Good idea Less -think that should be the basis for the class .
Rolf ,I forgot where your from , but lets start a thread on the proposed international F-20 class and list the existing cats that would race within it -Tornado -Eagle -Ventilo 20 w 10 ft beam -
etc ,then allow others imput on the rules variables TAKEN CATEGORY BY CATEGORY

Crew weight boat weight sail area trade offs being the most contentious area generally .

DO YOU HAVE THE EXISTING 4 OR SO BOAT TYPES AND THEIR BASIC SPECIFICATIONS.

I would suggest a very basic A class type basic box rule to begin the class ,then let it evolve based on class partisipants .
As Less noted the B class exists but needs updating to reflect existing designs and modern material weights.

The big question ,how does a 376 LB Tornado compete with a 200 +LB mARSTOM ? Spin area compensation ,-jib compensation , then we have to verify this in realistic design theory terms and hope it proves out on the race course.

Perhaps a basic B box rule only is best

Hey, we dont need to call it F-20 something if the B-class rules are resurrected, it just happens to be the B-class

I tried to find the last revision of the B-class rules, but was unable to find them. I did browse trough the A-class rules tough, and they seem very sensible and easy to adapt.

Some boat data:
M-20
L 6.1 m
W 2.93 m
All up weight 115 kg
mastheight 10.5 m
Sa upw 22 m2
Sa downw 44 m2
Ref: http://www.marstrom.com

Tornado
L 20 foot
W 10 foot
All up weight 170kg
Mastheight 9.8m (approx)
SA upwind 25m (approx)
SA downwind 47m (approx)
Ref: http://www.marstrom.com

Carbon Eagle 20
Length: 6,10 m / 20 feet
Beam: 3,00 m
Mast Length: 10,3 m
Main Sail Area: 19,25 sqm
Jib Sail Area: 4,80 sqm
Spinnaker Sail Area: 28 sqm.
Weight (with spinnaker): 145 kg
Ref: http://www.eagle-cat.com

Taipan 5.7, not a 20 foter, and not 10 feet wide either in it's original form, but a very potent platform. Macca widened it to 10 feet, put a carbon mast on it with a selftacker and feels pretty competitive. Out of production tough
Weight 142Kg
Length: 5.7m
Width: 2.5 or 2.6 meters (2x1 formula again)
Upwind: 23.3 (but can add 0.5 more with a extreme squaretop)
Downwind: 27m
Ref: http://www.ahpc.com

Ventilo Pulso
L: 6.09m
W: 2.9 or 2.55m
Mast length: 10.5m
Upwind: 22m
Downwind: 46m
Weight: 162kg
Ref: http://www.ventilo.ch/

Any others?


Perhaps it would be a good idea to consult with some designers what a sensible minimum weight should be for now, and allow designs below the limit to use correctors?

There have been rumors from time to time of a new 20 from Vectorworks. Might be worth chatting with Matt to find out what he has in mind. Clearly a successful Formula class would need to represent a viable business proposition for someone, and presumably Matt has had to think through that side of the equation.

Mark.

Rolf,
The original B-Class rules (circa 1960) were very basic -- maximum 20 feet in length, maximum 10 feet in width, maximum of 235 square feet of sail area. I can't remember if there was a minimum weight.

I'm quite certain that the Tornado was originally designed (about 1967) to exactly fit the B-Class. The Tornado is now, of course, an international class on its own, and changes the class has made have nothing to do with the old B-Class, which no longer exists as far as ISAF is concerned.

If anyone were to ask me, and they probably won't, then I would reply that you guys shouldn't go below 130 kg all-up weight. It may actually be wise to set the min weight at 140 kg. Reason, Builders want to be able to produce hulls relatively cheaply and 20 foot hulls with such a rig will take alot of load. Producing such hulls below 35 kg per hull may be a bit much to ask. Especially if you want to the rig to allow for a jib. I know that the jib has gotten a pretty bad reputation over the years but that is undeserved, especially for distance races the jib is a booster that you want to have on board.

