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H9 15cc Carbon Cub

Discussion in 'Giant / Scale ARF Build Threads' started by AKNick, May 8, 2016.

   
  1. AKNick

    AKNick 150cc

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    Thanks for the tip, unfortunately richening the low end compromises the transition, and would die. I played around with it quite a bit. maybe the top end needs to be richened so it doesn't lean out when bringing down the throttle rapidly. It's still emitting some black breakin residue, so I think I'm just going to run it and not chop power for a while.
     
  2. Bill Herbert

    Bill Herbert New to GSN!

    I would love to hear more about your setup and how it is working out. I have the same plane on the shelf waiting to be built and the RCGF 21cc is the engine that I was looking at using. Before purchasing the engine I really want to ensure the setup is going to work out. It would be great to hear how the plane flys on this setup.
     
  3. AKNick

    AKNick 150cc

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    I have done more engine tuning and have the engine running much better as previously mentioned. I actually don't have a flight report yet... I was disassembling the plane to take it to the field when my dog backed into the rudder and broke the servo case (internal stop). So waiting on that. Mounting the 21cc twin engine was tricky (throttle servo location, and pretty tight for twin ignition wires), and from what I have heard these small 10cc cylinders take a while to break in. If I was to do it again I'd use a single 20cc or 30cc, I personally think the plane is a little heavy so a 20cc should be just fine for scale and basic aerobatics. I think the 30cc engines could be easier to hand start, where as this 21cc is almost impossible with out an electric starter. Just my 2 cents on this. Need the weather to cooperate so I can fly! uurrrg!
     
  4. AKNick

    AKNick 150cc

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    New servo installed, cowl back on, batttery topped off, looked outside... rain :frown: for the next two days in the forecast as well :thumbsdown: Looks like I'll have to wait until Thursday fingers crossed.
     
  5. AKNick

    AKNick 150cc

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    image.jpeg Maiden complete.... Engine is still very finicky. Had to richen it more inside the cowl. Full power takeoff was scale, I really wanted more power. Plane tracked strait w/no trim but was super touchy. The wind picked up and was swirling around so that didn't help the over all feel of the plane which felt glitchy. Very pitch sensitive like a tail heavy situation. After about 2min I felt like the LH flap was twerking out again, I watched two death spirals and then caught some lift, engine quit, threaded the plane past some tall alders and a gap in some hemlock trees, pitched/stalled down to the field and the fancy gear planted the plane on the ground LH main first, pitched up, broke the tail wheel off, RH main touched down followed by the wing tip. Only damage was the tail wheel from a two foot tail wind stall! Wow.
    So in conclusion;
    cons: need more power, seems like a heavy plane, engine not performing very well.
    Pros: responsive, gear works great, nice looking scale plane.
    Overall thoughts: not the relaxin Sunday flier I was expecting for a maiden. Need to figure out a few issues at this point. Has potential!
     
    Last edited: Mar 24, 2017
  6. AKNick

    AKNick 150cc

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    Ok I just found this out. The second batch of carbon Cubs have an amendment to the center of gravity. This is why mine flew so cruddy.
    Old manual = 151-159mm or 5 7/8-6 1/4
    New manual = 100-120mm!!!!
    I am so lucky to still have it in one piece!

    Once I fix the tail wheel, retune the engine..., and take the lead out of the tail I'm going to brave the skies again.
    Already swapped the faulty intermittent flap servo.
     
    pawnshopmike likes this.
  7. AKNick

    AKNick 150cc

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    Man I feel bad I left this thread on pretty much a bad note... I started tinkering on this flying machine again.
    So many good reviews of this engine and plane (separately) I'm thinking there must be a way to solve this.
    Took the lead out of the tail. Swapped positions with the fuel tank and the ignition module (kinda wondering if the dirty side was was too close to everything else). So now the fuel tank is a little easier to see, and access the fuel dot. I also took the liberty to replace the tail wheel with a much larger one.
    One more thing I realized was that I never did take the chance to play with different propellers. After doing a bunch of research I found that the size of the prop (16X8) was a good choice... but I also found a review that used a 17X4W APC that had decent numbers, so I just so happened to have one! I've had in the past an engine with a cruddy idle that just needed a little more mass to keep it spinning low rpms... mabye this will cure that issue. Modified a spinner nut by basically drilling out the front so the crank shaft threads almost come even with the tip of the spinner nut - this will help dramatically with using an electric starter.
    Now I just need some time off and decent weather to continue.
     
  8. AKNick

    AKNick 150cc

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    The larger/heavier prop lets the RCGF 21cc idle great. I tried APC 17x4W, 16X4W, 16X6, and the previous wood 16X8. I have no numbers but after doing some engine runs I cannot seem to get this engine from Idle to WOT without dying, unless I slowly transition. Punch it, and it dies. Adjusted the LSN and HSN about a 1/4 turn on either extreme (1/8 turn on either side of where I had it) to see if that helped which I could find the symptoms of rich and lean... but no happy spot. Engine is still producing black residue out the exhaust can get it to idle and run WOT without fading. Remembering before it would die when power is chopped, which has reversed now. :face-palm: Maybe the props are too heavy? maybe a larger wood prop like a 17X8 dunno, I feel like this shouldn't be tearing my hair out. Might be time for a DLE20 and a new cowl.... but this little twin is so CUTE!!!
     
    Last edited: Apr 7, 2017
  9. AKNick

    AKNick 150cc

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    @Terryscustom What are your thoughts on my little 21ccT RCGF engine issue? Maybe you can sense my problem lol
     
  10. Terryscustom

    Terryscustom 640cc Uber Pimp

    What prop is recommended? That engine has barely got enough power to get out of its own way so 17" is asking a lot.

    Needles will need very fine adjustment so 1/8 to 1/4 turn is likely one extreme to the other
     
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