Dear A class member,

As you all know, the IACA held a ballot in August 2001 with regard to the
hydrofoils? issue. A large majority of IACA members, including myself, chose
to rule out (previously permitted) hydrofoils from the A Class Rule.
At present a small group of A Class sailors are deftly trying to get round
the wording of the new rule, which clearly states that ?Hydrofoils shall
not be permitted in the ?A? Division, by proposing artful interpretations
of this latter.
In fact, the sole meaning of this rule is that any device that generates
a lifting force that can reduce the displacement of an immersed hull must
remain prohibited.
Therefore, and since it is without doubt that any inward-canted or round
boards generate a sizeable lifting force proportional to the canting angle,
(in demonstration of my statement I have below attached calculations by
Mr Giorgio Bergamini (Engineer), who is a member of the ISAF Multihulls
Committee and the designer of the two Italian C Class catamarans that challenged
the USA in the Little America?s Cup in the early 80?s), canted or round
boards must be forbidden as specified in the present A Class rule and for
this same reason also T-foiled rudders.
I do not think there is however need to demonstrate the advantages of canted
or round boards; proof that such boards work can be seen in the ORMA 60?
boats which have been fitted with canted boards for 10 years and now all
have round boards. The same will certainly happen to the A class if we do
nothing to prevent it, and if it does, I can assess the additional cost
for each A cat owner at around 2.000 Euros.
As founder of the CAT ?A? Italia, which was the first A class catamarans
association to be established in the world, and as long time designer and
the main builder of A class catamarans, my intention in this letter is to
denounce to the competent bodies of the ISAF, to National Authorities and
to all the ?good? IACA members the unsportsmanlike behaviour of this minority.
I believe that if nothing is done immediately to re-establish the right
rules of the game we can expect an imminent proliferation of new A cat designs
with slender hulls, solely intended to sustain the weight of the boat and
the helmsman while still or moving slowly, and fitted with inward-canted
or round boards thus allowing our beloved cat to ?take flight?.
I wonder why nobody has yet tried to stop such an evident breach of the
A class rule when other much less ?harmful? rules, such as pumping, have
been severely enforced in other classes.
At the latest IACA assembly, which was held during the 2004 A cat Worlds,
the subject was raised and heavily discussed, also as regards the presence
of five A class catamarans with inward-inclined boards.
In the end, those who sailed such catamarans, succeeded in passing an original
interpretation of the hydrofoils rule (aimed also at covering themselves
from future problems with regard to the beam rule): canted boards shall
be allowed by the class rule on condition that, when in their fully-up position,
the distance measured between the perpendiculars to the extremities of the
same boards is 2,30 m at maximum (i.e. the maximum beam in the A class).
Not surprisingly this interpretation does not prevent using the much more
promising round boards.

If we do not stop this unlawful experimentation, within a matter of months
90-95% of existing boats will become obsolete. This uncertainty creates
confusion among A class members.
On a daily basis, I am requested to fit new BIMARE A cats with long and
narrow boards not too inclined, short and wide boards very inclined, round
boards etc.
The chaos that will occur in the absence of a timely decision on this subject
is easily foreseeable.
I therefore appeal to the ISAF Multihull Committee, the A class builders,
the technicians and all the interested parties, to clarify once and for
all the hydrofoils? issue.
Sincerely
Mr. Lallo Petrucci



Appendix

The hydrofoils? effect according to the calculation of Mr Giorgio Bergamini

Test boat: 16? catamaran
Boat weight: 105 Kg
Crew weight: 120 Kg
Overall weight: 225 Kg
Boat?s speed: 6 m/s

With standard parallel daggerbords :
Immersed volume: 225 dm3
Hull drag: 215 N
Daggerboard drag: 55 N
Rudder drag: 14 N
Overall drag: 284 N

With round daggerboards (ray=1 m ? surface 0,194 m2) at heeling angle of
15°:
Immersed volume: 145 dm3 (then Lifting force 80 kg)
Daggerboard drag: 64 N
Rudder drag: 15 N
Overall drag: 227 N

With round daggerboard the overall drag is lower by 57 N or by 25% (57/227).

The conclusion of Mr Bergamini is that a boat fitted with round boards has
a 25% lower (friction plus wave) drag than the same boat fitted with standard
parallel boards, the same advantage could be achieved by lengthening the
hull by 25% (from 16 to 20 foot) or reducing the overall weight by 25% (from
225 to 180Kg).


