Curved Lifting Foils on Cruising Cats??

[Doug Lord]

Why not?
From "Foilers!" and Catana: http://www.catana.com/index.html.en

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click on image:

[masalai]

Hi Doug Lord,
Always on the leading edge, which is admirable, but on Cruising cats? Is it necessary there as most cruising is to go look at everything as there is no real hurry... Racing boats? Well that is where that technology should be applied... I do not put racing slicks on my 'town-ride', nor do I supercharge AND turbo-charge the engines on my saildrives...

[Doug Lord]

Originally Posted by masalai

Hi Doug Lord,
Always on the leading edge, which is admirable, but on Cruising cats? Is it necessary there as most cruising is to go look at everything as there is no real hurry... Racing boats? Well that is where that technology should be applied... I do not put racing slicks on my 'town-ride', nor do I supercharge AND turbo-charge the engines on my saildrives...

======
Masalai, I discovered this accidently when checking out one of my favorite sites. I guess there must be people with different definitions of "cruising". It probably would not have occured to me to do this but then again I don't know why not. Some people like to cruise in leadbellies, some like to cruise in multies. The more I think about it it may not be such a bad idea-IF it actually has any practical benefit-like increased speed etc-which I'm not convinced of.
It is interesting, though-at least to me-but I'm still unconvinced.....

[masalai]

Hi Doug,
I too fail to see the merit in this "go-fast-gear" as in cruising mode, I probably will not have the 'deck-apes' available to constantly keep up with the tweaking and adjusting to maximise VMG... Besides I would rather move quietly and stress free to enjoy the journey or appreciate the view as I pass...

My recent cruise was a solo run of 450 N. Miles out to Sth Percy Island and then back under power (twin 20hp diesel engines) which give a maximum speed of about 7.1knots... Going up I got up to 19 knots by surfing the waves... Coming back, to avoid the seas and headwinds, I snuck close along the shoreline at 4 to 5 knots... With a lot of fancy go-fast gear, I would have missed out on the best part of the trip...

[waikikin]

I think there may be advantage beyond some possible performance in that the boards might intrude a little less to interior & unlike some straight canted boards, when in the "up" position might not hang out past the line of the hull/rubrail. Regards from Jeff

[daiquiri]

Originally Posted by waikikin

I think there may be advantage beyond some possible performance in that the boards might intrude a little less to interior & unlike some straight canted boards, when in the "up" position might not hang out past the line of the hull/rubrail. Regards from Jeff

Good point. If the outer hull walls at the station where foils are located have roughly semi-circular section shape, then foils could run along outer walls with minimal impact on interior living space. Nice example of how the actual reason for a shape of an object can be hidden beyond what appears to be the most obvious one.
Cheers!

[Doug Lord]

If there is extra speed as a result of these foils that would be good for some people but there are also likely to be handling benefits reducing any tendency the hull has to bury, damping the boats motion in "heave", perhaps damping pitch. These are things that have been noticed on beach cats with curved foils.
One of the main benefits of curved lifting foils vs,say, straight angled foils is adjustability: the angle of incidence of the lifting portion of the foil can be adjusted w/o affecting lateral resistance and the "lift" portion of the foil can be reduced w/o affecting lateral resistance.
But I'm not sure that anybody cruising on the Catana 59 is going to fool with that-unless, of course, they're racing a Gunboat....

[Hussong]

Originally Posted by masalai

Cruising cats? ...Is it necessary there as most cruising is to go look at everything as there is no real hurry... Racing boats? Well that is where that technology should be applied... I do not put racing slicks on my 'town-ride', nor do I supercharge AND turbo-charge the engines on my saildrives...

On target analysis for the question posed by this thread.

What happens to a cruiser with foils of this type when he pulls into the harbor in Zanzibar with one foil broken off? Does he go to the local boatyard to have one built, or is it a monumental expense to buy one out of the factory and have it flown in?

There could be angry owners and plunging sales of the design until they go back to boards that can be fabricated just about anywhere.

[masalai]

Hi Hussong,
I just got in, thinking of expressing concerns that the one-off builder, like myself would have great difficulty in building the centreboard case and a smooth moving (especially when the board is working) of the inserted board.
Alignment would need critical and very careful alignment and positioning, think cantered slightly aft would cause the hull to dip when fully extended ... cantered slightly forward, expect additional lift... and slightly misaligned to the fore/aft line of the hulls ? erk.... - - - - Imagine shoaling waters and the urgent need to lift the boards - Oooops too late...

On that, you have the punch line....

On target analysis for the question posed by this thread.

What happens to a cruiser with foils of this type when he pulls into the harbor in Zanzibar with one foil broken off? Does he go to the local boatyard to have one built, or is it a monumental expense to buy one out of the factory and have it flown in?

There could be angry owners and plunging sales of the design until they go back to boards that can be fabricated just about anywhere.

The world needs more open-&-analytical-minds...

[waikikin]

Originally Posted by Hussong

On target analysis for the question posed by this thread.

What happens to a cruiser with foils of this type when he pulls into the harbor in Zanzibar with one foil broken off? Does he go to the local boatyard to have one built, or is it a monumental expense to buy one out of the factory and have it flown in?

There could be angry owners and plunging sales of the design until they go back to boards that can be fabricated just about anywhere.

Of couse it is possible to break a board, in another light that gives someone something to do in repairing or replacing it. These vessels are quite expensive to start with & when comparing the costs of repacement parts possibly small change(not to me!) to the owner of such a vessel if they can truly afford one. I'm sure that during purchase negotiations a spare could sweeten the deal if its an issue. All the best from Jeff.

[Steve W]

Cruisers with multis tend to like the shoal draft aspect and damage to a board is not uncommon, i would think that lifting foils would be difficult and expensive to replace (especially in Zanzibar as Hussong pointed out). I favor symetrical constant chord boards which are interchangable from port to stbd and realativly easy and inexpensive to replace anywhere.
Steve.

[Doug Lord]

There is no reason a constant chord symmetrical or asymetrical curved board couldn't be interchangeable side to side.....

[Steve W]

I dont know much about the curved foils at all but it seems to me that in order to be interchangable from side to side they would need to be A/ perfectly semi circular and B/ both ends would need to be finished the same and C/ it wouldnt be able to have any form of recesses in the board itself for lifting tackle as the board would need to be able to be inserted upside down to use on the opposite hull, you cant just turn it around as you would have the trailing edge forward.
Steve.

[Doug Lord]

Those are fairly simple requirements easily achieved. The board won't move unless the trunk is part of a circle unless it has a super complex trunk which some small boats have. For a cruising application( where you probably don't need them in the first place) seems like a piece of cake to make them interchangeable.

[Steve W]

As long as you are raising and lowering them manually i agree.
Steve.