I'm looking for a relatively flat cut spin (lightly used?) suitable for my Supecat 20. I've got the ability to run a 28' luff max. Would a Tornado ar I20 kite work? Any and all opinions welcome. Many thanks! Dave 509 276 6355

Hello Dave

great cat design with 12 ft beam --this provides a wide platform and hardware attachment point for the spin clew and changes the basic measurements of a spin along with sheeting angle as compared to a more standard 8.5 beam cat design --
Suggest contacting the S C factory --
http://www.aquarius-sail.com
Very nice folks ,they most likely have a used or new spin available at a reasonable cost along with hardware pole snuffer packages or availability to them ,
-a good sail loft that specializes in cat sails would also have this available .
see Catsailors ads .
hope that helps -
Happy sailing
Carl

Hi Dave

I think the luff lenght of the T spin is 30 feet. The I20 has a longer luff length then the T. (Taller mast) Consider raking the rig aft... a longer pole and a higher spin bale to use a used tornado Spin.

Mark

OK, I'm currently running a 14' 4" pole w/ the tip maybe 1' above the plane of the hulls. The bail is mounted 42" above the hounds (1/3 of the distance between the hounds and the top of the mast, as per the boys @ Aquarius). So, thoughts on raising the bail further up the mast (what are the proportions/measurements on the Tornado and I20 masts)? And what pole lengths (and dia. and wall thickness) are these boats using? My impression is that these 2 classes are likely to have the fastest spin designs, would love to hear more opinions? Thanks! Dave

Hi Dave

I remember setting the spin bale on a friends P19 mast much higher then the oft quoted 1/3 of the distance between the mast tip and the hounds. Check the archives. Dave?? has rigged another P19 exactly like the Tornado and he may have the spin bale height measurment that he used.

You can also check the Tornado site. They spec out where the class legal bale is on the T mast in their rules..

The I20 carbon mast is not a good model to copy from.

Hi Dave -hi Mark

some factors in spin area and forces as applied to the SC 20 -
The SC 20 has a 12 foot beam and large deep bows with plenty of volume . Both these hull platform design features add stability and allow this 20 to be driven much harder without capsizing and there by increasing the loads on the spin and mast section much more than an 8.5 beam cat or T which also use different mast sections with different stress in bending characteristics .
The designer is aware of the designs mast section wall thickness and characteristics and its limitations ,--using a T or different design as a guideline for spin tang location is being illiterate of the larger loads the SC platform will place on them in higher windspeeds AND the very different mast section characteristics .
story on the subject --
Like most things in life I learned this the hard way though approx. 20 years ago. I built a 20 cat with flat bottom hulls w 12 ft beam ,but used a H-18 mast section on top of which placed a then new comptip on top of the 28 ft mast extending its length to 35.5 ft . I also added a huge hi aspect ratio spin with 450 sq ft of area ,-the shoulders were huge much like the assie 18 chutes .
An extra set of diamond wires was needed to support the mast and it had a SERVEERE S curve in it under evan slight loads ,which is the first or early indication mast failure is imminent.
The cat was entered in the World 1000 mile race ,but fortunately retired early due to numerous tuning problems not yet worked out none of which least was the mast problem and huge loads the spin introduced ,-
Any way the purpose of relaying this early experience was to emphesize the importance of applying total proper engineering principles ,including platform and specific mast section loads . The exellent designer of the SC already has these worked out and properly applied .

have fun
Carl

OK boys, I'm sufficiently chastened, am now unlikely to rasie the bail. That leaves more mast rake (will that gain me much luff length?) and/or longer pole (currently 14'4"). Carl, are you intimating that the T or I20 spin is too big for this boat?
Thanks for the input, it's much appreciated!

Dave

Hi Dave

didn,t mean to chastise or presume to lecture ,-but try to offer experiences as a fellow catsailor would sitting on the beach after a great day of sailing ,-have been through spin shapes etc on cats since the Pro Sail days in developing kites for the pro racing series on H 21s -
All types sizes and shapes were tryed on these cats ,
we had some early ,really doggy ones and watched others just fly by downwind ,--then we bought what the winning teams were using ,and voula !! we started moving up the pack and evan won some.
The Hobie 21 had wings which we mounted the spin blocks on at the aft end further outboard ,--funny part was rookies would forget to tie the plug in wing to the crossbeams and ,--sure enough the wings would be pulled out by the spin forces and be flying around on the end of the spin sheet line.

The spin fitting experiences latter on the N 6/0 for the early Worrell 1000 races may provide some insight ,--We talked at length to Randy Smyth at the time 1998-he was cutting huge 450 sq ft spin for the 6/0s which I ordered ,--nice spin ,--
it was a monster to handle though,-Randy maxed out the spin luff by using 14 and 15 foot spin pole lengths that were set low to the water ,--and also by using very extreme mast rake set up. Both these things plus added spin area made the boat very fast downwind ,the extreme mast rake helped balance the helm . Designers refer to this effect on the helm as the center of lateral resistance to center of effort relationship ,--by calculating sail area center or center of effort on the sails -{C E } with the
[C L R] ,which is center of lateral resistance .Basically the calculated center of underwater profile of hulls boards and rudders in their relationship in design function in tracking and balancing the side forces from the sails.

If you design a cat with boards way forward on the hulls with mast centered and sails aft in design profile it would move the CLR forward and cause weather helm ,-the opposite occuring in reverse . Most cats were designed with main and or jib only in mind in calc of this balance.

