That is common a misconception.

Example : Throw a dice 1.000.000 times and calculate the average value per throw.

That value be very close to 3.5, but I assume everybody would have figured that out for themselves.

Now, does that mean that you are most likely to throw a "3.5" each time you throw the dice ?

Or how small is the error between any real throws and this average "3.5" ? It's error is always AT LEAST 0.5.



Another example : Nobody races the Supercat 17 design in any significant way anywhere. Basically you got one or two geezers pottering around the course on it maybe twice a year, beer cooler close at hand. We can gether their race data for a 1000 years and still not get an accurate rating for the Supercat 17 that way. Now you say, who cares about any Supercat 17's ! Then I say, how are the M18, M20, F14, and a score of other newly launched boats different ? How long would it have taken for the F16's to be rated right, we're still waiting for it in the USA. Maybe 10 years of waiting should do it ?


Some people should read up a little bit on rating history, there are good reasons why yardstick systems were abandonned in favour of measurement based rating systems. There is no point in making the same mistakes all over again.

Wouter

Another misconception is that clever people get jobs <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> Wouter please accept the fact that some people are prepared to think outside the box and experiment. You keep on harping on about formula based ratings being the be all and end all of rating systems but surely a guy of your intelligence can accept the fact that we don't all weigh 75kgs. So on this note I'm calling it a day and as we say around here "let the proof be in the pudding"

Wouter,

measurement systems are equally bad. They typeform the development of boats, and often in bad directions. Just look at the IMS monohulls with wooden keels and lead in the bilge.. The same is valid for formula classes like the F18 and our own F16 class (e.g. hooter/code zero vs. spi debate).
The most "correct" rating system would in my opinion be a personal rating for each sailor/team on specific boats. But in the end, sailing is a sport where you choose your classes and live with your choices. Pretty much like any other activity you choose to do.


Will be very interesting to see what happens with your system Mark! Please keep us informed.

Hi all,

I can olny agree to that, maybe I would say both are equally good. You need certainly both rating systems to verify the numbers of each system.
The only fair system is one design class racing. But live would be so boring without the discusion about the right rating... So, to add some fuel in the fire: I would appreciate if measurements rule don't use rated sail area, but true sail area, because I pay my sail maker for true area. I am sorry for the H16 sailor, but boats would be better in future.

Cheers,

Klaus

Rolf, I agree that IMS got silly, but then they were trying to control / legislate for everything.

This is the strength of Texel / SCHRS, simple enough for EVERYONE to understand, open and published rating method (unlike some of the leadmine ratings that are black box).

It also depends what you want to achieve....

If you want to reward the person who sails better than they usually do, then you need personal handicaps. If you want to reward the person who sails the best in a fleet full of poor sailors, then you use PY type systems as they rate the boat and the sailor, if you want to reward the best sailor, you use a formula based rating system such as SCHRS and Texel.

No rating sytem is 100% accurate, and it depends on what you are trying to reward. PY and rating systems do not reward quite the same things.

One of the overriding reasons SCHRS changed from 2 to 3 decimal place rating was becasue we were starting to see people design boats to the rule and not "good" boats.

IMO the rule needs to be:

1, Open so people can understand what happens when they change something
2, Simple so it can be understood.

BUT, people also need to understand the different philosophies behind the systems.



One thing that the Dart 18 class do very well is that they also have a "personal" handicap at their open meetings, each person has a handicap and this varies after each event based on where you finish and the handicap of those that are infront and behind you. There are "handicap" prizes at each event for those that improve the most.

Don't BS me, Mark.

I know what I'm talking about.

Besides, I think it is surprisingly funny to be considered an "inside the box" thinker for a chance.

Wouter

Scooby
I think you should lay out the fundamental assumptions for the two systems.

A measurement rating system... ASSUMES that the significant performance factors are rated and your formula captures the real performance of the boat relative to all of the others. but ... the Hobie 16 sailors complain.... the uni sailors complain. So, this measurement rule is not perfect.

A performance-based system ASSUMES... that the boats being rated are in good racing shape. Using race data from dead classes is a problem... it is unlikely that the boat has new sails and good foils, therefore when you update the current rating with this bad data it blows up the measurement... eg the Supercat ratings.

This is easily solved by including race data ONLY from classes which host a major one-design championship in the last 2 years. The rating gets frozen when the class stops hosting a major championship.

