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Thread: World speed record with 250mm (or under) size quad

  1. #31
    Pilot boopidoo's Avatar
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    To reduce drag from the arms I was thinking of another solution. A freely rotating 3d printed thin shell (superlight) that always directs itself to the airflow. That way it won't have an adverse effect on handling which a fixed airfoil can have. I could model up something if I sucked at explaining. Of course this solution only really works if cylindrical arms are used.

  2. #32
    Navigator Adrianm1972's Avatar
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    Cylindrical arms = lots of drag.

    I think airfoiled arms set at some angle like a stator vane in a jet engine would be better. Yes, its will always want to drift forward due to thrust vectoring when hovering however, when at the optimum angle for forward flight at speed it will have the least amount of drag/frontal area. This would give the best speed and I think thats the point of this thread.

  3. #33
    Pilot boopidoo's Avatar
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    I think you misunderstood my post, it was to reduce drag and also wouldn't need an optimum angle/thrust/speed combo to work, it would always work. I guess I'll have to model it to explain what I meant, did anyone understand?

    But yes, cylindrical (without my proposed solution) would be draggy, but probably not as much as boxy arms from milled plates.I would definitely not use anything that could affect controls though and that would be airfoils, they tend to do that in airflows. IMO the best would be to have a low drag platform that has a neutral effect on controls at all speed/pitch/thrust combos.
    Last edited by boopidoo; 10th March 2015 at 06:21 PM.

  4. #34
    OSUFPV - KF7VFT
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    Why not actually use the arms for lift? That way when you pitch to a specific high angle the motors thrust is almost entirely being used for forward motion while the arms generate the required lift to oppose gravity. I understand that the airfoils would generate pitching moments of their own but perhaps if you level set the FC at the high angle you could use some PID correction.
    Formerly: rcgroups.com/forums/member.php?u=308733

  5. #35
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    as you have a 'I' shape frame could you make your booms pivot/roll forward on a servo linkage in conjunction with the throttle and pitch?, then your fusealge would remain level and aero dynamic in fast forward flight

  6. #36
    Cor blimey, guv'nor!
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    Quote Originally Posted by boopidoo View Post
    To reduce drag from the arms I was thinking of another solution. A freely rotating 3d printed thin shell (superlight) that always directs itself to the airflow. That way it won't have an adverse effect on handling which a fixed airfoil can have. I could model up something if I sucked at explaining. Of course this solution only really works if cylindrical arms are used.
    Yup, I've done this.

    Not sure how clear my screen-grab is below, but these are 3D printed and clip around a 14mm carbon boom. They're loose enough to rotate should the airflow be great enough.



    Last edited by Ian Davidson; 11th March 2015 at 06:17 AM.

  7. #37
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    Don't forget that you may have to adjust the chord-wise CG of those fairings in order to avoid flutter.

  8. #38
    Pilot boopidoo's Avatar
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    @Ian
    Yes! That's about exactly how I would have done it. Bruce has got a point but if they're really light it won't matter as much.

  9. #39
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    Love the thread, we go to the salt flats every few years to watch the land speed records being challenged. What is the bar at for this sub 250 challenge?

  10. #40
    Fretsaw Jedi Roboforcer X2000's Avatar
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    Quote Originally Posted by shawn45 View Post
    Love the thread, we go to the salt flats every few years to watch the land speed records being challenged. What is the bar at for this sub 250 challenge?
    Welcome to the Lab!
    My calculations were over 200km/h of prop pitch speed, but of course it's just a theory. Reality will show shortly
    If you're a noob, copy 1:1 what somebody already flies without too much questions, you'll find the answers later.
    PatrikE: I don't see anything wrong in your dump...
    Derrick:
    you are flying it LOS... You are doing it wrong.

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