Propulsion and Foil Design for Hydrofoil

Discussion in 'Hybrid' started by Vanlaure, Dec 21, 2013.

  1. Vanlaure
    Joined: Dec 2013
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    Vanlaure New Member

    I am very new at this so forgive my ignorance. I am looking for help in two areas: (1) formula(s) to help me calculate the size of 2 electric DC motors needed to lift a maximum of 70 tons at 50 knots on plane, and (2) the formula(s) to determine the dimensions of the hydrofoils for this same craft. I am looking at a hydrofoil that is 40' long and 16' wide flat bottom barge-like craft. I plan to use fully submerged hydrofoils with a self-stabilizing foil solution. The bow foil is an inverted T type single beam and the stern foil is an inverted double beam T type foil with the two electric motors directly mounted to the foil. Any help would be greatly appreciated.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    70 tons is massive for any 40 foot boat, let alone one going 50 knots, the power requirements of your prospective vessel may need to include gas turbines !
     
  3. daiquiri
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    daiquiri Engineering and Design

    Not even gas turbines would suffice here, I am affraid. The weight and dimensions of this boat simply preclude planing or hydrofoiling as a technical choice.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I'm sure if the govt handed over a couple of billion a contractor could find a solution. :p In any event, even if the scale and ambition of it were to be adjusted somewhat, it would still be a multi-million dollar project, and the basic feasibility, technically speaking, would have first to be established before worrying about details. It is more than likely just a pipe dream even if he has millions to throw at it.
     
  5. Vanlaure
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    Vanlaure New Member

    Boy that hurt. So, I know I can move approximately 70 tons in an LCM type craft, but what I take you all are saying is that I cannot get it on plan? What weight might be more reasonable given similar dimensions?
     
  6. CDK
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    CDK retired engineer

    7 tons instead of 70 would be more realistic, or a hull length of 120 ft instead of 40 to achieve planing speed. Not with electric propulsion of course, the weight of batteries and electric motors are prohibitive even if the distance to cover would be less than a mile.

    Anyhow, the 40x16= 640 sq.ft. is way too small to lift 70 tons. Pulling an elephant on water skis seems easier to me.
     

  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Maybe you can move 70 tons in an LCM-8, but the best you can do is displacement speeds (12 knots, lightly loaded, considerable less full up).

    A project like this will require a considerable amount of professional help. Simply put, your requirements currently aren't realistic, though addressing and achieving SOR goals are possible, but again, you'll need some expertise with this.

    What is your design budget and time frame for this project? Assuming you've looked into the costs associated with 70 ton, high speed, high tech vessel builds, design costs would be a very small percentage of the total project outlay.

    Having the mind's eye that I do, a picture of T foil for a 50 knot, 70 ton craft s just astounding, but hey, with enough research, testing and naturally, money . . .

    The Pegasus class (PHM-1) got up to 50 knots (I think), but these where considerably heavier and larger, with 18,000 or so HP. Maybe you should look into the Tucumcari class (PGH-2), which was considerably smaller (around 70' if memory serves) and the USS Flagstaff (PGH-1). None of the PGH's have survived and only two PHM's have survived.
     
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