You are correct about the effect of poor sailors. The major problem for a performance system is getting the data from races that have enough well sailed boats with the top sailors in each class competing in the full range of conditions. If the top three F18 teams are competing against the top three F16's teams you can ASSUME that the skill set of all 6 are about the same... Therefore, the difference would be the boat class. Throwing poor sailors of a class into the mix will blow up the rating system. Averaging the top performance of poor sailors over time cannot solve the problem of getting the boat's rating correct. The assumption is the sailor skill levels are comparable is incorrect.

EG.. You can't take an F16 class rating from data in the USA because the grass roots nature of the class means it is not populated with accomplished racers . Using this data to rate the F16 against the Nacra 20 or F18 and A class fleets which has many more experienced and highly accomplished racers leads to an unfair rating.

The solution... IMO for performance ratings.... is to use the measurement prediction rating until the class hits the benchmark of two national championships.... then weight open championships like the Alter qualifiers or any other major championship (Catfight and Spring Fever) heavily when you compute the rating. Hell… if the F16 had a championship start 5 minutes after the F17 nacra championship … the correct rating would be locked in pretty quickly Likewise with events like the Tradewinds… (times on the first place finishers around the track )would work to getting the proper ratings.

IMO, handicap rating systems need to adjust the policy for the 21st century. Otherwise, it’s flaws significantly outweigh the flaws in the measurement systems.

Mark raised it , and it really pisses me off that we in uk use a formula that went to an extra decimal point and then makes a sweeping assessment of crew weight at 75 kgs , I weigh 118 kgs !!!!!!!!!!!!!!!!!!!!! but have to sail as fast as someone carrying 43 kgs less than me , stick that in the formula and see what fdifference that makes ,

Why in a measurement formula can we not assess crew weight far better and fairly , afterall theres plenty of weight equal lised classes that seem to cope with self regulation in weight declaration and settings .

Texel is no better in that respect .

and with modern rigs there is NO time when extra weight is an avantage .

And before any says it , I find with type 1 diabetes it is extremely difficult to lose weight

SCHRS uses formula that predicts boat performance based on the criteria the rule rates such as sail area, width, length etc to produce a theoretical speed for the boat and so a rating.

Each boat is different and so gets a rating based on these data points. The way to think of this rating is that it is the rating for a boat that is sailed perfectly! Now we all know this cannot happen, but if it did, then boats would finish together. This is how measurement systems work. Measurement systems can only measure a certain number of items.
-I’ll accept that a 3:1 downhaul is not as efficient as a 8:1 and so you cannot flatten the mainsail so easily, but should SCHRS (or Texel) have a rating point for Downhaul efficiency ? I don’t think so as we’d end up with 1000 rating points and the system would be impossible to use manage.
-I’ll also accept that not all hull forms are as good as each other, but should Texel or SCHRS insist that each hull is measured and so a Coefficient of Drag for each hull is defined? It would be impractical.
-SCHRS and Texel also assume that the boat is in good working order.
-SCHRS and Texel also only measure a subset of all available data’s – the rules need to be manageable – more on this later.

The Hobie 16 should be fast, it’s fairly light (145kg) has fairly large sails, but it does not have plates, it gets an allowance for this.




Yep, dunno exactly what PY (or US PY) does, but I believe that factorise the results to try and remove anomalies.
PY systems require results to produce a handicap.
It is known the PY systems do get bent by the “quality” of fleets and also by how hard the boat is to sail. Classic example is how the Musto Skiff Handicap is going down. Few years ago there were a very few people who could sail these boats and so the handicap was kept slower by the “average skill factor” in the fleet, as more people have learned to sail the boat, the PY has dropped. Measurement systems provide a rating based on the performance of the boat, not the sailors and the boat.

As an aside I would expect the F16 PY handicap to drop as we learn to sail these boats. This is because the “crew skill factor” is coming into play.

Problem with only using data from classes of a certain size is that they do not get a rating, few hours measuring a boat and about an hour on a PC and you have an SCHRS rating (or Texel).





I agree that you cannot assume that the skill levels in fleets are the same, this is an area where measurement based systems win out. Because the rule provides a rating based on the theoretical speed of the BOAT, when sailing under a measurement based system, the BEST sailor should win as they have sailed their boat closer to its maximum potential.

