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  1. #1

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    New & unusual

    Greetings guys.

    As a complete newcomer here, I hope I am posting in the correct forum.
    Below is a creation of mine I would like to turn into reality. It is modelled in Blender 3d and hopefully sometime in the near future also in balsa/foam etc. Before I hear comments regarding the practicallity of it all, let me assure you that I am well aware of the problems regarding counter rotating props, flying planks etc. Who was it that said we do things 'not because they are easy, but because they are hard' ...

    Needless to say I have created a few problems for myself. If it is unclear on the picture let me explain a bit. The propellers are counter rotating, sort of in the middle of the fuselage, this obviously creates a problem as the fuselage in front of and behind the propellers are stationary. How can I connect the two?
    Has anybody got an idea of a good wing airfoil for a flying plan?

    I would like to go electric initially, because I think it would be the easiest and cheapest approach. Once the hickups are ironed out, I would realy like to build a gas/nitro version.

    Thanking everybody in advance
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  2. #2

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    RE: New & unusual

    ORIGINAL: whereismyisland
    Greetings guys.
    As a complete newcomer here, I hope I am posting in the correct forum.
    Below is a creation of mine I would like to turn into reality. It is modelled in Blender 3d and hopefully sometime in the near future also in balsa/foam etc. Before I hear comments regarding the practicallity of it all, let me assure you that I am well aware of the problems regarding counter rotating props, flying planks etc. Who was it that said we do things 'not because they are easy, but because they are hard' ...
    Needless to say I have created a few problems for myself. If it is unclear on the picture let me explain a bit. The propellers are counter rotating, sort of in the middle of the fuselage, this obviously creates a problem as the fuselage in front of and behind the propellers are stationary. How can I connect the two?
    Has anybody got an idea of a good wing airfoil for a flying plan?
    I would like to go electric initially, because I think it would be the easiest and cheapest approach. Once the hickups are ironed out, I would realy like to build a gas/nitro version.
    Thanking everybody in advance
    It looks very cool, but quite apart from the prop issue, you've designed it to need elevon control instead of aileron+elevator. It's going to be an absolute pig to balance and fly smoothly under different conditions unless you lengthen the front to back chord length. I've made a couple of elevon planes, and they are easy to get wrong.

    As regards spinning the counter rotating props, it's not actually so difficult. You'll have to make a tube that bearing sit on, and use bearings with an inside diameter almost as much as the outside diameter. the props will have to be made to fit around the outside of each bearing, and have an extention tube with inside cog teeth. Use radial slots in the tube to pass gears out to engage with the prop inner gear.

    Alternatively, make a custom brushless motor, magnets on the outside, windings in the centre with a hollow core big enough to pass fuselage structural members through. Not so difficult.

    p.s.
    I haven't got anywhere near enough experience to recommend airfoils, but you need to find something that works well with elevons, i.e. it doesn't try to curve too much in the air, and doesn't stall too easily when it's facing the wind the wrong way. Many of these decisions involve some serious thinking about tradeoffs.


  3. #3
    Scar's Avatar
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    RE: New & unusual

    I think a custom double outrunner motor with a long common shaft could provide (1) mounting to the fuselage, and (2) mounting the nose in front. Props would have to be custom made too, because they'd mount directly to the outrunner housing.

    If you think that sounds expensive, wait until you decide to introduce an internal combustion engine into the project.

    Good luck,
    Dave Olson
    The true soldier fights not because he hates what is in front of him, but because he loves what is behind him GKChesterton

  4. #4
    Gravityisnotmyfriend's Avatar
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    RE: New & unusual

    It's an interesting design, but doing something just cause it'd difficult to do is not really a good approach to aircraft design. Unless I'm missing something, I don't see any advantage to putting the props between the engine and cockpit. But, I see many many disadvantages.
    The mathematician sees the glass as twice as big as it needs to be. The engineer sees it as full with a Safety Factor of 2.

  5. #5
    tommygun32's Avatar
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    RE: New & unusual


    ORIGINAL: whereismyisland

    Who was it that said we do things 'not because they are easy, but because they are hard' ... [img][/img]


    The only answer I can come close to providing you with is John F. Kennedy.

    Good Luck
    The rest of your life starts now. Go Live It!

    Team Terribles

  6. #6

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    RE: New & unusual

    Needs elevator, period, place the trust element far more forward to make it work, otherwise, this will NOT fly, the airfoil, might as well be flat in this stage, it's the last thing you should be concerned with.


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