bikerbc

Yes Tom I believe your rite ,I think I read that someplace Cub's must be powerd by four stroke engines . I hope you love your Cub enough when it is finished to put it aside for a short while , while you learn the basics of flying . A trainer will make learning to fly so much more fun and far easier . You could buy an ARF and use all the servos and engine from your Cub to get you started . Your new club might even have a club trainer you can borrow . Talk to the guys and see what they advize.

52larry52

My Feedback: (1)

bikerbc, That "4 strokes only in Cubs" rule must be a Canadian law ! Down here in the deep south it's "run what ya brung", or "fly what you can afford". Just kidding of course, but I do have several Cubs with two strokes and pitts mufflers. At the time I built/assembled them I went with 2 strokes for cost reasons. The pitts muffler seems to improve the sound to a tolerable note, not as good as a 4 stroke but when properly powered and flying at 1/2 throttle or less, it's OK. Four strokes are better but sometimes budgets get in the way. My latest 1/5th J-3 Cub has a Saito 65, my 1/4 scale J-3 has a Saito 120, and I'am not sure what my new 91" Phoenix Super Cub will get. Just got the ARF today and trying to decide on a powerplant. Hell, when I was a kid I powered my Cubs with a rubber band ! Let the OP power his Cub with whatever he can get hold of.

jester_s1

I have the Hangar 9 .40 size Cub which is pretty close to the size and weight on your Cub. I have a Saito .72 in it and would say it's an appropriate engine. Takeoffs are short and the plane can cruise at less than 1/2 throttle. I can't get unlimited vertical, but I can fly scalelike aerobatics with it. So I'd suggest that class of engine for yours if you want to fly scalelike (Saito 65, 72, or 80) or go bigger to a .91 if you want it to be wild.

MouthFull

well I think I am going to go with the 4 stroke. The hobby store had a gasoline engine for a little bit more that the 4stroke. What do you guys think about the gasoline power engines?

52larry52

My Feedback: (1)

MouthFull, In a Goldberg Cub, a four stroke glo engine in the previously advised (by jester and others) 50-70 size range would be my 1st choice. They do sound better than both gas or 2 stroke glo, and will fly that Cub in a very scale like fashion. If your runway is paved the 52 will be all you need. If you fly off grass a 60-65 will pull the Cub thru the grass for needed takeoff speed, and if float flying is in your plans then a 70 four stroke will do it all well. It sounds like a four stroke is within your budget so buy one that is sized to the type of flying that you will do. Mount it either over 90 degrees so the head sticks out the right side of the cowl (to match the fake engine sticking out the other side like a real J-3) or inverted with the engine head sticking out the bottom of the cowl. For engine cooling reasons you want the engine head exposed to flowing air in flight. I would urge you to do the over 90 degree mounting for ease of operation for a beginner flyer. This mounting works well and looks good and scale like on a J-3 Cub. For engine brand, Saito , O.S., or Magnum would get a thumbs up!

TomCrump

Ya, I agree. A four stroke, in the 50 to 70 range is the way to go. I had a 70 Surpass in my Goldberg Cub and it had plenty of power.

jester_s1

I disagree about the .52 4 stroke. I had a Magnum .52 in my H9 Cub. Granted, it was a bit heavier due to having a painted fabric finish on it, but not overweight by any means. The .52 could just barely fly the plane. I could take off and land ok, but it couldn't cruise at anything less than 3/4 throttle. It had no vertical performance at all and couldn't even do a roll without losing altitude in the knife edge portions even with full rudder deflection. The .52 did fly the plane, but it didn't fly it well and had no extra power to pull through the wind or do aerobatics. A Saito .56 is a step up in power from the Magnum .52 (Saitos just make more power for their displacement), but if you're not trying to make an engine work that you already have there is no advantage to getting a .56 over a .72.

52larry52

My Feedback: (1)

Jester, Yea, I think you are right. Thinking about what you said, a magnum 52 is pushing the lower limits of engine size on this plane. I retract my advice on the 52 magnum. I just installed a magnum 52 in a smaller, lighter airplane (a Pilatus Turbo Porter) and it's a good running nice match for the Porter, but the Porter is 2 lbs. lighter and 13" less wingspan than the GB Cub. It wouldn't be so sweet in the larger Cub. Your point on buying the larger engine if you're buying new, not using existing equipment makes sense. The cost difference is small.

jester_s1

I don't know everything by any means, but I have been down this road. Thanks for the agreement.

