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  1. #1

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    Hobbico Avistar C.G. Range...

    Using the Great Planes C.G. Machine, my Avistar is balanced at 2.75 ".
    Here is my problem:
    The instructions that came with the plane suggest the C.G. is @ 3.25" for your "first flights".
    Another place I read, it says the C.G. Range is between 2.5" & 3.5".

    Should I really be concerned where my C.G. is at or should I add weight to bring it to the 3.25" mark?

  2. #2

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    Hobbico Avistar C.G. Range...

    Tower's specs list the CG range between 3 5/8" to 4 1/2" back from the leading edge with 3 5/8" as a docile starting point.
    At 2 3/4" your a little nose heavy which will probably be OK but it might make flaring for a nice landing a little more difficult. Have you tried moving the battery a little further back?
    The more you fly, the more you buy.

  3. #3

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    Hobbico Avistar C.G. Range...

    I forgot to mention that I already moved the receiver/battery tray as far back as possible.

  4. #4

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    Hobbico Avistar C.G. Range...

    I haven't checked Towers web site but I built 2 of these last summer and I saved the manuals so I dug them out and checked. The manual says "The balance point is located 3-1/4" (83mm) back from the leading edge. This is the point at which your model should balance for your first flights. Later, you may experiment by shifting the balance up to 5/16" (8mm) forward or back to change the flying characteristics". It also recommends not exceeding the stated cg range. I balanced both planes at the 3-1/4" mark and both planes flew excellent and handled perfectly. I was pretty impressed with the overall quality of the planes.

  5. #5

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    Hobbico Avistar C.G. Range...

    Sorry I did forget to mention that I added about 1/4 to a 1/2oz of lead to the tail of the plane to get it to balance on the recommended cg. I cut a 1" opening in the fuse ahead of the stab, coated the weight with epoxy and glued it in. Covered te hole with a scrap of Monokote.

  6. #6

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    Hobbico Avistar C.G. Range...

    Well I did all I could...
    It's to a point where it is balanced @ 3.25" with a roll of electrical tape about 3.25" down from the back window..

    Now I just need to see what that weighs!

    Photo 1

    Photo 2

    I just don't understand....
    I buy an ARF version of a plane, build it as specified in the instructions, make absolutely no alterations and yet we have to add .25 - .5 oz of weight to get it properly balanced.
    Very frustrating.

    EDIT: I also just emailed Hobbico with the problem... lets see what they say.

  7. #7

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    Hobbico Avistar C.G. Range...

    What brick of an engine do you have up front to cause this?

  8. #8

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    Hobbico Avistar C.G. Range...

    I have what came with the kit...
    an OS .40 LA.

  9. #9

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    Hobbico Avistar C.G. Range...

    ufdfireman,
    Don't get frustrated, most ARF's end up needing a little lead here or there. A half ounce is nothing.
    The more you fly, the more you buy.

  10. #10
    hookedonrc's Avatar
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    Hobbico Avistar C.G. Range...

    I had the same problem with mine. It flies great with the OS46FX that I mounted, but there is enough lead in the tail you can use it as a weapon. During training, the tail was broken off on one of my better take off's. Pulled back on the throttle when it was about 5 ft off the ground instead of the elevator, snapped the tail right off when it hit. Was able to fix it and have used it for the last year. Still have the weight though.
    Will add something clever and witty if I ever come up with something.

  11. #11

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    Hobbico Avistar C.G. Range...

    ufdfireman,

    Wierd. I guess it's part of the manufacturing irregularities. Best to get it balanced, though! Stick Jammer is right. .25 to .5 oz is nothing.

    clear skies.

  12. #12

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    Hobbico Avistar C.G. Range...

    You'll never notice the weight. The farther back you can get it the less you'll need. There is a solid former in front of the stab so I put the weight in front of it.

  13. #13

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    Hobbico Avistar C.G. Range...

    Thanks for the help everyone....

    I got it all balanced now... put it inside the fuse. in front of the stab like bullseye suggested.

    Now I just need to patch the hole with covering!

    Thanks again

  14. #14

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    Hobbico Avistar C.G. Range...

    I put one of these together for may dad las weekend and it too needed about 1/2 oz of lead in the tail to ballance. It has an ASP 46 which i am sure is a bit heavier than the reccomended 40.

    Yet to see how she files due to weather

    Ben in SC

  15. #15
    MinnFlyer's Avatar
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    Hobbico Avistar C.G. Range...

    Don't feel bad about 1/2 oz. I just completed an ARF that needed 3/4 of a POUND for nose weight!

    BTW, It flew great.
    Mike B. AMA# 42400 www.gettingairborne.com
    Ultra Sport Brotherhood #2 - Waco Brother #188 - Cub Brother #2

    \"Those are my principles. If you don’t like them, I have others.\" - Groucho Marx


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