Spin area applied to cat design is still developing .
It begane with early design used in several classes and has a long history making a comeback for use in the last decade with better asymetrical shapes -configurations and snuffer systems.
Bill Roberts noted Arc designer patened an earlier version,
many have added over the years .

Most new modern cat design utilize snuffer systems and spin ,-they basically double the horsepower -downwind and broad reaching , they are just plain great fun .

Tests for the Olympic Tornado class changes recently and updates to spin use revealed an ideal size and aspect ratio and spin pole length in balance. This size was adopted for use .

In the U S modern type spin development was different , Randy S popularized the spin in earlier Worrell 1000 races using one very successfully on a P-19 ,-seen on the cover of numerous sailing publications.

In 88 the Hobie 21 with spin was used for 2 professional sailing series .-Prosail and the Ultimate Yacht Races -seen on N B C Sports .
Randy moved up to the 40s ,-but a number of excellent sail lofts produced very different spin for use on the 21s -
North --Hood -Smyth ,-Aussie chute ,-and others .
Carlton at that time used a Hood chute very successfully and developed an on tramp retrieval sysytem .

Numerous other spin developments occured ,-some of the most interesting was again by Randy S for the N-6/0 for use in 98-99 Worrell 1000.

By using more extreme mast rake and longer spin pole he developed huge 440 +- sq ft chutes with large overlap areas being sheeted off the back crossbeam location.
Other teams used more moderate sized spin -340 range area and showed to be more versital and as fast or faster in many conditions . The exception was light to moderate wind speed . -
This is very common in the Worrell 1000 with typical lighter seabreeze in the morning slowly building as with most coastal areas with the increased seabreeze as land heats up in the afternoon.
The largest gains in distance racing are actually made in light wind conditions . The time sailed is much greater so the light air days are where most differences in finish times occur.

A little different game in accumulated time, Bret and Rod the Austrailian team ,-Randy.s nemisis would often finish ahead on breezier days but never could make up the larger differences Randy put on them in lighter conditions .

From this some conclude that large chutes are better -faster etc etc . not true .

There are numerous design elements that come intergrally into play .
Aspect ratio is one ,-and slot area between mast and spin is another overlooked aspect .The modern new designs with no jib like the 18 hts that also have smaller high aspect ratio spin design do this for good reason,--it is faster.

Rating spin area for cat design presents some unique problems . Current P rating sticks on a one penalty increase fits all approach wether its a 200 or 400 sq ft spin .

Texel adopted ideal spin sizes per Tornado tests and applied progressive sizes per length categories with added penalty for any sizes over . 4 points are added to each spin rigged cat .

ISAF uses a better approach rating actual spin area as 10 % of total in rating formula equation. It also subtracts r-jib area from spin area .
What is needed is an added spin efficiency rating per aspect ratio also to accurately rate spin rigged cat deasign .

This is proposed in the TIP rating .-

Here are factual historical reasons to change to design measurement based rating --from current P-rating

Per research of Derek Kelsall and John Shuttleworth. Extensive correspondence in the english monthly Multihull International. A.o. in nr. 117 of october 1977. basic rating formulas for multihulls were further established .
In 1985 during a symposium in Annapolis a number of experts spoke about a simple system. A.o. the late Hugo Myers, one of the advisors for the original IOMR system, was an advocate for a formula which had the same general form as the final Texel Rating formula.
In the period from 1982 to 1984 there was a change over from a pure statistical system like the PY handicap system, to a pure measurement system. In the beginning, naturally, the IOMR system has been used, being the oldest one, adopted by the IYRU since 1974. But a period of experimenting started with the english formula of Kelsall and Shuttleworth and other formulas. In 1985, after consulting a.o. the american scientist Richard Boehmer.