Consider the results from the Tornado results from Sail Melbourne; looking at the results http://www.sailmelbourne.com.au/race-results/2008/tornado/series.htm the finishing times are spread over around 15 minutes from front to back of the fleet, but more significantly the top 10 is still spread by 2 or 3 minutes at least. That’s going to be a few %; Now as Bundy and Ashby won, we can assume they sail the boat the best over the regatta. Would we expect Bundy and Ashby to wind in the F16 if they turned up to Mumbles this year; I would! Skill factor makes a difference in a PY system as it uses the performance of the boat, it does not in a measurement system.




SCHRS came about because people wanted to race new boats with a rating at once, not have to wait for the returns to come in before they can have a defined and stable and justifiable rating.

In an ideal world we would have 100 of each class of boat sailing against each other class of boat every weekend, then we WOULD be able to use PY as the returns would be statistically significant. We do not have this situation and so measurement based systems are the way to go.

Returns based systems work when you have ENOUGH RETURNS as this will factor out the skill factor as with 100 (or what every one decides is enough boats) boats you have enough good people at the front of the fleet.

To quote www.schrs.com:




SCHRS is evolving; The management group do meet electronically on an ad-hoc basis and exchange 1000’s of emails each year.





The problem with trying to compare SCHRS / Texel with PY systems is that they do not measure (and reward) quite the same thing.


SCHRS /Texel rewards the person(or persons) who sail their boat and make the least mistakes, i.e. sail the boat to it’s greatest potential


Returns based systems provide a handicap based on the history of the boats results. Thus this will provide a rating based on the speed of the boat AND the skill of the sailors that sail them. YES you can use data analysis techniques to remove anomalies within this data but it will not be perfect. PY rewards (to an extent) the person who sails the boat with the best handicap the best.




[color:"blue"] If people want to propose amendments that they feel should be included (as stated before) and can propose such amendments that are manageable, understandable, will not overly complicate the rule I will read the emails and make all the suggestions available to the other members of the management team (email address is on the www.schrs.com website) and we will consider them all for inclusion. I cannot promise that they will be included in future, with ALL measurement systems they need to be simple enough to be used. Simplicity is important, otherwise they die as they are un-useable.
I must stress that these changes must be manageable and verifiable with the simple enough to be used on a day-to-day basis by all.
[/color]

I sympathise with your situation, we looked at crew weight adjustment for a person as part of the rating system but rejected it because:

1, How do you ensure the helmsman is the weight they are claiming? (and so handicap?) - put everyone on the scales before each race?
2, How does the race team know what handicap you are on today? Different crew = different rating, after Christmas different rating, mid winter (more gear) different rating, mid summer (light summer shorties) different rating!
3, How do you manage a race series if the handicap for the boat changes each time the crew or crew KG changes?
4, Do you thus impose on the race team to insist that the same crew sail the boat for the series and not get fat at Christmas or thin to get the shorts on in the summer.
5, What happens if you change weight thru a season / series? Do you have to go on the scales before you leave the slipway between each race / day? What happens if it's hot / cold when you go on the scales?
6, Some classes such as the Laser 5000 had weight equalisation systems, do you propose that we insist that each class changes their class rules to implement this - not going to happen!

It would be a nightmare to administer for people entering races – how many people would query / protest for a claimed weight?
Would people turn up early for races each Sunday morning so they can go on the scales?

It would be a nightmare to produce results for a boat that had different handicaps for a number of races in a series.

They can but then the Race Committees will simply refuse to use it as then they will have to check crew weights at each event.

The issues with a measurement based rating system can all be traced back to what a RC accepts and doesn't accept.

One person once said that there is no reason why a measurement rating system can be just a very elaborate VPP (Velocity Prediction Program) that is used by record breaking designers who do BBQ and IDEC. Technically he is correct. Hell, we can even train an artificial neural network to do the job as this assumes no prior knowlegde of the system that is modelled.

The problem of course is that the RC's NEED to use it. When it becomes to involved or complex then THEY refuse to do so; even when the numbers are much more accurate. Final result the handicap system needs to be actively dumbed-down to make sure that RC will accept and use it.

One of such simplifications is the fact that ONLY one rating number for all courses and all conditions is created. Making this very accurate is technically impossible, but it is key requirement by RC's. Any yardstick system will suffer from the same problem.

Wouter

in a word wouter "bollocks "

enter a regatta , state your handicap on entry form , whats the problem !!!! or are all r.o's in your world as pedantic as you ???

