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  1. #1
    F4U Corsair's Avatar
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    CG for the Nitroplanes (CMPro) Katana 120v2

    Trying to find out what the CG should be for the Nitroplanes (CMPro) Katana 120 v2. katana 120 v2
    Experience is something you aquire after you need it!

  2. #2
    opjose's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    From 20-30% of the MAC.

    To "eyeball" it, measure back about 25% of the chord length at the "indent" along the LE of the wing off the fusealge.

    You can push it further back, but I find 20-25% to be pretty good.

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

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    F4U Corsair's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    Yes, I'm familiar with the MAC method, but this airplane has a double swept wing design (tapers on both sides) so do I add just the front "s" measurement as listed on the cg calulator or should I account for both which would then end up being the same as the root cord - the tip cord? Another guy told me to start with the position of the wing tube, this comes to about 6.5" from the LE which isn't too far off my MAC calculations of 6.25-7" for 25-30% MAC. Does anyone have the manual for this airplane, I would really like to see what CMP recommends, I've search high and low on the Internet and havn't found any reference to the CG or the manual for this bird.
    Experience is something you aquire after you need it!

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    opjose's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2


    For the Katana measure back from the LE "indentation" as per the following image.



    Normally if the C.G. is at or in front of the wing tube you are fine.

    The Katana is a 3D plane, and as such everyone adjusts the C.G. to their liking.

    What is perfect for me, may appear tail heavy for you.

    I adjust the C.G. on this plane so I can fly it level, hands off, at 80% throttle BOTH upright and inverted.
    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  5. #5
    F4U Corsair's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    OPJose, thanks for the pic, yes I did measure the cord at the indent. The issue I have is that the it's 15.75", so about 4.8" at 30% (max). The wing tube is lining up at about 6" back from the leading edge. If you have time, could you measure your cg so I can set mine the same. I don't want to maiden it super super tail heavy, and would like to double check this before taking it up the first time. I'm ok with 30% maybe more, but don't want to have a bucking bronco the 1st time out (my old ticker can't take that anymore). I appreciate your help and input! DG
    Experience is something you aquire after you need it!

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    opjose's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    I don't remember what I currently have it at, but I would suggest you start with 4", which should put you squarely in the "safety" zone.

    Fly the plane and trim it out.

    Then flip it over and see how it behaves upside down.

    Also try an approach.

    With my C.G. set neutral, my plane tends to balloon up just before landing.

    All of my C.G. neutral 3D planes do this... e.g. my Funtanas, Katanas, Giant U-Can-Do, Twist, Yak 54, Profile Edge 3D, etc. and it took a while to get used to it.

    I plunked a plane or three down quite hard on landings, breaking out the gear, before I learned.
    The plane will balloon up, stall and fall straight down, breaking out the gear... so it is far safer to move the C.G. forward at first, which prevents or eliminates this.

    When you fly it the first time, try a few very high slow speed approaches, and if you see this tendancy, be prepared to hold the nose down a bit at landing.

    Also learn the stall speed... it will be slower than what you may expect... unless you have a super heavy engine, this plane will crawl accross the sky.... and works best with a lower pitch high thrust prop.


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

  7. #7
    F4U Corsair's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    Thanks, I'll give that a shot, I had a used SPE40cc so I put it on this bird. I knew it was tail heavy and needed nose weight so I thought what the heck, maybe it will balance and then I have usable weight. I don't intend to fly fast but will give it a shot at 3D moves. Overall dry weight RTF came out at 13 lbs. so a bit heavier than I hoped but not too bad. Hopefully, it still floats well, and doesn't drop like a rock without thrust. The airframe is really built well, and I'm impressed. It may not be as light as some of the newere 10-11 lb. airframes available now, but it's not flimsy and won't break if you pick it up wrong. I'm still going to have to add additional nose weight, so I'll first move the 2 batteries to the firewall and go from there. I've flown 3d profiles, twist, and a few others so I'm not a newby, but this is my first gasser and there largest airplane I've owned so I wanted to be a bit more cautious starting out. The only mod I've done is to add a much larger and strudy aluminum landing gear a friend gave me, so I can swing a larger prop (18-22"). Overall, the airplane looks good and it looks like you like the way it flys. There is not much talk or info. on this model on the Internet. I would have thought that at the cheap price they have it on sale for, lots of folks would give it a try.

