I'm sure a few will be sceptical but a better mouse trap is definately possible when rating catamarans. As always the truth is in the middle and so the better rating system is lcoated somewhere between the European single numbers measurement systems and the Multi numbered yardstick numbers.

I tried to improve on the rating system by adressing as much issues as I could without complicating the rating system. Over time I listened to what sailors AND race organisers were asking for and tried to strike the optimal balance between the two. I also included preferences of both camps so that both have ground to accept the proposed systems over the older and arguable outdated Texel/ISAF and Yardstick systems.

Two years ago I tried to convinced the Texel rating committee to accept the proposals or at least include several mods into the well know Texel system but the effect was neglectable. I quite as advisor to the texel committee shortly after that.

I know would like to use this post and thread to explain the upgrade system to the world and hope to provide all the catamaran sailors with a more satisfying rating system.

I have not much trust in the established rating system committees simply because they are to much politically and emotionally attached to their old systems that have became stagnant as a direct result.

Just as with the Formula revolution it will again be up to the sailors themselfs to force a change or accept living with inferiour systems.

To proof my arguably big words I will use this thread in the comming weeks to present the upgrades and modifications and present a working system at the end. I will provide this system as is and free of charge although I will be very grateful when my imput is credited when using this system. If only to help me get into analyses and mathematical construction jobs that I enjoy and hope to be good at. At least that will give me some return on my time investment in all of this.

Last Note : I began to play with the idea to design such a new/upgrades system when some 4 years ago I was challenged to design a better system on the old Catsailor forum. This was often after lengthy posts made by Carl Roberts. I took the challenge and so here it is.

Regards,

Wouter

The project resulted in two improved systems :

First the NMBR system;

NMBR stands for New Measurement Based Ratings; This system is the most simple compromise between the wishes of both sailors and organisors and adresses the wished of both the measurement system fans as well as the Ameican/Australian sailors. This system is the one I think can bring the world together under one rating system setup. It is measurement based just like Texel and ISAF to cut down on maintainance work and to prevent rating creep. However it is fully intended to be alot more flexible than the current Texel and ISAF systems. It is intended to progress with the times. Afterall Texel was acceptably accurate in the 80's when all boats were very similar however it lost it accurateness when all kinds of new design came into play during the 90's. The Texel continued to ignore the changes and lost as a result. NMBR recognizes this and aims to prevent this from happening again.


Secondly the MBSR system;

MBSR stands for Measurement Based Simulated Ratings. This is actually more comparable to what yardstick systems try to do but fail at often. It takes know dependencies related to different setups and simulated back a rating on a set of parameters. This system is actually intended for distance races where normal assumptions underlining both Measurement as yardstick systems are not satisfied. No matter how you turn it both type of systems assume that a triangular course or a windward-leeward is sailed. This however is seldomly the case in distances races.

Each system shall be covered independently in this thread about a better mouse trap. They can however be made compatible.

The thing to remember is that the systems are constructs. They are based on logical framework, of some abstract level, but never the less their machines that can be altered or modified when that is so desired. Neither of them have a parameter regression or a statistical processing as the working core, meaning we administrators of these things understand how it works in detail and so their is no black art to confuse the sailors. OF course their fundamentals are based on various forms of statistical processing and dependency regression but only at the basis. Or more concrete example. The shape of the current texel formula can NOT be explained physically, the workings of Yardsticks system include many distrubances that are assumed to cancel one another out, simply because we have to assume that or accept that what we do is ill determined. Both NMBR and MBSR systems do NOT suffer from black boxes like that.

It is understood that even these improved systems are not perfect or even 100 % accurate. The desire for simplicity prevents that. However the only thing that really matters is that they are MORE accurate and MORE dependable than the current systems in use. That should be enough.

Wouter

Header post

Header post

Wouter and all,

Basis #1
Spin beach cats and non-spin beach cats CANNOT race as 1 class.

As funny as it sounds, down here, a trend ( by PRO's)to lump ALL beach cats into 1 class, spin and non-spin alike. Even when the non-spin and spin boats have enough entrants to form a class, by the regatta's published rules.

The POR's premise is, " they all have a Portsmouth number, don't they?" Of course, the spin boat skippers get real quiet, while the non-spin cat skippers fall over on the ground.

As clear as it appears to you and me, regattas dominated by monohull-minded officials cannot see it.

So, please Wouter, in the new rating formula, STATE IN BOLD LETTERS,

NON-SPIN RATINGS DO NOT CORRELATE WITH SPIN NUMBERS

Thank you.

I hope the Rolex Committee in St. Thomas sees this.


regards,
Bruce
St. Croix
USVI
X 17 normal

New Measurement Based rating Catamaran handicap system (NMBR)


The goals of this system is to provide the sailors of small catamarans (up to 22 foot , 6.70 mtr length) with a more dependable and generally accepted rating system. It's intended use is in open class racing on closed course regatta's.

The main characteristic of this system is that it is completely measurement based (Like Texel, SCHRS) and therefor does not require 'rating development time' for new designs as is the case with yardsticks. Nor does the rating numbers show any creep over time when good crews either enter or leave the class. An added advantage of the system is that everything can be explained on physical grounds. There are no more magical black boxes.


Back ground and correct use of the system

Lets be blunt, a rating system does not have to be highly accurate. Of course with sufficient effort and resources one can implement a very complex Velocity Prediction Model and get spot on rating numbers. However there are also two good reasons why this has not been done in the past even though the technology to do so has been around for some time.

