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  1. #1
    thailazer's Avatar
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    Engine Choice for a 73 inch J3 Cub.

    I bought out a fellow's RC hobby here and ended up with a radio, Spitfire kit half built, several rolls of covering, a flight box, lots of accessories, and a 73 inch span Clair J3 Cub. I plan on recovering and re-hinging the Cub and will put either an OS Max 35AX or an OS Max 46AX in it and am having trouble deciding which engine. The wing was built with very little dehederal and ailerons so it might make a nice aerobatic sport basher. I already have a 35AX in my Tiger 2 so getting another one would help build "that twin" later on down the line, but I am thinking a 46AX would give this ship some real punch. The plane looks well designed and well built and could handle some aggressive sport "non-scale" flying.

    Let me know your opinions on what you would do. Do the 46AX engines really use that much more fuel? Would it be too much power?
    Tiger Flyer #49

  2. #2
    skylark-flier's Avatar
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    RE: Engine Choice for a 73 inch J3 Cub.

    Definitely put the 46 in it. I've got a GP Cub with nearly the same wingspan and the original OS40LA wasn't really enough for it. She's a floater, no doubt about that, but she needs a bit of oomph to get off the ground in a reasonable distance to start with.

    Yeah, there's practically no dihedral on a Cub.

    I fly several planes with 46-class engines in them. If you're not "maxed out" with the RPMs all the time you'll get about 1 minute/ounce fuel. I use mostly 10oz tanks with my birds, a couple have 12 oz. with plenty of time in the air per flight.
    Dave W. TSgt, USAF/ESC (Retired, 1968-1990)
    AMA #94881, VR/CS #208
    " Old-school" C/L (1955) & R/C (1973) Sport Flier
    SIG Kadet Brotherhood #69, SIG Brotherhood #109, Cub B'hood #198, Glowhead B'hood #51
    Flying field coords: 38.650863,-78.44985

  3. #3
    thailazer's Avatar
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    RE: Engine Choice for a 73 inch J3 Cub.

    Thanks Skylark. Looking at the original box, I misread the brand name as it was quite faded. It is actually a Flair RC kit.

    http://www.flairmodels.co.uk/Aircraf...tageframes.htm
    Tiger Flyer #49

  4. #4
    Spitfire222's Avatar
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    RE: Engine Choice for a 73 inch J3 Cub.

    I had a GP .40-size Cub and it was powered by an OS .46LA, which was more than enough. With that said, I wouldn't have gone with a smaller power-plant than that. If I remember correctly, it had a 12oz fuel tank, and I could get longer flight times than I wanted (15+ min with plenty of fuel to spare). I think you'll be happy with the .46, good luck!
    Vincent

  5. #5
    thailazer's Avatar
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    RE: Engine Choice for a 73 inch J3 Cub.

    Just checked with my local dealer. He has the 55AX on sale for 3 dollars more than the 46AX. Having a Tool Time moment here.
    Tiger Flyer #49

  6. #6

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    RE: Engine Choice for a 73 inch J3 Cub.

    Though it is a bit of an overkill in my opinion, I would not pass up such a deal as you can always use the left stick for throttle management when necessary.

    Karol
    When inverted always remember that down is up and visa versa

  7. #7

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    RE: Engine Choice for a 73 inch J3 Cub.

    I have two 1/5 scale cubs..( 80 " ) The GP fabric covered cub and the hanger 9 40 size ARF...I would not hesitate to use the OS 46 on your Cub...I have two OS46ax motors and they are my favorite motors...They have lots of power and they are very economical to run...The Cub has little dihedral...It will not be very aerobatic with a full size wing...You need a clip wing if you want an aerobatic Cub..Yours might be a 1/5 scale with a clip wing..What is the cord? The cord on my 1/5 scale cubs itis about 12"....Fuse is about 51 1/2" from the prop drive washer to the back of the rudderThey are floaters..Watch the takeoff..Make sure you have flying speed before liftoff or it could stall and crash...Cubs are notoriously hard to get of the ground..You need learn how to do it...That being said they are very easy flyers....I love my Cubs...The bigger the better....I am using 4 stroke motors on my cubs because I like how they sound...I also do not like to over power a cub...Cubs (unless you have a clip wing) just seem more scale putting around the sky...That is just my opinion..There are many Super Cubs out there with Tundra Tires and tons of power and flaps that can take off and land in just a few feet but a normal J3 Cub to me should just putt putt around maybe a slow roll or two and a stall turn here and there...I have a buddy that flys his completly differently than I fly mine...He ripps around the sky...He has a 1/4 scale with a DLE30 in it....He tore the fire wall rite out after the first 3 ftights...He had to redo the whole thing...I have a OS 120 4 stroke in my 1/4 Sig Cub...I fly at about 1/2 throttle most of the time...Thats the nice thing about this hobby...there is enough room for us all...
    Ken , Biker BC Cub Brother #6 Ultra Sport Brother # 100 Tiger Club # 7 Pulse Brother # 1 Sig Brother # 58 Top Flight Brother # 9

