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  1. #1
    green river rc's Avatar
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    1/2 A electric

    I'm planning my next project, a 1/2 A C/L model called a Cobra. I would like to build it electric but have no experience with electric C/L and very little with RC. What motor and battery combo do you suggest, what about a timer or ESC, not sure what I need. Any of you fly electric C/L?
    With the parts left over, Im going to build a motorcycle.

  2. #2
    skaliwag's Avatar
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    RE: 1/2 A electric

    Forgive me not knowing what a 1/2A Cobra looks like. What engine was it designed for.
    Real Airplanes have Round Engines and Two Wings.

  3. #3

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    RE: 1/2 A electric

    This is a copy of the plans that I sent to him. I got five (5) copies in case others might want a set. I will let them go for my cost.

    EDIT: I just looked back through my records and found the cost off the copies. I can send them for $5 a copy. That is a few cents under my total cost.

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    Howard

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  4. #4
    green river rc's Avatar
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    RE: 1/2 A electric

    Got a jump start today, will post some pictures soon. Gave up on the electric idea, going with a NIB Norvel .061. Funny thing though, I dug out my engine today and it has an RC carb on it, I was thinking it was a C/L engine, oh well I guess I'll just wire open the carb. BTW I only gave $25 for it a few years ago at a shop that was closing...lucky me!
    With the parts left over, Im going to build a motorcycle.

  5. #5
    skaliwag's Avatar
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    RE: 1/2 A electric

    What size lines are you thinking of flying on?
    Real Airplanes have Round Engines and Two Wings.

  6. #6
    green river rc's Avatar
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    RE: 1/2 A electric


    ORIGINAL: skaliwag

    What size lines are you thinking of flying on?
    I have been using .008" X 42' on a simular model. I'm in search of a tank right now, may have to make a custom job, Brodak has a nice tank but it's a little expensive.
    With the parts left over, Im going to build a motorcycle.

  7. #7

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    RE: 1/2 A electric

    I have seen some of the larger electric powered CL models and they are using the following parts. I assume you plan on using a brushless motor with a Lipo battery.

    brushless motor
    speed control
    Lipo battery
    Zigras timer

    You need the zigras timer to start the motor and then shut it off after a predetermined time.

    http://www.windyurtnowski.com/#ztron

    The electric stunt examples I have seen have been the larger models but the same priciple should apply to the 1/2a electric motor.
    Fred Cronenwett
    Float flying and scale

  8. #8

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    RE: 1/2 A electric


    ORIGINAL: Lightfoot

    This is a copy of the plans that I sent to him.* I got five (5) copies in case others might want a set.* I will let them go for my cost.

    EDIT:* I just looked back through my records and found the cost off the copies.* I can send them for $5 a copy.* That is a few cents under my total cost.

    Sexy plane, almost make the "Pinto" look simple

  9. #9
    green river rc's Avatar
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    RE: 1/2 A electric

    Been making some progress despite of waiting on materials. Notice the homemade tank, my grandfather was an old control liner and was and still is very resorceful, he once told me "If you aint got what you need make it".
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    With the parts left over, Im going to build a motorcycle.

  10. #10

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    RE: 1/2 A electric

    I have 4 more sets of the plans for the 1/2A Cobra. If anyone is interested just send me a PM.
    Howard

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  11. #11

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    RE: 1/2 A electric

    That's a nice looking little airplane!
    Cant wait to see it when finished!

    David

  12. #12
    green river rc's Avatar
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    RE: 1/2 A electric

    I have ran into a little problem, while waiting for my skins to come in the mail ,my cores my buddy cut for me bowed on me. I have tried to straighten them by bowing them in the oposite direction but so far no luck. I have not spent a lot of time on them yet but I'm sure I will figure something out, they are not usable the way they are and recutting would only do the same thing. Anyone have a suggestion?
    With the parts left over, Im going to build a motorcycle.

  13. #13

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    RE: 1/2 A electric

    Sounds like a fairly common problem with foam cores. Sounds like you are going to sheet the cores?

    If so hopefully you have the upper and lower "cut off" foam peices.
    If so keep up with what went where.
    Is so no problem.

    Round up some heavy books.
    Vacuum and wipe cores real good!

    Put the bottom cut off on a flat straight, strong surface.

    Glue the edges of sheets together to create sheets big enough to do one side completely and trim to about 1/2 inch bigger in all directions than your core. Make 4 big panels of sheeting.

    Glue your sheeting to one surface of each wing.
    Titebond is a good choice as it will loose weight over 6 weeks or so gives lots a working time and is strong.
    Spread it thin with a bondo squeegee.
    place one sheet in the cut off cradle and place your core into place and stack the next cut off( cradle on both sides) and do the same to the next core. stack a big pile of books on top. Dont over kill with the weight I guess an extreem would do damage.
    Make sure cores are straight in cradles. Let this dry 24 or so hours, longer if you can stand it.

    Now unstack all, leaving bottom core in cradle. If your sheeting is stuck to cradles leave them stuck.

    Do the same for the upper skins and restack and weight.

    If the cores were cut from a straight block and stayed flat on bench while cutting this should get you straight.

    If your sheeting is stuck to cradles its easy enough to destroy and peel the cradle foam off finis with sanding block.

    2nd method if you have no cradles or every thing is whacked out.

    Coat core and inside of skin with thin layer of Titebond glue with squeegee. let dry 24 hrs

    Put core on flat surface with bow up.
    Place skin on core and a straight weight along spar and trailing edge so that all is held flat.
    Heat up your iron to high and between the weights slowly iron from the middle of this area out to root and tip.
    This will bond the 2 glue surfaces together even better bond than normal method.