The first reason is the system major design goal has always been that it must be practical in application. Complex system are quickly disgarded by both sailors and the race committees. Sailors don’t want to wait long for the results nor want to work with large confusing tables of ratings for their own craft. Race committees really don't want the hassle and delays that these complex systems bring with them.

The second reason is that a highly accurate system is useless in real life application. After a certain minimal accuracy the final scores hardly change. Typically the spread between crew ability in a one-design class easily leads to spreads of 20 minutes per hour over a complete fleet. This where inaccuracies in a decently accurate rating system will only account for offsets as big as 1 or 2 minutes per hour racing. This leads to the situation where the net result of a much more accurate system is only that one or two crews move one or two places up or down, not much else. Very often the top 3 listing doesn't change at all. Therefor; the challenge is to design a system that has sufficient accuracy and then concentrate on making it as practical as possible. Making it so to both sailors and race committees.

Why a new rating system at all ? Because the current systems are either impractical or have a fundamentally and unacceptable large inaccuracy. Several systems used today did well in the past but have lost accuracy due to increased variation between the catamarans of today. Comparing a Hobie 14 to a Prindle 18 is something else than comparing the same Hobie 14 to a rare, lightweight, cat rigged modern doublehander like the Marstrom M20. It is not that the old systems have deteriorated but rather that they are now required to cover a much more diverse fleet. Something for which they were never developped. To get this corrected is the responsibility of the new rating system

A point of note is that rating systems can be made relatively more accurate by making them less sensitive to factors beyond a Race Committees control. Such factors are a gradually changing wind direction or changing wind strength. Note that these impact negatively on a one-design class just the same. However in some cases it can be proven that an open class fleet is impacted more by these factors. A good trick is to group together boats of similar performance or setup. With sufficient participation a regatta can then be made up of say a spinnaker fleet. a low performance fleet and a singlehander fleet. A change in wind strength will impact differently on a spinnaker boat than on a singlehander but much the same on two spinnaker boats or two singlehanders. To maximize rating system performance in this way will always be the responsibility of the race committee and not of the rating system. However the rating system can still maximize the accuracy when rating a diverse fleet under relatively constant conditions and it should very much try to do so.

The hardest test is to accurately rate a fleet of 20 boats or less, as at most clubraces, here one is forced to group all makes together. However here we also arrive at some responsibility of the sailors themselves. As indicated earlier a one-design crew may finish anywhere between 1 second to 20 minutes behind the leader. In a small fleet of different type catamarans the difference between the first finisher, who finishes in 60 min, and last finisher is typically just over 30 minutes. This means that on average there is a gap of 1.5 minutes between each placing. With an rating system inaccuracy of say 1 minute per hour (2%) the chance that 97 % of the placings won't change at all with a more accurate system is very big indeed. Even of the crew that do exchange places, nearly all will only climb or fall one position in the final listing. Meaning that if you weren't in the top 3 to begin with that you most definately lost the race on skill rather than on ratings. That is under the assumption that the use system is accurate to 2 % or less. This is arguably not the case with the systems in use today.

From this we take away that there is at least a 20 minute spread in crew ability per hour and only some 13 minute spread between a Inter 20 and a Hobie 16 as a result of boat design. This should focus the attention of the crews on learning to sail better. However it must also be said this is only possible when a rating system satisfies the experiences on the water rather accurately. Not prefectly, but accurately enough so that any offsets are dwarfed by the differences related to skill. The rating system should at least do what feel logical to the sailors. That will go a long way to have it accepted by them.

This leads us to the design goals of the NMBR system.


The design goals of the new handicap system

-1- Must produce new ratings immediately as soon as a new production or one-off model is available.
-2- Must produces the regatta results quickly and transparently.
-3- Must be practical in use to both the sailors and race committee.
-4- Must adjusts the ratings according to input parameters that feel right to experienced sailors.
-5- Must strikes the best balance between accuracy, complexity and required processing during a regatta
-6- Must be relatively easy to maintain or fine-tune with time and increased understanding
-7- Must show no obvious or significant bias in any conditions to any design.

Significant, as used in point 7, is defined as 'must not contribute to the end result in a share larger than
1/10th when compared to crew skill'. Peferably less than 1/20th


Improvements

Older systems often used statistical data or a limited number of measurements to arrive at a rating. With the decline of catamaran racing and racing with smaller fleets, the statistical systems have trouble preventing rating swings due to influx of good crews as well as getting enough data points to make a dependable estimate for the performance. Measurements systems on the other hand still only measure a few parameters and implictely assume that all other aspects are the same between boats or do not matter. Of course the last assumption can not be supported anymore. There is too much to be done in order to remedy a statistics driven system. In addition, its working core is slave to a reality generating both good and disturbed data and that is to all-encompassing to be fully comprehended by an unskilled human brain. That leaves us with working out a new system using the concept of the "measurement based systems'. Despite its own drawbacks, this system provides the most accesible basis on which to base a new system. It is easily explained to unschooled sailors and its framework allows adaption to future developments. However, in order to provide a foundation to such an adaptation an ongoing statistical analysis of new developments will have to be performed . This is also needed to check wether the system is still up to the task. A measurement system may not be allowed to become stagnant and drift away slowly over time.

It was expressed by many sailors that the current measurement systems fail on points like correctly rating the addition of a spinnaker to a cat-rigged catamaran relatively to adding a spi to a sloop rigged boat. This is now a well understood phenomenon. Another good example it the problem of certain boats becoming relatively faster with increasing wind while others relatively slow down. Think of respectively a Hobie 16 and an Inter-20 in relation to a F18 catamaran. Current available systems do not adress these issues well enough and it is now possible to predict a likely handicap winner on basis of the wind conditions. The new system will correct these points.

