Need engine for Piper Cub
 

Hi all,
I've started the build on a BalsaUSA 1/4 scale Piper cub. I'm still trying to decide what engine to use. I pretty much want to use a gas engine. Who out there have used a gas engine on this model? Could you tell me the brand of the engine, how well it pulls the cub, and how much modification it took to fit it to the airframe. The ideal engine for me would be gas with little modification to the airframe and completely covered by the cowl with only vent holes in the bottom for cooling air flow.

Cheers,

Dan

RE: Need engine for Piper Cub
 

Mine is a quarter scale Clipped Wing Cub from World Models. I have mounted a Brillelli 26ss gas engine on it. Running an 18x6 prop it pulls it with a lot of authority. Not sure how much the Balsa USA Cub would weigh but I would thing this engine would pull it very scale like.

RE: Need engine for Piper Cub
 

Hi Dan,
Like 25 years ago, this same Balsa USA cub was powered by 60 size engines - thats around one HP. An engine like HB-61 running a 14-6 at around 9000 rpm was considered sufficient for it. I had one. They looked scale but never felt or sounded real in the air.
15 years ago, this same Balsa USA cub was best powered with an opposed twin like an OS Gemini (I think it is 1.8). This I think would be the ideal scale combination - looks and flys like real.
Now, I have recently seen this same 1/4 sacle cub with a zenoah GT-80 - looks outrageous, at any power setting above idle it flys nothing like a cub (well cubs never did prop-hang, did they?) but throttled down to idle and it looks, flys and sounds like a real cub.
Unless yours ends up very fat and heavy, 26 cc is a lot of power for a 1/4 scale cub.
my 2 cents.

RE: Need engine for Piper Cub
 

A friend is building one, powered by a G26. It should be plenty.

I haven't seen the installation, so I don't know if he made any firewall modifications. I don't forsee any problems, though.

RE: Need engine for Piper Cub
 

I'm building two of them right now. A J-3 and an L-4. I'm planning on somewhere around a saito 100 to 120. Final weight will decide that. I didnt want gas because I like the soft putt-putt a cub makes while floating around. Theres one that flys over my house from time to time and it looks beautifull just meanndering around. There doesnt look like a lot of room in that cowl anyway. I'll have the dummy engine on the cowl, just dont want a lot of un-necessary stuff hanging out.
Edwin

RE: Need engine for Piper Cub
 

Although it is just a Cub...the appropriate power plant will largely be determined by the type of flying you plan to do with it. Some Cub pilots will only fly slowly, and scale like...others will want to attempt every airobatic maneuver in the book...including 3D stuff. So, with that in mind, step back and consider well your expectations.
As a point or reference, I fly a Dave Patrick 1/4 scale Super Cub (full size, 105 inch wing) with a Saito 1.50. The plane has a lot of scale details added and with the very large bush-pilot sized wheels, it weighs in at about 14 pounds. The Saito 1.50 is more than adequate power to fly very nicely in a very scale manner...that is...slowly, at much reduced throttle settings, and flying the wing...rather than flying the motor. And the four stroke motor just sounds so nice.
Your desire to go with a gasoline motor in this size airframe brings you to the core problem....which is...the weight of the gas motor for the power it produces. For example, the super reliable Zenoah G-26 is a marvelous powerplant but the weight makes for a very heavy wing loading on many planes, as well as upsetting the designed CG. I have also heard the mention that gas motors make more vibration, especially at low rpm's, and consequently place greater stress on the airframe.
Dont misunderstand my suggestions toward glow in your application. I am a big fan of gas motors, and I do use them where they are appropriate.
Gas motors do become much more appropriate when the size of the plane gets up to the 3rd scale area, and on warbirds that generally need a lot more nose weight anyway. There, the heavy weight is better carried by the larger wing, and in many cases the weight on the nose helps get to a correct CG without the need for additional lead bolted onto the firewall.
The smaller gas motors simply dont have the power/performance to weight ratio that the glow motors have. Fuel economy is spoken of, but in reality the actual fuel cost is not much of an issue at all...unless you are flying exceptionally long flight times and flying so much that your batteries are going dead every day at the field.
Our flying gang flys a gaggle of Great Planes PT-19's at many warbird and big bird events around the state of Florida. We have installed a G-26 in each of them...which is much more weight than the 1.20 size airframe was spec'd for. They do not fly any faster with the gas motor, but the weight on the nose causes problems. Typically, the plane has a tendancy to nose over on take-off You have to power up fast and hold a lot of up elevator early in the take-off roll. Some of the guys have resorted to bending the landing gear out forward to help counter this nose over tendency, but it would have been so much easier to just go with the lighter glow motor. One guy did actually go with the glow motor, and he flys right along side us and has no problem keeping up with the formation!
I hope this is helpful in making an appropriate selection.

RE: Need engine for Piper Cub
 

The white one is a J3 Cub kit modified into a PA12, the yellow one is a stock J3. Both fly very well on either a Zenoah G23 or a G26. Like the G26 better in the PA12, G23 in the J3.

RE: Need engine for Piper Cub
 

Well considering a Brillelli 26 only weighs a whopping 2.5 pounds RTF with standoffs muff and ign. I dont really see weight being n issue. A Saito 100 weighs roughly 1.3 pounds.. I dont think there will be an issue with weight at all since lots of guys are running G-26s and the Brillelli 26 is lighter.

