Curved Lifting Foils on Cruising Cats??

[Hussong]

I think that you are right, Steve. The process of lifting a board out of its trunk by hand limits the discussion to the cruising boats that are small enough to allow such an effort. Big boats have big boards and the attachments for lifting that board become the design as much as is the foil in the water. Offering a single spare board for bigger boats requires that the lifting points be completely integrated in the design, that the fixtures not interfere with the immersed hydrodynamics and the design puts a decent skill set requirement on the person effecting the repair. I think it might be difficult to find that guy in Zanzibar.

It seems that the application requires a lot of specialized solutions compared to the typical straight board answer. It also seems that the benefit does not make a lot of sense compared to the assumed potential problems.

[Doug Lord]

Originally Posted by Hussong

I think that you are right, Steve. The process of lifting a board out of its trunk by hand limits the discussion to the cruising boats that are small enough to allow such an effort. Big boats have big boards and the attachments for lifting that board become the design as much as is the foil in the water. Offering a single spare board for bigger boats requires that the lifting points be completely integrated in the design, that the fixtures not interfere with the immersed hydrodynamics and the design puts a decent skill set requirement on the person effecting the repair. I think it might be difficult to find that guy in Zanzibar.

It seems that the application requires a lot of specialized solutions compared to the typical straight board answer. It also seems that the benefit does not make a lot of sense compared to the assumed potential problems.

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I see no reason why a constant chord symmetrical or asymetrical curved board can't be designed to be used on either side of the boat regardless of the method of moving the board. Especially a board on a "cruising" boat.
However, based on the information provided about the Catana 59 I'm very skeptical that curved foils will provide any substantial benefit like they do on race boats. We'll see....

Interesting comparisons:

The Catana is 11% heavier than the Gunboat at light displacement and the Gunboat has a reputation for speed.

Gunboat 66 racer/cruiser
--light displacement=34,000lb
--Upwind SA- 2232 sq.ft.
--Downwind- 2583 sq.ft.
=======
Catana 59 racer*/ cruiser
--light displacement=37,800lb
--Upwind SA- 2120 sq.ft.
--Downwind- 2583 sq. ft.

From the Catana website:

*All this has culminated in the new Catana 59. A Catana with incredibly streamlined hulls, classically elegant, and offering astounding performance. The sail plan is borrowed from racing vessels, with a short mainsail that is easy to manage and a larger foresail. Moving away from the legendary daggerboards that made the Catana shipyard's name, this catamaran is fitted with revolutionary curved daggerboards, to create a hydrofoil effect. The result is an extremely safe and comfortable boat that achieves astonishing acceleration and an extraordinary cruising speed.

[oldsailor7]

Perhaps I'm just a retrograde old sailor. But for cruising multihulls, what is wrong with fixed low aspect ratio keels. They have many other advantages than just preventing leeway.

[Hussong]

I like that you can sail in thinner water, that you can let the tide go out and sit on the keels and that you don't have to worry about a trunk getting mashed from a grounding, but don't they also have a collection of problems, as well?

[oldsailor7]

All leeway preventing devices have their good and bad points.
I scrapped the dagger board on my Piver Nugget to get space for a fold down double berth. I replaced it with twin surface piercing boards pivoting down from sleeve boxes at the folding deck joint. They proved to be a real pain.
I subsequently removed them and fitted a Norm Cross style LAR keel.
It transformed the boat.
I armoured the leading edge and bottom of the keel with Half round metal strip and had no problems with grounding. We used to sail it straight up the pebble beach on Fox island and tie up to a tree for the night.