You're right with regard to the canted hulls - there is nothing that says they're not allowed. However, the rule was changed with regard to the daggerboards specifying that they must remain in the vertical plane of the hulls.




EDIT: sorry - I should have mentioned that this is from the F18 rule set.

The amount of angle on an A-Class daggerboard is only limited to the maximum platform width that must include the boards fitted in their pockets with the tip flush with underside of the hull. Due the slender hulls, there is not much more room than about 5 degrees angle.
As a matter of fact the boards of AHPC newest boats were made by Peter Saarberg and were within 1 mm from the maximum platform width upon measurement. Luckily a piece of the top part on the outside on both boards broke off by accident to keep it well within the class legal width limit, such a lenghth those boards are now.
In the boat area one could see that the tendence for dagger boards is defitely longer and narrower with a 1:10 w/l ratio.

So the conclusion on canted boards is that they dont seem to work on small cats, but they dont hurt you either? Sounds quite vague to me..
It seems to me that the trend for canted boards have died out, as the latest models come with 'regular' boards?

Hello all,

The canted centerboards is a better way to stabilize the boat upwind. I am sailing on a a-class which i made 2,7mtr width and it works. Because the boat is more flat upwind, so the flow along the sail is more attached to the sail in chop conditions. This means that i can sail higher upwind. For example: 1 race we had force 4-5 bft and i was sailing 4 to 5 degrees higher (alone) than F18 and F20. So i think it will work out.

Regards,

Hans Klok [color:"black"] [/color]

Any A class is capable of out pointing an F18 or an F20 (with advantage -VMG) by more than a "few" degrees simply by its hull shape, rig configuration, weight (or lack there of) etc, etc, regardless of the centre boards being canted or otherwise? So a comparison to these other classes cannot really be taken as any sort of “conclusive” result?
The only comparison would be A class to A class, - one with and one without (canted boards).
Hydrofoils by the way are of an asymmetrical profile generating lift only in one direction, due to their shape and their movement through the water, the centre/dagger boards referred to as “cantered or not cantered” are of a symmetrical profile that will generate lift on either side of the foil, depending on their angle of attack relative to their direction through the water.

This is a common mistake. If this was correct, airplanes with asymetrical section wings wouldn't be able to fly upside down - and they can. The appendage being symetrical or asymetrical is not the real issue.

What your statement neglected is the angle of attack. Given enough angle of attack, a canted symetrical daggerboard may lift a boat out of the water (although not as efficiently as an asymetrical daggerboard) - so it behaves like a hydrofoil.

Conversely, a non-canted asymetrical foil generates only lateral lift to both sides (although not as efficiently as a symetrical foil) - so it is not a hydrofoil. It does not provide vertical lift until the boat heels.

Conclusion: the rules need a better definition of "hydrofoil". But a proper definition is quite a challenge because with a bow up atitude, a "plain vanila" vertical symetric daggerboard will provide vertical lift as the boat heels. And the hulls as well, even without heeling!

How do the A class rules define "hydrofoil"?

Hey Luiz, what you have said is actually the same as I wrote? but with added examples. I never said that hydrofoils would not generate lift on either side under the (extreme) conditions you give, such as aircraft wings which, when the plane is inverted the angle of attack of the foil is increased to such a degree that lift can be generated on their “flatter” side more than the lift on the curved surface and in so doing the aircraft can remain flying etc, but there is a great penalty in drag incurred to do so. Symmetrical foils, as I said generate lift on either side of the foil depending on their angle of attack to their inclination to the direction they are travelling through the water.
Rudders are symmetrical foils and obviously generate lift on one side as well as the other whenever their angle of attack to their direction through the water is altered, and therefore, they then turn the craft in the desired direction.
What I was offering, principally, is the well established, defined fundamental, difference between the main functions of a hydrofoil and a (symmetrical) foil, (which is not considered to be a hydrofoil even though a symmetrical foil, as I said, can be used to generate lift equally in two desired directions)
When a hydrofoil is used on water borne craft, the foil is generally in a fixed attitude to the longitudinal length of the boat and the, profile shape lift that it generates is always “upwards” at (or about) 90 degrees to the waterline of that boat. This is due solely from the asymmetrical shape of that foil
This is the same for most aircraft, and in the instance you give of a plane, the tailplane elevators and the Aerolone on the wings alter the “angle of attack” to the wind direction passing over both the wing and the tail plane. In the case of the asymmetrical shape of the wing, the Aerolone will actually go a long way to altering the “shape” of its exposed “profile” to the wind, of that wing, from that of a fully asymmetrical shape when flying “right side up” to more of a symmetrical shape, to the wind direction when the plane is inverted, and of course most commonly, elevators are symmetrical (not always though) in profile and take over a large percentage of the work in keeping an aeroplane flying when inverted.
The best example of symmetrical foils on a boat generating lift in a multifunctional desired directions (other than the rudders themselves) is a fixed, (in the vertical plane) rudder that has a, non-adjustable “T” foil attached to it below the waterline. When the boat starts to pitch down at the bow with the boat travelling forward, the T foil is angled down in relation to its forward direction. Due to that angle change, lift is generated on the under surface of that symmetrical T foil and it “pulls” the stern down (and conversely the bow upwards). The same applies when the bow pitches upwards. Lift is generated on the upper surface of that symmetrical T foil (for the same reasons) and the stern is lifted upwards (conversely the bow moves downwards) ergo pitch is greatly reduced.
This same principle applies to symmetrical dagger boards that are canted (particularly canted inwards). Due to the “pitch” of the boat, and their continually changing inclination to the forward horizontal direction of that boat, they will generate lift in a desired (at that moment) direction.
So symmetrical foils on a boat can generate lift that is “desired” in both upward and downwards directions (or side to side as in rudders), whereas “hydrofoils” on a boat will generate principal lift only in one direction all the time. That amount of lift (of a hydrofoil) is a variable directly proportional to the “speed” it is travelling. (They obviously generate some lift in the horizontal plane as well i.e. acting to reduce “leeward drift”, but that is generally secondary to their main function)
For boats, the function of a symmetrical foil is more “dynamic” while the asymmetric foils function is mainly “static”
P.S Luiz, these examples are primarily "as they apply to boats" so that the extreme angles of attack as described with planes, (there are other many and varied applications as well), simply should not be applied in this instance.

The reason most of the sailors were so inconsistent was the fact that the wind hardly blew over 5 knots and most of the racing was drifting.

The A2 is a champion downwind in the light stuff too.

The a-class rule about foils is that the maximum angle of the boards is so far angled that when the bottom of the centerboard is full inside the hull ( bottom hull is bottom board) the measured width on the top of the board is not more then 2,3 meter. This means that boat is never more than 2,3 mtr's in width. This means that you never get the extreme foils like the Icarus.

Hans

I assume curved foils are banned ?

There is a guy in Holland who had tried curved one's and it is allowed but he has to stay inside the 2,3 mtr

Hans