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Suggestions for L-4 Cub motor

Old 01-10-2009, 06:50 PM
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DAKOTANOVASS
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Default Suggestions for L-4 Cub motor

I have a Carl Goldberg L-4 cub that is in need of a motor. I am wanting to put a four stroke into it. Also should I mount the engine inverted, sideways or upright. I would like to conceal the motor as much as possible. So I would think inverted. Any problems with having a four stoke inverted. Any pictures of an existing set up would be great.

Thanks

Terrell
Old 01-10-2009, 07:10 PM
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khodges
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Default RE: Suggestions for L-4 Cub motor

I'm assuming that the Cub is 1/5 scale, or thereabout (84.5 in. wingspan is 1/5 scale). If so, anything in the .56 to .70 range will fly it (4-stroke). I have the Sig 1/5 and have a .65 Saito in it, mounted inverted. The only visible part of the engine is the tops of the valve covers, the rest is completely within the cowl (see pics). Now, the .65 is no longer made, but the newer .62 is the same size as the .56 and is shorter from crank to valve cover than the .65. It should conceal very well inside the cowl if you invert it. The small holes in the front of the Cub cowl should be enough to allow cooling air in, just make sure you have an outlet that is about 1.5 to 2 times larger. I haven't had any problems with mine overheating. To allow the exhaust to exit the bottom of the cowl, you may need to find some kind of 90 degree fitting, or find one of the older style 90 degree elbows.

The glow plug will be difficult to get at with the engine inverted, so either an on-board glow, or a remote plug will be a big help.

The other thing is measuring from the firewall to the prop hub with the engine mount you want to use. I used a DuBro antivibe mount and had to recess the firewall a bit.
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Old 01-10-2009, 08:26 PM
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Default RE: Suggestions for L-4 Cub motor

The Goldberg cub I have has a 76.5 in wing span. So its probably considered 1/6 scale. I have heard of some people using OS FS 48's in them. I figured I would aleast need a 52 up to a 70 to fly this plane so it would not be under powered. Is their any problems starting them inverted.

Terrell
Old 01-11-2009, 01:05 AM
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Default RE: Suggestions for L-4 Cub motor

A .56 should be plenty and then some for power, as the .65 flies the 1/5 scale very well. The .56 will stick out a bit from the bottom, but might be worth looking at how well it fits otherwise. I have no problems with any of my inverted 4-strokes, and I have had as many as 5 of them, all Saitos. Just make sure your tank height is correct with the spraybar, and get the needles set correctly, and it will run just fine, the engine doesn't care which way it is pointed.
Old 01-12-2009, 12:40 PM
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Default RE: Suggestions for L-4 Cub motor

Anybody else out their with four strokes in their cubs, I would like to see more of them.
Old 01-12-2009, 01:15 PM
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Default RE: Suggestions for L-4 Cub motor

I have a GP ARF cub 81in wingspan. It flew for many years (10) on an old ASP80 4c that performed like a modern 65. when it was no longer serviceable I switched to a Magnum 90 4c. both these engines where great for flying in the wind. But last year a Saito .50 4c came available so I installed it. The bigger engines had a problem in fine motor adjustment when flying scale speed, either had to much or to little T. the. 50 solved that problem scale speed at ¼ T instead of 2-4 clicks. But the smaller engine brings with it a whole new learning curve. After a stall with the bigger engines I could be flying again in 20ft of vertical lost, with the 50 we are at 60ft. with the old engines I could gas it and go without a care in the world on takeoff. With the 50, some time on the ground rolling out is required, keep it level and it will lift when it is ready. Keep the climb out level and at the end of ground affect she will level off and most times loose altitude, specially in the wind. Just need to remember to keep it level and eventually it will level off then resume climbing. Maneuvers all have to be planed to account for the low power, and long stall recovery. Its fun.

Joe
Old 01-12-2009, 02:12 PM
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Default RE: Suggestions for L-4 Cub motor

I do have a OS FS 90 I could put on, but its so darn heavy and would stick out of the cowl so much. Right now their is a guy trying to sell a ASP 80 on RC Groups that had one in a GB cub, but beings you said it is not servicable, probably not worth buying. Right now its a toss up between an OS 48 or OS 70 unless I find a deal on something else.

Terrell
Old 01-12-2009, 06:11 PM
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Default RE: Suggestions for L-4 Cub motor

Go with an electric motor! I have the H9 Cub with an Eflight Power 60 in it and it will go straight up. You could go with a power 46, but it's nice to have lots of power for getting out of trouble. I can fly about 20 minutes on one battery and you can't see anything sticking out of the cowling.


