l'hydroptere.ch

Discussion in 'Multihulls' started by DennisRB, Oct 11, 2010.

  1. DennisRB
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    DennisRB Senior Member

  2. pogo
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    pogo ingenious dilletante

    That is the ideal solution, hardly to reach.
    For this reason stepped hulls have either flat wide aft sections for stabilizing and/or inverted T-foils for stabilizing. Sometimes both like l`hydroptere.ch.
    See wide transom on starboard hull:
    http://www.martin-raget.com/09-10-2...optere-CH--1ere-sortie,fr,ipf1658p160n73.html
    See inverted T-foil for stabilizing and controling angle of attack of mainfoil and/or forward sections:
    http://www.martin-raget.com/09-10-2...optere-CH--1ere-sortie,fr,ipf1658p160n18.html
    See l`Hydraplaneur ,planing on bow sections but still stabilized most of the time by aft sections:
    http://www.youtube.com/watch?v=AY0ssDA70gY

    pogo
     
  3. Doug Lord
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    Doug Lord Flight Ready

    It's obvious in the picture below that the widest part of the bottom is at the step-the hull drastically tapers as it goes aft. This type of stepped planing hull is stabilized in pitch with the rudder t-foils.
    I'm still skeptical of a hydrofoil catamaran with proportional beam narrower than Hydroptere and that uses four foils and four surface piercing foils-two fully submerged lifting foils on the rudders,two vertical surface piercing foils for the rudders and two surface piercing lifting main foils. That configuration
    has been slow on many different variations of hydrofoil cat. Hopefully, these guys have got it figured out.
    And another remarkable thing about this boat that I mentioned earlier: it is one of the only full size catamarans I've ever seen with an almost square configuration. Like everything about this boat: very interesting!

    click on image:
     

    Attached Files:

  4. Doug Lord
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    Doug Lord Flight Ready

    -----------------
    Dennis, I have a hunch that this boat could plane with or without the steps being deployed. I would think in lighter air they might sail with no steps deployed like(I'm guessing) in your picture. It would be a matter of testing and design when to deploy the steps and I'd think it would be in more wind like in 0040 when it is clear that the windward step is deployed. I'd think the steps would be deployed when the boat can just fly a hull.... and that the increased speed and drag reduction would then lead to deploying the foils at a certain speed "marker"-perhaps during a tack with the steps left down.
     
  5. pogo
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    pogo ingenious dilletante

    No.
    Not always.
    Planing in it`s designed speed-envelope a stepped hull is stabilized by it aft- sections touching the water.

    Relying only on the inverted T-foil for stabilizing,
    the aft sections would run out very narrow for less wetted surface/less drag.

    Furthermore a stepped hull planes with little bow-up attitude, limited (stabilized) by the flat aft sectins touching the water.
    Generating this bow-up attitude only with an inverted T-foil rudder means negative lift , which is contraproduktive.

    U see, for certain speeds one needs no inverted T-rudder but flat aft sections
    and
    sometimes u even need no step for having the fastest planing boat.

    pogo
     
  6. pogo
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    pogo ingenious dilletante


    Ääh...how many foils ?:confused:
    I´ve counted 14.:cool:

    pogo
     
  7. Gary Baigent
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    Gary Baigent Senior Member

    Alain Thebault looks happy - but I would be concerned; the boat looks just plain heavy (what is its weight?) in the light airs and is dragging lots of ****, transoms, bow down (the twist is to be expected) - this boat is not going to be a light air flier, like most cats because the hulls are sticky in design, sharp angles and flat areas. Early days but the boat looks wrong; they'd have been better off doing an extrapolation of the tri Hydroptere configuration. Just imho of course. But I'll eat my words if in a breeze the boat climbs out and flies.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Hydroptere.ch

    Here is 0040:

    Picture from SA-taken by Giles Martin-Raget:
     

    Attached Files:

  9. P Flados
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    P Flados Senior Member

    Although the performance is probably defined by the outer hulls and the overall dimensions, the presence of a center hull in the water while at rest probably makes the craft officially a trimaran. However, given that this is project is all about a "flexible platform for prototype testing", I am sure that it could easily be made into a Cat if desired.
     
    Last edited: Oct 11, 2010
  10. Doug Lord
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    Doug Lord Flight Ready

    ====================
    The Hydroptere.ch people describe it as a catamaran.....
     
  11. P Flados
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    P Flados Senior Member

    I understand that some people think the call "their boat" what ever they want. However, I believe I learned to count past two before first grade. It may be a test platform the behaves like a cat, but trying to get around basic standards for boat designations just messes people up.

    Trimarans have all kinds of center hulls, big, small, wide or skinny. If it is in the water at rest and displaces water, it is a hull. Just because this one is kind of small and does not extend very far back does not make it go away.

    Again, it turns into a cat by substituting an “above the water structural beam”. I seem to remember one of these on a some large expensive boat sailing out of Valencia for a few days earlier this year.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    ==================
    I still have a hard time believing that they actually want that pod to touch the water. It sure does but I can't see any good reason for it....
    ---
    It just occured to me: they have a single daggerboard that goes thru the pod-maybe they think it will have less chance of ventilation if the pod is slightly immersed in pre-foil conditions?
     
  13. pogo
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    pogo ingenious dilletante

    Blödsinn !!

    pogo
     
  14. Cheesy
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    Cheesy Senior Member

    I doubt that, in the conditions that the centre hull is in the water there will be very little chance of ventilation on the centre board.... low speed low power. I was going to comment that it looks like a tri as well but was beaten to it.
     

  15. Doug Lord
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    Doug Lord Flight Ready

    ==============
    You're probably right....
     
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