When the IOMR and the simple T R formula are both supposed to be good, then it must be possible to express the set of formulas of the IOMR in the form of a simple power formula. Using a multiple regression analysis method on various collections of boats it has been a surprise that it was possible indeed. With such a high correlation between the results, that the simple power formula found, can replace the set of IOMR formulas.
What is said basically means that a formula of a type like the TR formula is a universal formula for multihulls. The formula is easy to adapt for all circumstances.
As the IOMR, the english (MOCRA) formula as well as the TR formula approximate the performance of optimal boats, additional corrections are possible and sensible for designs which are not optimal. That has been done in the TR system in the same way as has been done in the original IOMR (PMA) system in California.

The TR formula is metrical : 100 / (0.99 * RL0.3 * RSA0.4 / RW0.3)
To serve boatowners in the USA where crews use imperial measurements (feet, sq. ft. and lbs) you only need to change the constant factor from 0.99 to 0.3397. Simple and practical.


With the IOMR written as a power formula :

100 / (1.00 * RL 0.311 * RSA 0.42 / RW 0.318)

you only need to change the constant factor from 1.00 to 0.3275. for use in any area where people work with imperial measurements and weights.


--more on the rating development -

There are 4 formulas available to approximate the performance. Bruce nrs (1967), IOMR (1968), KSP since 1976, Texel Rating since 1984 Edmund Bruce, pioneer of Amateur Yacht Research Society, died 1973.
IOMR = International Offshore Multihull Rule (California, 1968).
KSP = Kelsall Shuttleworth Performance. (MOCRA formula, around 1978).
TR = Texel Rating by Nico Boon, 1984, slightly modified in 1993.

8.

IOMR, KSP and TR use length, sailarea and weight (displ.) only..

RL = rated length, RSA = rated sailarea, RW = rated weight. (kg.).

General form of these formulas : 100 / (c * RL p * RSA q / RW r).

Bruce (metr.) =2.5209 * RL 0 * RSA 0.5 / RW (1/3 ).
Bruce (imp. ) = 1 * RL 0 * RSA 0.5 / RW (1/3 ).
MOCRA (metr.) = 100 / (2 * RL 0.5 * RSA 0.5 / RW 0.5 ) .
MOCRA (imp. ) = 100 /(0.5 * RL 0.5 * RSA 0.5 / RW 0.5 ).
TR (metr.) = 100 / (0.99 * RL 0.3 * RSA 0.4/ RW 0.3)
TR (imp. ) = 100 / (0.3397* RL 0.3 * RSA 0.4 / RW 0.3).
IOMR (metr.) = 100 / (1 *RL 0.311 * RSA 0.42 / RW 0.318).
IOMR (imp. ) = 100 / (0.3275 * RL 0.311 * RSA 0.42 / RW 0.318).

IOMR here, is a "translation" into a powerformula of the IOMR formulas.

9.

Above Beaufort 5 or 6, stability of a design is the limiting factor for speed. A rating has to be calculated then by using the smaller sailarea making heeling moment = righting moment. No other formula required..
In very light winds use TR (metr.) with c = 0.89 and RSA ^ 0.5..
(rev.7/96).


---end Texel info -

We can use this base system very easily in N A -

We can modify it to existing conditions in N A
Per existing design and race preferences -

Believe the TIP rating outline addresses these , combining the best elements of Texel -ISAF and Prating .-

The advantages of this system are numerous -

Advantages

Utilizes the best features of the 3 main current rating systems in use ----Tex. Isaf and P. =TIP

Provides an accurate proven rating number for modern cat designs, --no provisional number is needed-


Eliminates the page of modification factors that utilize a one penalty factor fits all approach regardless of the size spin ;jib ;main mast height, -etc.

Provides a much larger base pool internationally of base rating information to help verify rating accuracy.

Integral rating system, more compatible to promote large class racing groups in N A .

--Would enjoy others getting involved to author as a group this improved rating system for use in N A --

Carl

This time I took the time to read your post.

