Turbo Raven 1900mm 30cc

jhstantonjhstanton Club Members Posts: 33
I have this RC model and almost finished building it. I am confused on the CG for this plane. The manual that came with it is on a CD and shows an Extra 330 at times in the photos when they reference some thing. The manual shows the CG at 130mm but in a discussion of the plane on Hobby Kings web side a person says he contacted the manufacture and the CG should be 163.5mm. I am good at 163.5mm but tail heavy at 130mm. Has anyone flown this plane? If so what should the correct CG be? image



Comments

  • SootySooty Christchurch NZClub Members Posts: 6,110 ✭✭✭
    Go with the measurement closest to 1/3 wing root and set it up a fat finger forward of that point to start with and then gradually move it back.



    As one of the old time scratch builders who never had a manufacturer to refer to we just guestimated a start point slightly forward of 1/3 root. Never failed.
  • jhstantonjhstanton Club Members Posts: 33
    Sooty,



    Since this is an ARF and I did not build the wings what is the best way to get the average wing cord? Do I measure the wing only excluding the ailerons say three places to get the average wing cord image
  • jhstantonjhstanton Club Members Posts: 33
    Sooty,



    Never mind I was think I needed the average cord of the wing. I reread your post and you mean 1/3 of the root cord. I thank you and I'll measure that and start there. Thanks for you help. image
  • SawdustSawdust Club Members Posts: 6,763 ✭✭✭
    jhstanton:



    " a person says he contacted the manufacture and the CG should be 163.5mm. I am good at 163.5mm but tail heavy at 130mm. "



    I can't say where it actually should be on that model and I'm not trying to be argumentative but you've got things arse about there. Assuming you're measuring back from the leading edge of the wing 130mm would be a fair bit more nose heavy than at 163.5mm. A bit unusual that they mention a figure to within half a millimetre too.

    Sooty's rule of thumb method is a good reliable basis to start from no matter what any instructions say, to see if or how much difference there is, it's surprising how often the instructions are way off. Sawdust2015-02-27 20:30:39
  • jhstantonjhstanton Club Members Posts: 33
    The root cord of this plane is 13.5" (343mm)not counting the ailerons so at 1/3 of the root cord is 4.5" (114mm) that means the CG is just in front of the wing tube. I would have to add another lb to the plane to get it at 4.5" (114mm) The CG that come with the plane says it should be 5.11" (130mm) and I have it balanced there. I will start from there and work with it as I fly. Thanks for all you help. image



    image
  • DaithiDaithi Belfast,IrelandClub Members Posts: 8,708 ✭✭✭
    5.11" sounds more correct as the ailerons (in level position anyway) are simply a part of the wing and need to be added in when measuring the chord.



    If you can find some long grass, try test gliding it (or under very low power) and see how it flies. If iot dives, then reduce the wight up front and if it stalls, increase it. Once it can fly in a shallow dive, then power up and use the radio for final trimming
  • WTWUKWTWUK CornwallClub Members Posts: 13,610 ✭✭✭
    I too was under the impression that ailerons are part of the wings oddly enough!



    As for test 'gliding' that is exactly as I do mine - if they are capable of gliding that is! When I did it with the ol' AXN, I must have got it spot on, as it just kept on gliding! lol!!!

    And believe it or not, the Vampire glides very well too!!!



    And of course, not with helicopters and multi legged things! lol!!!
  • jhstantonjhstanton Club Members Posts: 33
    I did the maiden flight yesterday and the CG at 130mm is to far forward so I'll move it back to the suggested 163mm. I also had a problem with the ailerons fluttering real bad that I have to fix.



    I only a short flight because of the ailerons but the Turbo Raven with the EME 35 flew very well and had more than enough power for unlimited vertical. image
  • DaithiDaithi Belfast,IrelandClub Members Posts: 8,708 ✭✭✭
    That sounds as if you may need more powerful servos for the ailerons if they are fluttering due to external forces



    Edit: It's equally possible that the push rods are too light and need to be stifferDaithi2015-05-03 22:13:21
  • SootySooty Christchurch NZClub Members Posts: 6,110 ✭✭✭
    How the hell did you managed to get it back in one piece with the C of G so far forward?



    A tail heavy plane can be a nightmare to control.



    Did you forget the simple old finger balance test under the wing with the tank empty? At 130mm the tail should have well and truly dropped towards the ground.



    I usually maiden with C of G under main spar and then when tank is full it takes off slightly nose heavy and stable enough to get all the trims sorted.
  • CAMMERCAMMER Club Members Posts: 508 ✭✭


    You're right with your "finger test" method Sooty, I think at 130



    the model would be in a nose-heavy condition compared to 165.



    As Daithi suggests check servo strength. on gassers I always sleeve



    push-rod wire with 2mm i.d. carbon tube epoxied on.



    Check the horns and clevises, aileron flutter usually leads to



    "catastrophic failure" about 2 seconds later. image

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