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lift vs weight

Discussion in 'General Discussion' started by auck, Jun 2, 2013.

  1. auck

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    currently i'm using a 9x4 prop for my phantom. planning on getting the Arris CM2000 gimbal also. the current consensus is that flight time will only be around 5-7 min long. i want a longer flight time, so short of shedding a few hundred grams of eq, i was wondering.....

    if i was to switch from a 9x4 prop to say a 9x5, 9x6, or even high pitch (if they even make thsese), would that create enough lift to allow for a longer flight time?
     
  2. gardenroute

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    Do you any have experience with 9" propellers on the Phantom? Improve somehow flight characteristics?
    Battery life, smooth flight, stability, performance during lifting? Vs. stock 8x45 ?
    How to change settings gains?

    Arris CM2000 - this gimbal I was also interested in ...
     
  3. tanasit

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    I just want to see the differences of the flight time using different props. I chose: Phantom stock; Graupner e prop 8x5; GWS 3 blade HD-9050x3; Master Airscrew TB2318 (cut tip); APC 10x3.8 (cut tip). I tried to keep the other factors the same so I used the Phantom stock 2200 mAh pack charged until the light was solid green (Phantom charger) and let the pack sit to stabilize the voltage surge about 30 minutes or so. I let the pack cool down after each test before another charging. The pack was used earlier about 5 cycles. The room temperature was about 40F throughout. The flight time started when it lifted off and I hovered at eye level with ATTI mode until it landed under the fail safe condition. I also recorded the sound level at 2 meters. And here are the results:

    Prop time (min:sec.) sound (dB)
    Stock 12:48; 83
    Graupner 12:40; 84 adjust throttle a few times
    GWS 13:39; 83
    MasterAS 8:33; 84.5
    APC 10x3.8 cuttip 13:54; 84
    Gemfan 9x4.7 14.06; 86 stable, hold atti well
    APC 9x4.5 oscillation!
    FC 3-9x4.5 11:31; 92 adjust throttle 2 times
    FC 9x4.5 11:42; 90 stable, hold atti well
    Gemfan 9x4.7 14.22; 86 stable, hold atti well Nano-Tech A-Spec 65-130C
    Carbon 9x7 13.29; 90 slight oscillation (´âáreduce Pitch & roll to 80%)

    Later I added a few more different props.
     
  4. TickTock

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    Thanks for that data - amazing what a prop can do. Would be interesting to add 200g of weight and try again. I wonder if the Gemfan 9x4.7 will still perform as well under load.

    On my Phantom, using carbon 8x4.5s at a steady hover, my flight time (full charge to auto-decend) dropped from 10:36 to 7:30 when I added 189g of weight (853g unloaded, 1042 loaded).
     
  5. Gizmo3000

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    You have to kind of view it as bicycle gearing, or gears in a transmission.
    putting it into a higher gear or putting larger tires on a car won't necessarily make it faster or go farther because the engine will have to work harder.
    putting on a prop that moves more air will only make it harder for the motor to turn.
     
  6. tanasit

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    Generally speaking, you are right assuming that the the diameter of the prop is constant.
    Also most motor have the specifications showing the biggest prop they can handle.
    European RC flyer prefer the geared motor for better efficient by swinging larger props at lower rpm but for our purpose, the Phantom requires the speed of the motors to control the flight attitude so I think the biggest prop that can go on with stock motors would be 9x5 depending on the AUW but 9x4 is preferred if that work for you.