If I may I would like to make you aware of the very dominant role of daggerboard aspect ratio number in the ISAF system. Something this leads to remarkable results where a board of say area= 0,2 sq. mtr. and depth = 0,75 mtr. will be rated no faster than the same boat with a miniscule daggerboard of say area 0,05 sq.mtr. and only depth = 0,35 mt.s (one quarter the size of the bigger board)

Also their is some arthmatic in the ISAF rule that makes singlehanders rather fast when compared to doublehanders.

Also the carbon to alu correction factor is strange as their is more performance difference between a mast with spreaders and diamond wires and a smooth mastsection (like H16) than there is between a carbon mast and alu mast, both with spreaders and diamond wires.

Please do not introduce those three "funnies" in your system.

for the remainder I think that you are pushing the TIP system a little bit too hard.

One more thing that is limiting spinakers size and shape is the fact that with increasing speeds the angle of attack decrease and only moderately flat and short footed spis can operate efficiently at those angles of attack. Even in light winds where the critical "twice the windspeed" barrier is quickly reached. It is my expectation that we'll see an even more pronounced trend to higher aspect and flatter cut spis over the years to come, even for light wind performance on windward-leeward courses.

Naturally Beam reach course, which may be the predominately course on the Worrell I don't know, are much less limit in this sense. This may explain the succes of teh huge spi of the Smyths.

To all; Guys, the development of this things is quickly entering the area's of complex interdependencies and therefor simple comparisons based on simple models and assumptions can lead to incorrection conclusions. We must be careful and take this into account.

Wouter

thanks Wout ,

Really looking forward to racing a F-16 sometime this year in N A
-Will be on a Formula 18 ht Jav-2 for the Worrell
should have opportunity to try F-18 in CRAM which has a mixed group this year . Demo boats are sometimes available from the boat dealership.
There was a F-16 last year at the C F regatta here in MI but I did not know it was available to race or would have .

Should be a great year for racing --
new slogan --have a Formula day !! --joking
rather than the ad --have a Hobie day

appreciate the input ,--
am aware of the "funnies " none of those 3 noted would be added in , do understand the danger of adding too many bells and whistles on an already brilliant rating system .
ISAF is directly dirived from monohull rating classses and some factors do not translate proportionately ,-mainly because of the huge differences in speed particularly in the higher wind range .
Typical monohulls will have a top hull speed of 6 knots -where we can hit 26 ,--they just do not relate directly .

With a timed handicap system either ,-it is a big eror made ,
average times in monos with little total speed differences are very different when trying to apply the same timed averages to very high speed cat designs .
Multihulls are completely different species to categorize and rate.


We have some existing conditions and design preferences here to adjust to is all .

Original Texel set up with 3 windspeeds -
Do you have the original formula for the upper -
how did that move .
We have the current updated tex rating
and a copy of the lower which is not needed .

Would appreciate any info help advice etc ,
it is a little overwhelming ,-there are certainly more brilliant people with much more expertise and experience in several areas ,-math ,-statistical annal.-sail rating,-and experience with Texel itself that we need good guidance from .

It is time for this in N A --past time .
will ease up on it ,-hope others undrstand the merits of it and the enthusiasm .

Carl

Carl

To answer the question more directly -

The rating system proposed uses the base equation of Texel ,-proven refined , which all say does a great job of rating modern cat design .

added for N A because we have different spin sizes mainly due to generally lighter average wind conditions here , and the basic spin history as roughly outlined in post above , and av. windspeeds raced in ,
Propose using the ISAF spin rating formula applied in place of the added 4 pt per specified size in L category Tex portion , replacing that only .

Plus an added spin effeciency factor ,-spin added designs will still average 4 but some may more accurately reflect a 3 or 5 pt faster rating .--Some really huge chutes ,-like a masthead type for example more as they should be rated.

Some N A versions like the Nacra 6/0 for example would more accurately reflect true speed potential with this spin calc method which subtracts jib area and considers spin aspect ratio which lessens the total rated area of larger overlapping less efficient per area type chutes like some 6/0s currently use .

