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Need engine and servo suggestions on new build

Old 07-05-2013, 09:08 AM
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daddyrabbit1234
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Default Need engine and servo suggestions on new build

Hi, I'm looking for suggestion's on what engine and which servo's to use on my first build. I'm gonna go with a gas engine on this one. Would a DLE 20CC be too big? Here are the plane specs. It's a Piper J-3 Cub with fiberglass floats.Specifications:•Wingspan: 70.6 in (1795mm)•Length: 45in (1145mm)•Wing Area: 682sq in (44sq dm)•Flying Weight: 5.30-6.0lb (2400-2700g)Recommended Setup:•Motor system: G32 4250-800KV brushless motor•Speed control: 80A ESC•Prop: 14 x 7 or 15 x 6•Servo: standard servo (5pcs)•30C 4000mAh 4S LiPODescription for float setThis is a fiberglass float set. This set includes a pair of fiberglass floats, a water rudder, strut set, pushrod, tube and hardware. The color is white so you can paint it to a color of your choice.Specifications:•Length: 840mm (33in)•Weight: 1000g (2.20lbs)•Color: White•Construction: Fiberglass
Old 07-05-2013, 10:16 AM
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JohnBuckner
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Default RE: Need engine and servo suggestions on new build

A seventy inch J series if it is even remotely close to scale is going to be far too small for a 20cc gas engine. Remember J series cubs had most of their engins hanging out the side. Its definitely not going to fit the cowl very well and think about where you are going to stuff that ignition box.

Also I seriously am suspect the idea of converting something that was intended for electric to to a gasser. Sure it could be done but really? What a headache.

John
Old 07-05-2013, 10:26 AM
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RCKen
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Default RE: Need engine and servo suggestions on new build

John hit it right on the head. That is way WAY too much engine for the plane you are considering. There's nothing wrong with putting a bigger engine than a plane calls for, but in your case you're more than likely going to find that you won't be able to physically fit the engine in the plane. Also, not knowing the exact manufacturer of the plane you are considering I can't see the full specs. But the specs that you list only show recommendations for electric power. Many airframes that are intended for electric power can at times are not suited for a fuel engine, and much less a gas engine. Gas engines subject can subject the airframe to a lot of vibration, and if the plane isn't designed to handle the it you can find the engine will destroy the airframe pretty quickly.

I wouldn't recommend this engine for this plane.

Ken
Old 07-05-2013, 06:43 PM
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Default RE: Need engine and servo suggestions on new build

Bad as I hate to, daddyrabbit I have to agree with Ken and John. A J-3 cub with a 70" wingspan would fly well with a .40 style Glow engine. A 20 CC gas-burner is three times the weight - at least - of such an engine. 20CC gas burner is equivelent to a 1.20 Cu.ins glow. (I think that is right) Your airplane is I am betting an ARF.
It will tke much added structure to hold that 20cc to the rest of the airplane and the wings will probably go BY-BY at the first strong pull-out. The wing structure in all
cubs that I have seen come with very much less than the structure that I then provide.

An example some years ago 6-8 I forget, there was a local guy that just had to have the biggest engine he could find in any of his planes which never lasted very long.
This day he was flying a 40-60 size Sport model ARF from a reputable company with a Zen. G-26 up front. He was doing crazy things, and most of us stayed under the shelter. Well he made a bad landing and tumbled a bit. Back to the shed to fix things and a new prop. He started to start under the shed and was questioned as that was against Club Rules. Well that G-26 wanted to fly but he was holding the model, and tacking IN FRONT so the G-26 said, "OK I will go by myself! " [:@]

Problem is it did not go by itself but took the right hand thumb, forefinger and 1/2 the middle finger with it. He slowly left RC. He was lucky that one big burley fellow hosted him into his Truck and got him to a Hospital.

I later examined that machine. It did not - in my learned opinion - many years, have adequate nose structure to support a good .40 much less a G-26.
If one uses the standard structure of the standard ARF, then one is asking for big trouble, especially after a few bad landings.

My models come out heavy, but I don't have structure failure, except when someone quickly moves the Limbo Pole in a Fun Fly. DRATS!!
Old 07-05-2013, 06:51 PM
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daddyrabbit1234
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Default RE: Need engine and servo suggestions on new build

. I contacted the mfg and they said this plane was designed for electric or glow power. They recommend glow 2 stroke 0.40 -0.56 or 4 stroke 0.52 - 0.56 As for gas they recommend the evolution 10cc
Old 07-05-2013, 07:01 PM
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daddyrabbit1234
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Default RE: Need engine and servo suggestions on new build

Thanks Hossfly for the info. Your point is well understood. I'm not looking for crazy power. I'm just looking for a gas engine that will work on this plane and fly well. You see I don't know these engines very well as to what will and wont work. I don't want anything to do with glow. I think I'm going to use the Evolution 10cc gas and hope its a good fit. This is an ARF and I assume there will be some going over it to do some extra glueing and maybe a reinforcement here and there as needed. I've come to find this is common practice with even some of the higher end ARF's.
Old 07-05-2013, 07:38 PM
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jester_s1
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Default RE: Need engine and servo suggestions on new build