--now add a huge spin set well forward on a long spin pole
-draw out a diagram -calulate CE and CLR -THEN add a huge spin forward ,---what happens to the CLR to CE balance ?--
Right ,--the sail area is now well forward causing lee helm due to the now imbalanced relationship of CE to CLR.
Due to the addition of spin area well forward of the cat and its originally designed CE for main and jib sailing only ,THE SPIN WHEN SET now creates a balance problem .--
How to move some sail area back aft with spin added to the sail plan ? --right again --mast rake !!,draw a diagram with two overlay mast positions ,one for and one aft if this is not visually clear .

So now with the more extreme ideal mast rake aft for spin what happens in the up wind mode with spin down ?,--right also ,-more weather helm and lesser balance and speed upwind, particularly in light to medium wind conditions .
The 6/0s set up for the huge spin with extreme mast rake were doggy upwind compared to the standard 6/0 rig set up with much more verticle mast position ,-They could sail right by upwind ,---there in is the trade off ,-and there in the difficulty a designer has in adding a spin to current conventional cat design.

The 6/0 now uses a 348 sq ft spin ,-and some use a 270 sq ft spin ,-both have similar speed ,--are much easier to handle ,--balances better ,--steer better and more responcivly--and reaches much better .

On the SC 20 the designer has worked out the ideal spin size --luff length --pole length --hardware placement etc ,-

If you want to experiment ,don,t let me convince you not to ,but ---perfecting design is often a trial and error process involving time and $

have fun -spin. are added horsepower,-they develop huge amounts of power and lift down wind ,often more than crews can handle.

hope that is helpfull
Carl

Can you say that again Carl?

Hi Eric

yes ,tend to ramble on a bit too much sometimes ,--but with positive and good intent. ---always nice to know your looking out for me

So --when are you going to enter the Arc 21 in the Atlantic 1000 ??,-think the good people at SC would be very pleased to see one or more entered and lend some support ,------ need a co-skipper ?
Happy Holidays
Carl

Jus kiddin'! Does the 21 fit the rules? I was under the impression 20' was the max length.

Hi Eric

the att pic of the Arc 21 w dark blue spin looks great -
maybe you could give Dave the source of the spin --costs etc and report on how well you like it with suggestions for sailing angles and techniques of setting and retrival ,snuffer set up etc etc .

On the Arc 21 in the Atlantic 1000--there are many good reasons to include the Arc 21 -
The great texas race has an Arc 21 and allows the 8.5 beam arc 21 ,-it seems equal or very close to other similar size cats in speed

The Tybee 500 Atlantic 1000 site states ---
copy ---The race will be governed by the Racing Rules of Sailing, 2001-2004, except as may be changed by the Sailing Instructions of this race. Class rules will apply with the exception of equipment prescriptions detailed in this notice and the Sailing Instructions. Classes will consist of 18 and 20 foot production catamarans with beams no more than 8.5 feet and spinnaker rigged by the factory, except as changed by this Notice of Race. Classes shall include, but not be limited to:

Inter 20 - factory spinnaker
Nacra 6.0 - New England 6.0 spinnaker
Hobie 20 - factory spinnaker
NAF 18 - factory spinnaker
Open - factory spinnaker rigged
Portsmouth .6300 or below.

end copy --comment --I don,t think anyone would mind if the Arc 21 was included in this list ,-it rates how in P ? I,m not sure ,-we might check its comparable rating in Texel and ISAF as well to substantiate it being equal to the current 20s --although the best indicator is its performance in the very similar Great Texas race event .

I would prefer to sail an Arc 21 for 1000 miles if one were available or for charter for the 05 Atlantic 1000 ,
The rules for the race should just outline basics for boats and let the sailors modify them as needed for this type of extreme specialized event . Being stuck with {class rules}} intended for protected water type buoys racing that do not allow safety modifications or reinforcement or heavier replacement parts ,-or basic seamanship modifications like reef systems needs to be thought thru and changed from this {{class rule}} mentality ,--
They allow exceptions as prescibed ,--but the race organizers should not be placed in this position ,--much better to just allow the sailors to modify within basic existing cat designs available .
The 1000 mile race and numerous other similar events is another good reason why a Formula class in this size range is needed .

--Another approach may be a rating rule ---this is like the Americas Cup historically has used. A rating rule for a beach cat race may be to -take the ISAF -Texel comparative number with the I-20 which is the model and accepted fastest current 20 class cat design --factor in the P rating number average to the Texel ISAF average at half the difference if any exists {{They may match}}-
If a boat rates within it or lesser may be used and modified not to exceed basic designed L W B and sail areas -though modified in any way sailors may wish ,-and also allowing any boat to use or change to any others componants including boards rudders hardware snuffer system mast and equal sails .

We would see safer faster innovative cats and a great race .

Hey Carl.
That was great! And I do follow what you're describing. I'm just forever doing these upgrades on a budget, trying to find used gear I can afford. My experience with Aquarius is that they're more interested in selling me their wares than trying to help me figure out the optimum dimensions for my boat. So I'm out here attemting to glean from the experiences of you, the owners of similar boats. What I'm hoping for is pole length, dia, wall thickness, alloy; spin area, luff length, cut (flatness?); track radius and length(and sources) for self tacking jib (particularly the relationship between foot length and track radius); thoughts on endpole vs midpole snuffing and affordable snuffers (I can sew the bag).
So I'd love to hear from you guys sailing Ts, I20s, 6.0nas, H20s. Eric' been great with this stuff. And thanks to all, this site's a blast!

Dave