    Thanks again for your help, I'll let you know how it turns out. DG
    Experience is something you aquire after you need it!

  8. #8
    opjose's Avatar
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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    A 40cc should give the plane incredible pull.

    Let me know how it goes.

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

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    RE: CG for the Nitroplanes (CMPro) Katana 120v2

    Hey guys, I "nosed into" your thread looking for the same elusive CG for this aircraft. I bought mine from a fellow modeler and assumed I could get a decent manual from the manufacturer. What a joke! The Chinese to English translation would be hilarious if I wasn't seriously attempting to put this thing together. Relying on my experience alone for assembly, I pretty much tossed the so-called assembly instructions. The "manual" I had was apparently for a different aircraft and it told me the CG was 85mm (3.34") from the leading edge. This is incredibly too far forward, especially for a 3D aircraft! I was planning to place the CG on the wing tube but thought some of you may have already experimented here, and I was right. RC Universe is a great resource. I think I'll try just forward of the tube as a starting point expecting more stability until I fly it. After that I'll start moving it back until I get the agility I want in this 3D aircraft. I'm using a DLE-20 based on cost and the raves our club members have for this power plant. It should haul this one around quite nicely. I'm going to need nose weight unfortunately even cramming all of the equipment up front. Thanks for the advice!

  10. #10
    slamn sammy's Avatar
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    I'd like to know how it did with the 40ccer! I'm putting a DLE50 on mine. Let me know how it works. Contact @ ( deadmeataircraft@gmail.com ).good luck! :-). P.S. l have been buying 22x10 from hobby shop's and paying $30-34.95 for them. I started buying the 21x14's for $7.95 & the 22x8 &10's from Hobby King, there made out of beech wood also, where I was using on my 100ccer's 26x10 prop's and paying $40-50.00 a prop! I'm buying the 24x14's for $7.95 and the 22x8-10's for $14.95! HK. Check it out! For all u scale guy's running the Q40-42's & z38's, the 18x8-10's are $5.95! The down side is that it takes 2 to 3week's to get them, to get them cheaper! To get them sooner it cost more!.... ( THE SAVE'S IS WORTH THE WAIT ). They come from hong ion! Some times, you can find them in the USA warehouse and get them sooner!
    Last edited by slamn sammy; 09-06-2013 at 01:05 PM. Reason: mis spelling

  11. #11

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    A 50CC? That will haul it around!

    Dave

  12. #12
    slamn sammy's Avatar
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    LOL..l know it will, I'm not looking for speed. Going to use a 21x14 slow fly prop from Hobby King. I have it on a Gold Wing MX 2, with a DLE 55 and it pulls the gut's out of it! LOL.. I'm going to us this for 3ding around. Just hopes it will stay together??

  13. #13
    slamn sammy's Avatar
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    Katana 160

    I just it will stay together! Lol... I'm going to 3d it only. I got four racer's for speed. + a 30% Mx2 with a DLE 55 that go's good. ,;-}

  14. #14
    slamn sammy's Avatar
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    What's up? Be careful! I was watching a u-tub video of some guy's flying one with a Home lite 25ccer' looked like it was fixing to fall out of the sky! I was going to install one mine, till I seen that video. Would thank the DLE 20 make more power. I figure the CG by measuring from the LE to the TE and marking the hafeway point, then, I measure from the hafeway point to the LE and mark hafeway . That's 25%! Good place to start! Most kit's start at 30%. I like the 25%. More stable! I found that the wing tub is not always right for starting with the CG. Most of the time, I end up on the wing tub, (BUT) after I fly it a bet so I know what the plane will do! I also start with 1\4" elevator on low DR, On high as munch as I can get. I have a DX8, so I have 3 rate switch's, so on my DR's start at 150% high, 70% med, and 30% on low. My Expo, 70%,50%,30%. High to low. On the DLE 20, try a 18x8, I found the over propping is better to start! Than adjust. Good luck and post with the out come! P.S. STAY OUT OF THE TREE'S! LOL.... '-)
    Last edited by slamn sammy; 09-06-2013 at 02:11 PM. Reason: DEE,DEE,DEE..........


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