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Foils for powerboats

Discussion in 'Technical Discussion' started by PacBlue, Nov 28, 2017.

  1. PacBlue

    PacBlue Senior Member

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    When will they arrive for powerboats? Some (very few) large yachts have tried stern foils, Navies have used them over time but have abandoned them in the modern era, and sailboat design has keyed into them, what about motoryachts?

    https://www.sailingworld.com/americas-cup-36-monohull-revealed

    http://www.jetfoiler.com/#intro

    I know there of a sportfish application giving them a try now, but who will be the first production powerboat builder to truly innovate their product like sailing has? Can you imagine the possibilities!
  2. Bill106

    Bill106 Senior Member

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    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!
  3. PacBlue

    PacBlue Senior Member

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    The great part about this forum - members with hands on experience of all crafts!

    In the '90s, Westport teamed with Boeing to do a fan-assisted (2 located on the upper deck) foiled passenger vessel that is now somewhere in Hawaii, do not know if it is running. It had a retractable bow and stern foil and looked pretty funky, I heard the crashes when it came off the foils was pretty spectacular.

    Another site that follows this stuff, looks like Yamaha has a small powerboat option (at one time):

    http://www.foils.org/library/bibliograpy/hydrofoils-around-the-world/

    The Russians seem to have the most interest commercially speaking.
  4. Pascal

    Pascal Senior Member

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    The answer is probably not to have the foils lift the boat out of the water but rather to lift the boat enough to reduce drag and increase speed. If you get just a foot or two of lift, drag decreases dramatically.

    If look at the new foiling monohulls (vendee globe) they are significantly faster even though they don't lift out of the water.

    Is it worth the added costs in a production boat? Maybe, maybe not
  5. rcrapps

    rcrapps Senior Member

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    A prime concern for interisland ferry systems in Hawaii is whale strikes.
    I remember the hype and concerns over this.

    Also East Coast US (FL) concerns.

    I can see Billy Bob in charge of a super SF, at speed, on foils asking: What whale???? Mother in-law on board????
  6. Bill106

    Bill106 Senior Member

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    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 :cool:

    Attached Files:

  7. PacBlue

    PacBlue Senior Member

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    I could envision the under 20' crowd getting it first. Lifting the entire hull out of the water with lower installed hp, some king of jet drive with the foils. Some creative genius just has to have the vision like the sailboat guys do, powerboat innovation is lagging behind.

    I think the hi-speed stability question can be addressed by the right foil area, and then that wake will be practically nothing! With the growing population of 70 -80mph CC Catamarans, I think the questions about operating at speed are already front and center.
  8. YachtForums

    YachtForums Publisher/Admin

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    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.
  9. PacBlue

    PacBlue Senior Member

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    Would be nice to see some of that 'trickle-down technology' make its way to the powerboat market, seems like most of the innovation in todays powerboat is in hull windows and fold-out terraces.
  10. bstet

    bstet New Member

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    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.
  11. PacBlue

    PacBlue Senior Member

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    So the 37m foiled powerboat is highlighted on yachtforums news feed. Now that's something to talk about, 50 - 60 knots, make those 30 - 40 knot motoryachts look like they are standing still, nice to see that innovation / concept!
  12. PacBlue

    PacBlue Senior Member

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    Unusual spray pattern off the transom/swimplatform, would not help those in the cockpit underway.
  13. CptnMaxwell

    CptnMaxwell New Member

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    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.
  14. MountainGuy

    MountainGuy Member

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  15. PacBlue

    PacBlue Senior Member

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    I think the ferry applications all point towards the fact that it is an easier solution to design for a specific load/speed requirement. Like the Russian Ferries, these are true foil applications where the entire hull is lifted above the water surface.

    The Technicraft link had a good read about their foil assisted design approach and highlighted the fact that the foils' angle of attack needs to be adjustable in order to be more useful over a wider range of speed. I imagine that the foil assist is only lifting the hull maybe 3" - 6", but even that incremental amount is enough to realize benefits in reduction of form drag and dynamic displacement/sinkage.
  16. Capt J

    Capt J Senior Member

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    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.
  17. Lepke

    Lepke Member

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    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.

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