Hydrofoil boat design.

Discussion in 'Hydrodynamics and Aerodynamics' started by lassjus, Jan 21, 2013.

  1. lassjus
    Joined: Jan 2013
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    Location: Oslo

    lassjus Junior Member

    Hehe,, Sorry, I understood it now. Not magic really, just something that is forced to the surface that controls the tilt of the foil. I like the Yamaha one, but in that case you would have to reverse the lift of the lever, right, cause it is going backwards instead of forward? It would lift the other way than the way you want the foil to go. If I am thinking right here.
  2. Number4

    Number4 Previous Member

    You are on the right track lassjus,
    Aircraft with elevators at the front are called canards (french for duck), most of the aircraft you will have seen have a tail elevator.
    Kotaro Horiuchi, as Doug says is a guru on foils.
    Lots of his stuff on youtube, lots of hydrofoils.
    Also check out L'Hydroptere, and the new Americas Cup boats, plenty of good stuff here in the multi hull section.
  3. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Power Foilers

    Here is the system used on the Rave, Osprey, Skat and F3 foilers. It uses a "wand" surface sensor to move a flap on the main foil port and stb.
    Wands are used on most , but not all small sailing foilers, especially including the Moth and R Class. They may have some application in power foilers. I think I remember that the forward foil on the Yamaha had a real small wand....

  4. Submarine Tom

    Submarine Tom Previous Member

    Balance is critical.

    Yes, linking steering to banking or leaning or roll is brilliant.


    Have you seen the Dutch canal solar boat races on YouTube?

    One of them shows an interesting yaw/roll controller in the "pod" where the wing and strut meet.
  5. neo1988
    Joined: Jan 2013
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    Location: CANADA

    neo1988 New Member

    The biggest issue is Weight. Generally speaking aluminum is lighter than fiberglass. This is a consideration for fish-ability, ride, and "hidden costs". Another thing you have to consider is "How are you going to get it to the water"? You could pull a aluminum boat with a 4 or a 6 cylinder...
  6. Submarine Tom

    Submarine Tom Previous Member

    How much weight and how much power are we talking about here?
  7. El_Guero

    El_Guero Previous Member

    OK, use the plans you have to build your first boat.

    You are in a 'hurry'. So, time spent trying to understand what you are doing is really a little wasted.

    But, a simple overview.

    Hydrofoils are not the same as aircraft. That would be like saying aircraft are the same as spacecraft. IMHO.

    The self-leveling hydrofoils are MUCH simper to work with until you have the experience to go to the next level.

    Written differently, until you understand how simpler hydrofoils work, the more advanced forms will be a bit much.

    Here is a great resource: http://www.foils.org/upright.htm

    Keep us updated.

    And let us know when you hit something in the water ....

  8. tspeer
    Joined: Feb 2002
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    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    I think you are misunderstanding some key points about the Stevenson Sportfoil. Stability is essential in designing a hydrofoil and the stability comes from the interaction of the foil and the boat's dynamics. Some of the interactions may not be intuitive.

    Do you notice how the dihedral angle of the front foil is greater than the dihedral angle of the rear foil? This is important for the heave (vertical) stability of the boat. If it weren't for the need for roll stability, the rear foil could be fully submerged. But using a T foil up front, with no feedback control system, would give the boat unstable coupling between pitch and heave.

    The dihedral of the rear foil does not cost very much in terms of lift. Calculate the cosine of the dihedral angle, and you'll see what I mean. But the dihedral will keep the boat from rolling over when going straight and will make it bank into a turn instead of falling over toward the outside of a turn.

    Some basic criteria you need to build into your boat include:
    - The forward foil must be more heavily loaded (lift per unit area) than the rear foil for pitch stability. When the boat assumes a more bow up attitude than its trimmed equilibrium attitude, there needs to be a net bow-down change in the pitching moment.
    - The forward foil must be more sensitive to a change in flying height than the rear foil for stable pitch-heave coupling. When the boat flies higher than its trimmed equilibrium flying height, there needs to be a net loss of lift from the foils and a net bow-down change in the pitching moment.
    - When the boat yaws from its trimmed equilibrium attitude, there needs to be a net change in yawing moment in the opposite direction.
    - When the boat develops a sideslip (leeway) angle, there needs to be a net change in the rolling moment that is in the opposite direction from the sideslip.

    I think you should make the Stevenson design as drawn, and then experiment with different foil configurations after you've gained some experience with foilborne operation. The hull may not be sexy, but it's easily built, has a low center of gravity, and the foil configuration is proven. After all, the point is to get up on foils, and then the hull doesn't matter very much. Once you're flying successfully, you'll have a much better idea of where you want to make changes.
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