An extra issue is the fact that some features of the system appear to be randomly applies or randomly applied. This is not good for the trust that the sailors are expected to put into a handicap system. Clearly a system that is not credited by the sailors themselves will go nowhere. This issue is also adressed in the new system.

Of course each system has its good points and its bad points so in developping the new system we have combined the good points and improved on the bad ones. And of course we have introduced a few new elements as well.

To cut down on required effort to get the system operational, the decision was taken to use as much of the parameters of the old systems as possible in a unmodified way. The end result is that we introduced 1 new input value and recycled all the known parametes and values into a new framework. When required this limitation can be abandonned and even more accuracy or simplicity can be introduced.


Important decisions

First, we have dropped the old standard class. Also known as the reference design. This design (class) was assigned a fixed rating from which all other ratings were derived. It acted as a pivot around which the other rating derived their (relative) meanings. This used to be the classic Tornado, that doesn't exist anymore. In other cases it was the Hobie 16 design, arguably unrepresentative of modern catamaran fleets. The new proposed standard is the Formula 18 class because of its large global presence and it expected domination in the future. Already cat sailors are basing their own performance to sailors in this class as there are always a few of them around. The F18 class is also very representative of modern catamarans racing as a whole. After all the foreseeable future looks like it will be dominated by formula classes.

Later in the project it turned out that the rating of the (new) Tornado class (double trapeze, spinnaker, bigger sails) is constant under the new system with the F18 standard. Ergo the new Tornado class may be regarded as sort of a second standard. The same applies to the Formula 16 class which actually intents to race doublehanders and singlehanders on the same course. This latter class may proof invaluable to fine-tune the ratings of the singlehanders to that of the doublehanded standard class. It is expected that these three classes together will provide a sound base which will produce dependable statistical data to proof or improve the rating system. Such key proving points (classes) are very important in keeping the system up to date and accurate.

Second modification involved the use of modest averaged adaptation. When a dependency was found to be present but insufficient data was available to quantify it really accurately then the concept of an 'centralized educated estimate' was used. This may sound inaccurate but it is actually a good way to improve on the accuracy while keeping the complexity of the system low. Compare it to the game where two people have to give a number between 0 and 10 and the one closest to the mystery number wins. One can choose to name 2 or 8 and be either really close or not close at all. An alternative is to choose 5 and be reasonably close whatever the mystery number may be. Of course, not choosing at all is assured to loose. Hence making an educated guess near to an expected average is always better than doing nothing. In the follow-up iterations the optimal point can easily and quickly be found. This binairy approach is the most simple and quickest way when using the very simple 'More' or 'less' qualifiers.

Thirdly, the parameter expressions were kept simple. An example, the number 1 may have been used in places where 0.98 would have been closer to the truth. However a formula with 10 parameters all containing 3 digits quickly becomes a very confusing expression. If using a single digit number only created an off set of a few seconds it was decided that this was an acceptable price to pay for reducing complexity and increase the ease of use. Remember that by creating the same offset in ALL ratings will cancel out much of the impact of such an offset. Nothing changes in the listing if all handicapped time results are off set by the same amount.

Fourthly, the model of the catamaran was kept simple. A single heeling force estimate is made for identical sail areas and luff lengths even though in reality there may be aerodynamical differences in the rigs. Examples of differences are : having a square top sail or not ; having a very low boom, having skegs or long boards. It is possible to include these differences and be more accurate but it will add a lot of complexity and will make using the system impractical really quickly. Think of what needs to be done when a crew decides to entlarge their square top ? The race and rating committees don't want this hassle and nor do the sailors. A difference was made were sufficient swing in rating was expected. An example of this is the way in which a mainsail and a jib contribute differently to a the heeling moment. A cat rigged catamaran with a given sail area will therefor have a different heeling moment estimate from a sloop rigged catamaran with the same sailarea. This while two different F18 implementations will get the same estimate. It is expected that the round-off error are far to small to constitude any serious threat to accuracy.

Fifthly, the ratings are split in two groups. One group gives the rating for below double trapezing wind condtions and the other group gives the ratings for above double trapezing wind conditions. In both groups a second rating is available for the spinnaker equipped version. This is a simplied version of the wind dependent ratings systems. It is adviced that when 2/3 of the fleet is double trapezing when going upwind that than the high wind rating group willbe used. NOTE, this can be dependent on the composition of the fleet. A fleet of A-cats with a few other singlehanders may qualify for this transition at a lower windstrength than a fleet of Hobie 16's with a few other doublehanders. It is left up to the race committee to decide which group of ratings is used.

It should be noted that the Race committee can make a decision for the use of either number on observing the fleet along. No wind measuring tools are required. Also the transition from non-trapezing tot trapezing is arguably the most important transition from one wind scale to another. Different designs diverge here a lot more than at other wind scale transitions. This both minimalizes complexity as make usage more practical while maintaining the most important performance related transition.

Last, it is strongly adviced that the ratings are used on closed loop courses. This maybe triangles. Windward- leeward loops or even rectangles as long as the point of the start is also the point of finish (by approximation). The ratings are derived for such courses. The new system allows ratings to be calculated for exclusive upwind, exclusive downwind and exclusive reach legs as seen in one–way distance races, however accuracy is expected to suffer a little in these applications. It was decided not to fully fine-tune the system for this application as that would add complexity disproportionally to the frequency this feature would be used. A specilized system can and will be developped for this specialized use. Strong grouping of similar boats (not from performance perspective but from the perspective of general setup) will greatly improve accuracy in these applications although it is understood that the ratings will be less accurate than when used on closed courses.