Also I wouldn't decide for a very big sail area. Look more to the balance you are trying to achieve. Sometimes less is definately more. Pardon my example but the F16 has the SAME upwind area as the Hobie 16 design and shares even its hull length, still it is a huge amount faster. The trick is all in optimizing the RATIO'S and not in just supersizing the specs. In this respect, going smaller may actually be faster. This holds for the hull length as well.

Think along the lines of

20 ft length (although I think 19 foot would be faster because of better ratio wetted surface to prismatic ratio)
10 ft wide
9.5 mtr tall mast (less overall weight means less volume in the bows so don't make the mast taller)
18 sq. mtr. mainsail with max 9.1 mtr luff (aspect ratio 4.5 more than F20, F18 and tornado, less than A-cat)
5 sq. mtr. jib sail with about 6 mtr luff (otherwise the bridles will be too far forward, bad for loads and dive recovery)
21 sq. mtr. spinnaker with a long luff (Narrow spis are fast much more than when keeping stacking area in there)

Maybe even get 22 sq. mtr. spi is you want to come out at 45 sq. mtr. total area.

Wouter

Wouter, getting the ratios right is the challenge for the designer. As I see it, the formula just defines a box to work within.
If the goal of this class is to provide an opportunity for some experimentation and development, the parameters of the envelope need to be large enough. Hence, I dont see a reason to limit mast height. Yes, let the uni-rigs play as well, then we will know if they really are the best on distance racing as well. Personally, I think a jib is a very good thing to have on a boat for distance racing.


As for minimum weight, I have sent some messages to some knowledgeable persons (both designers and builders) to ask what they think a sensible minimum weight should be. Hopefully they have the time to answer.

Great input , perhaps it is finally time to resurect or rather use the non existant {thanks mary} B class outline similar to the A class rule . Also perhaps as Wout noted adding some definition or rules to limit development .

As Rolf noted previously the starting up of a B class or F-20 type class requires all the help and people it can get .
Wout did an excellent job with F-16 ,already has the basic data and procedures required outlined and I,m sure all interested would be very pleased to have that experience applied to the rules aspect and establishment of this class.

I would like to see it outlined and published rapidly and possibly applied in the Tybee 500 next May , which already has some T teams interested as well as other new B class cats {myself inc } -perhaps a Marstom or two again,-and possibly several others or reps from the various 20 builders that wish to establish their boat with racing credentials to race in this new class category in the Tybee 500 ,as seen on OLN tv .
The race organizers have already indicated that if 5 enter a class category will be provided , --preferably with seperate start time .

I think the basic specs of existing 20s as listed should be used as rules basis , need some time to study them myself but agree with consulting the designers and builders and following their basic advice and proposed outlines , Matt inc ,though obvious differences exist and will need to be worked out .

Please ,any offer proposals they wish to see incorporated in the rules and class structure.
Wout Rolf and all , this being an International class I think it is important to have numerous people form a base group interested , My organizational skills are obviously lacking , so please someone offer to act as group administrator until class officers can be elected .If no one else will I'll volunteer BUT WOULD PREFER someone more qualified and capable take the reins .

Thanks ,-this is very exciting, my interest has been waining but this class will bring me for one back into more active racing again .
Carl

If the I20 is going to be a slug in the class, or not even qualify, then count me out.

I'll go make an F18 for half the money.

Can someone help me by translating the rules on this site:
http://www.f20.nl/
I can't run them through bable fish because it is a picture and not text.

Thanks.

I am quite sure the I-20 will fit within the B-class box. How much sailarea does it have?

Will it be a slug? Perhaps.. I dont know. But consider that the point in resurrecting the B-class (or a derivative of it) is becouse we want higher performance boats and some room for experiments.
I am quite sure there is a large enough number of I-20's to keep the class healthy and active. Our toughts and ideas should not be viewed as a treath to the current F-20's and I-20's. As others have said here, the I-20 is strong in the US.

Are you considering building an F-18? Great if you do, but consider where you will find the mast and crossbeams. An old T can be donor for a B class rig/beams (might need new aft-beam), and then you just need foils, hulls and new sails to have a competitive B-class. Thats one of the attractions for me (plus that we mostly do distance races and need the speed. We are a beefy team who will not be competitive on a F-18)

Carl: What exactly is it you want? I'll report back when/if I get some feedback.

