A-class, "hydrofoils not permitted" violated?

Harkan,

There was a clarification diagram on the USACA website under rules, under the measurement heading, which has been recently removed.

Absolutely. And that brings us to the core of the hydrofoil issue:

Dynamic lift occurs to all boats in movement. If it wasn't for the existence of static lift (displacement), banning hydrofoils would make as much sense as banning aerofoils from planes.

I believe the only way to eliminate the dynamic lift components is to keep the boat still. This path leads us to reinventing the buoy.

Interestingly, the conceptual evolution of a displacement (hydrostatic) boat follows almost the same path as the lighter than air (aerostatic) craft:

- At rest they are pure displacement vessels.

- When they move, both inevitably generate some dynamic lift, so speed is improved with streamlined forms. (that explains why a buoy and a baloon are spherical and a boat and a zeppelin are streamlined)

- Then, it is natural that both start using the (inevitable) dynamic lift: they receive apendages for steering, stability and damping (rudders and (flippers or boards)).

- Eventually the dynamic lift starts to assist or replace part or all the flotation. The boat shape becomes apropriated to generate lift (plane) and/or receives hydrofoils, deflection strikes and the like, while the zeppelin becomes thinner and receives wings.

- In the end, the baloon becomes an airplane. Motor boats could just follow the same path, but sailboats have a power limitation (wind) that makes positive flotation indispensable.

Conclusion: is it possible to ban dynamic lift? Hardly. Would it make sense? Only if we want to sail streamlined buoys.

All the best,

If the statement is there, you can win a protest against anyone with a daggerboard or rudder. Really.

Anybody got a copy of ISAF Equipment Rules for sailing?

Look up hydrofoil.

Then look up daggerboard and rudder.

I dont have the document, but as it was just explained to its all defined. Daggerboard is defined as being near the centerline of the hull. Hydrofoil is

not near

the centerline of the hull. Rudder is what you would expect.

So Wouter's interpretation of hydrofoil being a

waterborne foil

and Luiz's assertion that

all foils generate lift

are not valid for the sake of this argument. What matters is the ISAF definition.

So if your daggerboard is not in line with the centerline of the hull, it's a hydrofoil according to ISAF's equipement rules of sailing. The ISAF's definitions are what the measurers use, so its that definition that matters.

Under this definition, any boat with a board that is not in line with the centerline of the hull is not an Acat and cant compete. There are boats competing today that are outside this rule, its just not been enforced.

Seems like canted hulls would also be illegal then, depending on the definition of

ceterline of the hull

.

you have two hulls and two centerlines...no problem.

Bill,

My comments earlier were a bit tongue in cheek. I was (am) aware for quite some time that we agree on these points.

It was just when I made similar comments about 4 weeks back I was accused of hating the A-class. My recent comments were a sting to those people.

My appologies if I give rise to a misunderstanding.

Wouter

Ohhhh ! Brilliant Jake. Absolutely bleeding sharp. What a way to beat the rule.

Place the daggerboards under a 10 degress inward angle and have the hull both canted outward by 10, ehh voila according to the whigs at ISAF this boat is not using any hydrofoiling effect to lift it out of the water. Because the starboard daggerboard in in line with the port hull centreline.

Wouter

Two non-parallel centerlines? How do you define centerline?

The diffference between a 6 degrees outward canted symmetrical board (hyped up development of yesteryear) compared to an 6 degrees inward canted symmetrical board when the luff board is fully lifted is 30 kg on a doublehanded F16 with crew on trapeze = (20% of the total saildrive perpendicular to the centreline of the boat.)

The A-class has less righting moment and less saildrive byt the ratio of 20% will still hold. Roughly speaking 15 kg lift on the A in the same situation with the crew trapping.

When allowing boards to go to 15 degrees inward angle the difference becomes 50% of the total saildrive perpendicular to the centreline of boat (= 75 kg on 2-up F16 and 37 kg on A)

Calculating the difference between these boards and the banana boards is not easy to do without agreeing on the specs of the banana board first. For all I know the bananaboard can be twisted towards its tips, making it a symmetical daggerboard near the hull and an permanently positively angled lifting foil at its tips. I will need to know the cord and radius of arc of the banana board and the amount of twist or fore-aft angle in its (hull) slot (= gives incidence angle)

Basically a 0.16 sq. mtr daggerboard with a 0.20 mtr cord (aspect ratio = 4) can rather efficiently
create 75 kg force perpendicular to its plane. It can produce even more force by then the lift drag ratio will be less attractive. So if the daggerboard is L-shaped then a horizontal tip of 0.20 by 0.20 can produce 25% force. Of course we have ignored some efficiency effects here but such a L-shape form can be used as a good first approximation of the curve banaboards which tip reaches 0.20 mtr seperation relative to the centreline of the part in the daggerboard well (assuming this one is on the vertical).

It seems to new A-cat anti foiling rule allows up to 0.30 mtr seperation between the vertical and the tip of the banana board = approx 38% of saildrive transformed into vertical lift (= effective weight reduction craft)

It is not hard to calculate these things using theory; it is just that there are so many factors that need to be fixed/chosen for a value can be produced.

Wouter

I'm pretty sure that the rule reads that each board has to be in line with its own hull centerline.