Even that Evolution 10cc is going to be extra heavy for that plane. 70 inches is a true .40 size Cub, not for the hotter .46's most of us run. I have the Hangar 9 .40 size Cub that has an 80 inch wing. A .46 flies it faster than scalelike with enough power to do fairly short takeoffs and realistic aerobatics. Mine flies on a Magnum .52 4 stroke which is less power than your standard bushing .40. Your plane really will be best with glow power, as gassers this small are considerably heavier and don't make as much power. I see these small gassers as a niche product for guys who mostly fly big planes but want to keep one or two small birds in their fleet. I'm going to suggest a Thunder Tiger .40 pro as the appropriate powerplant for scalelike flying but still enough oomph to push through moderate winds, or OS .46 AX if you want to do really big loops or fly it off water. Anything more than that is just overkill and will stress and shake the airframe until something breaks.
Old 07-06-2013, 08:19 AM
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Default RE: Need engine and servo suggestions on new build

Hi!
Yeah! Agree. A 10 gas engine will fly the CUB real bad! Too big (Powerfull) and heavy engine for that small CUB.
A .48-.56 four-stroke would be perfect for it...or a .35-.40 two-stroke like the OS .40-.46 LA.
Old 07-06-2013, 12:02 PM
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Gray Beard
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Default RE: Need engine and servo suggestions on new build

I built the Goldberg 76 inch Cub for a friend that was going on floats. It only calls for a .40 or .46 glow engine. All he had on hand was an OS .91fs so I did a lot of reinforcing in any stress areas. The added engine weight was a good thing though to get the CG. The plane is so over powered the throttle is never over 1/4 stick. If you don't want to go with a small glow engine maybe you should think about going with the electric? Cubs and electric motors are a great match.
Old 07-06-2013, 01:14 PM
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JohnBuckner
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Default RE: Need engine and servo suggestions on new build

OK irrespective of whatever the questionable recomendation of the manufacturer is I have a suggestion for you to ask of them and its really a simple one: Have they ever actually flown that little cub with a gassor engine (any gassor)? I already know what the answer is gonna be and that is silence!


Now lets talk turkey about something else that is critical to this electric to gas conversion (I am not talking about electric to glow) and make no mistake if you really do this you are a test pilot with your wallet.

Electric motors are Smooth, structure is always done lighter. Now next down the smooth scale is two stroke glow engine, A bit down that scale are four stoke glow engines and guess what at the bottom are those gassers that you seemed so determined to stick on an electric airframe.

Now don,t get me wrong, I have done a fair number of electric to Small glow conversions and they are certainly succesful but going from an electic directly to the Shake and Bake gasser. What a recipe for a disasterous and disappointing conversion.

OK once agine here lets talk a little more about the miss match that you are proposing and agine another factor that has not yet been pointed out. I am sure you have not thought this out (certainly not your manufacturer) .

Look at the photo I posted its one of my gassors that happens to be be a 55cc but what I wish to point out is that shinny ignition box right behind the engine. That box and the attendant high tension cable is going to be virtually the exact same size on a 55 or a little 10cc. Which means you gotta find a place to stuff it close behind the engine. Look at that thing and think about it.

Look now at your cub or any cub: They have a very short nose, They have a very deep windshield and not much cowl area. This area is pretty much consumed with your fuel tank (This is a problem with many cubs even using glow engines and no ignition boxs. So where are you gonna put that pesky box on your airplane that is to small to stuff all that stuff. I know make it real ugly and hang it under externally, ya sure.

You need to if you already own the airplane to either go as designed with an electric system or convert to glow and small glow at that, which If I were to do it would be an OS .25/35AX no more.

If you have not bought it yet and you want a gasser get an appropriate larger cub.


John
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Old 07-06-2013, 01:23 PM
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Default RE: Need engine and servo suggestions on new build

I agree that a 20cc is way too big, I have a .40 Carl Goldberg j3 with a 79" wing span, I have a 46sf on her and its great. I originally had a 61 K&B on it and it was too heavy, the torque on the engine made it a nightmare on the ground with ground looping.
Old 07-06-2013, 02:38 PM
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Default RE: Need engine and servo suggestions on new build

why not go to your field where you fly ask the guys there and go from there have you been flying long?
Old 07-06-2013, 03:20 PM
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jester_s1
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Default RE: Need engine and servo suggestions on new build

daddyrabbit1234 hasn't been flying long. The regulars on the forum were helping him figure out the beginner basics just a few months ago. Now I'll say what the OP probably doesn't want to hear, but it's the truth. Cubs are not beginner planes. I haven't seen you fly, but given the time it's been since you were asking about trainers and such I would be surprised to see you with the ground handling and rudder skills that it takes to fly a Cub well. They are very nice relaxing planes once you have those skills (on calm days at least), and I highly recommend that pilots get one as they progress through the hobby to build scale flying skills on. But they do require a good feel for ground handling and they will sideslip on you real quick if you aren't good at coordinating turns. I don't recall what you are flying now daddyrabbit1234, but if you haven't already been through the trainer and then basic sport plane phase (Ugly Stick, 4 Star, Easy Sport, etc preferably as a tail dragger) then you're not ready for a Cub.
Old 07-06-2013, 03:27 PM
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pitts150hp
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Default RE: Need engine and servo suggestions on new build