Wouter

You are completely right and I will give such a statement more prominance in the final wordings.

Still, the NMBR system allows to rated the two more equally to eachother. Simply by the fact that when using to rating numbers, one for sub trapeze weather and one for trapeze weather, we can assign a heavier hit to a spi in one of the two ratings thus approximate the swing in performance difference more accurately than a single number system can.

It is not perfect but it is already a step up from the single numbers Texel and ISAF systems

It is also a step up from yardstick as experiences gained in one particular class of catamarans (F18 ? to say H16's) can then be easily extrapolated to all catamarans. Also the one with small or inactive fleets.

Please keep the suggestions coming.

I think I have designed a better system already but I KNOW it can be better still ! With your help we can make something really good

Wouter

Again I remind everybody that the NMBR system is a construct using the foundamentals of the Texel and ISAF systems. Used these as a starting point to facilitate acceptance. A complete new formula would be better but could probably be too much change in one go. If it isn't then wait and read MBSR thread later.

The issues

-1- Single handed cat rigged boats like the A-cat, M18 are rated to harshly. Some lightweight double handers are so too (M20)

-2- Cat rigged boats with a spinnaker are rated wrongfully against sloop rigged boats with spis.


There is ample anecdotal evidence for both points and even some dependable evidence. However we must all realize how difficult it is to get good dependable data. This is also the achilles heel of the yardstick systems. One really needs to do alot of pre-processing to determine wether a race result is dependable or not.

But what we DO know is this.

Texel and ISAF are relatively accurate when rating middle to heavy weight cat rigged cats without a spi to middle to heavy weight sloop rigged cats without a spi. Afterall this was the data set on which both systems were regressed. Say the span P16, H16, Dart 18, P18's, TheMightyHobie18, nacra 5.2, nacra 5.5, P15's H17 that sort of stuff.

It is a well known fact that sloop rigs are faster around a course when no spinnakers are used even though they difference may be rather small on the upwind leg itself. But only when the right balance is struck between the area's of the main and jib and when the same mast lengths are used. Things maybe different when one of these conditions is not satisfied (A-cats ?).

Both Arvil Gentry and Marchaj show in their respective works that adding a jib has the following effects :

-1- The suction zone on the main near the mast is disturbed leading to less drive produced by the main. This shaves of the low pressure peak. It also prevents the main from stalling easily resulting in a forgiving flow over the main. So it produces less drive BUT is more constant and stable doing so.

-2- The updraft of the main and the low pressure zone above the main result in the jib experiencing extra low suction on its lee sides at reduced apparent angles of attack. At a right balance in area's and slot width the jib will produce twice the force per area as the mainsail.

-3- When going upwind the main must be pulled more inline with the centreline of the boat and the boat must be pointed a little lower.

-4- When going downwind the boat can be pointed lower and the sails stall less easily at these high angles of attack.


If you run the numbers on this you'll quickly end up with a intepretation of the situation where

-1- Where the looses of drive on the main equal about 1 times the area of the jib leaving just 1 amount of jib area to produce extra drive. As a rought but relatively accurate measure.

-2- The factors work against eachother on the upwind as good as cancelling one another out.

-3- The factors work together on the downwinds making the sloop superior here.


Often the sloops carry relatively more area than a comparable cat rigged boat and so the sloops may often be a little faster on the upwinds as well. However we'll get to that later.

Obviously the main benefit of the jibs are found on course that are not upwind beats, although some benefit may still exist there. When a spinnaker is fitted to both boats the spinnaker takes care of most things the jib did. It prevents the main from stalling too easily and provides a large skewing of the apparent wind the main experiences allowing the boat to be driven deep. The jib has almost lost all its benefits except for the small upwind gains.

The problem with Texel and ISAF is that they keep regarding to downwind benefits of the jib as independent of flying a kite. This is arguably very wrong and most sailors know this from personal experience.

I refer to Tornado Alive comments for more data on this :

http://www.catsailor.com/forums/sho...6986&page=&view=&sb=5&o=

He gave us some great data on the comparison. I noted it down and research how it compared to what the theory said. It seems the two are pretty close together on this.

Therefor the remedy is quite straight forward.

An example :

Take two identical boats with equal size cat rigs and add a jib to one of them. of about 25 % size than the speed gain is as is currently predicted by Texel. Note how Texel and Yardstick system seem to converge on most boats, suggesting that Texel does do a few things right : I refer to Sam Evans for more info :

http://www.catsailor.com/forums/sho...8033&page=&view=&sb=5&o=

So lets keep this feature. Now if we add a spinnaker to both boats than the speed increase due to having a jib as predicted earlier reduces. A good "averaged estimate" is that 2/3 rds of the gains are lost because both boats now use a spinnaker.

We can therefor roughtly compensate for this by reducing the jib area to a fraction of what it was when both were
sailing without a spi. This fraction will only account for the gains found on the upwind legs. Finding this fraction is key but not really that difficult. I have used a constant I have matched with various race result in the example version of the system, it seems to predict performances well.

This correction has the effect that all sloop ratings remain unchanged (bulk of the raced boats) and also leaves the cat-rigged cats without spi rating the same to their non-spi sloop rigs. The only ratings that are impacted are the cat-rigged cats with spis which are definately a minority at this time and are relatively new to the game. Minimal impact for a significant improvement.

In effect we issue a larger speed increase to the cat-rigged setup when they add a spinnaker than we do to sloop rigged boats adding a spinnaker.

The modifications is simple and easy to implement. While still leaving the spinnaker modification independent so we can modify that one to make the comparison between spi and non-spi boats more accurate.

