There is a lot of confusion about the difference in the Portsmouth and the Texel handicapping system. Some people seem to think that their boat ratings are very different and that the Order of Finish of a race would always change if the other was used.

Some people believe in the Texel system because it is strictly a mathematical formula which does not consider “on the water” results, but this is not correct. In October , 2001 Texel “adjusted” the formula for single-handed boats because REAL WORLD RESULTS had shown that singles were not finishing high enough in handicap races. Some adjustments were made in March 2002 also.

Some people believe that the Portsmouth number is a guesstimate which changes radically every time races are reported. This is not correct either. As numbers are reported they are added to the database and help to refine the number.



These two handicap systems simply use a multiplier to arrive at an adjusted elapsed time. Assuming two perfectly accurate, linear rating systems, if boat A is rated 10% faster than boat B in one system, it should be 10% faster in another system. Therefore the ratio of one system HC multiplier to another, should be a constant.



In an attempt to compare the relative accuracy of the two systems, I decided to compare the ratio of the Texel number to the dPN (Texel/dPN) of all the cats I could find which were apparently identical in the US and EU and had been sailed enough in the US to get a valid dPN. The lower the ratio, the bigger the advantage for a given boat to sail under Portsmouth instead of Texel.



This would hopefully provide a multiplier that could be used to convert a Texel rating to a Portsmouth handicap and vice-versa.



11 Single handed boats



1.52 - Dart 18(1), Prindle 15s, Supercat 15

1.53 - A-class

1.54 - Hobie 14u

1.55 - Nacra Inter 17R

1.56 - Nacra 5.5 uni, Paper Tiger, Seaspray 15

1.57 - Nacra Inter 17, Hobie 17u



1.54545 average



Anomalies not used for calculations:



1.44 - Nacra 450

1.45 - Formula 16hp (Taipan 4.9 w/spi. modification)

1.47 - Hobie 14s, Taipan 4.9 unirig



29 Double-handed boats:



1.52 - G-cat 5.0, Prindle 18, Trac 16

1.53 - Formula 16hp, Hobie 18, Nacra 5.0, Nacra 5.2, Trac 18

1.54 - Dart 18(2), Hobie 16, Mystere 6.0, Nacra 5.8, Nacra 6.0, Prindle 16, Tornado Sport

1.55 - Mystere 5.5, Nacra 5.5 sl, Prindle 18-2, Prindle 19, Shearwater, Supercat 19

1.56 - Hobie 20, Nacra 6.0se, Taipan 4.9

1.57 - Formula 18HT, iFormula18, Supercat 20

1.58 - Tornado classic, Ventilo 20



1.54621 average



Anomalies not used:

1.39 – Shark

1.45 - Nacra 570

1.70 - Tapan 5.7 w/spi.



Composite average (uni and double): 1.5458



Summary:

The numbers and their results turned out much closer than I had expected. With the exception of the various anomalies, the range and average for the two categories was almost identical. The anonomalies were either very old boats which were no longer raced by the “hard core” but still made it to a few races, or new boats which had aparently been given an erroneous dPN in the beginning.

The smaller, older, less raced boats generally made up the low end of the two groups. They are usually raced by the more casual sailor in a less than pristine condition (sails, rigging, etc.). This would very slowly drive down the dPN.

The high end of the ratios was generally the bigger, more high tech boats that are usually raced by the hard core. I would expect those boats to be in serious racing tune.

The center of the unis was anchored by the Hobie 14, the most widely sailed and raced uni in NA. The Hobie 16 is squarely in the middle of the doubles.



Conclusions:

The concept of a single value, 1.5458, which can be used to convert a Texel rating to a dPN number, or vice-versa, appears valid.

This study shows the weaknesses of the Portsmouth system when a boat is either very new or very old. These flaws can be to the skippers advantage, such as the Shark or Taipan 4.9 or disadvantage, such as the Taipan 5.7. Racing under Portsmouth, in a one hour race, a uni Taipan 4.9 w/spi sailor would get a five minute “head start” over the Hobie 17, compared to Texel. That explains some of this years results. A Taipan 5.7 w/spi. sailor would give the average boat (1.546) a five minute head start. No wonder Rick is selling his.



This study also shows that the Portsmouth system, with enough data, is as accurate as the Texel system for establishing a handicap baseline.

I hope this will encourage people to forward their HC race results to Darlene at US Sailing so she can keep the numbers as accurate as possible.



P.S.

Anybody got a good Shark for sale? I might be able to win some races with one of those.

Nice job.



Well laid out, informative and easy to understand.