A personal statemen of Giorgio Bergamini

Dear Lallo,

with reference to foils? issue pertaining to A class catamarans, pending
ISAF?s official ruling, I, as a member of ISAF Multihulls Committee, am
glad to offer you my technical opinion on the subject.
In brief my conclusions are:
1) the hydrofoils? effect occurs at any angle of inclination of the boards
with respect to the vertical defined by the mast;
2) if the boards are parallel or canted outwards, i.e. if respectively the
plane passing through the boards is parallel to the vertical passing through
the mast or cross it above the water level, in such a case the hydrofoils?
effect is limited, if not, in certain circumstances, negative; then such
boards are to be held allowed by the A class rule;
3) canting the mast to windward with respect to the platform has roughly
the same hydrofoils? effect as inclining the boards by the same angle inwards;
4) take this as a rough approximation, an increase of 1 degree of the inclination
of the boards with respect to the mast is equivalent to an increase of 1%
of the hull?s length, hence a proportional increase of the boat?s speed;
5) also the inclination of the board with respect to the plane passing longitudinally
along the hull or the use of asymmetrically profiled foils may make a
boat faster or better balanced as well as the asymmetry of the hulls prohibited
by the A class rule since its inception;
6) For all these reasons, in order to promote a fair competition among A
class cats and A cat sailors any inwards canted boards, i.e. any board whose
plane cross the vertical passing through the mast below the water level,
as well as any mast capable to be canted to windward, as well as any kind
of longitudinal asymmetry of the boards with respect to the axe of the hulls,
is to be held NOT permitted by the present A class rule.
Sincerely
Giorgio Bergamini

Australian A Class Members
Hydrofoils
There is an international debate ongoing regarding the rule prohibiting hydrofoils.
The debate is one of a number of interesting threads on the A Class online forum
advertised on our website. It is worth a look.
As it is written, the rule depends on the definition of “hydrofoil”; point #8 under IACA
measurement guidelines says,
8. Hydrofoils are not permitted.
On face value, a clear and simple rule which prevents the use of hydrofoils in IACA
events. So what is the problem? Well, for a start, aren’t centerboards and rudders,
hydrofoils? Sure, that’s a technicality, but I think we risk technical arguments
damaging the class sometime in the future.
Most of the forum participants, including myself, regret the introduction of a rule that
limits development of the class. That is too bad because a majority voted in favour of
banning devices designed to lift both hulls out of the water. I guess we collectively
imagined A Class scooting around on skis and were fearful of losing the current
balance of cost and competition.
However, what if someone developed a device that generated vertical lift and this
device was not the ski type hydrofoil we imagined? Far fetched? We already have
seen angled boards which test the definition. Have you seen the “banana” boards on
the latest US C Class? Would they be legal? I imagine arguments could be
presented for and against - I believe it is unreasonable to ask our measurers to
decide on the eve of any regatta – and I imagine the arguments would rage on if
such a device won a major regatta.
I believe a revision of the rule is pointless. My proposed solution is for the AIADCA to
lobby other nations to have IACA delete the rule as unworkable. I hope we can get a
consensus at the meeting in Hervey Bay at our next championships.
I look forward to the discussion.
Regards,
Hamish Sinclair
AUS 797

I can well imagine the re-tooling cost scaring an existing fabricator of "A" cats, but how much will it cost the competitor? Yes, the production costs are passed on, but to assume a faster (smaller hulled) boat will ultimately cost more is foolish. Consider for instance, the Hobie, which would cost more than most equivalent boats today, if you started from scratch. Why do we doubt that Technology and technique can provide a cheaper, better product?

Now I haven't designed any C-class catamarans in the 80's but the numbers presented look funny.

For example in order to create 80 Kg lift (about 800 N lift) the drag of the board is only increased by (64-55) n = 9 N or about 0.9 kg. So the efficiency of such a foil is 80/0.9 = 800/9 = 89 = Cl/Cd (= lift/drag ratio)

This is the most efficient foil (either air of hydro foil) that I have ever seen ! With such foils a human powered vehical could lift a 350 kg from the ground or above the watersurface. Now many universities has tried really and human powered flight has only been barely reachable. They had to hire champion cyclists to peddle the craft and all weighted less than 150 kg including the pilot.

A good foil does a ratio between 10-30; so no where near 89 !

Also the mr Bergami (or somebody else when he didn't) makes a very deceptive statement :



This is simply WRONG. Overall drag (the kind that determines final speed) encloses MORE than only the hull related drags. So any savings need to be devide by a number bigger than 227 N that was used here. Result the ratio will drop.


The next statement is obviously made without careful investigation :




This is very wrong. This totally disregards all the higher (non-linear) dependencies than are linked to the designs. You can't just say that 25 % lower hull friction has the same result as making the boat 25 lighter. Same for the other statements.

