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  1. #351
    opjose's Avatar
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    RE: Its Bobcat nice

    Eh, you normally want to balance a plane with the retracts down.

    I doubt it will make a big difference in the Bobcat, since it's main retracts open to the side, instead of aft or forward.

    The nose gear retract will change the C.G. but the effect should be minimal.

    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  2. #352
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    RE: Its Bobcat nice

    FBD and opjose
    thanks for the reply.

    FBD, I should have been more specific as I did put retracts in mine. In any case, you guys answered my question(s) and I know what I need to do. thanks again.
    My biggest worry is that my wife (when I am dead) will sell my R/C stuff for what I said I paid for it.

  3. #353
    opjose's Avatar
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    RE: Its Bobcat nice


    ORIGINAL: Flyboy Dave

    ....empty....the tank sits almost on the C/G.

    FBD.
    Ok, that brings up this question:

    The original manual on the Bobcat was far off on the C.G.

    Someone here at RCU determined that the C.G. should be around 10.3". That has "stuck" and seems to be what people are using.


    However does the 10.3" figure represent an empty or full tank?

    Could it also be why the original manual was so far off?


    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  4. #354
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    RE: Its Bobcat nice

    As stated above, the tank is pretty much on the CG. I suppose it wouldn't hurt to double check it with the tank full to make sure you aren't tail heavy. Myself, I balanced it with the retracts up figuring that when the gear is down the nose wheel will cause the weight to move forward. A little extra nose weight won't hurt on landings and takeoffs but being too tail heavy might effect the way it flies. I didn't check it both ways though. Might not be enough to matter at all.

    Blessing, Terry
    Live simply. Love generously. Care deeply.
    Speak kindly. Leave the rest to God

  5. #355
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    RE: Its Bobcat nice

    ....yes, set the C/G at 10.3 to 10.5
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  6. #356

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    RE: Its Bobcat nice

    Don't wanna get off topic but I am thinking of running either a Thunder Tiger .46 or a Saito 83. Which one will be better? So far, I'm hearing that everyone is putting larger engines on these planes so I'm leaning towards the Saito 83. Probably run a 3 blade 12x6 or 12x8 for ground clearance. Anyone agree? Please help!

  7. #357
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    RE: Its Bobcat nice

    While the 4 stroke Saito's are great engines, remember that a 4 stroker produces less output power with similiar displacement compared to a 2 stroker.

    That is, the Saito will be just about equivalent of the Thunder Tiger .46.

    In your shoes I'd just opt for a larger 2 stroker, like the .75's everyone here is using.

    I'm using a GMS .76 2 stroker in mine.

    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  8. #358

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    RE: Its Bobcat nice

    I was hoping that I wouldn't have to buy another engine. I guess I'll cancel my order and get something that will work for the two engines I have already. Or perhaps get the .25 size bobcat. Oh well [&o]

    Unless someone out there needs a .46 Thunder tiger that is brand new. I just broke the engine in on a bench for a couple of tanks. I'll trade for a 75 Tower Hobbies engine plus a little cash if it's worth it. Any takers?

  9. #359
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    RE: Its Bobcat nice

    ....the Saito will fly it just fine....I have a YS .63 in mine and it's OK.

    FBD.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  10. #360
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    RE: Its Bobcat nice

    You can use the TT46 pro.... but adding a jett-stream muffler to it will be a big benifit. Use a 10x6P prop. Power is pretty good, and the resulting aircraft will weight less than those using the big-block engines.
    Bob Brassell
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  11. #361
    opjose's Avatar
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    RE: Its Bobcat nice


    ORIGINAL: Nitrodan73

    I was hoping that I wouldn't have to buy another engine. I guess I'll cancel my order and get something that will work for the two engines I have already.

    Unless someone out there needs a .46 Thunder tiger that is brand new. I just broke the engine in on a bench for a couple of tanks. I'll trade for a 75 Tower Hobbies engine plus a little cash if it's worth it. Any takers?
    As others have already posted, it WILL fly fine with either engine, since you already have them.

    You will not attain the super screaming speeds people are getting out of this plane with the larger engines.

    You will however find it quite respectable.

    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  12. #362

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    RE: Its Bobcat nice

    Thanks for the help. I'm not looking to have an extreme speed airplane but I want it to be fast and powerful. I will try using the TT 46 pro and if I need to, switch it out if I'm not happy. Thanks again guys!

  13. #363

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    RE: Its Bobcat nice

    We have a BobCat and it really moves with a Tower75. It seem very difficult to get it trimed. At full power it wants to climb like crazy. After it's trimed, slow down and it decends. These are not minor movements it's eithere up or down. Any suggestions???

