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  1. #1

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    Not wanting bellcrank

    I'm converting my R/C Gee Bee Z to CL. I've already had a few conversations and help, from others, in another Thread. Thanks for that.

    What I don't want are "slots" in the fuselage side for the bellcrank/control lines. I'd like to have only two small holes with grommets.

    I'm thinking some kind of roller set up, or possibly just changing a grommet from time to time because of wear.

    Are others eliminating these slots for some other cleaner set-up? Is there a system?

    OR! Is it possible that the control lines will be in the wing only? If that's the case, I'm home free!

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    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  2. #2
    downunder's Avatar
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    RE: Not wanting bellcrank

    Unfortunately you can't really have the lines inside the wing because the CG of the model will be located well above the wing which would cause the model to fly rolled outwards. A couple of ways to avoid having large slots in the fuselage side would be to use a circular bellcrank where the leadouts wrap around the bellcrank and just roll off it with control movements. Another possibility is monoline as used in speed models but it'd be worthwhile building a trainer to get used to how it all reacts. What I'd do though is to use a quite large bellcrank, at least 4" but the bigger the better. That way the variation in line spacing from neutral to full up/down at the bellcrank could be kept to a minimum.

  3. #3
    JohnBuckner's Avatar
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    RE: Not wanting bellcrank

    Indeed you would be wise to bite the bullet and use over wing standoffs with a large bellcrank located somewhere near the vertical CG point with fuselage side exits. The KISS principle always trumps complexity just for the sake of a couple of exit holes.



    It is afterall control line and the lines on anything are always going to be obvious.

    John
    \"Keep your controllines tight\"

  4. #4
    vertical grimmace's Avatar
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    RE: Not wanting bellcrank

    There is no reason why you could not have small exit holes in the side of the fuselage though just for the lead outs. Maybe you could fabricate a removable lead out guide at the tip when not flying? It will have to be there though for sure. It could be made out of a transparent material so it will not be as easily seen. You do need to adhere to the vertical CG though.
    \"let\'\'\'\'s just say, they will be satisfied with less\" Ming the Merciless

  5. #5

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    RE: Not wanting bellcrank

    I put a small metal eyelet in the side of the fuselage and wear and having the leadouts bind has never been a problem. I use a normal bellcrank and have the lines exit the fuselage in a straight line. In the extreme throw of the bellcrank the leadouts are rubbing the side of the eyelet, but never a problem. Remember regardless of where you put the bellcrank you can draw a straight line from you handle, leadouts to the CG of the aircraft. The bellcrank location is not critical, the location of the CG and the leadout guide is critical. On my larger models I have adjustable leadout guides to adjust the line tension and trimming of the aircraft.

    On my Piper cub I had to drop the leadout guide several inches below the wing surface so that the model does not roll inboard or outboard. If the leadout guide is too high it will roll the aircraft towards on the Gee Bee. If the leadout guide is too low it will raise the left wing and roll the plane outboard.

    Takeoff on the Gee Bee are always interesting due to the short tail moment and engine location.

    Land softly,
    Fred Cronenwett
    Fred Cronenwett
    Float flying and scale

  6. #6

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    RE: Not wanting bellcrank

    Wouldn't the weight of the wheels balance out the upper fuselage weight?

    Maybe I could run the wires out the wing?
    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  7. #7
    downunder's Avatar
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    RE: Not wanting bellcrank


    ORIGINAL: Avaiojet

    Wouldn't the weight of the wheels balance out the upper fuselage weight?

    Maybe I could run the wires out the wing?
    I must admit that when I first looked at your photos it crossed my mind to say (in fun) that if you had lead wheels and fairings then you could run the leadouts through the wing . Seriously though, the amount of weight needed would be excessive because the engine and fuselage is so far above the wings.

  8. #8
    JohnBuckner's Avatar
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    RE: Not wanting bellcrank

    It could only work if the wings had considerable dihedral to raise the leadout guides to where they need to be and that airplane does not have anywhere near enough.

    This is just like the common problem the fellows have with scale airplanes and their cowlings. Its the 'hole in cowling' syndrome you know where they absolutely refuse to allow enough cooling inlet air, worse cooling outlet air or have a reasonable hole anyway to adjust a mid range needle, worse the main needle let alone change a glow plug or simply clear a loaded engine through a glow plug hole.

    Failure to do any of the above so often results in short lives for the airplane controlline or RC.

    If you insist on having the leadouts to low for such a silly reason then the reward will be an akward flying airplane constantly dragging its outside wing looking just well, silly and everyone is gonna notice, even casual spectators.

    That conversion is really Cool and would love to see you finish it and be reward with a nifty prototypically flying airplane but that ain,t gonna happen unless you use some common sense in the conversion.

    Put the leadout guide and preferrably the bellcrank where they need to be and that means wires out a fuse side hole and an over wing standoff leadout guide.

    John

    \"Keep your controllines tight\"

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    RE: Not wanting bellcrank

    OK, OK! I get it!

    A model that flies well is better than one that looks good and flies like, "Holly crap Batman!"

    How far up the fuse side should I go?

    However, with inertia pulling the model out and the weight mostly on top, wouldn't this counter act the weight and drag of the flying wires? Possibly?