If someone have connections within Hobie Co., Nacra or AHPC, it would be great if you could ask them what they think about minimum weight and sailarea.

Mike,

Mainsail:
18m2 + half mastarea
Dacron/Mylar
maste height max 9850mm above mainbeam

Spi:
Weight class 1-2: 23m2
Weight class 3: 25m2

Jib:
Weight class 1-2: 4.15m2
Weight class 3: 4.85m2

Hulls:
max length: 6200mm
max width: 2600mm
material: polyester

Daggers:
max 7kg

Rudders:
max 3 kg

Crew:
Class 1, 135kg tot < 150kg (including correctors)
Class 2, 150kg tot < 165kg (including correctors)
Class 3, 165kg or more

Security equipment:
1 paddle, min length 1meter
1 towing line, min 15m long 6mm thick
1 righting line, min 6m long 10mm thick
2 PFD's (dont understand what "op lichaam te dragen means". Dragons who like to drink tea perhaps..)
1 compass fitted to the boat

Dont forget your measurement letter..

Thats all there is there.. (I hope, perhaps Wouter can correct me if I have done any mistakes translating)

Sorry, I'm having too little time to keep up with my own class work. So I'm not checking this data, you are on your own guys.

Wouter

I have recieved some feedback from both designers and builders. They suggest a range from 125 to 135Kg's as minimum weight. That weightrange is achieveable for a 20 footer with a jib both for manufacturing and homebuilding (in plywood if need be)in their opinions.
I would suggest a minimum weight of 130Kg's, based on that input.

Another issue, well debated earlier, is the 10 foot beam. It's viewed as an detriment for the average sailor Joe, not beeing able to put it on a regular trailor. Options are either a tilt trailer, disassembling, or some sort of folding/sliding mechanism. Personally, we use 1 hour to tear down our boat for travelling, and two hours to put it together again. We can leave the boat with the mast up at our club, so we dont rig the boat every time we want to go sailing.
Having sailed a cat with a 10 foot beam for some years now, I would not consider a high performance cat like what we are discussing here with a 8 foot beam. Even if it's more convenient when you need to trailer the boat around.
If assembling the hulls/crossbeams/trampoline platform is to much, I seriously suggest a kind of tilt trailor. There are many types of tilt solutions, but one of the best one I have seen used the area under the boat as a gear-storage/camping shelter. It looked kind of like a scewed metal tent, provided great storage and a place to sleep if need be, plus, I think it helped with the aerodynamic problems of trailering a tilted 20 footer (crosswinds and meeting trucks).

2 PFD's (dont understand what "op lichaam te dragen means". Dragons who like to drink tea perhaps..)

"to be worn on the body", although I quite like the idea of a tea-drinking Dragon

Rolf, suggest you go with 10ft beam, or even unrestricted. If guys don`t want the extra rigging time or tilt trailers they can go with 8ft beam and add racks like skiffs, the F16 rules actually allow for this as well, if the boat is less than max. allowable specs (2,5m)you can add wings / racks such that the boat width plus one extended rack is at or less than max. beam.
Would be fun to see 20ft cats with massive rigs and huge racks out pitchpoling all over, make good tv coverage

Right Steve, to be worn on the body of course.

Racks are a good idea if trailering is a large problem! Are they included in min. platform weight on the F-16's, or are they 'extra'?

I would like to limit sailarea, but let the 'daredevils' put extra high masts on their boats if they want to. I was considering putting racks and a Tornado rig on a 16 footer once, but never got around to it (in hindsight, I am glad I never did. Would have been a real pitchpole machine).

1.3 Boat weight

The minimum weight of the boat ready to sail, excluding non permanently fitted wings, is fixed at :

1.3.1 Singlehanded mode (cat rigged with gennaker) : 104,0 kg. (= 230 pounds)
1.3.2 Doublehanded mode (sloop rigged with gennaker) : 107,0 kg. (= 236 pounds)

So min. weight excludes the wings / racks. Just have to make them really light then, eh ??
(Above from F16 class rules, not to confuse F20 interested parties, in answer to Rolf`s question.)

The boat Wouter described is already out there, known by the name of "Super Taipan 5.7", right Macca?