BAMA Ratings Discussion

2013

Objective of the Discussion

• Discuss the various rating methodologies and gain a mutual understanding of their pros and cons

• Determine if we want to have one ratings methodology or multiple ratings methodologies (depending on the class of boat)

• Write-up final decision and apply ratings based on the written guidance to provide consistent results– “Consistent” does not equal “Fair”

Fundamental Issues

• How a rating is determined is different from the overall process regarding applying for a rating, appealing a rating, and challenging a rating.

• Ratings can be applied in a Time on Time manner or a Time on Distance manner

• There are two fundamental ways of determining ratings:– Predictive– Observational

Overall Rating Process

• The YRA has a well defined process describing how one applies for a rating, the appeal process, and challenging a rating.

• BAMA’s process currently mirrors the YRA process.

• However, how is the rating determined in the first place? And how is it updated?

Ratings Rules can be Grouped into 2 Main Categories

• Predictive Rule:– You take a lot of measurements of the boat and then

use a complex algorithm to predict the boat’s speed– Examples of this type of rule are Texel and IRC

• Performance Rule:– You use a boat as the base boat and then rate the

other boats as plus or minus to that base boat based on observed performance

– Examples of this type of rule are PHRF and Portsmouth

Time on Time vs. Time on Distance• TOD is how PHRF is calculated

– It assumes that it takes a boat a fixed number of seconds to cover a mile – regardless of wind speed

– Therefore, if a boat that rates 0 takes is assumed to take 560 seconds, a boat that rates 40 is assumed to take 600 seconds to cover the same mile

– The problem is that with high performance boats, unlike displacement monohulls, the rate at which they cover a mile greatly varies

– The problem is that very fast boats can not continue to accelerate indefinitely as the wind speed increases, but they remain very fast in light winds• In light winds the high performance boats will almost always win• In high winds the slow boats will almost always win • This is what BAMA has historically observed – dominance of the maxi beach cats in light wind races such as

the Great Pumpkin vs. the results of boats like Aotea in heavy wind DHFs where they placed at the back of the pack as they would have needed to average over 30 knots to win on corrected time

• TOT is how Texel and Portsmouth are calculated– It is assumed that the ratio of boatspeed between boats is constant

• So, if a fast boat is 50% faster than a slow boat in light winds, it should be about 50% faster than a slow boat in high winds

• This ratio holds up much better than TOD

Ratings Methods

• Predictive:– Texel

• Observed Performance:– PHRF – Portsmouth– Golf

Texel• Predictive Rule:

– Depends on many measurements of the boat to then utilizes a formula to determine predicted speed

– Utilizes Time on Time to score races• Pluses

– It is the way that most multihulls around the world are raced, so easier to compare our ratings to boats around the world

– Percentage differences of speed between boats are somewhat constant over relatively large variations of boat and wind speed, and thus can produce a more accurate first-order approximation for race scoring

– Non-political: formula generates the rating– Can be converted in PHRF using a conversion method

• Minuses– Not rated the same way as the monohulls in the Bay Area so need to ensure that Multihulls are

not racing against monohulls directly (SSS, beercan races)– Utilizes Time on Time so PHRF race committees might have difficulty/resistance to administering– Great difficulty in slotting into pursuit races (i.e. Three Bridge Fiasco, Great Pumpkin)– No flexibility if observed performance greatly differs from predicted performance

PHRF• Observed performance system that provides a single handicap number

that adds or subtracts a fixed number of seconds per mile from a “0” boat.– The boat is assumed to be raced to its full potential

• Pluses:– YRA uses this system so we are in line with the monohulls– All race committees on the bay know how to calculate results using the system