MouthFull

Ok I have a spektrum transmitter and receiver. I have futaba servos and I went to plug in the servo to the receiver and the plug has a tab on it causing it to not plug in. Can I remove the tab and plug it in? It looks like it will plug in if I remove the tab. Next I was thinking about an on off switch and maybe some type of plug so I can charge the battery in the plane without taking off the wing, should the hobby store carry something like that? or should I just remove the battery to charge?

52larry52

My Feedback: (1)

MouthFull, Yes you can just cut that tab off with your hobby knife. Futaba uses them so you can't plug the servos or extensions backwards. Now it's up to you to get them plugged in correctly. There are a couple of different styles of outside charge ports available. Ernst sells one ($3-$4) that gets mounted by it self usually near your on/off switch. You can also get one that is part of an upgraded on/off switch that has a little sliding door to cover the charge port when not in use ($10-20). Your local hobby shop should carry these or Tower Hobbies has them.

MouthFull

Is there a way to know which way to plug them in? if its backwards will it ruin the receiver? I was at the hobby shop today but I think the guy was new, I asked about the switch and charger but he said you make them yourself but when my grandpa was alive he had his all in a kit.

52larry52

My Feedback: (1)

If you plug them in backwards you won't "blow any thing up" , they just won't work. Do some kind of color code on the connections to show yourself the right direction to plug them in ( drop of matching color paint, small matching color sticker, crayon mark, etc. what ever works for you). Go to Tower Hobbies site....punch in part #LXE 963, that's the Ernst charge recepticle @$2.89. Then look at pt #GPMM1000, that's a great Planes switch & charge jack mounting set @ $3.89. These both use your stock type on off switch. Tower does not seem to have the the other type I mentioned, a switch with a built in charge port. I couldn't find those at Tower. I buy those on Ebay, (RC airplane parts) from time to time when I see them listed. Oh, and BTY your hobby store sucks....most of them do today. See if you can find one in your area that has a good supply of RC airplane supplies. They are few and far between. Hope this helps.

TomCrump

I use the his fot the switch/charge port. http://electrodynam.com/rc/usw/index.shtml

MouthFull

This site is horrible to use with a phone. The site could not find this post. I had to type in Google. Any ways I have a .70 magnum 4 stroke for this now. What size prop should I should I use? What battery should I use?

bikerbc

From what I could see it looks like a MAS 13-6 K series prop is recomended for break in on your Magnum 70 4 stroke . As too the battery you have too make several choice's . If you want to use Ni-mh or Ni-cd I would recomend using only the 5 cell packs . Spektrum dosent like the lower voltage of the 4 cell packs . I usually use Life RX packs . For your size of plane I would use around 1800 -2000 mAh

MouthFull

yea they recommended a 5cell 2000mah. will that last a while in the plane?

MouthFull

the plans recommend a 14x6 for .60-.91.... Will the 13x6 be a big difference from the 14x6

jaka

Hi!
A 70 four stroke can swing many prop sizes. For a CUB a 13x6 or 14x4, 14x5 is suitable. But remember that different brands of propellers perform differently.
If you want good performance and a "quiet" prop APC, RAM or Graupner G-Sonic are the best.
Never ever should you use a white tipped MA prop. The are loud and doesn't perform as good as those I mentioned above.
When it comes to what batteries to use anything from 5cell 600mAh NiCad or 5cell 2800mAh NiMh or 6,6V 800-1800mAh Life batteries could be used.
5cell 2000mAh will be fine!

MouthFull

Sweet I am going to buy a 2000mah battery and charging port tomorrow. I should have pretty much every thing. I don't think I asked yet but the hobby shop recommend I use 20/20 fuel. Motor is a 4 stroke magnum .70 does that sound right?

JohnBuckner

My Feedback: (1)

What is the elevation where you plan to fly?

