Airboat with Horizontal Fan

Discussion in 'Projects & Proposals' started by tom kane, Nov 2, 2010.

  1. Jeremy Harris
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    Jeremy Harris Senior Member

    If you're persistent enough you can make darned-near anything work, but the real question is: "will it work efficiently?"

    Water jets are a good example. They work and are a good solution for a propulsion system where a propeller would be impractical or a hazard. Are they efficient in terms of converting fuel into motive force? Not really, a decent, properly matched, prop will usually beat a water jet in terms of propulsive efficiency over a broad range of operating conditions.

    The same is true of fans and propellers moving air. Ducted fans can have a high efficiency over a limited range of operating conditions, but generally a propeller will be more efficient overall.

    With dwindling fuel resources and increased fuel prices optimising efficiency seems pretty important, so deliberately going for an propulsion arrangement that, by its very nature is going to have poor efficiency seems to be a step in the wrong direction.
     
  2. tom kane
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    tom kane Senior Member

    Now there are the facts,I agree, except that dwindling fuel resources bit.May be oil fuels but the whole Universe is a mighty fuel resource so don`t worry. I don`t think that jumpjet fighters and all of the other craft that change the direction of their airflow to work can be very efficient so I am not going against convention. I most always carried a mast and sail in my boat for taking short cuts over shallows and for emergencies but that is not efficient in time and I could not go in the direction I wanted.
     

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    Last edited: Apr 24, 2011
  3. tom kane
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    tom kane Senior Member

    Just a few more craft with Horizontal fans
     

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  4. bigbowen
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    bigbowen Junior Member

    Hate to point this out tom but the craft you site are aircraft, Am I missing your point?
     
  5. tom kane
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    tom kane Senior Member

    The horizontal intake technology is the point.These aircraft do not have to fly do they.I am not trying to make a boat fly but have a propulsion that has no obstructions below water level that can go anywhere (reasonable), and a propeller as main driver.
     
  6. nimblemotors
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    nimblemotors Senior Member

    airboats have been used in swamps for a long time, require almost no draft at all, in fact, can move on land as well.
    http://www.tunicaqueen.com/airboat.htm
    But as mr. harris points out they are not as efficient as propellers in water.
    Of course, in a swamp, a propeller would be a highly efficient way to stay put
    until someone with an airboat came to pick you up. :)

     
  7. tom kane
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    tom kane Senior Member

    The images of the aircraft also illustrate the lifting effect of a horizontal fan. the idea to have an air propulsion for realy shallow and obstructed waterways and a trimmable water propeller or outboard for deeper clearer water is the essence of advancing the old fashioned air boats to something more in keeping with envoromental issues and tourist comfort.
     
  8. nimblemotors
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    nimblemotors Senior Member

    Yes I missed that point. Having the fan horizontal would indeed be different than a traditional airboat. I've never been on an airboat, but I'd suspect the comfort problem is from the noise? I would think you could improve the comfort without changing the basic operational function, by enclosing the motor and ducting input air around the passenger area or similiar ideas.
    What environmental issues does an airboat have?
    A hovercraft uses horizontal fans, have you seen those?

     
  9. tom kane
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    tom kane Senior Member

    Some images in this thread show attemts to make an airboat more comfortable for rescue work ect., A horizontal fan will give lift as well as propulsion in effect overcoming a bit of gravity force or making the craft lighter so easier to push about with a air propulsion. Here in New Zealand noisy air boats would not be tolerated in Tourist areas or populated areas,nor even allowed to disturbe nature. Hovercraft are also noisy and difficult to control but small ones for personal transport are getting quieter and more usable.
     
  10. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I get it. Not in anyway a hovercraft, but would get some lift from

    the fan sucking straight up.

    Would also get lift without blowing spray all over the place like a hovercraft.

    I don't think could be as good as vert-fan at generating thrust per horsepower.

    It might be a lot quieter than a vert-fan, or have a more useful layout(or not).

    Interesting idea.

    Might be able to go in reverse without blowing air all over the passengers(unlike an vert-fan in reverse).
     
  11. tom kane
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    tom kane Senior Member

    Obviously some thought gone into those comments, Thank`s Squidly-Diddly.
     
  12. Yellowjacket
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    Yellowjacket Senior Member

    Your fan, although it is sucking air from above, it doesn't create lift if you have the elbow below it that is turning the air to the horizontal.

    If you could create lift with the horizontal fan it would be somewhat akin to lifting yourself by your bootstraps. All of the lif you create in the fan is reacted by the elbow. That cancels out the lift, look a the momentum change, that is what creates lift in an open system.

    It moves forward because you create a momentum change in the horizontal, but you don't create lift. You need to have an air cushion chamber under the hull to create lift, the elbow can't create lift.
     
  13. tom kane
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    tom kane Senior Member

    What you say sounds ok however running a model on a set of scales indicates a loss in weight. the main object to using air propulsion is to have a clear bottom to navigate shallows.
     
  14. tom kane
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    tom kane Senior Member

    A horizontal fan or rotor creates lift ( overcoming gravity)on a helocopter, The helicopter rises through an accelerated down draught of accelerated air particles passing over the body of the craft generated by the fan or rotor (lifting it by its shoestrings). The forward movement is created by cyclic pitch control of the rotor diverting air particles backwards over the body of the craft causing it to tilt forward.
    Is that much different to a airboat with a horizontal fan?
     

  15. Boston

    Boston Previous Member

    ya but the helicopter doesn't have a gigantic elbow redirecting the flow off the rotor attached to it, that and no the helicopter lifts into a low pressure area above the blades from the higher pressure area under the blades, its part air foil effects and part pressure, I don't think the vertical air flow is helpful, actually considered waist.
     
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