Jeff
Old 01-12-2009, 08:09 PM
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Default RE: Suggestions for L-4 Cub motor

I have a Great Planes 90" wingspan with a 120 Magnum 4 stroke inverted in it. I'm thinking a 91 would be OK so I might just swap them out. Mine is completely enclosed in the cowl.

Gibbs
Old 01-15-2009, 10:13 AM
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Default RE: Suggestions for L-4 Cub motor

I have just bought a OS FS 70, should be a good size motor for this plane. I would think it would fly scale like at half throttle. Anybody with experience with this set up.

Terrell
Old 01-15-2009, 10:34 AM
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Default RE: Suggestions for L-4 Cub motor

Hey guys,

Lots of good advice, I have had several cg cubs through the years
and my favorite way to mount is sideways with the valvecovers out
the side and a dummy on the other like the real one. with that said
nothing is as fun as a .91 with a clipped wing. The .70 will be a blast
and fly it great.
Happy Flying,

Ty[8D]
Old 01-15-2009, 10:55 AM
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Default RE: Suggestions for L-4 Cub motor

Question about mounting the engine sideways. Doesnt it effect the handling, with all that weight hanging on one side or do you counter balance it.

Terrell
Old 01-15-2009, 11:27 AM
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Default RE: Suggestions for L-4 Cub motor

Terrell,

I have not had any balance probs,it doesnt seem to matter about that. I do not have any weight at all on mine
with the .91, just move the equipment to adjust weight(bat,rec,maybe servos). My span is 64 inch clipped and
then some. Ive had this setup on atleast 6 of these cubs, must be one of my favorites. you can go to my gallery
and see the one i am flying now.I dont know how to put my pics on here yet,sorry. I'm building a full size wing
for it now to use some floats have'nt done that yet in all my years of flying,cant wait.p.s an electric motor is
great for starting my nitro motors,HA HA just kidding! good luck

Ty

Old 01-15-2009, 11:55 AM
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Default RE: Suggestions for L-4 Cub motor

Dirtrod

Did you have to cut out some of the fuselage to mount your motor sideways. With the FS 90 I have I would need to do that and then the gas tank is to low. The carb on the FS 90 is mounted on the side instead of being centered on the jug. Which means I would have to try and raise the gas tank outlet up to match the spray bar. One other ?, would you have the measurements of the firewall for the thrust lines.

Terrell
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Old 01-15-2009, 06:14 PM
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Default RE: Suggestions for L-4 Cub motor

Terrell,
On mine i had to dremel a spot on the side just for the intake mabey 1/4 not much.
on mine it called for a 1/4 inch plate on the firewall but with the 4-stroke it is not needed.
I will check on those measurments i have the plans and the instruction man.If you
use the .90 you wont put your bat and rec under tank so i rase it up with some styro.
I will get back to you with those measurments. What cub is it ,the anniversery addition?


Ty
Old 01-15-2009, 06:18 PM
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Default RE: Suggestions for L-4 Cub motor

TY
I do not know which kit it is, I bought it second hand.The info you are sending my way is greatly appreciated.

Terrell
Old 01-15-2009, 06:52 PM
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dirtrod
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Default RE: Suggestions for L-4 Cub motor

Terrell,

there is no real measurment to give you the way it shows you mount the top motormount
basically all the way to the top and then hold the bottom one up to the motor and mark the holes.
It might be about a 1/8th in from the top you will need to put a small washer on the left bolts
for some right thrust . just one on each left bolt.Are you useing a two piece mount?

Ty
Old 01-15-2009, 07:13 PM
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Default RE: Suggestions for L-4 Cub motor

I wasn't planning on using a two piece mount, but I suppose I might have to go buy one.
Old 01-15-2009, 07:24 PM
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Default RE: Suggestions for L-4 Cub motor

Terrell,

Just hold it up as high as you can,and keep the crank dead in the middle .Dont forget the washers
its a little more important with the bigger 4-strokes especially on take off.Hope i helped some.

Ty
Old 01-16-2009, 10:34 AM
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Default RE: Suggestions for L-4 Cub motor

Upon closer inspection of the firewall, I could make out the centering lines through the paint. So it wont be a problem to put the mount on. Now I have to fill in all the holes in the firewall. Should I mix some milled fiberglass in the epoxy or just use it straight to fill in the holes.
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Old 01-16-2009, 04:43 PM
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Default RE: Suggestions for L-4 Cub motor

Terrell,

I would think that just epoxy should be fine, the main thing is to seal it off from the fuel. If you had some small dowels to put in the holes then epoxy would be good as well but not nessacery.You are going to love your setup. I do beleive your model is a an
anniversary add. from the picture.

Ty[8D]

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