Friday, 13 June 2014

Pusher with polyhedral

I have never tried a 3 channel rudder elevator throttle plane so thought I'd give it a go using the orange slim wing and pusher fuselage.

RET planes need some wing dihedral to enable turns due to the lack of ailerons.

I fixed the ailerons in place and removed the servos. This simplifies the plane greatly, the wing is just a wing, no servos or wires, apart from rudder and elevator.

The CF spar was removed and a bent 200mm x 10mm diam ali tube inserted to set the dihedral. The wing extensions were hot glued in place at the desired polyhedral angle. The wing seems to be strong enough without a CF spar.

I increased the rudder area, but after the maiden reduced the throws for smoother control.

The 1500mm x 200mm wing and flying weight of 630g gives a wing loading of about 21 g/sq dm (7oz/sq ft) which is great for gliding and slow flying.

This plane is a delight to fly, so slow and steady. If I had started with something like this the learning process would have been much quicker. I can trim it to fly hands off in big lazy circles and it takes care of itself.



Wingspan - 1.5m (59")
Chord - 200mm (8")
Elevator servo - TGY 900 9g
Rudder servo - TGY 500 5g (stronger servo might be safer)
Motor - Turnigy 2822/14 1450kV
Prop - 7 x 4.5"
Airframe weight - 520g
Flying weight - 630g with 1300mAh LiPo (gives 20 min slow flying)

Sketchup Plans










15 comments:

  1. I was thinking about building a similar plane for a friend. I was wondering what esc you would recommend for this plane as well as whether you went with a 2 cell or 3 cell LiPo.

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    Replies
    1. Hi Steve. ESC is the recommended 30A although I used a 25A with no issues for a while. It cruises along with throttle just under half. Battery is 3S but I suspect a 2S with bigger prop will be fine.

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  2. Many thanks for putting all this info out on You Tube etc. Helping me enormously. I learned to fly RC using Peter Holland's Soloist in the late 1980's and stayed with all balsa vintage models, Junior 60, Black Magic, etc. After a long break from aeromodelling just started again, after retiring, but balsa costs a bundle, so very pleased to find out about Depron...and finding out how to build models with it. Just going to have a go at building this polyhedral wing. Thanks again for the lessons.

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  3. Where is the CG ? at 25% of root chord or 30% of Root chord?

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    1. Hello Ashish. About 25% from memory. I haven't flown it for a while.

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  4. Thanks Andrew, actually i was building a single boom pusher with 40 inch WS, and 10 inch chord(KFM2 step airfoil) and wanted to know if 25% would work...
    Also what should be the distance between Wing trailing edge and Hstab's Leading edge?

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    Replies
    1. I have not tried KFM airfoils but I would start with 25% and see how it flies. My wing TE to stab LE is 267mm. Anywhere between about 200 and 300mm would be OK. There is no definite answer.

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  5. Hi Andrew
    Thanks a lot for sharing your experience with others
    I've 3 questions
    1- how can I build a polyhedral wing?
    2- can I use 1200KV - 1.3 Kg Thrust Brushless motor with larger prop. (10*4.5) instead of
    2200kv motor and 7*4.5 prop.?
    3- which rc do you recommend futaba sg14 or jr xg14?

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    Replies
    1. Hello.
      1. Watch my video on adding dihedral https://www.youtube.com/watch?v=aaMfiCI1Z0Q then cut off the wing tips and glue them back on at an angle.
      2. As long as the prop clears the boom. You would need a taller fuselage
      3. Taranis is the only radio I would recommend.

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  6. Hi Andrew
    Thanks a lot for sharing your experience with others
    I've 3 questions
    1- how can I build a polyhedral wing?
    2- can I use 1200KV - 1.3 Kg Thrust Brushless motor with larger prop. (10*4.5) instead of
    2200kv motor and 7*4.5 prop.?
    3- which rc do you recommend futaba sg14 or jr xg14?

    ReplyDelete
  7. Andrew,

    I really enjoy your videos and the music you choose is perfect. I can't remember if you mentioned the polyhedral measurements in the video if not could you please provide them?

    Cheers

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    Replies
    1. Howdy. Do you mean the wing dihedral? All measurements are in the post above and dihedral is in the video.

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    2. Thanks Andrew for the prompt reply. Sorry if my question was confusing. I am new to the hobby.

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  8. Andrew,
    I can only find XPS foam in 25mm thick sheets. Would it be a problem to glue two sheets together for the fuselage?

    Thanks

    ReplyDelete