Stepped Hulls

Could two SMALL foils be fitted between the outside sponsons and central hull of a trihull vortex design to achieve the same results with the consequently reduced risk of fouling ropes and floats, while still gaining the reduced wetted area - fuel speed gains?

And in addition - would it still heel into corners if you can't the outboards?

C'mon - someone out there must know!!!

Cheers!

[Tom Lathrop]

Ya got me Trouty. I'm still a bit amazed at the speed increase claims for the retrofitted foils. Sure, they can reduce wetted surface some, but can they make that much difference? In addition, the foils will be heavily loaded and generate more drag per unit area than the hull bottom. I guess I'm skeptical.

[yipster]

hydrofoil supported catamaran

someone out there must know

I am sure of that, but not many, and only hope to see more reactions, for -like stepped hulls- this is the better powerboaters stuff.

here my 2 cents of thoughts:

I take it that you mean 2 smaller (shorter?) one side mounted foils bended more backwards to slide trough debris? Guess smaller foils may result in other profiles and surface dimensions, giving other lift and drag sums. The vertical reinforcement struth in the pictured hysucat also explains that shorter and one sided framed foils would need more strenght and support as Tom said.

Seperate smaller foils mounted on the same location may ventilate, miss the deeper going centerpart and -even with the canted outboards i like- may not give good heeling?
The pictured hysufoil is allready so shallow it made me wonder about remaining wave and wsa on the hull versus performance gain.

Autowing (working demo) program at http://www.argo-group.de/service/downloads.php that can be used for foil lift calculations.

yipster
some more foil info at: http://www.aae.uiuc.edu/cetan/hydrofoils.html
http://lancet.mit.edu/decavitator/Basics.html

[yipster]

furthermore i remember the wings you could bolt on the drives ventilation plates... no good, they break all said but somehow that way you would get trimmable stern foils.

[yipster]

in PBB magazine #88 an article on the john plum series of stable and efficient stepped hulls.
page 94 shows a design from the author on a V hydrofoil stern stabiliser.
interesting!

[FRANKIEFRANKIE]

Wetted Surface is means nothing in stability. The first thing to look at is angle of attack. Foils are an unnecessary appendage with the right engineered bottom. We just went through this with a customer that was convienced his cat needed foils to increase speed. It did nothing. Why do we keep adding to a problem instead of fixing what we have? Engineer your hull by an engineer with expertise in your boat type. Do not go to a sail boat designer to build a speed boat. Go to people who have tested all hulls and appendages via towing models. Ask them questions. One day these people will be gone and we will think that all that information we have to program computors with came from the computor.

Just my two cents.

Happy boating, Frankie

[Davor]

Try KAFALI method for stepped and stepless hulls.

rgds

Davor

[FRANKIEFRANKIE]

Not familiar with the term but if you mean constant section and straight you are right.

[Frans X L]

My colleque and I have done a few boats using Dr Hoppe's foil system and they definitely work.
You do have to do a costing as to what is cheaper. ie designing and installing a foil system or simply buying bigger outboard engines.

here is Dr Hoppe's own web site:

http://www.hydrofoildesign.com/Default.asp?Page=Home