Wouter

Arguably both the Texel and ISAF systems use of only one rating number for accurately predicting performance over the full spectrum of wind strengths from 3 knots to 25 knots is a big ask. This is especially problematic when looking at spinnakers.

On the other hand the average DPN of yardstick in no better in this respect and many Race Committees dislike the 5 individual ratings that some yardsticks use. It requires much more effort from their part to measure the right wind speed and it makes rating calculations more cumbersome. Also in principle the ratio between different ratings numbers is surprisingly constant while the individual numbers vary. This is hardly effective. Alot of trouble for not much gain. Add to this that you need a minimal amount of data for each group to make an accurate regression and you'll get the picture of the work involved. It in no wonder why many RC just use the default numbers and be done with it.


The proposel to solve this deadlock is to have two rating numbers instead of 1 or 5 or more. 2 allows more freedom to improve accurate prediction for arguable very different conditions (trapezing and non-trapezing) and is alot simpler to use and maintain than 5 numbers.

Arguably designs will really only differ in performance on the threshold of going from non-trapezing conditions to trapezing conditions. It is the transition from always sailing under maximum achievable power to sailing under maximal controllable power. As a result there is not much to be gained to sub devide these two very different regions in more sub groups. So lets take the transition that is really important and forget about the rest for sake of ease of usage.

Also it is alot easier for a RC to determine which rating they should use just by looking at how many of the boats are trapezing. If this ratio is less than halve, you use the low windspeed rating, if it is more than halve you use the high wind rating.

By dividing the performance predictions in two groups of numbers we can also compensated FAR more easily for the swing in performance experience by singlehanders and spi boats when the transitions from sailing in light winds to heavy winds.

For example : the singlehanders and spi boats will get relatively faster ratings in the light winds group when compared to their ratings in the high wind groups. We can split any offsets that may exist in halve using this setup without really increasing complexity of the system used.

There is also a lot less potential for conflict. Either halve the fleet was trapezing on the upwind or they weren't.

For further details I refer to the posts about the individual mods.

Wouter

We all know that changing conditions impact differently on spi boats than they do on non-spi boats.

We will never be able to fully compensate for that unless we are willing to use a lot more complicated systems.

However we can much reduce the offset that we percieve in the current systems.

Example :

Spi boats tend to witness their largest gains, relative to non spi boats, in 5-12 knots conditions. This would largely coincide with the non-trapezing group of conditions. Above 12 knots of wind the difference decrease, minimizing at the far end of the scales (25 knots). This is arguable a constantly changing curve spanning the range from 3-25 knots. Approximating this actual behaviour by two horinzontal lines (averages in their own segments) is always better than to approximate it with just one horizontal line over the full spectrum.

By decoupling the spinnaker hit in the trapeze and non-trapeze segments of the windspeed we arguably cut the current ofsets in halve.

It will still be not perfect but yet alot better than we have no. Hopefully, probably, enough to get good ratings for club races were there aren't enough boats to group spi boats with spi baots and non-spi boats with non-spi boats.

In the working example I will provide later I have chosen, on data available to me, to hit spi boats harder in the sub trapeze conditions than they are in the trapeze conditions.

Wouter

Double handers and single handers :

The split in rating numbers between trapeze conditions group and a non-trapeze conditions group also allows us to correct the issue we have with rating singlehanders accurately with doublehanders.

There are many reasons why a singlehander generally performs better in the light stuff than in the strong stuff. We can't not compensate for them all for that would make the system to complex to use comfortably.

We can however take a few big important factors and correct for them thus arriving at much smaller offsets then before. Offsets that could well be to small to matter anymore when compared to sailor skill.

Beyond a doubt the most understood and arguably the largest factor in this is righting moment when compared to heeling moments. We have seen 18 squares clean up at Curacau when doublehanded while seeing singlehanded 18 sq. being left behind. There is one thing that is different between these boats. The same experiences are found in classes that sail their boat in two modes like the Taipan 4.9's. Lets use that experience.

The second biggest factor is control. It is just alot harder for a single hander to control and tune his boat in the heavy stuff than it is for doublehanders. Especially when flying a spinnaker solo as well. This factor can easily be included into the system by a weighting factor. That is in addition to the righting moment / heeling moment compensation.

There are certainly more factors as well but arguably the net gain that compensating for these can give are much reduced.

For arguments of simplicity I have decided to stick with these compensations and see if any others are still needed in the future. I do not expect that to happen. Certainly with these two compensations we will have sliced the offset to a fraction of what they were before.

Also the good part is that the Texel system contains all the data needed to implement these mods except width. For this reasons these mods are frightingly simple to implement. And also easy to maintain.

To calculate the righting moment / heeling moment ratio we use a simplied formula that contains known and noticeable offset with regard to reality. However it can easily be proven that these offsets are about the same for all designs and therefor the ratio's between designs are largely unaffected by that.

Example :

When taking a ratio of two numbers that are both 10 % of the mark and equal of sign than the ratio itself is only about 1% of the mark. Therefor you need not be very accurate in the base numbers as long as you can garantee that all offset are similar sized and have similar signs. That can be proven.

Proposed :

Heeling moment estimate = mainsail area * 1/2 * luff length main + jib area * 1/3 luff length main.

Righting moment estimate = weight boat * 1/2 * width boat + weight crew * (width boat + 1 mtr)

Notice how all input data is available in the Texel rating handicap system with the exception of the width.


In order to achieve aour accuracy we need to assign a reference design. For that we use the Formula 18 class.

