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  1. #1
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    Static Thrust of a Single Blade Propeller VS. Two blade, Yes I said Single blade :)

    http://www.youtube.com/watch?v=MwU5dcPN1Fs

    Tell me what you think guys?

    I think my tests reveal the Single blade prop is more efficient as it consumes the
    same wattage at the same thrust. On the surface this doesn't sound more efficient however consider the single blade must run at faster RPMS to achieve the same thrust which obvious drives the motor out of its efficient zone. My theory is an 11/12" single blade prop running at slower RPMS will generate more thrust than than 10x4.7 at a
    watt savings.

  2. #2
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    Very interesting! But I don't know what to make of it all... Yeah, I've read that one-bladed props should be more efficient, but what you're saying is that with our gear (APC props and standard airplane motors), we don't get it more efficient?

    Yes, might be worth a try with 12" props too. Might show totally different readings. Just be careful so your counter weight don't gets loose, I imagine it would be extremely dangerous, so consider it a fired bullet...
    Smart people don't need a signature.
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    Quote Originally Posted by OldGeek View Post
    http://www.youtube.com/watch?v=MwU5dcPN1Fs

    Tell me what you think guys?

    I think my tests reveal the Single blade prop is more efficient as it consumes the
    same wattage at the same thrust. On the surface this doesn't sound more efficient however consider the single blade must run at faster RPMS to achieve the same thrust which obvious drives the motor out of its efficient zone. My theory is an 11/12" single blade prop running at slower RPMS will generate more thrust than than 10x4.7 at a
    watt savings.
    IIRC a bunch of the old time control line racers used to use single bladed props. I'd wager there is definitely a reason that you don't see more of them in use though.

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    OldGeek,

    Thanks for your experiments - its always nice to have data! Here's my $0.02:

    1) If this setup produces the same thrust for the same wattage, won't the battery duration be the same?
    2) My understanding is that the counterweight has to be "tuned" to a specific RPM. If so, it will be unbalanced a good portion of the time since the quad props are always changing speed.
    3) Did you change throttle settings between the tests, or were both done at full throttle? If you had to increase the throttle for the single-prop, then it means that the max thrust capability is reduced compared to the standard prop.
    4) The manufacturer typically recommends a max prop speed (which is probably ignored by most quad builders :-). A single blade may have less stresses due to the reduced vortecies, but I expect the max speed would still be similar. The upshot is again you'd be limited as to the top speed and therefore thrust, or you'd be doing more damage to the blades.

    Sorry to be so negative - but you did ask.

    - Roy

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    Quote Originally Posted by RoyLB View Post
    OldGeek,
    Thanks for your experiments - its always nice to have data! Here's my $0.02:
    Agreed, this experiment was for me to prove/dispel (in my mind mostly) articles/videos I come across.

    Look at this guy, says good things about his field tests with single prop, but no real
    data to back up the gains/losses...
    http://www.youtube.com/watch?v=wxY9s...feature=relmfu


    Quote Originally Posted by RoyLB View Post
    1) If this setup produces the same thrust for the same wattage, won't the battery duration be the same?
    My test thrust was 500g target. At 500g static thrust both roughly put an 80 watt load on the motor obviously same usage = same flight time. My guesses are that increased diameter single blade props will react similar fashion. I don't like guesses left untested so I will test soon.

    Quote Originally Posted by RoyLB View Post
    2) My understanding is that the counterweight has to be "tuned" to a specific RPM. If so, it will be unbalanced a good portion of the time since the quad props are always changing speed.
    I ran the prop from 10% throttle to 80% throttle (never max) during which the prop never seemed noticeably out of balance.

    Quote Originally Posted by RoyLB View Post
    3) Did you change throttle settings between the tests, or were both done at full throttle? If you had to increase the throttle for the single-prop, then it means that the max thrust capability is reduced compared to the standard prop.
    Yes, one was at 500g target and the other at 700g. Neither prop needed full throttle.
    This test leaves no doubt in my mind that not all the 2nd blade thrust is lost in the wash as some would argue. However it does reveal to me that maybe a considerably amount is... time for tachometer

    Quote Originally Posted by RoyLB View Post
    4) The manufacturer typically recommends a max prop speed (which is probably ignored by most quad builders :-). A single blade may have less stresses due to the reduced vortecies, but I expect the max speed would still be similar.
    Agreed, however my goal is static thrust at lowest cost/watt. The max. speed of the APC 10x4.7 prop is 65000/10 (6500). At this speed most thrust calculators put this prop well over 1kg thrust. That would put out 4kg for a single quad at 100% throttle.. bad My quad is 1.6kg. What I want is 1.6kg +/-10% thrust at the lowest possible wattage.

    Quote Originally Posted by RoyLB View Post
    The upshot is again you'd be limited as to the top speed and therefore thrust, or you'd be doing more damage to the blades.
    Sorry to be so negative - but you did ask.

    - Roy
    Not negative at all, just critical thinking 101. Thanks for you thoughts.

  6. #6
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    There was one guy doing this with single rotor helis ..

    http://www.youtube.com/watch?v=AD9juUWL5iU


 

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