# thoughts on lack of hydrofoiled cats?

Discussion in 'Multihulls' started by ijason, Jan 23, 2009.

1. ### FrostyPrevious Member

Ive book marked that Doug --thank you, and i think you got it ,--- the 63412,---looks about right for what I want but it will have to be a flat botton to it because of the materials I intend to use.

Incidentaly I am awful at maths but anyone know what lift a foil such as this would produce if I made this foil out of two peices of 1 inch ply glued together and shaped.

The winglet would be 4 feet long and a chord of 2 feet, at say 15kts?

Using 2 of these "winglets" one on each side I would think 500Kg each uplift would be sufficient to get some increase in performance and lessen wetted area.

Do you think this about right?

2. ### FrostyPrevious Member

Is there no young mathamaticians could help me out here?

I did forget to mention that the angle of attack on take off would be about 7 degrees and I would think level off to about 3.

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### Ad HocNaval Architect

Frosty
If you can get a graph of the foil profile, which has the lift/drag data, then i could assist. I cannot find my Abbot-VonD 'Theory of Wing Sections' book, which has all those sections.

4. ### Guest62110524Previous Member

bladerunner boats in NZ

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### PortTackerJunior Member

Just idle thoughts from a practical standpoint.
I don't believe a foiler for cruising is likely effective solution. Certainly not "economical."
It might be more fuel effecient at speed than a conventional hull, but it still takes a lot of fuel to go fast - there is no way around that. I doubt I'd want to make a passage at 4x the speed using 20x the fuel, beside the weight-size-power-weight-size-power spiral you'd get into the carry all that fuel. So if you are contemplating a powerful fuel-hungry vessel, you might see some fuel savings with foils, or more speed for the same fuel, but you are not going to see high speed and sipping fuel at the same time.
Then there's reliability - hit one sunfish (the fish or the boat...) and end of game. I like things that don't break easily, or at least still work fine when bent.

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### ijasonJunior Member

@porttracker. ha! 'work well when bent' is a very good goal. i am admittedly not familiar with the functionality of foils... beyond the lay-understanding that once the craft is in flight the amount of drag from the water is substantially reduced - and i then deduced that perhaps once you spent the fuel to get up to speed to flight, you could then run along at a higher speed very economically due to the much reduced drag.

perhaps not!

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### robhercDesigner/Hobbyist

Actually, there are several of us who are working on improving the efficiency of displacement hulls by using smaller foils to support only PART of the boat's weight. Supporting ANY of a boat's weight on foils can reduce the displacement (and, thus, the wetted surface) of your hull, thereby reducing overall drag & improving efficiency. You don't have to "fly" your boat to realize efficiency gains from foils.
On the other hand, though, all foils are a bit less durable than a good hull, so I guess reliability is a trade-off here, as is cost.

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