    Also. For power I'm using an old but NIB, OS 80 R/C. Swings a large prop. This engine is suppose to have great power, but another modeler said it only has the power of a .40.

    I'd like to believe the guy is incorrect.

    Anyone know this engine?

    Charles

    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  10. #10

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    RE: Not wanting bellcrank

    If your lead out guides on the wingtip are at the same height as the vertical position of the CG on your airplane, all should be well.

  11. #11
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    RE: Not wanting bellcrank

    And to find that point one could just set the height at or level with the center line of the crankshaft or just a little below.

    If you want to find it precisely cut, fabricate and install the leadout guides now in such a way that the airplane can be suspended by the guide above the left wing. Simply find the point on the plate that the airplane will hang perfectly straight down and that is where you make the guide holes.

    Why you are at it I would make this plate adjustable fore and aft for flight trimming. The idea is to allow the lines to be adjusted from ninety degrees to fuselage axis to slightly aft of that point. In other words this allow the airplane to point slightly to the outside of the circle. This fore and aft adjustability of the guides will be important in trimming the airplane to stay on the lines, I.e. keeping it from chasing you across the circle.

    John
    \"Keep your controllines tight\"

  12. #12
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    RE: Not wanting bellcrank


    ORIGINAL: Avaiojet

    However, with inertia pulling the model out and the weight mostly on top, wouldn't this counter act the weight and drag of the flying wires? Possibly

    Come on Charles, Ya'll keep on making rationalizations like that and you are gonna talk yourself right on into screwing it up!

    Its a Bit chen project do it right.

    Can't help you on that particular engine as I am not familiar with it.

    John

    \"Keep your controllines tight\"

  13. #13

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    RE: Not wanting bellcrank

    Seriously guys, this model will never have a sparkling performance so a bit of roll out due to the vertical CG being too high will not be earth shattering.I would invert the engine fully to get that CG as low as possible and just run the wires through the wing and be done with it!

  14. #14
    downunder's Avatar
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    RE: Not wanting bellcrank

    I'm guessing your OS 80 has an upturned carb at the rear of the engine and uses two glow plugs. If so my son has one of them and it's a very nice engine indeed. It's a ringed engine so needs about an hour of quite rich running in. They're not quite as powerful as the Enya 80X that we also tried in his model but then again, not many 80's are as powerful as the Enya . If you do decide to invert that engine as was suggested, then it's a simple matter to remove the two screws holding the carb body to the crankcase and flip it around so the carb faces up. That makes tank height easier to match up with the carb.

  15. #15

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    RE: Not wanting bellcrank

    Rotating the engine could be a good idea. This would bring the weight down a bit.

    The lead-out adjustment was brought to my attention before. This is probably the only way I can control line tension properly?

    I would still like to eliminate slots in the fuselage.

    Nice ideas and thanks for the help.
    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

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    RE: Not wanting bellcrank


    Sorry!

    Boy do I owe you people an apology.

    I just remembered, some time ago, I acquired a three line bellcrank for this model. I actually forgot all about it.

    That takes care of hiding lines, unless I go electric on the throttle, which I doubt I will do.

    I'd like to keep this old school.

    Charles
    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  17. #17

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    RE: Not wanting bellcrank

    On thinking more about it, I have built several Old Time Stunt airplanes, for example, the Sterling Yak 9, which have leadouts below the vertical CG. I made them fly level with outside wing warp. Not a perfect solution, but they flew acceptably. So, for your application, if you run the lines out the wing, maybe a little down on the outer aileron would make the airplane fly level.

  18. #18
    Clancy Arnold's Avatar
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    RE: Not wanting bellcrank



    Charles
    The pictures below show the technique I use to set the leadout guide.

    The first picture shows adjusting the vertical location of the line guides for flying wings level.



    The second picture shows adjusting the line guides horizontally to have the model hang slightly nose down to retain line tension.



    Clancy

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    Clancy Arnold
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  19. #19

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    RE: Not wanting bellcrank

    OK, I get the idea. The way it hangs is the way it flies! Correct?

    Charles
    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  20. #20
    Clancy Arnold's Avatar
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    RE: Not wanting bellcrank

    Charles
    To answer your question, here are pictures of it flying.
    Note that I am carrying some Wing Warp to trim the wings level, also some right rudder for line tension.
    Is that cheating?

    Clancy
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    Clancy Arnold
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  21. #21

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    RE: Not wanting bellcrank

    WOW!

    That looks great in flight! Kinda makes me want to get my Gee Bee completed.

    I can't warp my wing, but I did think about adding a rib or two.

    Thing about that is the look.

    Thanks for that info and a lift in spirit.

    Charles
    Owner: CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder." cfcgraphics.com

  22. #22

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    RE: Not wanting bellcrank

    Hello Charles,
    It is important to make the plane hang level, or in other words to get the leadouts lined up with the vertical CG position.
    Small leadouts will interfere with the 3-line bellcrank working properly.

    Instead let me suggest that you make a roughly 1/2" tall by 4' long section of the fuselage side removable for flight. Possibly you could make it a door.
    If, like many scale builders, you make the leadout guide as a removable wire clip that plugs into the wing, then you can remove the clip from the wing, coil the leadouts and stow them all just above or below the bellcrank and then replace the panel for static judging.


    best regards,
    Dean Pappas


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