Why are daggerboards not asymetrical like an aiirplane wing with the flat side facing out? It seems like it would provide a lot more lift to windward and as the windward hull gets higher out of the water causing the leeward dagger to "lean", would'nt this create lift on the hull thus reducing wetted surface area of the hull and creating less drag from the hull? I realize that you would have to raise the windward dagger on every tack and that lift also creates drag but would'nt the benifits of the lift outweigh the penalty of drag? Am I overlooking something obvious?
Don Caldwell

Cogito, the last Little America's Cup C Class cat had assymetric daggerboards that they raised each time they tacked. Evidently it owrked, as Cogito beat Yellow Pages pretty easily.

http://old.sailingworld.com/guycogit.htm

I think the "obvious" maybe part of what you're not seeing; that is that how many boats do you think a builder would sell if the crew had to raise a board on every tack. Its hard enough to build a boat to sell much less add that extra work to sailing it properly not to mention how many times the boards would be rammed into the wrong hole by someone "who can handle it"...

There is demonstrated proof that Asym boards work better but ask your self how many catsaiors care??? Most are not serious racers and just want to sail with as little hassle as possible.

As far as demonstrated results among the average catsailor that races a couple of times a month that is unclear.

So for the general public that you are trying to build a market share with keep it simple...just look at the wave and Hobie 14 resurgance...

thom

There was an interesting discussion about it some time ago, so I posted a message there (with no content), bringing it back to the top of the line. Take a look - it's worth it.

The concept certainly works but its praticity for a beach cat is arguable. It seems that a symetrical blade with automatically adjustable angle of attack would work better. They use it in the 505 class (mono). There was a discussion about it, too (but I did not find it).

If you want to take advantage of the full capabilities of an asymetric daggerboard (better known as hydrofoil), it pays to incline it, so that it also lifts the boat reducing its wetted surface. The inclined asymetric daggerboard is called "Bruce Foil" or "surface piercing foil".

If you don't want to tack the foils, the easier solution is to put them in a tri and raise the amas a bit, so that when one foil is in the water the other is raised out of it. The resulting tri is either an Open 60 (hydrofoil lift around 10 to 20% of displacement) or a Catri (total foil lift around 90% displacement).

If you go for a total foil lift of 100% you will end up with Hydroptere - a totally airborne open 60 foiler. If you replace the Bruce Foils by totally submerged foils, you will end up with the Hobie Trifoiler or the Rave. The three of them use need mechanical controls to constantly adjust the angle of attack and maintain stability.

If you are curious about hydrofoils, visit www.foils.org.
If you want to know more about the other boats, it is easy to find directions to any of them through search engines.

Cheers,

For what it is worth.

I just came back from the Paris boat show and the new 16 ft Ventilo Zipo (said to be designed for the F16) has assymmetric daggerboards. The guy at the stand did advice to raise the one on luff when racing.

Here I some pictures of this new design and will post them shortly on a website. The Zipo has a new planing hull design and I have pictures of that too.

Wouter

Planing hulls? where is the planing surface located?

...and asymetric foils too! Quite a combination for a cat. Are the foils vertical or inclined?

Thanks,