You know, stats have a habit of making your mind numb!



Here in the Caribbean, we sail to Texel. There was talk of going to Portsmouth, but a certian I-20 sailor balked at the idea when the stats showed that his boat had to give the Tornado SPinn time in light airs!......ha! (....well ...it turned out to be very light airs,...and the formula held true,....the Tornado needed time......)



For example,..the re-rating helped me.



My I-17 normal was sailing well at a Texel # of 111 last year( no spin),......this year I got a present,...a number of 115!



Formulas work for me!



Bruce



St. Croix

JUst want to say that I thought that your post was a very well made one.



Wouter

Sam,



Which DPN wind range did you use to do the comparison to Texel. I've noticed that the middle wind ranges compare to Texel but the High or Low wind ranges very much more.



Mike Hill

H20 #791

The important caveat is "assuming linear performance"



This is not the case in the real world.



The problems with using a single number (Texel or DPN or ISAF) is that a boats performance is not linear over the wind range that we sail at and so it won't be "fair" at some windspeeds. For example... Bruce used the I20 versus the Tornado. The F18HT class is extremely non linear in its performance. This boat owes time to the 20 footers in beufort 3 and under!



Since the goal of any handicap rating is to normalize the boats and allow the crew work to decide the outcomel PRO's must use the windspeed adjustments to ensure fair racing.



Distance races are problamatic. Most clubs use the strait DPN number because it may not be reasonable to assign a windspeed for the entire course.

Good post -thanks

We should be comparing the rating systems, the other method is to list race results in both Texel and Portsmouth for direct comparison which Sailwave scoring can do and post them here on Catsailor.

If race info was made available, individuals could build a database, obviously many are interested.

-Design knowledge, including info from such a database with conditions on the race course, helping us all understand and-creating better faster more seaworthy, SAFER -catamaran design should be of interest and priority to all.

--Do we best accomplish this with a rating system based on design features of L- B- W- SA Ar . as is part of the basis of ISAF and TEXEL RATINGS or should we be using Portsmouth based on average times.

The problem with av. time rating is it often reflects human performance {top skippers in the latest top class } as opposed to true potential of design.



This partial article below from S B today as an indicator of the sophistication of comp. simulation and quest for design knowledge. As this type of design application becomes more readily available and accurate it will be very easy to decide which type of rating system is best in the near future.

-From S B -

-To come up with USA71 and USA76 it has taken more than 300 sailboat races recorded on our Oracle database. The design team have tried and tested over 400 different hull combinations to derive the final product. Utilizing computer simulation, they have tallied several million races. This is an incredible feat and the feeling around here is electric." - John Cutler, Oracle, Racing, from a story in the NZ Herald, www.nzherald.co.nz/sports/

-END

If there is a desire to rate skippers performance for club racing a combination Portsmouth and skippers individual handicap {as used in other sports } may be a better solution.

This is successfully used in several clubs.



-The historic problem with design based rating like Texel or ISAF which uses more design info in its basic calc. to arrive at a rating number is not enough info factored, but as we read design info and comp simulation performance programs are becoming more accurate and may be applied.

The other historic problem applied to any rating system has been to figure out ways to beat the system, {human nature }

as Sam jokingly suggested in Portsmouth by finding a rarely sailed -raced boat with a favorable rating.

The other problem has been designers looking for {rule beaters } often creating an undesirable feature or extreme type of design. -In catamaran ratings we counter this by favoring good basic seaworthy design features, as Texel ratings seems to do.

-Both rating systems may establish a similar base and definitely results from one should be used to modify the other, but believe the base priority should be on DESIGN, so we can learn and benefit from the knowledge as opposed to just handicapping racing for ourselves based largely on skippers performance which we all know and see varies greatly.

- Most catsailors prefer one design type racing and Formula type racing particularly for major championships and distance racing , but the need to rate boats in some form will always be needed to race smaller groups of different types together, its always fun too.-



Sail safe, have fun

Carl

Mike:

I used the dPN number for my calcs. I didn't want to get too complicated. Since the Texel does not have different numbers for wind strength, I would expect the middle ranges to be more comparable. This shows the main weakness of Texel.

Mark:

I did not say "assuming linear performance", I said "linear rating systems", which is what Texel and Porstmouth are. The fact that boat performance is not linear is why the Portsmouth system uses different wind ranges and even separate adjustments for distance races.. It is a simple, though time consuming, way to make NON-linear adjustments.

Clubs should always use a windspeed PN, even if it is an average from the entire race.