This gives the F18 class a flat rating over the full spectrum of the wind speeds. Arguably a benefit in itself.

Wouter

The construct of each rating system is based on relative performance of each boat to a single reference. It is not required that such a reference is an actual design or class but that does have its benefits.

The old standard was 100 and was assigned to the Tornado under Texel although the true reference was the H16 at 116. The number 116 was taken because that was the numbers use for the H16 in an older rating system. Such are considerations of legacy. Sailors soon forget to origins of such things and therefor following up on legacy benefits is useless.

Yardsticks in general use funny numbers. Often somewhere between 50 and 80 or between 110 and 160. Such choices result in unnecessary calculations and also in corrected times that have no meaning.

If a design with rating of 70 sails for 60 minutes and is corrected to 42 minutes and looses to a boat with a 41 minutes corrected time many sailors think that the first boat had to sail 1 minute faster to win.

This is wrong as 41 * 100/70 = 58 min and 34 second. Or 1 min and 26 secs to slow to win. An increase of 50 %

It is MUCH MUCH smarter to assign a rating of 100 to the most prolific design. Arguably this is, or will soon be, the Formula 18 class.

Than NO handicap calculations need to be performed on the F18's, their elapsed time is also their corrected time. Less potential for errors as well.

In addition a 110 rated boat sailing 60 minutes with corrected time being 54 min 33 sec; that was beaten by a F18 coming in at 54 min, had only to finish at 54*110/100 = 59 min 24 seconds to win. Or 36 sec faster. As you can see this very closely approximated by the 33 second in the corrected time results.

So keeping all ratings as close to the reference of 100 is very beneficial. Centering this rating 100 among the group of boats most often entered in races makes comparison alot more easy to both the sailors and RC's. The F18 class is neatly centred between the F20, Tornado's and A-cats on one side and the bulk of the (older) 16,17 and 18 footers on the other. Neatly being defined here as being proportionally closer to the classes that will see most boats enter => F20's, Tornado's, F18's, F16's, A-cats and the faster Hobie's and Nacra's of the past.

For these reason choosing the F18 as the reference class has many advantages. And therefor we choose to do so.

Wouter

Wouter,

Very interesting reading. I will read it again after a less stressful day at work. However, I have one immediate concern :



F18 is a box rule, but a development class so the boats should get faster over time. Witness the difference between an old Dart Hawk and (say) a Nacra F18. You are not going to win any races on the Hawk, yet they rate the same in your proposed system.


The only way to have a boat that has a flat rating or 'core rating', is to use a boat that has totally strict rules like the Dart 18, Dart 15 or Hurricane 5.9. These boats will only get faster as people learn to sail them (which I would suggest has now happened - the only speed gains will be via new techniques such as wild thing, or the adoption of new sail cloths or build techniques).

Sorry for the O/T but,

You don't have a significant other in your life do you?

(either that or you never sleep)

Hi scooby -good on ya wouter -good beginning -

Historically rating systems have never lasted without being rethought and revised in different forms periodically ,-the best being one with the greatest simplicity able to renew and change with changes in the craft themselves over time.

Agree w scooob and will also wait for a less stressfull work day and be brief,-or is it holiday stress already ?,

to answer your question scooby ,- think what wouter meant in using the F-18 as a benchmark of sorts for rating is not a specific F-18 cat design but instead the measurement parameters that form the F-18 class used as a common model or benchmark of comparative speed.
Conceptually for consistancy and fairness in rating it is important to comprehend all craft as design measurement based rather than a specific boat by brand or class with huge variation in class brand rules ,-it only leads to inconsistancies .

Wouter has some great concepts in the attempt to rethink and update a design measurement based rating rule ,-

My 2 cents currently would be for the development of a combination rating system that would use the current yardstick pn with its attempt to equate real time to distance traveled in windspeeds in that same scale and familiar numbers , but used as a correcting factor to design measurement based dirived numbers though in more simplistic basic formula than Wouter is beginning to describe. Taking the approach of design measurement rating only historically leads to reinforcing current trends in design, thus the need for only basic definition in the design measurement aspect of L W SA plus beam and basic crew spin jib relativism ,--adding a yardstick system in combination should correct any major errors or omissions in the vast array of variables in design and wind seas conditions from there much better than either rating system does independantly as per currently used.
By using both systems they could both be simplified greatly and compliment or correct one another and would certainly become more accurate if adopted internationally providing more verification of the yardstick aspects in larger numbers ,--along with some added thoughts in ranking racing sailors in basic skill levels to correct this aspect further .
The simplification of the design measurement portion would be from the reliance on the yardstick aspect to compensate lesser design features that historically make design measurement rating systems counter productive by penalizing excellent design and thus to design progress and creative development. A design measurement rating system only in an effort to compensate all design variables makes them too complex to comprehend ,-the end result being a complex partial effort at total design annalysis subject to differences of opinion in design values in the equation.
There are numerous other reasons to develop a combination rating system that become clearer as it is thought through.

Outlined ---the combination rating system would not use the rated formula and proceedures in determining weight length or sail area ,-a simple direct boat weight -o a length -and sail area used ,-in a base equation ,
-Sounds like your working through proven proportional factors added for spin -non spin -jib -main only sail plans and single or 2 crew variables ,--this would keep it simple -and again the yardstick added to this as compensation for lesser design variables at a correcting percentage should be more verifiable over time with larger input sources internationally and a ranking system for racing sailors to compensate skill level unknown to some extent of the yardstick aspect .
The model end power formula of Texel similarly used but now in very simple form easily understood and calculated .
Think the end number factor in the power formula could be scaled to corespond to the 5 windspeeds currently used in Pn rating . Porportional aspects as to the division of length weight and sail area in design are established though some would state sail area is over emphasized in the equation . Again the correcting factor of the current yardstick system applied as a percentage factor should compliment the design measurement basis ,-there would be no need for the one size fits all approach modification factors currently used in Pn being replaced by actual sail area L B W measurement base numbers .

