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Thread: Polars

  1. #1
    Join Date
    Nov 2013
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    Humboldt Bay
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    Default Polars

    Does anyone know where I can find polars for a particular boat? Is there a website, formula or sailmaker to consult? Any help is appreciated, thanks.

  2. #2
    Join Date
    Aug 2015
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    24

    Default

    Here's a few links to some that you may get lucky with:

    http://jieter.github.io/orc-data/site/

    http://www.blur.se/boats/

    http://l-36.com/polar_polars.php

    U.S. Sailing Sells them: http://store.ussailing.org/browse.cf...age/4,158.html

    I wasn't able to locate any for Althea and ended up generating them in real-time on the SHTP using the polar plugin for OpenCPN. I wrote a bit about it during the race.

    HTH!
    Last edited by brett; 09-19-2016 at 07:40 AM.

  3. #3
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    Nov 2013
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    Humboldt Bay
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    Default

    Thanks Brett,
    I did find the OpenCPN site. I felt kinda silly for asking about polars when I can barely fly a spinnaker, but I felt I was missing some kind of secret knowledge. Anyway, I figured out it's something one has to experiment with on one's own boat.

  4. #4
    Join Date
    Jan 2010
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    2,396

    Default

    Quote Originally Posted by Steevee View Post
    Thanks Brett,
    I did find the OpenCPN site. I felt kinda silly for asking about polars when I can barely fly a spinnaker, but I felt I was missing some kind of secret knowledge. Anyway, I figured out it's something one has to experiment with on one's own boat.
    With a beautiful boat like yours I don't know how you can feel silly about anything. I also see instruments on your boat. My understanding of polars is that I would need to have instruments into which I would input the polar information. Except that ... DM's instruments consist of a fish finder/depth finder and my handheld garmin gps. I guess instead of concerning myself with polars I'll just keep on sailing by telltales and put on that woolen hat as the weather here starts to feel ... polar.

  5. #5
    Join Date
    Sep 2007
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    3,069

    Default

    It got intense just before the 2006 SHTP when two of my out-of-town competitors arrived with shore crews. One was a sailmaker, flown out from the right coast to help the skipper get ready. They walked the docks at Marina Village, sizing up the competition, asking what our ratings were, etc.

    I'm not as seat-of-the-pants "old school" as Philpott. At the other extreme I'm not a fan of routing software. I'm somewhere in between, using a page of upwind and downwind "targets" printed out and taped up in Rags' cockpit.

    With the mind games being played before the race I decided it was time for action. Rags was backed into her slip so the page of downwind targets would be clearly visible. I made two sets - the real ones and the "other" ones I taped in the cockpit. (I'm not telling which set is in the attached photo.) This was successful, as I caught the skipper and his sailmaker staring at the targets with dismay. "WHAT'S your rating again?"

    I'd encourage the OP to contact Bob Perry and ask for the targets generated from his designer's VPP for the Tashiba 31. This will give you most of the information you need.
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    Last edited by BobJ; 10-05-2016 at 10:17 AM.

  6. #6
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    Jan 2010
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    Quote Originally Posted by BobJ View Post
    Name:  Targets.JPG
Views: 228
Size:  458.8 KB
    Now THAT'S a screensaver!

  7. #7
    Join Date
    Sep 2007
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    3,069

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    That's my work computer and I never change that desktop image - it's motivational.

    Ken Stuart's PS37 SECOND CHANCE, Rags of course, Jim Kellam's Spencer 35 HAULBACK (Jim is in the dinghy) and a local Columbia 26. I think Jeanne Socrates took the photo from NEREIDA. Both Jim and Jeanne "kept going" after SHTP's and completed their first solo circumnavigations, Jim after the 2004 race and Jeanne after that one (2006).

  8. #8
    Join Date
    Jul 2015
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    56

    Default

    Ahhh.........Polars can be a very entertaining rabbit hole that one may descend into. For high end offshore race boats they form the backbone of tactical decisions, navigation and sail selection. I found it a fun process to learn about how they are used in company with navigation software. Be warned however:

    1. Polars ultimately are refined for your boat, the conditions and the crew......(you could have inshore full crew polars, offshore single hand etc etc etc) This is a long long process to be done well.
    2. Polars are nothing more than entertainment without accurately calibrated instruments (a long complicated and often expensive process)
    3. Polars go hand in hand with navigation/routing software which is another time and money sink (again can be quite entertaining)

    For sailing to hawaii I used them at a very basic level and essentially refined them as I went along. If you can't find polars for your boat get some from a similar boat. They won't be that different. I found it helpful before I left to play with weather data and the routing software. Picture what route I would take and then see what the routing software would calculate. This helped me to develop a better sense of where the critical decisions to be made are.......

    The issue for long races is that I was not able to sail anywhere near my boats polar potential for 24 hours. I could for 1 hour.......so over time you get a sense of what your "average" performance is like....then you get a better sense of where you will be. Again time and practice.

    Most of the time I did something like Bob did above (heck he recommended it to me). I also had an list of sails and there apparent wind angles and strengths. This allowed my tired brain to not have an entirely wrong sail up. Apparent winds are easy to calibrate by the way............

    And even more simply I just always knew where hawaii was.....set up the boat to sail comfortably/fast for wind and waves...... and made sure it was pointing close to Hawaii. Anything more than 20 degrees off Hawaii I made sure was a tactical decision (sail into better wind) or offset by better boat speed.

    Enjoy!
    Chris

  9. #9
    Join Date
    Sep 2007
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    Capitola,CA
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    Default

    Chris is spot-on with his description of polars and their use offshore .... Instrument calibration (boat speed, compass, wind angle and wind speed) is critical for accurate polars. As is the set-up of the boat. If you calibrate polars with a dirty bottom, full water tanks, solid prop not aligned, mast-head wand misaligned etc., accuracy suffers significantly.

    I believe commercially available polars are also computed for the assumption of smooth water, which is rarely the fact. Waves, upwind or down, almost universally slow the boat from optimum.

    It is good fun, and education, to compute your own polars through trial and error. As well as making a sail combination vs. windspeed/wind angle chart. With a little practice and note taking, it is not rocket science figuring what you best average boat speed for the conditions is, within a 10th of a knot.

    Having this information available on hard copy helps immeasurably when tired, and saves on time and energy lighting up the computer.

    My 2 cents.

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