2- A 2nd upper windspeed rating category is proposed .-
original Tex rating used 3 windspeeds,but no one used it ,or use the current P-rating 4 windspeeds ,--too difficult to interpret,-leaves room to manipulate results .
A 2 only is proposed -non trap conditions ,---and trap conditions -3 range per beaufort .at 8 --This is apparent to all racing .
Beam effects will be added in calc ,-and non board correction ,-plus the movement in the base calc in upper speed reflecting l weight and sail area effects per upper windspeed.

#3 is a H A F --Handicap Added Factor -
By using a non spin formula class {modern design} rating as target in each length 14 15 16 thru 22 we can use P-rating -{more long term historic based rating numbers } to add to the Tex base rating . This will help older class boats in original form with common lesser design feature not factored in .
Things like heavier masts -rigging and sails ,-lesser board depth and configuration ,-etc ,-per outlined design ctiteria .
The conversion factor per scale in different system allows us this comparison and handicap average applied .

similar approach and method current Tex. uses for spin by targeting ideal in length category . Here we are applying the method to older design with lesser features .
No modern cat design will be effected already in comparison rating equal .

The only perfectly scientific alternative method to accurately handicap older boats in original form would be a complete design annalysis of every design feature applying a correct efficiency factor in proportional percentage to each .
-- NOT PRACTICAL ---yet ,---We do have P-RATING STATS .to apply .
This is important to keep records of race results and continue to find ways to improve rating .

A N A speed week ,-where all types of boats are tested is really needed .
And once N A changes rating systems .A ranking could occur ,just as the Tornado class does ,but on a large scale.
From this catsailors could be assigned individual handicap numbers then applied . A category could be added at events for individual handicap as well . This would give new sailors and youth sailors who improve the most recognition and further really help promote the sport .

long term vision ,--but really needed .
Gary Jobson and a number of noted sailors have suggested a similar future for the sport ,-basically centered around good catagorical class groups which existing established classes -development and formula classes provide and this rating system helps promote .

A winning formula for the sports future success !!!

Carl

-

-wanted to expand on the other future benifits and extentions of this rating system ,--better options that derive from it .
.
-- once N A changes rating systems .A ranking system could occur ,just as the Tornado class does ,but on a large scale.

Times kept at the local club level can be averaged just as they are now in P RATING ,but on an individual basis .
Just as in golf or other sport with handicap . This allows sailors that improve the most to recieve a trophy or award ,-great for new sailors and youth sailors to recieve some recognition and encouragement .
If we want to promote the sport what better way ,--This is much more benificial that the current mixed up P-rating by class handicap . You are handicapping that group of sailors in class ,--just not very realistic or intelectually honest for catamarans .

Dingies it may partially work because they have max, 5 -6 mph top speed , have raced in mixed dingy fleets of Interlakes- Flying Scotts ,-etc there is little speed difference .
shifts and tactics are the key aspects of races on very small courses .
Catamarans however hit not 6 but 26 often --speed and design is the game at 4 times the speed of dingies and their handicap rating P-rating was dirived from .

Design based rating for cats is required .
An individual handicap system can be then added with all its promotional and new sailor -youth sailor benifits .
If a parent wants to allow their children to skipper ,new crew -girlfriend etc etc -these types of great options open up ..


From this any catsailor that wanted ,-new sailors and youth sailors in handicap class could be assigned individual handicap numbers on a larger scale then applied . A category could be added at events for individual handicap as well . This would give new sailors and youth sailors who improve the most recognition and further really help promote the sport at larger events as well .

Gary Jobson and a number of noted sailors have suggested a similar future for the sport ,-basically centered around good catagorical class groups which existing established classes -development and formula classes provide and this rating system helps promote with these types of more direct individual handicap developing from them .

These types of individual handicap systems are already used in several sailing clubs very successfully .

Once individual ranking -rating groups were established it would also really help accurately review race results to evaluate the combination rating system .

A speed week with all types of boats and design would be another great method of reviewing design rating , sounds like that is also in the works for the near future.

-Carl