Also there is another fenomenon at work that limits the amount of lift that can be generated by an inclined board. The lift is NOT unbounded. It comprised of two factors ; -1- cavitation, -2- total force balance around the whole craft.

***

I wrote this so that readers know that these numbers are not accepted by all. I even doubt by many.

***


On a different topic.

I'm quite amazed that they used a 16 foot, 105 kg boat with a 120 kg crew as example. Sounds like an F16 to me !

Of course the F16's allow both T-foil rudders (and have them even) as well as inward canted boards. HOWEVER, you may only cant them to a 6 degree angle to the vertical ! Rule 7.13 of the F16 class rules. Any designer better take that into account or risked getting banned from the F16 class. So the 15 degree angle in the example is not allowed in the F16 class. We decided to allow inward canting boards to not arrest a little development, but we did limit the possible benefits.

Curved foils are allowed but may never arc passed the 6 degree inclination. That is the official intepretation of rule 7.13

Wouter

I'm sorry if this sounds a bit harsh, but all these words you could have summed up as "waaah waaah waaaah".

Seriously, if the A's pride themselves on being the most "efficient, hi-tech" catamaran class out there, then the rules need to be changed.

If this is a blatant infraction of the class rules, thats another thing, but really, I'd expect the A-class to adopt the latest and greatest before all the rest of us.

If the A class wishes to ban hydrofoils and become more restricted in design because sailors do not want to make boats obsolete then may be they should make themself an OD or Formula design.

But the A class is a development boat and should not loose sight of this. As said on the A class thread, if they did this years ago..... Boats would be 20 kg heavier and still have alloy beams and mast.

But at the same time, rushing into foils would also be a negative and also expensive exercise. The class should put a temporary ban on foils for say the next 2 years and a committee set up with the assistance of a manufacturer such as Flyer to experiment with foils and enter events as an X class (experimental) with no result given to them in titles. Watch closely the moth development also and implement some of their ideas. When a good system is developed, have kits available and lift the ban.

World champion foil Moth sailor Rohan has recently purchased an A class. The A class association I believe would be foolish to not take advantage of this and approach him for assistance with developing the first foil catamaran class.

The A-cat class should decide what they want to be or split the fleet in two fleets.

Right now they ban all kinds of things that are seen in other classes and as a result they are passed left and right.

Things to consider are platform width, spinnaker, T-foil rudders, angled daggerboards boards, etc.

Even hydro foils have been extensively tested on catamarans by virtue of the Rave class. The A-cats are surprisingly less at the egde of designing than they used to be. More and more sail development is now going from F18's to A-cats in stead of the other way around. Like I wrote the A's are getting past left and right on what used to be their forte. That is except the part of part of boat price, there they are still king. (joke!)


Wouter

The main focus is the A-class sailors. If they are happy the class will continue to grow and attract new sailors.

What is the purpose of making the whole fleet of A-cats obsolete by adding gennaker, foils and increase width? To make it even faster? To attract new sailors? To make it more expensive and destroy the clean look of the A-cat?

If the sailors are happy with the current boat that is close to one design now, why should we start to change things?

The A-cat can give the F18 a match around the course (upwind-downwind). Compare the F18 with loads of sails, wires and other gismoz with the clean A-cat!

You can still build your own wing sail and use but no one bothers. How fun would it be to win a big race just because you could spend 20 000 euros on a wing sail?

No one has used a kite yet but I guess that the start could be interesting!

/hakan

Hey Hakan I wouldnt say that just yet. Look at this photo.
http://www.sefl3s.com/robi/cabb/cabb01.JPG
The fifth boat from left to right, the bright orange boat, is an A cat, it was sailed with a spin that day.

Link to thread

Are you sure that that A cat is not an M18 ?

I was talking about the same type of kite that they use for kiteboarding, not a gennaker. No mast just a long line up in the sky where the kite is pulling....

/hakan

Scooby,
I believe the orange cat is Bret Moss on his A-Class with spinnaker.

If it has more than 150 square feet of sail it is not an A-Class.

No, of course it is not a class-legal A-Class. But the CABB races are done all on handicap, so you can use whatever you want. It's an A-Class catamaran with spinnaker added. You have to still refer to it as an A-Class, because that is the class that has the base Portsmouth rating upon which the modification factor is added for the spinnaker.

Morning Folks,

I figured I would inject my 2 cents into this discussion. First of all, if you don’t sail an A class why do you give a crap about what the class does? The class is what the sailors in the class want, not what a batch of other weenies want. I am not out insisting that the F16 class should decrease their minimum weight to 90 kilos or that F18 boats should reduce their minimum weight to 120 kg and go to carbon wing masts. To me, both these things seem like smart ideas, but guess what, I don’t sail in these classes, and don’t care what they do.