  8. #8

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    RE: Engine Choice for a 73 inch J3 Cub.

    I have flown my Goldberg Cub, about the same size with a bunch of motors. I had a K&B 65, ST 61, O.S. 70fs, O.S. 48 fs, ST 45. The little 48 did fly it in a very scale manner. There was no vertical take offs, but it was nice to cruise around. The ST45 flew it pretty well. The ST 61 and K&B 65 were total VTO. IT would roll about its own length and then go straight up. It was a super sonic turtle. Best engine I used was the 70 four stroke. Plenty of power yet would fly around at a high idle and sounded so good. I am going to put a Magnum 70 in mine when I pull it down to do repairs.

    Buzz.

  9. #9

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    RE: Engine Choice for a 73 inch J3 Cub.

    You might want consider one of the OS 46 LA's diesels we have listed on ebay which will swing scale 12 X 6 at over 9000 rpm and a 6 oz tank for a 20 minute plus flight.
    Bob Davis, Owner - Davis Diesel Development

  10. #10
    thailazer's Avatar
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    RE: Engine Choice for a 73 inch J3 Cub.


    ORIGINAL: ddd

    You might want consider one of the OS 46 LA's diesels we have listed on ebay which will swing scale 12 X 6 at over 9000 rpm and a 6 oz tank for a 20 minute plus flight.
    Did opt for the OS 46AX but your suggestion is a good one. With the price of fuel rising, the torque and economy of a diesel is worth looking into.
    Tiger Flyer #49

  11. #11

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    RE: Engine Choice for a 73 inch J3 Cub.

    With the AX rather then the LA you may add you may add 1000 Rpm to the 12 X 6
    Bob Davis, Owner - Davis Diesel Development

  12. #12
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    RE: Engine Choice for a 73 inch J3 Cub.


    ORIGINAL: thailazer

    Just checked with my local dealer. He has the 55AX on sale for 3 dollars more than the 46AX. Having a Tool Time moment here.
    I had a similarilly sized J-3 (Goldberg) and flew great with an OS .60 on it.
    He who dies with the most toys wins!

  13. #13
    smkrcflyer's Avatar
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    RE: Engine Choice for a 73 inch J3 Cub.

    I have the GP .40 size cub with a Saito 72 in it and it's great.
    Steve
    Club Saito #638, Ultra Sport BH #67, Cub BH #71

  14. #14

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    RE: Engine Choice for a 73 inch J3 Cub.

    Hi!
    If you want to fly like the real CUB does on the wing and have relaxed flights...use a OS LA .40 and a 12x4 prop. If you want to fly it overpowered and totally distroying it's good flying characteristics... use a larger engine.
    Jan Karlsson - Supplier MVVS Products

  15. #15

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    RE: Engine Choice for a 73 inch J3 Cub.

    You are correct, however OS stopped making the OS LA 40 and replaced it with the .46 LA.
    Bob Davis, Owner - Davis Diesel Development

  16. #16

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    RE: Engine Choice for a 73 inch J3 Cub.

    I've seen so many Cubs that look like Cubs on the ground but in the air, they just look like another sport model zooming around because they have so much power. Everyone says, "that's what the throttle is for" and then they fly the plane fast and with a ridiculous rate of climb.

    I've had high powered planes and low powered planes and they are different pleasures and require different skills. If it were me, I'd enjoy the Cub for what it is. Full scale pilots at airshows do amazing routines with low-powered Cubs, but it is a different kind of flying.

    The LA 46 will swing a 12x4 prop just fine and provide moderate power.

    Jim


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