OK, I saw some of them up close in Key Largo, looked very neet but I am still unclear as to exactly what they are supposed to do. Do they help lift the hulls in all conditions, upwind and down, for less drag, or just downwind? And when sailing upwind on one hull, how is the leeway vs. a "normal" deep, straight, board?

Full disclaimer, I don't own an A cat but am intereted in any good, cheap, speed developments you guys come up with! I'm still drooling over Ben's wing, I think that could be further developed and be faster than a regular sail in flat water. Not sure about all the pitching in waves though.

As I understand the curved boats are just the natural evolution of the canted daggerboards. The concept there was to give the boat lift as you moved faster and most designed moved that direction in the last 10 years. Jury is still out, however, as to the benefits of full curved-- they are far more expensive to make and so far they are not tearing up the top racing spots.

Nils Bunkenburg, his factory is quite close to my place, is busy on modifying older A-Cats with curved dagger boards. They are standard on his own (Nikita A-Cat), and I believe that you'll see the new boards everywhere soon.

Ashby's new Flyer will be fitted with curved boards. That is when you will see it tearing up the top racing spots.

Must be something in it if Gashby is looking at it for his new design.

I'd be very surprised if Glenn does anything with curved boards until the outcome of the current IACA ballot of national association mebers on flying boats. If the proposed rule gets a yes vote then they'd be a goer. With a no vote the Commission chaired by Andrew Landenberger would be asked to revise the rule wording for further consideration.
There is an interesting explanation of the commission's considerations on the IACA website.
The general view of the current curved boards used at the Worlds seemed to be no real advantages over the commonly used canted boards. They do look good and have market appeal........... No one has been able to measure a difference though. It's certainly not an obvious thing like the change from pinhead to flat tops in 1988 or the change to carbon masts in the mid 90's.

John Dowling
AUS9

Gashby is currently running around on his prototype with straight boards however has mentioned he will go to curved boards later. I would assume pending outcome of ballot off course. I would expect the price of curved boards to add another couple of grand on the new boat price.

I think anyone must regard curved foils as just as much class rules inpsired as "potential benefit" inspired. I for one do not expect a meaningful performance difference between straight but canted boards and curved foils. I also feel that for true measureable benefits one needs canted boards beyond 15 degrees angle at least and no catamaran class rule allows that at this time, not even the A-cat class rules.

Wouter

Glenn Ashby's inward canted boards presently have symmetrical profiles. There are many possibilities for canted and curved boards to increase lift: many NACA shapes have been tested but few have been made up in carbon fiber. John Ilett has done many of them. It is not clear what the Marstrom profile is, or the Bimare profile. Who knows about the French???

I predict that curved boards will be developed with non-symmetrical profiles- to make A-cats fly even better! And fly they will. Fumbling with legal language to regulate this is/will continue to be ummm.....aaaa.....problematic.

Old story- Engineers say that a Bumblebee cannot fly, according to conventional aeronautics. The bumblebee, not knowing this, continues to fly happily.

As far as I know, the only real reason the boards are curved, is so that when you pull them up, the tops don't excede the maximum allowed beam of the boat, hulls and rudders included, is that correct? I mean, a straight board canted in at say 45 degrees, would provide much more lift than the curved ones, right? And I agree, they should be asymetric for even more lift.

It is one of the reasons; I'm sure there are others..

Board are curved in the big boats so that they dont hit the dock.

Did you think that up all on your own?

The current rule limits the boards to the maximum boat width (2.3m) in the up position with the lower end of the board flush with the underside of the hull. Secondly, in the down position, the limit is the ends of the boards are to be no closer than 1.5m. This obviously limits length and angle of canted boards and length of curved boards. The proposed rule intends to clear up an anomaly in this rule in which curved boards much longer could be used with one up and one down depending on which tack you were on. The tips of the boards would be still 1.5m apart but the longer curved board would be much more likely to produce "flying boat characteristics. The proposed rule is that boards be no closer than .75m to the centreline. There is no proposal to limit foil profiles.

Cheers
John Dowling
AUS9

Bob Baier (remember the discussion about him last year?) just won the first A-Class regatta of this year, so I guess the extremely canted boards really are faster.
http://www.seipi.it/vdp_09/dva_fin_ass.htm

You jest of course! What was the standard of this regatta. I note Bob Baier was 5th in the last Worlds and the third place getter in this regatta was 55th. What's an "extremely canted board"? The rules don't allow for a board to be canted more than the standard Geltek Flyer II or Egner Flyer II. I reckon he could have won this regatta in a bathtub.

Cheers
John Dowling
AUS9

I have to disagree with you there John, Bath tubs aren't class legal. You'd need two of them, to make it a cat.

You are correct of course - but be careful not to cant the tubs too far in case the drain plugs become closer than .75m to the centreline. You may also fall out of the tub and lose the soap.

Sail fast
John Dowling
AUS9

You definitly don't want to drop the soap at an A-Class regatta!

Is that because there might be some f18's lurking in the bushes?