    Move the weight over spar area back just far enough to be on the area already ironed area.

    Working from spar, center of panel out ward to tip and root until you get to the leading edge.

    Now move the trailing edge weight forward enough to do the trailing edge.

    Set to the side and do next core.

    Then come back to first core and do other side.

    Trim and finish up!

    Remember to move slow so heat penetrates sheeting.
    If you smell plastic/foam move a little faster. repeated fast passes will not do as much as slow penetrating passes.

    This heat bonding of aphlitic(spl?) resins is very stong and can be done with titebond or Elmers carpenters glue.
    IT WILL NOT WORK WITH WHITE GLUE!

    Take your time!
    I will work out.

    Hope all this made sense.

    David

    If I left something out someone please add it .






  14. #14

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    RE: 1/2 A electric

    I hope the above post made sense


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    RE: 1/2 A electric

    Be a proper controliner and do an I beamer. Foam wings are for r/cers, and bob hunt.
    Go knife edge your cub!

  16. #16

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    RE: 1/2 A electric

    Someone sent me an email about the Cobra plans in December. I made several trips to visit my kids and in the process of reading email on my home computer, my older son's PC and my younger son's laptop I must have inadvertently deleted the email. I apologize for that. If you will email again, I will respond this time. Again, I apologize.
    Howard

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  17. #17

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    RE: 1/2 A electric

    Have you made any more progress on your build. I would really like to see pictures of your completed model.

    ORIGINAL: green river rc

    Been making some progress despite of waiting on materials. Notice the homemade tank, my grandfather was an old control liner and was and still is very resorceful, he once told me ''If you aint got what you need make it''.
    Howard

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  18. #18
    green river rc's Avatar
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    RE: 1/2 A electric

    I had a buddy to cut the cores for me from pink foam board and they curled up pretty bad after they sat for a few days, no luck trying to straighten them yet. I ordered balsa and skins from Lone Star and it's hard as a rock. The project is currently still on the bench, I just have to get new cores and learn to like the heavy wood. As small as the cores are I may try to shape some by hand with pill foam, I have done it before with great results but that wing had no lead outs. So right now it's back to the drawing board.
    With the parts left over, Im going to build a motorcycle.

  19. #19
    green river rc's Avatar
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    RE: 1/2 A electric

    Replacement cores in hand, project back on track!
    With the parts left over, Im going to build a motorcycle.

  20. #20

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    RE: 1/2 A electric

    green river rc

    How is that project going on the 1/2A Cobra

    I do have a Pinto kit coming watching the tracking as I type.
    Would really like a Cobra plan and like some one said a nice "I" beamer
    have forgotten how to do them to many years ago ( I am now crying ) strewth! help.

  21. #21

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    RE: 1/2 A electric

    Pink foam is at least 4 pounds per cubic feet maybe more... like building with solid balsa and way heavy. Have new cores cut with white beaded foam if you must use a foam wing, that is 1 or at most 2 pounds per cubic feet. Foam works well with larger wings where you can core them but other than for racing I wouldnt use them on a wing of less than 400 sq inches and then only by coring out as much foam as I could.
    Bob

  22. #22

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    RE: 1/2 A electric

    From simple curiousity  what ever happened to the Electric notion?
     My data suggests that a 24 gram HK 2730 of 2500kv on 3S and 17 amps  will spin a Graupner cam prop (4.7 x 4.7) at 24K.
    MY 061 Norvel cannot  spin that prop anywhere near
     Add in a 10 gram ESC and even 100/120 grams for a decent duration battery  .. that's a pretty significant power source.  Easy starting too :-)

  23. #23

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    RE: 1/2 A electric

    newbie to the elec stuff. Do you have to use the Zigras timer? Can you just wire the brushless motor to a esc and battery with and on and off switch?

  24. #24

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    RE: 1/2 A electric


    ORIGINAL: jayseas

    newbie to the elec stuff. Do you have to use the Zigras timer? Can you just wire the brushless motor to a esc and battery with and on and off switch?
    Hi jayseas,
    Yes you do need a timer. A brushless motor has 3 wires and is (Although not in the true sense of the word) like a 3 phase motor and the controller energises the different sets of coils in sequence which then causes the motor to run. If you just connect the motor to the ESC it will do nothing (Although you should always treat it as live once you have connected the battery to the ESC). The ESC requires a signal (Usually from a R/C receiver) and is normally plugged into the throttle channel. The timer replaces the receiver and sends a pre programmed signal to the ESC to tell the motor to start, what RPM to operate at and then stop after a predetermined time. There are quite a few timers out there, the Zigras already mentioned is a great unit as are the Will Hubin timers, another is the JMP2 and Keith Renecle from SA produces another excellent unit (Which also has a governor allowing you to use cheap ESC's with no governor). Then there is the E-Flite unit which is pretty basic (But very cheap and easy to use).

    Hope this answers your question.

    TTFN
    John.



  25. #25
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    RE: 1/2 A electric

    The Eflight timer adjusts the rpm and time in one minute increments and is about $11 to $30 depending on where you buy it.  A switch would only work on a brushed motor with nicad batteries.  The ESC will usually cut off the motor at a certain voltage so it doesn't drain the batteries too low.  That will kill a LIPO.  Maybe someone knows what to do if the plane crashes with a timer.  A fuse maybe on the battery?  I got one that I haven't tried yet.  Of course I will never crash it!!!?
    Glow Head Hood # 7


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