  14. #364
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    RE: Its Bobcat nice

    ....Welcome to R/C Universe, Undertaker....[sm=thumbup.gif]

    ....where is your balance point ? The original instructions were wrong.

    Flyboy Dave.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  15. #365
    opjose's Avatar
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    RE: Its Bobcat nice


    ORIGINAL: TheUndertaker

    We have a BobCat and it really moves with a Tower75. It seem very difficult to get it trimed. At full power it wants to climb like crazy. After it's trimed, slow down and it decends. These are not minor movements it's eithere up or down. Any suggestions???

    Your C.G. on a .52 size Bobcat should be at 10.3".

    The elevator "neutral" position should be as per this part of the thread:

    http://www.rcuniverse.com/forum/m_45..._Bobcat/tm.htm

    The Bobcat should sit on the ground so that the airfoil has at LEAST 3-4 degrees of positive incidence. This means making sure that the front gear is longer, so that the Bobcat sits with it's nose slightly higher.

    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  16. #366

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    RE: Its Bobcat nice

    I am wondering how to determine what pitch 3 blade prop would equal an 11X 8 2 blade prop for thrust. I want to use a 3 blade pusher prop for the Nitro Planes Bobcat 50. Does a 9 x 7p 3 blade prop come close? Using a OS .61 engine.

  17. #367
    opjose's Avatar
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    RE: Its Bobcat nice


    ORIGINAL: orstraycat

    I am wondering how to determine what pitch 3 blade prop would equal an 11X 8 2 blade prop for thrust. I want to use a 3 blade pusher prop for the Nitro Planes Bobcat 50. Does a 9 x 7p 3 blade prop come close? Using a OS .61 engine.
    Thrust or speed? These are not the same thing.


    A three blade 10x8 is the same in PITCH SPEED as the 11x8 2 blade prop and equal in thrust.

    You loose a little for the lesser efficiency of the three blade prop, but not so much you would notice.

    A 9x7 3 blade prop is equal to a 10x7 2 blade prop, which is really too small for the OS .61.

    Most guys are flying their .75's with an 11x7 2 blade or an 11x8 2 blade. This is still small for the .75, so it may also be OK for the .61.


    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  18. #368
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    RE: Its Bobcat nice

    ....the 11-8 prop is perfect for the Tower 75

    FBD.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  19. #369
    still4given's Avatar
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    RE: Its Bobcat nice

    Hey Dave,

    Are you using the Graupner 11x8?

    Thanks, Terry
    Live simply. Love generously. Care deeply.
    Speak kindly. Leave the rest to God

  20. #370
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    RE: Its Bobcat nice

    ....no, the Zinger 11-8. I had a 12-6 on it.....not enough. The 8 pitch is working well.
    I should have went with the Tower .75 I guess.

    That reminds me....I have to straighten up the gear opn the Bobcat, and start getting
    ready fot this weekend. I'll be out there Saturday only. I have to be with a team at
    El Mirage on Sunday morning for the SCTA lake speed races.

    Next week is the Parker Az. Giant Scale races. I missed them last year. []

    FBD.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  21. #371
    still4given's Avatar
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    RE: Its Bobcat nice

    Looks like we will be there Saturday as well. I couldn't swing the Phoenix trip. I'll do my best to get my Bobcat back up and running.

    Blessings, Terry
    Live simply. Love generously. Care deeply.
    Speak kindly. Leave the rest to God

  22. #372

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    RE: Its Bobcat nice

    I am thinking of getting a bobcat 50 as well. How is it characteristics in flight? Is it arobatic (ie loops, rolls, inverted, flat spin etc)
    airborne crazy

  23. #373
    opjose's Avatar
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    RE: Its Bobcat nice


    ORIGINAL: airborne14830

    I am thinking of getting a bobcat 50 as well. How is it characteristics in flight? Is it arobatic (ie loops, rolls, inverted, flat spin etc)
    Eh, it's practically a Delta wing...

    Flat spins, etc, are not exactly part of it's repetoir... though you could attempt to force it.

    While it does loop and roll ( what plane cannot? ), this plane is really about carving BIG, BIG arcs in the sky at high speeds.

    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  24. #374
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    RE: Its Bobcat nice

    Thought yall might like a few photos... I received these the other day.

    Of note, Dub now has the LX muffler available in pusher configuration. Not shown here, but is similar to the image I posted in another thread.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Bob Brassell
    Jett Engineering - Engine Mfg Support Forum Host
    rjb@jettengineering.com or bob27s@hotmail.com
    RB-78

  25. #375
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    RE: Its Bobcat nice

    will he have one to fit the tower 75?


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