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How long to phantom 2+ props need to be?

Discussion in 'General Discussion' started by yorlik, Feb 11, 2015.

  1. yorlik

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    I read about carbon fiber replacement props after trashing 4 in one day trying to learn CSC motor shut off after landing. Obviously I gave up as I had no spares left! Each tip over snapped 1/4-1/2" off a prop. figured I just am not coordinated enough to pull both sticks down and center at the same exact time, so before they both get there, I am commanding movement with the right one and over it goes. So I learned to just land carefully and cross my fingers that the thing will not tip over in the 3 sec it takes to shut down.... So far so good.

    Brings me to my question. Seems everyone advertises "9 inch blades." Well, mine are (were) all 9.5" long! Is this something new? Any comments on buying 9.0" replacements? Seems to me the controller will just speed the shorter ones up a tad to make up for the loss of lift?

    Corollary to that then is reuse of the broken shorter ones.... I snipped off the longer end to match the shorter end and have some 9.0-9.25" long ones now.... used one and I see no difference. Will try the 9.00" long (shortened ones next). Anyone see any issue here?

    I have seen a zillion posts/youtubes around about "OH MY GOSH - you MUST balance each blade" on special expensive looking balancer. Before I noticed the first shortened one, I made a flight and had no issue. Later found one side was 4.75 (new length), other was 4.50"..... So since some folks seem to think balance is so critical, I DID balance my cut off ones by setting them on a knife blade in center. Comments?
     
  2. N017RW

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    Diameter, pitch, and number of blades are all factors when matching motors to props. There is a 'sweet spot' for each option and combination that provides the best performance for each. Thus length is just one part of the 'equation'.

    The first two digits of the prop # indicate the length. The second two digits are the pitch or the distance traveled in one revolution in a solid medium (i.e. no slip).

    So DJI 9450s are 9.4 inches long and in one revolution would translate 5.0 inches.
     
  3. Meta4

    Meta4 Moderator
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    Carbon fibre props have a lot of drawbacks and not much in the way of benefit.
    They are very unforgiving and break easily as well as being quite dangerous.
    Also .. for landing technique.
    Try just holding the left stick down for two seconds instead of trying to do the two-stick CSC.
    Or what a lot of people do is to simply hand catch rather than landing.
     
  4. msinger

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    Carbon fiber props are definitely more brittle (and dangerous) than the plastic props that came with your Phantom. If you must use them though, then go with these DJI props:
    There are lots of third party carbon fiber props. Most have poor reviews.


    CSC should never be used when shutting down the motors after landing. Always hold the left stick down for ~3 seconds and the motors will shut off.


    All three sets of my DJI props were not balanced, so I'm assuming that's a usual thing. Not all balancers are super expensive. I have the SpeedyTM prop balancer and found it works well.


    If you don't want to buy a balancer, you could buy just a prop balancing rod and set it on a coffee can -- or some other flat, level surface.
     
    #4 msinger, Feb 11, 2015
    Last edited: Nov 5, 2015
  5. yorlik

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    thank you!
     
  6. dptcalvin

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    What's the reasoning behind this?
     
  7. msinger

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    If you don't execute CSC cleanly, your Phantom could tip and the props will hit the ground. If your props hit the ground, you'll destroy those -- and, possibly an ESC and/or motor.
     
    #7 msinger, Feb 12, 2015
    Last edited: Nov 5, 2015
  8. jason

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    For one thing the manual is wrong about using CSC to shutdown the props. What happens when using CSC to shutdown is that the motors increase speed before shutdown causing the P2 to tip over damaging the props.
     
  9. dptcalvin

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    Interesting. I've used a combination of both CSC and holding the left stick down - never a problem. But I'll keep this in mind and use the left stick down method from now on. Thanks!
     
  10. yorlik

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    Thanks everyone for replies.

    CSC is exactly the reason I asked about shorter props - since I took out 4 in tip overs in 1 afternoon from trying to use CSC. No more tips with throttle down, wait 3 sec, anymore.....

    If anyone is interested, tips broke off and no spares does not mean your are grounded... just cut off the other end to match and you can fly more.... from my experience I can say the 6axes gyros compensate for the slight difference in lift between the 4 props and make it ok.
     
  11. BlackTracer

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    Funny story, one day a few months ago I encountered a guy flying a P2 with prop guards. When he brought it down, I saw immediately that one of his props was broken off, at least an inch short and frayed at the end. I said dude you probably shouldnt be flying with a broken prop like that and he said "Really? It flies fine!" And it did.