This basic approach in outline may be worth considering as better alternative ,--hope this is constructive and helpfull ,and also inspires others to think though an improved rating system that may be adopted internationally .

Happy Holidays
Carl

Lets just say that I need more sleep than most people, that I'm spending (losing, wasting even ? ) more time on a woman than I think is healthy, But that when I think things throught the pieces fall into place pretty quickly. In the past it would always end in headaches but I've become more skilled in taking the exit before I hit the wall.

Besides, it is simply a waste when it is doing nothing on my PC (or in my head) so I'm pumping it into the public domain and hope I give something back to cat sailing.

A man can dream can't he.

Wouter

A few answers that may either confuse you are come across as conflicting. However they are valuable enough to full understand.

From a measurement point of view even a strickt One-design class is a box rule. The whole idea behind a measurement based system is that of a box rule. The fact that Texel and many Yardstick converge on the same ratio's between boats suggests that the boxrule approach has merits.

With regard to the Dart Hawk, I think this design is still one of the better F18's around. Put a new updated set of sails on it and go ! I think that Dart hawk was victomized by the "bad perception virus". Its sales declined rapidly after the pounds rose sharply half way through the 90's. Then sailors assumed that the decline in sales was caused by the dart hawk being uncompetitive. Of course if sales drop you won't have as many boats in the class and then when Hobie starts buying away all the top crews than more and more people start to BELIEVE that the Dart Hawk is an uncompetitive design. Than it starts to feed on itself. I still think that the Dart Hawk is still one of the better product in F18 land. Just need to get the modern cut sails on that boat.

You refer to a difference between the Dart Hawk and nacra F18. Can you point me to data suggesting this ?

Dart 18, Dart 15 and H5.9 are simply to small as a class to act as reference classes. Furthermore only the Dart 18 has some international presence but only in Europe. Then of course the Dart 18 production will be discontinued in 2005 and it is badly situated in relation to other classes. Why use dart 18 as a reference when this design makes up less than 5 % of the fleet in all European regatta's with the possible exception of UK events. You will only get very very limited comparison data this way.

Also all the good crews are sailing in difference classes.

Also the Dart 18 design (and so to the Dart 15) are a far cry of being representative of the designs that currently dominate catamaran racing.

Last but not least; I see more merit in having a large, but less strict defined base to extract data from than a very small base of high restricted class. I can easily average out errors present in large block of data but I can't do that in very small blocks of data.

In simple word, from one perspective the named class maybe better as a reference. BUT when viewed from several perspectives the Formula 18 class as whole cleans the bank. Arguably a rating system can not be based on a single viewpoint that will make it very sensitive to errors and also very inflexible.

Sorry,

However I very much appreciate your input.

Wouter

I have personally a dislike for unsubstantiated modifications to any rating system. This means any adjustment for an old boat society (dead boat society) rating that is not specified as a general rule.

For example under the current texel system the Dart 18, Prindle 16 and Hobie 16 get their ratings upped by 1 point because somebody in the past decided that that was necessary. Why these boats and not others, what was the reason for this mod that was never specified in public ?

I can agree to such modifications to outdated designs to compensate for their relative backwards movement because the newer boats arguably have more refined features. However the selection proces needs to be general and verifiable.

Surely a case can be made that asymmetrically hulled designs like the P15, P16, P18, H14 and H16 suffer from not having boards or skegs. The idea behind the asymmetric hulls was an interesting one but we now know that it produced worse performing boats to symmetrically hulled ones with skegs or boards.

Therefor I propose that a list of 5 features (or lack of such features) is specified and that any design satisfying at least 3 of these features gets 1 or 2 points added to its rating.

I'm thinking off.

-1- Cat has assymetrical hulls without boards or skegs
-2- Cat has a mast unsupported by diamond wires or extra shrouds
-3- Cat has a pinhead mainsail
-4- Cat doesn't have a downhaul system nor a mast rotation system that can be continiously adjusted
-5- Cat doesn't have a smooth (rounded) transition from its sides to the deck (deck lips as on H16 and P16)

All these features pretty much add extra drag to the platform or limit sail control to such an extend that the rig is producing drive less efficiently than more modern cat designs.

This list effectively gives :

P15, P16, P18
H14, H16
Dart 15, Dart 18
nacra 5.0 (not the newer nacra 500) and Nacra 4.5 (not the newer Nacra 4.5

all an extra allowance on the ratings. I'm still debating wether this should be 1 or 2 points.

I do not favour or propose to have a statistical alogarithme produce offsets on calculated ratings. This is not verifiable nor easy in use. Also you get continious swings around a base rating depending on freak occurances in race data. Also this is sort of a black art and I'm not willing to saddle any rating committe official with the endless bickering that this so easily can cause.

Please note that statistical analysis may sound dependable and easy enough but often it isn't.

Example : A rating committee member when a race has been held under sufficiently constant conditions. Steeple chase 2004 contains very undependable data because of that freak low tide. A particular good race for the M20 in NL in 2003 was found to have contained a narrow wind band some 2 km out of shore that the M20's found together with one I-20 while the others tacked upwind closer to shore. Incidents like these very much skew data that very easily can cause an errornous swing in ratings. Checking all this is a [censored] load of work, I know because I don it. It involved number crunching and possibly phoning up participants to find out why the data does what it does. If anything this should be done on the background and no automatic link should be made to the rating systems.