• Minuses:– Multihulls have a wide performance envelope that a single number handicap

does not effectively capture – Determining how fast the boat will be when sailed “optimally” can be difficult– Can be discouraging for new sailors as they have limited opportunity to succeed– Difficult to determine ratings for “one-off boats” or boats with limited observed

perfomance

Portsmouth

• Observed performance system – performance relative to a “base” boat

• 3 different numbers depending on wind strength• Issues– Which number do you choose if you move from one

section of the bay to another? – What do you do about boats not on the Portsmouth

list? What do you use as your first rating?– Time on Time calculation is not utilized by most race

committees in the bay

Golf• The race results are analyzed and the size of each boat’s handicap is

computed to allow everyone an even chance of winning based on the actual race performance of their boat– So, a fast F-27 might have a rating of 38 and someone who has just joined the

fleet with an F-27 and has not had success might have a rating of 150 • Pluses

– All boats have a chance of wining– Decreases arguments regarding what is the “right” rating for a boat as it is just a

calculation dependent on actual results• Minuses

– Competitive racers can become frustrated if people who are not racing well win a lot

– Not rated the same way as the monohulls in the Bay Area so need to ensure that Multihulls are not racing against monohulls directly (SSS, beercan races)

– Great difficulty in slotting into pursuit races (i.e. Three Bridge Fiasco, Great Pumpkin)

Dash 750 – Example of Challenges• National Rating – PHRF 36• Texel Rating without spinnaker (Gary Helms’ application) – PHRF

60– What do you use for measurements for Texel rating rule?

• Need to measure sails and weigh boat, takes time and money

• Bigger floats than Sprint 750, so should be faster in heavier air theoretically – PHRF 30-33

• BAMA currently rates to “Central Bay Conditions”, i.e. heavy air– F-24’s are rated significantly lower than the national number (69 vs.

84) and are quite competitive– Should the Dash 750 also be rated below the national number?

• Observed performance to date says “no”• But it is a close relative of the F-24 so why not?

Rainbow – Example of Challenges

• Old “Smoky Room” PHRF was 90• First Texel based rating was 180• Auto-calculation Texel Rule PHRF is 320• “Raced-to” PHRF is in the low to mid 400s• Current rating is 261• Texel challenges– Not easy to weigh boat– Sails are from design specs only

Ratings Options for BAMA

• Two big issues:– How do you generate the initial rating?– How do you deal with re-rating boats?– The answers to both issues don’t need to be the

same• For example, you could use one rating rule for the

initial rating and then another for the re-rating and convert both to PHRF numbers

General Issues

• Do we want to be able to race directly vs. monohulls like in SSS?

• Do we want a non-spinnaker credit? If so, how big?• Do we want “one-design” ratings or each boat rated on its

own?– Example: large weight differences amongst the F-27s and F-28s

• Can you change your sail inventory and hence your rating mid-season?

• Should the committee re-rate mid-season?• Other?

Proposed Process

Proposed Ratings Process• BAMA will continue to rate boats under PHRF to enable widest

possible participation of our members in Bay Area Races• Initial Rating for all boats will be based on Texel but converted

in PHRF numbers– Utilizes established prediction rule to generate initial number– Committee will utilize:

• Direct measurements if member wants to provide them• If member is not interested in providing direct measurements then

committee will utilize either:– Most disadvantageous measurements from a sister-ship that has had direct

measurements– Design specs if no measured sister-ship

– Rating will be provisional

Proposed Ratings Process• Provisional Ratings can be:

– Changed by the committee– Appealed by the racer– Challenged by competitors

• The committee will review actual race data including:– Finish data– Skipper interviews– GPS tracks

• The committee will generate “sailed – to” ratings for races the boat has raced in and evaluate whether the boat is actually performing as the Texel prediction program indicated it should be

• If the committee determines that a ratings change is warranted it will provide a written explanation of its rational– The ratings changes will be dependent upon the committee members best judgments, but

they will be based upon actual results for the boat in question– Committee’s goal will be to base rating upon boat performance capability, not skipper

capability• Interviews with racers (including the skipper of the boat) about how well the boat is racing• GPS tracks