Carl:

Thanks. I hope my little exercise has validated BOTH systems and that it will silence some of the naysayers from both sides. I do believe that the added complexity and work of the Portsmouth System, increases the "fairness" of racing. Big thanks to Darlene et al.

P.S. I wasn't kidding about the Shark :-) LOOK OUT ALTER CUP!

Texel actualy decribed three formula's for three complementatry windspeed segments, but the users decided to use just the general middle section number. Much like most or many use just the D-PN in all windstrengths.



So in fact the Texel formula decribed the curves which are definately the better decribtion of the speed characteristic by three lineair relationships together approximating the speed curve.



So Texel was created less simplistic than it is used now.



Wouter

Hi Wouter



The euro I20 is even with the Tornado in ISAF small cat ratings. In this years PN's (the larger then EU) US I20 main owes time to the Tornado in B 2 to 3 and gets time at higher winds.



This seems reasonable to me!



the DPN has the Tornado owing time to I20 through out the wind range.

A single number system is simply limited with how fair it can be.



With respect to fairness and formula racing... the proof is on the water. If a boat meets the formula but destroys every other class on the water ... well so much for formula racing. Example the previous formula 20 rule won by Ventillo. The F18's seem to have it pretty well figured out... lots of competive boats at various price points. Time of course will tell about the 16 HP's and 18HT's formulas since its way to early to assess how well the formula works (But the boats are very nice in and of themselves)



Formulas are not gauruntee's(sp) for fair racing...

Note Carl's attempt at a US formula 20 rule... few sailors are leaping to sink their money into changes to meet an untested formula rule because they just don't think the changes will result in "even" boats on the water. Buy in... is the key to any formula rules success. The perception of fairness is key to enrolling the racers into the idea.

Rated racing is based in averages , this inherant flaw makes it unsuitable for use in major championship events as a true test of sailing ,navigational ,boat prep ,tactical and seamanship skills.



Most all catsailors prefer O D and now Formula racing -



The N A Open Formula 20 Class proposed , again is not mine but based in the i FORMULA 20 with modifications for use with existing conditions here in North America.,The N A Formula Class not yet officially up will undoubtable have modest beginnings but believe it will become popular over time as it has in Europe.

Catsailors given the option and choise of racing Formula will race it in increasing numbers as we are beinging to see. It has great appeal though will not be for everyone obviously ,and different Formula Classes will have appeal to different catsailors but believe there is a Class to suit all needs along with several existing developemental established cat classes .



No one should presume to have all the answers , no one will ,-I,m very happy to provide my time and energies towards a F-20 Class for N A that will really help revive the sport in a very fair honest positive way .



Please e-mail mark if you have some personal problem ,-you seem to be repeatedly making derogatory comment using my name in your posts .

regards

Carl Roberts

Carl,



Thanks for your work in trying to establish an even - open formula format.



Thats all I wanted to say.

Steve

Mark,



I agree with you fully. I just wanted to point out that it was not Texel system designers who decided to use just one number to rate speeds under varying conditions but more the lazyness of people for not picking up on and using these decribtions in teh extreme light and heavy parts of the segment.



How many did only use D-pn despite the fact that there were numbers for evey windspeed ?



That was my point.



WOuter

Thanks Wouter for referencing this ,--thanks Sam .
Good beginning to compare rating systems .

Looking into a distance race in Aug , would like to use a design based rating , but also display P-rating for comparison .
To Most if the 1.545 # is used will not understand the differences . A direct numeric scale from one to the other
with boat by boat comparison rating number --side by side is needed.
This must have been accomplished to some extent already ,
though not completely or in readily understood form .

Some Formula Classes have direct comparison numbers in all rating systems ,--like the Tornado -H-16 -A Class -now similar Formula Classes. Again the different points of beginning --different calc. used and different scale resulting makes it difficult to compare them directly,

With these types of effort the barriers and walls start to be removed and we find information and cross references complimentry systems and ways to improve the sport to benifit all.

Hi Carl,

> We should be comparing the rating systems,
> the other method is to list race results in both
> Texel and Portsmouth for direct comparison...

Why? :-))

The fact that there are N different ways of reasonably rating a boat clearly implies that it cannot and never will be an 'exact' methodology. Each rating sys will have it's quirks, but surely in general the better sailors will tend to win, etc etc.

I personally think that as long as the various rating systems are reasonable, it doesn't really matter which you use. Sure there will be some place changing but nothing dramatic... (?)

One bad tack in a cat and you can throw the decimal points of out the window anyway...

Or perhaps that's just one of my bad tacks... :-)

Regards,
Colin
www.sailwave.com