Again when a large block of data over various class and events suggests that a general modification is off the a modification should be made, but never when such a thing happens in an individual case with a very small amount of data.

Simply put It is also very weird when say an F18 shows some exceptional behaviour that is not reflected in the behaviour of other comparable catamarans. Therefor all things are better incorporated as general rules. This may leave som inequality in the system BUT by far in most cases these are neglectable in magnitude and to small to sacrifice stability and simplicity for. Remember the less then 1/10 th of the end result threshold.

Nor am I sure such statistical systems can be made to work effectively. I wouldn't know how and I know some stuff about statistical and probability math.


Wouter

I was just using the box rule as apointer to the fact the boats evolve and so that they get faster, so making a moving target the focal point does not appear correct to me.



Does it matter that there are only 8000 Dart 18's and 2000 Dart 15's (approx) in the country. OK, if you don't like the Dart, use the Nacra 5.0, 5.5, 5.8 and 6 ?

The dart 18 is not being discontinued and neither is the Dart 15. The Dart 15 Class association in the UK now 'own' the designa and the boat is being re-named as the laser centre no longer have involvement. The D15 will be made in Sought Africa starting sometine in 2005.

>>I was just using the box rule as apointer to the fact the boats evolve and so that they get faster, so making a moving target the focal point does not appear correct to me.


I do understand that however, there are other factors as that keeping adding points to the F18 choice. It is like choicing a car. It is wrong to only look at the retail price. Before deciding to buy one you also look at things like fuel efficiency, availability of spare parts, and the cost of them, Ensurreance cost, the amount that particular drops in value each year, etc. One particular care beat all others in one aspect BUT fail to convince in the others. Such a car will not be bought often.

It is the same with the reference benchmark. You look at only one issue not at the framework of several different issues. I invited you to do the last and determine how you think the Dart 18, Dart 15 and H5.9 classes stake up to the F18 class ?

In addition to that ; there is one very important thing in choicing a reference class. It must provide a large basis from which the take data and gain insight. We all know and race agains F18's. Currently there is not a single design that doens't race against F18's in a handicapped fleet in the world. If we were to choice the Dart 15 than how would we gether data on the Taipan 4.9 for example. I have never seen a Dart 15 ever race against a Taipan 4.9. Actually same applies to the Dart 18 and H5.9. This single issue alone makes a choice for these classes as a reference class unattractive. More strongly I think the original 100 rating class, the Tornado, is to thinly spread to act as a good reference class. There is simply not enough dependendable tornado crews around to gether data on all other design. Again how to rate US designed boats like the Isotope when it is rare to see tornado's racing in US events. And if they do than the comparison of the Tornado crew can not be averaged out of the Tornado fleet making comparions very dependent on the particular ability of that single crew. THIS caused larger errors than say a benchmark fleet of 5 to 10 F18's where the average F18 performance can easily be determined by averaging the F18 results of the first halve. Sure their will be differences between the individual F18's but these are quickly reduced to neglectable amounts by grouping their data. Then we are only left to investigate the crew ability of the crew sailing the rare, Isotope, Taipan, F18HT or other boat.

Again there are more considerations like discarting the need to do corrected time math on arguable the largest fleet in all handicap fleets (F18's) but the above reason alone itself places he D15, D18 and H5.9 low on the list.


Dart 18, Dart 15 and H5.9 are simply to small as a class to act as reference classes. Furthermore only the Dart 18 has some international presence but only in Europe. Then of course the Dart 18 production will be discontinued in 2005 and it is badly situated in relation to other classes. Why use dart 18 as a reference when this design makes up less than 5 % of the fleet in all European regatta's with the possible exception of UK events. You will only get very very limited comparison data this way.



>>Does it matter that there are only 8000 Dart 18's and 2000 Dart 15's (approx) in the country. OK, if you don't like the Dart, use the Nacra 5.0, 5.5, 5.8 and 6 ?


No it does not matter. And the same counterarguments can be had against the N5.0, n5.5 and others. There are simply not enough of them racing internationally. Also the skill included in these classes is way below the level in the F18 class at this time. over 100.000 were build of the Hobie 16 but even that is not a good benchmark when looking at all considerations. It's participation on open class handicap racing is declining and the setup is too much dissimilar to the modern designs that you will hand yourself an awkward benchmark. It is more and more becoming a class for recreational sailors and it is not even the largest class anymore in events like Texel. Well, at least not in the way the F18 class is. I know this can be a hard pill to swallow down, but this is not a contest of which class has the most tradition or deserves to become the reference class for reasons of history. This is a contest of which class satisfies the most demands that are linked to being a reference class and does so for at least the next 10 years.


>>The dart 18 is not being discontinued and neither is the Dart 15. The Dart 15 Class association in the UK now 'own' the designa and the boat is being re-named as the laser centre no longer have involvement. The D15 will be made in Sought Africa starting sometine in 2005.

Okay, I have my info and without being disrespectful I find signs that the Dart 18 class is being reduced in importance. Prindle 16 classes and others like the Nacra 5.5 and Nacra 6.0 already went down that route and there classes have been disbanded. In effect there are no active Dart 18 classes in the USA, Aus and Asia while there are active F18 classes there. If this is to be an international rating system than surely we must find a reference class with an international presence.

Again I wish to underline that I mean nothing disrespectful by any of these comments, it is just that in a broad spectrum a choice for the F18 seems to be strongly favored over the named alternatives. Thank you for your comments.

Wouter