BAMA Ratings Discussion 2013 - PowerPoint Presentation

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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