't that throw off the overall view? I mean, unless you're on a currentless lake.

    -Will (Dragonfly)
     


  10. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Who said anything about SOG??
     


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  11. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    I did not know that! Which model? I didn't see that on their NMEA2K 'Voyage Recorder'. Would be a cool feature.
     


  12. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,502 posts, 1,144 likes
    Catalina 36 MK1
    US Everett, WA
  13. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    I’ve read thru the document, and sadly it’s more of a toy. It generates a ‘polar’ rose using apparent wind not true, which really limits its usefulness. And the resulting roses, which have to be generated manually one at a time for each wind speed, are much too crude for actual use.

    38012785-C65E-44EB-8E9B-778F64E27497.jpeg
     


  14. Scott T-Bird

    Scott T-Bird

    Joined Oct 26, 2008
    3,829 posts, 862 likes
    Starwind 27
    US Barnegat, NJ
    This looks great and I hope to get a chance to take specific measurements so I can have polars calculated for my boat. In the meantime, the C&C 27 looks like it is the most similar of any boats listed. It is good to have the default numbers from that boat as a check against my measurements. It looks like the trickiest mesurements to get might be max cross-section area, wetted surface, beam at waterline & displacement. It appears that I have the weight of the lead keel imprinted right on the keel, but light displacement seems like it would have to be from the brochure and the weight of cruising gear is going to be an outright guess.

    There is another thread talking about fairlead placements for head sails, so I am left wondering why this isn't a factor that should be included for calculating polars. Doesn't upwind performance depend heavily upon correct sheeting angles? Our boat has the fairlead track on the rail, which is far outboard of an optimal position, it would seem. Are these calculations based on the assumption that optimal sheeting angle will be manipulated by inhauls, or whatever, to correct the bad positioning that may have been built into the boat?
     


  15. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,933 posts, 2,977 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    Polars always assume BEST POSSIBLE trim and sail area, regardless of placement of production hardware.

    That's one reason that boats that have published polars are normally focused on racing. They've been optimized.
     


  16. JRacer

    JRacer

    Joined Aug 9, 2011
    869 posts, 306 likes
    Beneteau 310
    US Cheney KS (Wichita)
    Nice! Now I have to get out the tape measure!

    With the J/24, it was easy, You are either passing or getting passed. ;-)
     


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  17. Kermit

    Kermit

    Joined Jul 31, 2010
    5,149 posts, 2,463 likes
    Hunter 260
    US Lake Murray Sailing Club, SC
    I have a feeling I speak for at least one other person when I ask...

    What’s a polar?
     


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  18. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,502 posts, 1,144 likes
    Catalina 36 MK1
    US Everett, WA
    It’s a diagram that tells you how fast your boat should go if your as skilled as @Jackdaw
     


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  19. Kermit

    Kermit

    Joined Jul 31, 2010
    5,149 posts, 2,463 likes
    Hunter 260
    US Lake Murray Sailing Club, SC
    Soooooooo.... polars are only useful to one person.

    Huh...
     


    Will Gilmore likes this.
  20. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,502 posts, 1,144 likes
    Catalina 36 MK1
    US Everett, WA


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