Please remember the sig cub originaly flewn a k&b 15 the cg cub flew on k&b 40 today a40 4st in sig or a 90 4st in cg works good .My cg cub in 120twin 4st and over powered a 90 4s twin would be my pick even with floats
Old 07-06-2013, 04:30 PM
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Default RE: Need engine and servo suggestions on new build

jester 1 i think you have me mixed up with some one else ive been flying since 1945>> all kinds trainers cubs>>> ducted fans for 15 yrs>> one wren turbine on a balsa enforcer for 4 yrs>> sorry about that happy flying and now into gas engines with 3 spacewalkers
Old 07-06-2013, 05:27 PM
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Default RE: Need engine and servo suggestions on new build

daddyrabbit, if your seriious about not wanting to use glow, you might consider the new NV 40GX which is a fairly new entry in gas. It uses a glow plug and therefore has no extra ignition box ( and weight) to contend with. Will spin an 11x6 prop with authority and should be plenty for the Cub your considering. There is a thread here on RCU where you can find out much info on this motor

T-man49
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Old 07-06-2013, 06:01 PM
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Default RE: Need engine and servo suggestions on new build

This plane calls for a .52 - .60 four stroke, this would look and sound a lot more scale.
No point in over powering a Cub, it won't do any tricks.

A 10cc gasser might fit, but it'll come out heavy.

And I agree, these are no beginner planes, at least not on the ground. On takeoff, they will become airborne long before the ailerons are effective, keep it on the ground to build up speed and use the rudder.

I had an 80" version and it was very tame in the air, a .90 four stroke was running just above idle and it looked and flew very scale like an slow.
Old 07-06-2013, 06:28 PM
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Default RE: Need engine and servo suggestions on new build

I'd guess this is the plane http://www.valuehobby.com/airplanes/...oat-combo.html
Old 07-06-2013, 06:48 PM
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Default RE: Need engine and servo suggestions on new build

If that is the plane you might want to strengthen the fire wall for a glow/gas engine. It looks like it was designed for electric.
Old 07-06-2013, 07:36 PM
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Default RE: Need engine and servo suggestions on new build

NV Engines sell a .40 6.5cc gas engine that runs on pump gas with 14% Klotz Benoil. It uses a glow plug no ignition box or batteries and it runs and idles great. Just advertised in MA
Old 07-06-2013, 08:01 PM
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daddyrabbit1234
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Default RE: Need engine and servo suggestions on new build

I've decided to shelf the evolution 10cc when it arrives and just go with electric for now. I ordered a turnigy outrunner with a 60 esc,6s lipo and a few other odds and ends. I'm scraping the bottom of my pockets at the moment due to all this buying. From here on out I'm gonna have to be like johnny cash and get it one piece at a time. I've been flying the 182 Cessna that I first started with and I've flown a couple of cubs at the field. That's what got me wanting one myself. The first thing I learned about the cubs was they tend to be real squirrely down the runway. Not so bad coming in though. While were on the subject I'd just like to say those 1/4 scale cubs sure do look tempting.
Old 07-06-2013, 08:57 PM
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jester_s1
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Default RE: Need engine and servo suggestions on new build

Well not to kick you while you're down on the spending issue, but you've spent a lot of money that there was no reason for you to spend. Don't get me wrong, I totally get it when you're new to the hobby and you can't wait to get new stuff, but you bought the most expensive engine you could have bought for that size plane before even finding out if it would work. How did you go about choosing your electrical components?
Old 07-06-2013, 11:15 PM
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Default RE: Need engine and servo suggestions on new build

Try taking off in the grass it will handle a little better.
Old 07-07-2013, 05:10 AM
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Default RE: Need engine and servo suggestions on new build

Your on the right track. Skip glow!!!!!!!!!!!!!!!! Stick with Gas and not glow. I do miss the smell of a glow engine but they are way too messy. I do not miss planes soaked in oil after a day of flying. The 10cc may be the ticket or electric. A little nose weight on some of these trainers and Cubs can be a good thing depending on the balance. I am strictly gas, electric, and turbine now. I thought I would miss a glow engine after I sold all mine but I do not. Plus, gas is so much cheaper then glow fuel.
Anyway, good luck!
Mike
Old 07-07-2013, 05:37 AM
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Default RE: Need engine and servo suggestions on new build

Goldberg Cub with Supre Tigre 61. Plenty-o-power for getting off smooth water and aerobatics. This thing would lomcevak! I love glow power. The power to weight ratio is better using 2-strokes than it is with gas sparkers which is an advantage with a float laden airplane.

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