John

MouthFull

we are only at 500 feet

JohnBuckner

My Feedback: (1)

Hey Mouthfull, thank you for the reply. Although many may never realize the importance of something referred to as "density altitude" and the importance of its effect on our models performance. Folks tend to forget about things like that if they never travel and fly at different elevations and that's fine. Some often never fly any place but the home field. Ok this density altitude is affected by elevation, temperature and the moisture content of the air.

High density altitude reduces the performance by requiring more speed over the wings to lift the airplane, it also reduces the airplane propellers ability to provide thrust and it reduce the engines ability to power that propeller.

What has all this to do with nitro content? Well one thing that many of us who live in mountainous areas can and do is choose nitro content based roughly the elevations of our home field and some times do use a different fuel when traveling to a different elevation. Now all this is excluding high performance use such as racing etc. of couse that's a subject for a different thread.

Let describe my home field (elevation 3450 msl) That's above sea level. The two stroke fuel of choice is 15% and four strokes do well on about 20%. Now just thirty miles to west of here down on the Colorado river the elevation is about 500 msl. Down there the fellows tend to use 10% for two strokes and 15% (18% oil) in four stokes. Now just a hundred miles to the east is Flagstaff and the field has an elevation of almost 7,000 msl Now the normal fuel there for two stroke is around 20 to 25% and for four stroke most use about 30 to 35%. Most lowlanders who attempt to fly there and insist on using their 10% never really get off the ground .

Mouthfull my best suggestion for you is you really do not need the 20/20 which will work fine in your engine of course, 15% (18% oil) will also work fine. You could also even use 10% nitro however for a four stroke I would prefer the higher nitro simply because it will aid in easier needling and perhaps a slightly more reliable idle.

John

blvdbuzzard

I am late to this thread. I have flown my CG Cub with many engines. I used a K&B .61, .65, ST45, O.S. .48FS, .70FS, Magnum .70 FS. To me, the best engine was the 70FS. Cruise around at 1/4 throttle, plenty of power, used it with floats and was fine. I built the full wing version. Mine was a total pig. I used 1 1/2 set of the 9 ounce bottles of epoxy on the fuse, Goldberg colortex covering, clear coated. Still flew like a kite in a breeze.

I flew at sea level, well about 300 feet above sea level. At 4,000 ASL where the air density could be really bad, up to about 6,000 plus and I flew at 75 feet below sea level in Imperial County. The .70 worked well at all the places I flew. I used 10% power master fuel and never had a problem. Yes the 20/20 will work, but I don't think you need it and I don't think the engine can take full advantage of the extra nitro.

If I was to do it today, I would go E power. Easy setup, lots of power, no clean up.


Buzz.

acdii

Cubs are hard to fly? I must be a pretty good pilot then, I have not experienced any of the bad habits mentioned in this thread with my SIG 1/5th Cub. If anything the problem I have is getting it to stick to the runway on landing.

Of course, slapping a Saito 100 on the nose *might* have something to do with it.

Hey Mouthful, on fuel, stick with 15% or less Nitro content, but you want 20% oil. For the Magnum they prefer you use full synthetic, so if you can get it, use 15% YS Wildcat 2 & 4 fuel. Its what I used in my magnums and they all run sweet on it, and start with a backflip of the prop.

Who said a Cub needs 5 channels? What's that 5th channel for? Rudder, Ailerons, Elevator, Throttle, ??

However, what everyone else said, train on a trainer first before flying the Cub, with its short coupled fuse, and large wing it is not an easy ground plane. It is no where near as bad as the SIG T-Clips 70 though, that is THE premier ground looping candidate on this planet. It is so rudder sensitive at slow speeds that just a touch too much and you are chasing it all down the runway. It also will take off before it is ready, which usually results in a wing stalling and a cartwheel. I even tried a Gyro on the rudder and it made no difference. All I can say is that plane requires a lot of take off practice, as that is its only bad habit.

My Cub on its maiden with a 14 x6 MA took off in 10 feet and went up like an F-15 on full burner. Surprised the heck out of me, but I got it quickly under control, trimmed, landed swapped out to a 15 x 6 Evo prop and now it flies like a Cub at half throttle, or a wild child at full.

Good luck with your Cub, stick a 70 ish on it and you will have one fun plane