Other classes with weight equalisation can manage without great fights and protests , why can't cats .

anyway i know us heavy weights will ALWAYS be advversely handicapped , although Scooby is sympathetic he is not prepared to do anything about the problem .

Why not for the sake of peace just hide the crew weight factor in the formula - as it cannot and will not be changed as there is no will to sort this problem out and stop rubbing it in our chubby faces .

It is a real pisser to think that as a "larger " cat sailor you have to sail a totally flawless race sailing at 120% of your performance envelope and hope your lighter counter weights make errors for you to have any hope of getting into the results .

Its a merry go round (not very merry for me <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> ) and I know I'll just have to put up with it ,I just like a moan now and again to let off steam .

Think Sailwave may have the begining of something there , but lot of work needed yet , good luck to him .

Why don't you just shoot the messenger, Codblow ?

I'm sure that will help.


Wouter

P.S. I'm not a light 75 kg sailor myself. Like I said I know what I'm talking about.

All rating rule have holes and weakness, that’s why designers get paid, to find the softness in a rule and exploit it. You will never get a rule like SCHRS or Texel to totally predict the performance of a cat with the limited information provided, have any of you seen the amount of information that goes into a top of the range VPP program and even with that it’s dead easy the bend the performance to what you want to see. We just have to relies that some boats will get nailed and some are on the pigs back, at the moment it’s favours heavy-ish powered up boats, but like all these things the pendulum will swing back and you will have the other group bitching about there rating, it’s all a matter of When. I think Texel and SCHRS has done a good job with the few basic dimensions to get boats on the water and racing. Maybe they just need to hide the formulas like the IRC rule, and keep it a black box rule.

So... you think a single number system (IRC Texel, SCHRS) can describe ANY boats performance from 3 knots to 25 knots?

To do so... would mean all of the boat's in the fleet have a linear performance curve!

The rule could require a supercomputer to compute but the output... a single rating number, will be valid over a tiny range of conditions.

the USA Portsmouth recognizes this fact of life and generates 4 ratings... Texel generated two ratings bands.

The problem is RC compliance and sailor interest ... the folks who are doing the scoring run a handicap race once or twice a year... It is difficult for them to come up to speed with a 4 number rating system. In practice somebody learned a primative program years ago... So, they get that person to come back and score the regatta each year.. As far as I know... the ONLY scoring program that handles the full USPN Windspeed or Texel wind speed rating system is Sailwave. It is simple to use and works extremley well.. BUT, in my world, the yacht clubs use javascore which can handle a single number .... Unless I do the scoring.... We can only expect a single number rating score...

Coupled with general apathy on the part of sailors in requesting wind adjusted or team weight adjusted scoring.... we get what we get....

Exactly.

Codblow, how much difference do you think 118kg vs 75 should make to your rating?

As I said, we've looked at it and it#s not going to work, But I'd like to understand how much impact you think it has.

What people fail to see here is that you need a single number, history had told us this over and over again, any rule that tries to have a rating for different conditions runs into trouble very fast. IRC rates Supermaxi's to 1/4 tonners very well and this has a single number system (it's not perfect but what system is?), IMS had many rating for different conditions and it's just about dead! Is SCHRS only in Europe?

SCHRS is the ISAF Cat system.

Linky

IMS had ratings for each leg and length of the course... by all accounts it is accurate but a PIA to use for the RC .. ... It contributed with other factors to the demise of the IMS.

IRC is working hard to gain acceptance in the USA. The cost of the certificate and the PIA to the owner to get an individual cert has slowed it's acceptance( PHRF is a lot cheaper and you already have a rating certificate ... just pay your 35 per year dues and you are good to go another year). The IRC racing has been viewed as fair from what I can tell. (IRC is not a problem for the RC since a single number time on time calculation is available in all of the scoring programs used)

SCHRS and Texel are not used in the states.... We don't have a really good reason other then traditionally we have used Portsmouth.

In practical terms... we have a bunch of boats that are sailed in the states but they have not been measured for texel or schrs (hobie 20 Prindle 19MX) .... So we don't have a complete set of ratings which automatically stops wide spread use of a measurement rating system. US Sailing and the Multihull Council have not taken on implementing a measurement rating system.

US Sailing manages the Portsmouth system for all of the monohull dinghy's as well and so managing two systems (portsmoutha and measurement) would be a lot to ask.

we do have a rating for the Hobie 20:

http://www.schrs.com/index.php?page=class&id=52