Low HP Foils

Discussion in 'Hydrodynamics and Aerodynamics' started by jesdreamer, Dec 22, 2015.

  1. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    The book I suggested earlier-and about a week of your time-would save you time and money.......
    Merry Christmas!
     
  2. jesdreamer
    Joined: Jan 2013
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    Location: Alabama

    jesdreamer Junior Member

    basic book on foiling

    Thanks Doug -- I plan to get the book asap --
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Your 12' boat situation doesn't seem conducive to foiling on low power. You're just too heavy and don't have enough power. You can reprop your brains out, but you have to get to foiling speed, which simply is a power to weight ratio thing. I have a fair bit of experience with foiling in semi and low plane speed modes and weight is absolutely critical, with restricted power arrangements.
     
  4. ch3oh
    Joined: Mar 2015
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    Location: fin

    ch3oh Junior Member

    This puppy is shipping in May. I think the foils might have a nice L/D ratio.

    Battery weight could be 69.4kg@150Wh/kg (guessing LiFePO4). A watercooled electric ~5kW OB weights 38.5kg (Elco EP-7). Foils might weight 40kg as they must be really thin and carry huge loads. Add 2 ~75 kg light adults and 100kg dry weight sans driveline, totalling 397.9 kg or 3.903 kN of lift.

    It's a 2-seater, so in order to make any sense it should hit 65% of it's max range of 100km with 2-up, hopefully foiling nicely at maybe 10 knots. Total electric efficiency could be like 68% (including OB final drive loss) and battery discharge 90%. So that's 3.5 hours of sunshine at 1.82 shaft kW, with a nice 75% eff. prop it's more like 1.36 kW. @10kt it's 264.4 N of drag. Let's say 70N of that is from OB foot, uprights and aero that's not associated with generating lift

    Adds up to L/D of 20.1, that's nice for relatively small AR. I hope santa brings me one. They used to advertise charging time on 110v too, but I guess they found out no u.s. marina had 120A fuses.
     
  5. markula78
    Joined: Jun 2016
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    Location: Norway

    markula78 New Member

    Hi

    I have worked some time with electric powered 2 person kayak. So adding foils to my corrent setup will work. But how to build it afordable.

    I started with and 1,3kW 12V side thruster to a 30" boat with 110mm prop diameter and 20kg of power. Got around 6,1 knot. But a lot of added drag, is and old brushed motor. And had just 0.42% efficiency.

    So now i use 40mm x 80mm brushless inrunner 3KW <0.85%(30-50kg), 1:16 planetary gearbox 0,95% 2 step and 185mm 5 blade prop.

    I get around 50kg of static thrust with 1kW of power. So out on the prop shaft is around 700W of power.

    But is this video that gave me a lot of data. But in my prospective, a good design hydrofoil.
    https://www.youtube.com/watch?v=1ubt1IZZIx8

    In 2:30 you se a large RC aircraft propeller. (Larger propeller diameter, with less pitch will give more efficiency). I will try to change mine 5 blade 185mm propeller to maybe 4 or 6 blade RC propelller.

    in 2:40 foils with 90Kg at 7,5 mph with 235W of power.

    Mine kayak is 60kg with litium battery and motor, and 70kg x2 = 200kg around 500W of power. So even if i just get a fraction of this resultants is great.

    But i have little knowledge of foil design. Maybe 2x T foils from alminium. Weld a frame from tubes, and clot in fiberglass and gelcoat to get a nice surface.
     

    Attached Files:

  6. serow
    Joined: Mar 2016
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    Location: UK

    serow Junior Member

    Are you describing a canoe?
     

  7. markula78
    Joined: Jun 2016
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Norway

    markula78 New Member

    Foiling Electric Kayak

    I am now make 2- T foils in glass fiber.

    Arial around 0,28m^2.
    19cm wide, and 1,55m Long.

    Made a wing from foam, clot it in 7-20 layers of glass fiber. Around 12kg of eatch foil.

    Estemated lift 100kg at 7 knots.

    Hope to test it in end of next week.
     

    Attached Files:

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