Capt. I must admit you gave me a laugh... I don't think I have ever heard someone talk about high wingloading on a cub.. it's all wing :)

RE: Need engine for Piper Cub
 

HI sinergy...yes...you are correct...I have to laugh too when I think about it. Of course the wing loading is marginally higher...but really...does it matter with that much wing. Not very much at all i'm sure! The balance is more affected than anything else.
Thanks for the comment.
jim

RE: Need engine for Piper Cub
 

Thanks everyone for the feedback. Just to restate my criteria. I'm wanting a gas engine that would be small enough to be completely contained within the cowl with out cutting holes to make it fit or modifying the airframe very much if at all. It must have enough power to fly the cub in a scale like manner. Lazy eights, wingovers, cub like rolls. I'm not into fast or doing knife edges. May decide to equip with floats at a later date. I think the zenoah engines would have the carbs and mufflers sticking out the sides.
Someone had mentioned in another thread the Evolution GT26 and I was also thinking maybe the RCS 140 might be a good candidate. I haven't heard too much about either engine as far as reliability or performance.

RE: Need engine for Piper Cub
 

Well most of the 26s are very close in size... What is the size of the cowl?

As far as the GT26 well it's a decent engine dont get me wrong... but it works far better on a pipe and personally I cant see spending that type of money on an engine like that for a cub.

Now if you were planning on crashing this plane sometime soon and wanted a 26 that you could slap a pipe on and have a nice little engine that's a different story :)

RE: Need engine for Piper Cub
 

I have just the engone for you. A converted Homelite on EI. I will sell it cheap- less than $100

RE: Need engine for Piper Cub
 

I run an Evolution 26gt (same as the MVVS 26cc) in my 1/4 scale cub, and it works great. Sounds real, and at lower throttle settings, flies real. The plug cap sticks out the bottom of the cowl, but other than that, it's entirely enclosed.

RE: Need engine for Piper Cub
 

What brand and type of muffler did you use?

RE: Need engine for Piper Cub
 

Dunno, whatever Pitts my LHS had in, I think its' a Bisson. THe top edge touched the cowl, but a couple taps with the BFH (Big F- Hammer) solved that.

RE: Need engine for Piper Cub
 

Do you think it was the wrap around pitts style or straight side style? Thanks

RE: Need engine for Piper Cub
 

Mine is the straight one that goes on the side. The wrap around most likely wouldn't have needed any persuasion, there's a ton of room behind the engine in mine, but the side is what was in stock.

RE: Need engine for Piper Cub
 

I am also in the process of picking an engine for a 1/4 scale Super Cub I'm going to build and so far the RCS140SE seems to be a good choice as it is compact and will spin an APC 16x10 at a speed that will give almost a 1-1 power to weight ratio. I realize that is not a big factor in a cub, but of all the gas engines I have ever worked with or seen in other planes, this one seems to be the best fit.
Using a Dubro Beam mount and RCS supplied Pitts Muffler it should fit nicely in a Cub or SuperCub cowl.

Like you I have not heard very much about the engine and would appreciate input from anyone who has experience with it.

RE: Need engine for Piper Cub
 

I have now seen the G26 mounted in the BUSA 1/4 Cub.

The owner went for using the stock muffler. In my opinion, it was a mistake. 2/3 of that side of the cowl had to be cut away. It's UGLY !!![&o] A wrap around muffler would've been a much better choice.

The ram air trumpet sticks oput the carb side.

With everything hanging out, it is impossible to mount the dummy cylinder heads.

While I feel that the G26 is a suitable motor for a 1/4 Cub, a wrap around muffler is a must, if yoou want to preserve any of the scale cowl lines.

RE: Need engine for Piper Cub
 

This thread is getting a bit old but it hits my question exactly. UPS brought a BUSA 1/4 Cub and cowl today as a late Christmas present. I've got a plane nearing completion and some yard work to finish up when the sun shines so I'm a week or so out from starting the Cub, but I'm of course wanting to lock down my engine selection to know what to do with firewall.

I've got a new converted Ryobi on hand that I'm thinking might work. The Ryobi being rear carb and exhaust fits completely within the cowl except the last half inch of the spark plug and a shorter plug might even solve that. The firewall would need moved back 2 inches but laying the motor and mount on the plan, that looks to be no issue.

Does any one think the 31 cc Ryobi is a poor choice... it weights 3.75 lbs?

RE: Need engine for Piper Cub
 

As the build progresses, you might want to test balance it with servos in the tail. The forward box definately strong enough to support it.
Edwin

RE: Need engine for Piper Cub
 

If you want an engine that is completely hidden in the cowl, including the exhaust, use what I have in my Sig 1/4 scale J3.........

Laser 150 4 stroke.

This engine is an absolute jewel and in the J3 makes just about the nicest flying combination anywhere.

Most gas engines will have something hanging out in the breeze on a narrow Cub cowl. So if you want to keep it as scale as possible go for the best Scale engine LASER .

RE: Need engine for Piper Cub
 

Hi All. Just read your suggestions on an engine for a 1/4 scale cub. I`m just about to start building mine from a Mike Smart design (UK designer) Its an L4 modified from a J3 plan. Trust me the ONLY engine to use is an OS 120 four stroke swinging an 18 x 6 prop. Forget your gas engines. we just call them "petrol" engines over here !. ALL of them are TOO BIG. It really is a case of size doesn`t really matter ! The sound of an OS is music to an aero modellers ears. I have thought long and hard about this engine and decided the ONLY way to do it is to use the OS and create two dummy cylinder heads behind the real ones to represent the Continental C65 engine of the original. This combination will give sound and presence in abundance. What do you all think to that ?