As far as the A class Catamaran goes, I do race one. I bought it because it was the most fun catamaran I had ever sailed, and I have sailed a lot of boats. I did not buy this boat because it was the fastest cat in the world, it is not. My previous boat, a nacra 6.0 was faster with and without the spinnaker. So what. I have no intention of sailing the A class with a spinnaker, increasing its width, etc. To me these are all stupid ideas that detract from the simplicity and inherent efficiency of the boat.

As far as rules go, at this time the class has decided not to allow foils that would make the boat completely foil borne. There is still a discussion about whether centerboards and rudders that provide some lift will be allowed. The problem arose in that the wording of the rule was truncated from what was decided in 2002 at the general meeting. The rule as written is vague and open to interpretation. At this point the class does not seem to have a consensus as to what to do. Some of the class members want to eliminate the rule entirely, allowing foil borne sailing, others want to keep the ban in place, but word it more clearly.

As far as my own personal feelings, I think we should continue to ban completely foil borne sailing, but allow the use of curved or inward angled dagger boards and T rudders. Ultimately I think this will lead to faster boats with a decreased hull volume and wetted surface with out much increase in cost or time and effort to set the boat up and sail.

Sail for the pure joy of sailing,
Sail A class

PS, if you want to sail a really fast boat, try a DN iceyacht. Until you have sailed into a leeward mark rounding at 60 mph in a 50 boat fleet you don’t know what excitement is.

Sail Fast
Sail DN

Eric Anderson A class US 28
DN US 5193

Eric,
You are right that people who do not own A-Class cats should not be telling the class what they should do.

I have loved A-Class cats ever since I saw my first ones back in the mid 1960's. Gosh, that's 40 years ago. And I have always wanted one, but now that they have come back, I am too old for one.

So I am going to give my opinion anyway. Right now the class is building/rebuilding very well. I do not see any benefit for the class to allow hyrofoiling in any sense of the term, whether it involves slanted or curved daggerboards or T-foil rudders or whatever.

You guys have what is, in effect, a one-design class at this point, with the only difference being the platforms/manufacturers. And it is a GREAT class with lots of top sailors participating.

Why would anybody want to fragment it by allowing hydrofoils in any way, shape or form? I think it would spell disaster for the class.

The people who want you A-Class sailors to do all the experimentation and development are voyeurs. If they want to try new things, let them do it themselves or in their own classes. Why should the A-Class mess up what is finally turning out to be a great class after more than 45 years since its inception?

I think there are at least a couple of quite defensible opinions about what makes the A class so great (apart from being a really fun boat to sail - of course, no disputing that): (i) the fact that it provides very close and competitive racing - your point I think Mary, and (ii) the fact that its very nature as a very loosely restricted development class has enabled it to evolve the great designs we see today.

I'm sure there is no single right answer to which of these is more correct. It is interesting though that debate about the right balance between tightly and loosely controlled classes has been around a long time. I always enjoy reading the 1951 exchange of correspondence in the NZ sailing magazine Sea Spray about the R class development skiff - the 2nd and last 4 links here:

http://www.rclass.org/1950/

I sail an A Class because it's light, fun to sail and deceptfully simple. An added plus is the great group of sailors that I have met since joining the class. Had I wanted to deal with more sails and lines, there are plenty of other boats to choose from.
Mary, a boat that's this much fun makes you forget that you may be getting older.

Gordon Isco

Also Bunkenburg did it and some A-cat sailors have done it in Netherlands as well and have done open regatta's with it.

Comments about it can be found on the A-cat forum.

I guess a few people did do it.

Wouter

For one thing, the A-cat class had no problem with making a whole fleet of A-cats obsolete when the carbon masts were pioneered of the wave-piercer hull shape. Come to think, so to with other things like square-top mainsails and glued in carbon beams. These things and others have happened over and over again since the early 70's when the A-cats were 115kg boats with only some 12 sq.mtr. sail on about 7.8 mtr mast (Unicorns)

So why is everybody looking weird at the guys wanting to do the next step by experimenting hydrofoiling or tilted rigs ?





Holaaa ! This is a major shift in the A-cat philosophy; you know, a huge step away from the mantra. "18 ft. long, 2.3 mtr wide, 150 sq.ft. sailarea and beyond that everything goes."





Yeah right ! That is why we always hear how they reached A-mark first only to loose the lead by those unfairly rated spi-boats.

Come-on Hakan, you know better than that.