Jump to content


PHRF


  • Please log in to reply
69 replies to this topic

#11 Willow

Willow

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 2,694 posts
  • LocationTauranga

Posted 26 October 2018 - 01:30 PM

Agreed, can't help but think if it was used more at club level it would be better.


  • 0

Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure... than to rank with those poor spirits who neither enjoy nor suffer much, because they live in a gray twilight that knows not victory nor defeat.

Theodore Roosevelt

 


#12 ScottiE

ScottiE

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 4,104 posts
  • LocationAuckland

Posted 26 October 2018 - 02:13 PM

Pretty sure the squadie now process all their results on PHRF as well as their own internal club h/cap


  • 0
After a decade or so of Euphoria . . . it's time to go Ballistic!
Anthony

#13 markm

markm

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 1,623 posts

Posted 26 October 2018 - 02:29 PM

I may be able to clarify one or two items here.

At present, PHRF is a combination of a committee assessment of a design and performance information from race results.  This has been the case for about the last four or five years, this year it has been formalised to the extent that we now publish the design assessment on certificates, it's referred to as 'base PHRF'.

Performance will affect the PHRF handicap that most racing uses but only to a limited extent.  For that season, that is 1.8% above or below the base PHRF, illustrated if base PHRF is 0.75, PHRF including results won't be lower than 0.737 and not higher than 0.763.

Whether this is big or small is of course a matter of personal opinion, there are certainly plenty of boats that would otherwise exceed these bounds so in that respect it's small.  That said, 1.8% is more than the equivalent of not flying your kite for half the time you otherwise could have according to most rating systems so in that respect it seems pretty big.

The base PHRF assessments are a subjective call from the PHRF committee.  This is a way of saying that there's no one approach we know of that works well for all boats.  Speaking for myself and how I approach my part, yes, will look at other rating systems, my personal favourite is probably ORC though the database I'm using has 56,000 boats and references 20 or so different rating and handicap systems.  We of course use the existing PHRF database, no point reinventing a PHRF if we already have one or something close. 

SNS made reference to old PHRF calculators at the beginning which I have a couple of versions of, one commonly known as shell regression from PHRF in the states which is the one used in NZ many many years back and a similar but updated one from the UK.  They work to a point as do the other approaches mentioned, as commented though all have some significant flaws and a lot of the 'subjective guessing' is more diplomatically phrased as understanding the strengths and weaknesses of the possible approaches and what's going to work best when.

Definitely not perfect which we know.  Could certainly put together a spreadsheet and publish it of what PHRF would be for all current boats under the traditional calculator.
Think I can promise a few smiles though wouldn't expect many claims of perfection, there are reasons why it was phased out 20 years or so ago.

Could probably do a second essay on why PHRF works as it does but I'll save that for another time, just comment that the objective is for PHRF to be an interclub level handicap for racing in NZ.  Not really trying to replace measurement ratings  and although it's sometimes used instead of or alongside club handicaps, it's not really intended to replace club handicapping either.


  • 0

#14 Knot Me... maybe

Knot Me... maybe

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 6,115 posts

Posted 26 October 2018 - 03:28 PM


Performance will affect the PHRF handicap that most racing uses but only to a limited extent.  For that season, that is 1.8% above or below the base PHRF, illustrated if base PHRF is 0.75, PHRF including results won't be lower than 0.737 and not higher than 0.763.

 

Does that mean if a boat scores a base of, in this example 0.75, if sailed well it will max out at 0.763, or sailed like crap drop to 0.737, but never go outside those numbers?

 

Here's a question no one seems to know the answer too. If a boat has a masthead kite but can only fly it to a maximum of around 8kts wind speed before the mast falls over due to it's type/configuration how does PHRF allow for that in comparison to a boat who has a carbon stick with jumpers so can fly mastheads in 30kts?

 

Nothing on the form seems to relate to how conditional some gear is or could be. It all seems a tad black and white in what is a very grey world.


  • 0

#15 markm

markm

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 1,623 posts

Posted 26 October 2018 - 06:10 PM

In answer to the first question, yes, you don't go below the lower limit no matter how bad your results, nor above no matter how good.

 

In answer to the second, you're rated and assumed to be able to use the gear you declare.If you can't use it most of the time, don't declare it would be my advice.

 

If in doubt whether should declare something or not, ask and we'll tell you what your base PHRF adjustment will be.  Be aware though if you declare a modification we will reassess your boat based on it's results at the same time as we adjust for the modification so you may go up by more than we change the design assessment by.  Unfortunately you won't go down if you do what we think is a performance improving modification even if your results indicate a drop.  Also if your change is a big one, new keel sort of big, then the odds are good we'll wipe your history completely, again, if in doubt ask ahead of time and we'll tell you what will likely happen.


  • 0

#16 Maté

Maté

    Sailor

  • Marine Forums Only
  • PipPipPip
  • 3,638 posts

Posted 26 October 2018 - 06:39 PM

Mark thank you for the excellent response, It makes a lot more sense now.
  • 0

"Never argue with a fool; onlookers may not be able to tell the difference." - Mark Twain


#17 mattm

mattm

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 281 posts

Posted 26 October 2018 - 06:44 PM

SNS, no system is perfect. The old one you suggest has many flaws. A big one is that if it’s black and white, boats can be optimised to suit the rule. This is a bad thing in my opinion, it can lead to ugly boats - see IOR, or boats that don’t want to modify to be optimised to the rule won’t have a chance at all. There will be many good reasons that system was done away with.

The current system works at least as well as any.

In reference to having a designer in the panel. I see your point. But, the others on the panel will know if that person is being biased, this why it’s panel. How many people with relevant knowledge do you think will be willing to replace that person, pour hours of time and effort into something, spend their week nights in meetings and studying results online, only to be thanked by becoming enemy #1 every time they walk into a yacht club bar, or by being attacked or having their work criticised in online forums.
  • 1

#18 Knot Me... maybe

Knot Me... maybe

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 6,115 posts

Posted 27 October 2018 - 07:43 AM

Interesting Thanks Mark.

 

Is there a list of what increases your number or decreases it?


  • 0

#19 Maté

Maté

    Sailor

  • Marine Forums Only
  • PipPipPip
  • 3,638 posts

Posted 27 October 2018 - 08:42 AM

In your case water would make a significant difference


  • 1

"Never argue with a fool; onlookers may not be able to tell the difference." - Mark Twain


#20 markm

markm

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 1,623 posts

Posted 27 October 2018 - 08:49 AM

No direct list as the application form implies most of it and given requirement to sail to a declared configuration, if you change anything that's on the form then it needs a dedclaration.  Noting though a catch all on the lines of any change which would reasonably be expected to yield an improvement requires a declaration.

 

For PHRF a like for like replacement of a sail does not require a declaration again noting though like for like isn't a case of my old main is like my new main, they're both mains just the new ones twice the size, if any measurement changes when replacing a sail, then let us know. 


  • 0




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users