Page 3 of 6 FirstFirst 123456 LastLast
Results 21 to 30 of 56

Thread: The Polars Expedition

  1. #21
    Join Date
    May 2009
    Location
    San Francisco
    Posts
    65

    Default

    Nope. Rating systems based on polars - which are VPP based - are a "simplification" of the real world that ignore important factors like waves (and a number of other tertiary effects on boat performance) . PHRF uses real world results - no simplification. Why you can build/modify/optimize a boat to any VPP rating system - giving you a VPP (rating) edge that is not based on real boat speed changes (ie you can make your boat rate slower then it really is). Whereas you cannot run this scam on PHRF. Sure PHRF has its problems too - for custom and low production boats where there is insufficient real world performance data - and infrequent (and too often sited) PHRF committee favoritism. If you think about how close these rating systems need to be to be deemed "fair"... predicting performance within 1% (6 seconds per mile or so)... its hard to get right.

  2. #22
    Join Date
    May 2009
    Location
    San Francisco
    Posts
    65

    Default

    Note polars are not the "end point" to judge if your boat is "fully performing"... its a VPP based "starting point". You then need to go out into the real world and see what your boat can really do... keep notes... determine what your target speed/wind angle/sea conditions should be. There are more then a few examples of the initial VPP polars being "way off" for some boats on some points of sail - something you can find out on the water - or talking to someone with your same boat that has taken the time to document the boats "real world polars" (not the VPP polars that are just a starting point). If you really want to pull on this thread to watch it unravel... one really needs to have driver specific polars... and then there is wally. http://www.ockam.com/2013/05/02/the-wally/

  3. #23
    Join Date
    Sep 2007
    Posts
    2,872

    Default

    Yes, the Skip polars for Ragtime! were faster than the Bob polars.

  4. #24
    Join Date
    May 2009
    Location
    San Francisco
    Posts
    65

    Default

    PacCup PHRF moved to Tim eon Time (from Time on Distance). There is a pretty good case ToT is "fairer" ("fair" being a dangerous word to use... very dependent on what you think "fair" means). Though I am not so happy with ToT - as its hard for mere mortals to know how you are doing... as the time correction calculation requires knowing when boats finish... not like ToD where you can calculate time allowances in your head in a few seconds. A lot of racing is emotion based... and something you cannot grock intuitively, even if its technically "fairer", may not be best for maximizing participation.

  5. #25
    Join Date
    Sep 2007
    Posts
    2,872

    Default

    The Can loved ToT in OYRA. I was told the change only compressed the corrected times (without changing the finish order) but it sure seemed to give that 273 rater an advantage!

  6. #26
    Join Date
    May 2009
    Posts
    215

    Default

    Quote Originally Posted by BobJ View Post
    The Can loved ToT in OYRA. I was told the change only compressed the corrected times (without changing the finish order) but it sure seemed to give that 273 rater an advantage!
    Bob groks that the boats with a higher rating seem to have an advantage....
    How does the PHRF committee reconcile the SHTP results into the NCPHRF ratings.... or do they?

  7. #27
    Join Date
    Nov 2007
    Posts
    343

    Default

    How does the PHRF committee reconcile the SHTP results into the NCPHRF ratings.... or do they?
    They do not reconcile as PHRF is based on crewed racing inshore..... not singlehanded racing offshore with a modified PHRF rating.

    These are the what the PHRF rating are based on:

    The Committee will assign ratings based on the following essential assumptions:
    1. The racing will take place primarily on and around the central San Francisco Bay
    2. The wind velocities will be an approximate median of the lesser winter wind speeds and the higher summer wind speeds
    3. The ratings reflect the prevalent use of traditional windward/leeward courses with a minimum of reaching legs or random leg courses.
    4. The yacht is in optimum racing trim and all normal equipment is on board
    5. The hull bottom is fair and clean
    6. The sails are in good condition
    7. The propeller folds/feathers or the yacht has an outboard that can be raised clear of the water
    8. The yacht is expected to be competently sailed

  8. #28
    Join Date
    May 2009
    Posts
    215

    Default

    Quote Originally Posted by solosailor View Post
    They do not reconcile as PHRF is based on crewed racing inshore..... not singlehanded racing offshore with a modified PHRF rating.

    These are the what the PHRF rating are based on:

    The Committee will assign ratings based on the following essential assumptions:
    1. The racing will take place primarily on and around the central San Francisco Bay
    2. The wind velocities will be an approximate median of the lesser winter wind speeds and the higher summer wind speeds
    3. The ratings reflect the prevalent use of traditional windward/leeward courses with a minimum of reaching legs or random leg courses.
    4. The yacht is in optimum racing trim and all normal equipment is on board
    5. The hull bottom is fair and clean
    6. The sails are in good condition
    7. The propeller folds/feathers or the yacht has an outboard that can be raised clear of the water
    8. The yacht is expected to be competently sailed
    Thanks for that... which leads to, who determines the modified PHRF ratings for SHTP?

  9. #29
    Join Date
    Sep 2007
    Posts
    2,872

    Default

    The Olson 30 owners' association.

  10. #30
    Join Date
    May 2009
    Posts
    215

    Default

    Quote Originally Posted by BobJ View Post
    The Olson 30 owners' association.
    Haha! I’ve heard people say the SHTP should be called “The Olson challenge” but this puts a whole new spin on things!
    Seriously though, how are the modified SHTP ratings determined, and are they ever “adjusted”?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •