FRCFoamies Mig 29 Scale Twin Prop

Discussion in 'FRCFoamies Plans' started by F1wanabe, Feb 24, 2017.

  1. I don't know if HK is getting out of them, just a quick little search on the 4 blade, yellow $ 0.90 , purple $0.30 . Price is right if you don't care what color.
     
  2. whatmovesyou

    whatmovesyou Top Gun

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    When you do this method, notice that only one motor (video) either increases or decreases causing a unbalanced yawing force about the CG. If you buy a aileron/elevator mixer like J121224 above mentions, it does it totally different.
    1) You only use rudder and throttle channel. You save a channel. No mixes!!!!
    2) When you set it up, it allows one motor to speed up and the OTHER to reduce the same amount.
    3) In addition, the rudder trim will allow you to adjust the rudder speed so it syncs the motors when running and the throttle trim will allow you to start spinning at the same time.

    Concept- like elevons, the elevators(now the motors) move in the same direction. So it adds /subtract the same amount of RPM's. That is hooked to the throttle channel. The ailerons where one goes up and the other down (motors) is hooked to the rudder and if you move it, one motor adds the same amount and the other subtracts the same amount. Now, there is no uneven forces, causing a smooth turn. (DX9)

    I use a GWS mixer on my duals, especially my transports so it doesn't jiggle in the turns.

    For those who use the mixing method in the video and it is a Spektrum, go to servosetup, roll the bar to the end and you will find a balance for the throttles to sync them thruout the full range. I used that when I did a 3 motor setup.
     
  3. I use the dal props as well. I also sometimes use the HQ props 5” tribaldes which are gentle (and more efficient) on motors and at the same time the plane is a rocket ship!

    The launch on the start of the video was about ~60% throttle and if I dont back down it would disappear in no time:

     
  4. F1wanabe

    F1wanabe Administrator

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    When I watched that for the first time I replayed it because I couldn't believe it took off like that! Only with twin counter rotating props can you get such controlled launches!

    Sent from my SM-N950U using Tapatalk
     
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  5. Not only that but I guess its a testament to this great design. I have had other planes with similar setup and they do fine until say 50% throttle but if you go beyond that, they behave very weird and become in unpredictable and feel like they have mind of their own - not the case with FRC Mig-29. I have gone full throttle and it would become even more stable, guess the blended wing design helps a lot!

    The only thing I would say though is if you have differential throttle, dont use similar rates when at higher throttle as compared to low throttle, it would be a little unpredictable in yawing (gotta bring down the rates). Guess, if you make the hinges not move with 1.1Kg of thrust/elevator then you would be fine. After all you would be pushing hinge’s and foam’s strengths to limit I suppose.
     
  6. F1wanabe

    F1wanabe Administrator

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    Great point, Malukk! I rarely fly fast so that is usually not a factor for me

    Sent from my SM-N950U using Tapatalk
     
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  7. TomMonton

    TomMonton Administrator

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    There is a lot of truth in this last paragraph. My first build pulled the linkage apart pushing on it through a turn. The one elevator control horn pulled out and on the next turn I was in trouble. I couldn't lift the nose evenly anymore so I had to gently screw it into the ground.

    The root cause failure was my own fault entirely but it did demonstrate the point that you are making here.

    Yeah it's always great fun to over power your planes but on a tail pusher there are some limits to bear in mind.
     
    Last edited: Mar 1, 2018
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  8. Rotorhead619

    Rotorhead619 Ace Pilot

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    Sorry for the question but:

    Using the mixer give you a variable thrust on both motors using yaw control.

    Using the transmitter on my changes the speed of one motor.

    Is this correct? I haven’t setup my electronics yet.
     
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  9. whatmovesyou

    whatmovesyou Top Gun

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    Yes. On park jets, it's okay to use the mix and get away with it.

    Planes like flying wings, blended wing bodies, STOL and VTOL planes that have 2 motors is where it shows up in the flight environment. It will cause excessive yaw (especially takeoff) when only 1 motor changes thrust and the other side doesn't.
     
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  10. F1wanabe

    F1wanabe Administrator

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    Jay found an awesome video on youtube. Thanks Tom Berger for posting, looks like a lot of fun!
     
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  11. Rotorhead619

    Rotorhead619 Ace Pilot

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    That’s a great video.
     
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  12. Rotorhead619

    Rotorhead619 Ace Pilot

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    Anyone have pictures of their electronics setup? Where are your esc’s and servos?
     
  13. jimbosflyin

    jimbosflyin Top Gun

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    I thought some one would have answered by now,there are some pictures posted through out this thread.I didn't take pictures of my set up but my esc's are under the naccels and feed threw the deck and then the wires run through the deck supports,once I was shore the motors were running the rite way (one counter rotating) I closed up the naccels.Here is a picture on how to wire the two esc's to the battery.Hope this helps you.
     

    Attached Files:

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  14. Here is how I did mine with regards to placement:

    [​IMG][​IMG]
     
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  15. And here is after its all closed up:

    [​IMG]

    All electronics hide in very well and esp. the ESCs get a lot of air flow with setup like this...
     
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  16. TomMonton

    TomMonton Administrator

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    Another example... post #179 in this thread.

    [​IMG][​IMG]
     
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  17. Rotorhead619

    Rotorhead619 Ace Pilot

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    I do remember those 2 options. I was wondering is anyone ran the esc’s all the way up into the canopy? Seems like a long way to go and a lot of extra weight in wires.
     
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  18. jimbosflyin

    jimbosflyin Top Gun

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    Keep in mind your COG,How many servo's your going to use and what size battery are you going to use.This plane can handle anything,I only used two servo's ,and a few guy's loaded them up.And of course what glue,heavy hot glue or the lighter like foam-tac.
     
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  19. You could get nose heavy really quick.
     
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  20. hwilton

    hwilton Airman

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    ESCs work best next to motors, better to extend the battery input wires
     
    Last edited: Mar 6, 2018
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