That was kinda my point. My boat's hulls are canted outward. As you look at the bows, they tilt inward at the top. The daggerboards and rudders are in line with the plane of each hull such that the hull, the board, and the rudder of the leeward hull is nice and plumb when flying a hull...many a-cats are that way (and so is the Nacra 20). I was just pointing out that it's tricky to define all this stuff...including what the vertical plane of a hull is.

One way of doing this is to remove the hydrofoil and min board tip distance rule and require that the centerboards and rudders must be straight and enter and exit the hulls through the centerline and that they are flush with the hull when they are fully retracted.

I guess that solid wings should be stopped also by require a min soft sail area or something like that.

I'm not sure how we should handle the case if someone shows up with a kite on their A-class.....

Or it's maybe time to try to find a single handed one design class, that is light, fast and has big turnout at the regattas. Any suggestions?

/hakan

Hakan

I think you are overreacting.

Ben's solid wing sail wasnt faster. No need to add a rule to legislate solid wings.

And so what if banana boards are faster? Adding them isnt going to be a big deal.

The CClass guys already proved that a foil borne boat isnt as fast as a catamaran with hulls in the water. So, the slippery slope to full foil borne cats wont happen, that experiment has already been done.

I dont see how adding a new curved daggerboard is going to make the boat worse. If you leave it in the current position it will help get the sterns out of the water downwind. Tell me why this is a bad thing?

A foil assist looks to be faster, but again I think thats were its going to stop. Go back and review the CClass experience, and then have a glass of wine and relax, its going to be ok.

I say we get rid of the

no hydrofoil

rule so all those off center daggerboard boats wont be obsolete.

Bill

I just did that.

The daggerboard is defined as

a retractable hull appendage, attached aproximately on the hull centreplane and not rotating, primarily used to affect leeway

.

The rudder is defined as

a movable hull apendage primarily used to affect steerage

The words

hydrofoil

and

foil

are not present in the document.

The axis are referred to the waterplane with the boat in measurement trim, not the waterplane when moving.

I see nothing there very helpful to prevent lift generating devices.

All the best.

The resticted rule set does pretty well to keep this in check - even if they neglected to publish it on the site.

No one seemed to upset about canted boards. A curved one with the same inboard and outbord limits keep the thing virtually identical in net force. It is impossible to restrict the board to be on a hull centerline as you then have to write a rule about the shape a hull can be as there may not be a centerline on an asymetrical hull. If you cant a symetric hull and put the board in straight, they are in effect now canted. Straight foils canted foils and limited curved foils all produce some lift forces. This is why the technical committee removed the hydrofoil reference and in its place restricted the limits of the foils.

These boats have been measured and allowed to compete, so for the time being the argument is moot. There are several petitions being submitted to address this and it will go through the proper procedure to be voted on by the class and potentialy have the rules rewritten to address it.

Say you could build a 50 kg A cat with 25 kg of movable weight added which can be displaced to windwards with a sheet. Would this fit the current A class rules?

It all boils down to the question if the A class really wants to be a development class or if at some point it just wants to abandon certain developments, which requires more and more restrictive class rules. The foil/wing is a secondary, although actual, issue, imho. More issues to come, for shure.

Hmmmn... did the A class experience the recent growth spurt because lots of sailors discovered they liked designing and building faster sailboats to race and joined the class and built or bought the latest design ...

Or did the A class grow because a lot sailors wanted a light weight, high performance single sailed boat with great international sailors at the top of the list and got a boat to play?

I know I waited to see how the class dealt with the foil issue the first time.... If they had voted Yeah on the disruptive foil technology... I would have waited and bought a boat for 1/3 the price.

Re Jake's A-cat AND MINE TOO:

My boat's hulls are canted outward, bows tilt inward at the top. The daggerboards and rudders are in line with the vertical plane of each hull such that the hull, the board, and the rudder of the leeward hull plumb when flying a hull

.
So--- the newer boats have the boards tilted in, so that they get lift from the boards when heeled at speed, a big advantage when doing the Wild Thing. To add insult to injury, it appears that inward canted banana boards provide even MORE lift.
By the way---- Lift = hydrofoils

Dave,

Come on...what would you know about the subject?

I have one of those Flyer 2s from Ashby which have the tilted in c/boards. One day got lazy and didn't bring the boards up and found going wild I could push a lot harder up to about 15 knots of breeze. The lift was good enough to help to keep the bows up and allow you to sit a bit further forward. Which meant the stern didn't dig in as much and in chop less rear beam slap. Above 15 knots you would want to bring the boards up as you wanted the sideways slip as the lift generated wasn't enough. But 8 to 15 I always keep down. At the Florida worlds only brought the boards when sailing flat and felt I had really good pace downwind.

This is my experience, and normally sail myself and use a velocitek to guage performance. The averages were better doing what I described for how I sail the boat.

The issue is being put to vote by the membership.

The wording is specifically for or against

curved foils.

This doesnt solve the question of whether straight daggerboards that are not in line with the hull centerline are legal or not.

Bill,

I would think that Canted boards and curved boards would be viewed and treated the same way. That is how I responded to the vote anyway. if canted boards which are already in use throughout the class, then banana boards should be too. As to obsoleting the whole class, my Boyer is probably close to being there anyway. Where I think this will effect the class the most is those who own newer boats.