Foils for powerboats

I built a little 10' foil hull many moons ago playing with the idea and I managed to get it working after a lot of trial and error. I feel it was only because of it's small size that I was able to make it work though. I ended up building a hand cranked rack and pinion type mounting system for the foils I could crank down after launching from the trailer, and a primitive (it was in the late 70's!) jackplate to lower the outboard as she built speed and got on the foils. Draft concerns come into play when you get into the bigger sportfish and motoryacht segment, at least on the east coast of the US and the Caribbean 6' draft is considered maximum for most popular destinations. Retractable foils would still be feasible but the problem is moving the driveline down with the big inboards, U-joints or flex cable driveshafts that can handle 2-3000 hp in constant saltwater immersion have yet to be developed (to my knowledge). I've also toyed with the idea of using hydraulics off the main engines and burying rotary motors in the foil to turn the props but the losses are so great (20%) you're almost defeating the purpose.

It may be possible to use retractable foils and a fixed driveline with surface piercing props but then you have other issues to deal with. A surface prop capable of pushing a big heavy boat when flying on the foils will have way too much pitch to ever get her up in the first place. Two speed gear boxes might be the answer to that but there's a LOT of R&D to be done to determine if it's even feasible. Most clients don't want to spend that kind of money on a maybe! That sportfish experiment you mentioned is actually sitting about 200' away from my desk right now, you can be sure it's being watched very hawkishly!

That is a big question Pascal but most sportfish on plane are already running on about 1/3 of their bottom surface already, I can see stability issues starting to crop up with much less (and I am always trying to get them lighter and faster!).

I've never gone by Billy rcrapps

In the 1980's, I worked for a defense contractor that built insertion vessels for special operations forces. We built a variety of high-speed platforms with protocols for stability at speed, low wake signatures and silent operation. Much of our original development work was conducted in flow channels with proof of concept models. The Naval Surface Warfare Center maintains an extensive archive of data on foil assisted craft. Active foils and propulsion systems are an area of specific interest.

It's been done on a 42', the Stealth 42 built in South Africa.

The boat was a demo boat with 350hp? Yanmars, and just didn't perform, they had trouble selling it. A guy in Naples bought it and had it re-powered with 450hp Yanmars and it got up nicely and would go 50 mph. If you throttled back it would stay up on foil at about 35 mph.

That catamaran would be considered foil assist where the foil is used for gaining smoother riding and some speed. Not designed to lift the vessel out of the water though.

Teknicraft in NZ design some along these lines and have had a lot of success in a ferry and commercial/military application. A good example is here - http://teknicraft.com/showcase/clipper-v
Finding the information on what they do is a little harder with a lot of browsing of the links on the site required.

I think for a sportsfisher application, foil assist is a better compromise, but just getting there fast is only half the battle. With the fish pulling ability of engine/hull/speed combinations being continually debated, a jet based catamaran with foil assist would be a hard sell until it has been proven to "pull" fish.

What is about the ferries used in Greece? http://www.aegeanflyingdolphins.gr/ They are used everyday for years...

The hydrofoil ferry in Hawaii was a gigant BUST. What happened with it, was when it was really rough the wave would hit the HULL bottom and everyone flew around the ferry, but then it fell off of plane on the hydrofoil and they couldn't get it back up on plane/back on the hydrofoil again in rough water. So they couldn't run on rough days.

If the hydrofoil doesn't get the vessel high enough out of the water, then every wave that hits the hull bottom can be either like going over speed bumps at 30 mph, or hitting a guard rail at 30 mph.......same with the fast catamaran yachts when the water exceeds the height of the tunnel space between the hulls.

I knew a crewman on one of the navy experimental boats. Debris in the water is a big issue. Many repairs that never made the news. One of the boats minus the foils was in Astoria, Oregon for years. Now it's half sunk in the Columbia River across from Astoria.

Well, technology has finally evolved and a solution to the issue of power transfer at varying ride heights appears to have been worked out, at least in smaller tender size boats. I don't know anything about this company but unless it's an early April fools joke, they seem to have made it work with electric drives (never saw that coming!) using two 320 hp. diesels for gensets. I wonder if I can talk them into selling a set of those drives, I'd love to try that concept on one of my hulls! Any YF members have an inside track?

https://foiler.com


Hope the link is OK Carl!

No worries! Links to innovation are encouraged.