Tower Hobbies J-3 Cub

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INTRODUCTION

With its distinctive looks, it is probably safe to say that the J-3 Cub is one of the most recognized and known airplanes in the general aviation category. The Tower Hobbies version of this airframe is 81″ wingspan ARF airframe which seems to accurately replicate the distinctive looks of the original and promises a short and easy build process to end up with an airframe that is both authentic and exciting to fly. As you look over the Tower Hobbies version of this airframe, you can’t help but wonder if this is a re-release of the Great Planes fabric covered version which is now obsolete less the fabric covering. Either way, this should be an easy and exciting project to take on so lets dig in and see what the Tower Hobbies J-3 Cub has to offer.

HITS
Enjoyable build
Performs amazing for a Cub Scale looks

MISSES
No electric option

DETAILS

Price: $179.99 (at time of review) Key Features

Excellent first sport-scale ARF-quick assembly, smooth maneuvers
One piece 81″ bolt-on wing
reproduces the full-scale aircraft, using CAD engineering and data from the original Piper 3-view drawings

Pre-built all-wood major sections are pre-covered in high quality heat-shrink film
Roomy radio compartment
One piece fiberglass cowl

Adjustable engine mount and decals included

Specifications

Wing Span: 81 in.
Wing Loading: 19.9 oz/fl2 Wing Area: 984 in2
Fuse Length: 49 in. Weight: 8.5 lb

FIRST LOOK

The Tower Hobbies J-3 Cub arrives in a sturdy albeit Spartan box with all of the major components individually wrapped and taped down to protect against damage from shipment.


While the J-3 Cub is an ARF, it does seem (dare I say it) that it is an older school ARF which expects a bit more from the modeler than the ARFs that you may be used to today which to me is something to look towards during assembly. The fuselage is completely covered with the distinctive Yellow Cub heat shrink film which is mostly wrinkle free and easy to shrink down although nowhere does it say what sort of covering it is. Looking inside the fuselage I was surprised to not find any evidence of laser burns on the hardwood parts which made be think that either I am not seeing them or someone painstakingly cut these parts by hand. Either way, the general build quality of the J-3 Cub is very good and I was hard pressed to find any fault during my initial inspection. A fiberglass cowl along with a mock twin cylinder engine are provided to give the J-3 Cub the looks that it deserves.

All of the control surfaces will be hinged using CA type hinges. The J-3 Cub promotes the use of “Barn Door” style ailerons which means that they replicate the looks of the original and are not simply a strip of balsa that runs down the complete length of the wing. The completed wing assembly will be a single piece bolt-on type wing but you need to plan to store and transport that 81″ fragile wing somehow.

Several bags contain the bolts, screws, hinges and various components that will be required to complete the assembly of the J-3 Cub. While an adjustable engine mount and a gas tank are provided, I was sad to see that there was no manufacturer option to make this an electric airframe. The struts that are provided are air foiled to cut down on drag and are documented to be an integral part of the wing structure and flying
without them is not recommended.


ASSEMBLY PROCESS

I started the assembly process by tackling the single piece wing. The wings are glued together using the provided three piece wing connector which is glued together and inserted in the precut slots on both wings. The ailerons are hinged using CA hinges and the servos installed in the precut bays. I found that the CA hinges provided with the kit were hard to work with as they were a bit on the soft side and hard to insert in the precut slots. I opted for some after market Great Planes CA hinges which I had in stock as they were easier to work with. You have to route the servo leads using a string with some sort of weight attached to it through the wing. The stabilizers and the control surfaces on the tail are installed in a standard ARF manner without any issues. The two elevator halves are joined with a U-rod as there is only one servo to actuate both surfaces.

The pre-bent landing gear are installed and attached to the fuselage per the manual. The manual recommends that you mark and cut off the extra length of rod that will protrude from the outside of the wheel and not allow you to screw on the yellow CUB cover properly unless you space the wheels outwards a bit. I used a rotary cutter and made quick work of installing the wheels in the proper orientation.

The tail wheel inserts in the rudder and a bit of work is required to cut a V-shaped slot in the bottom of the rudder where the rod will seat against. The control rods are not pre-installed in the fuselage. You have to mark and cut a small slot on the side of the fuselage and route the control guide tubes though the opening towards the servo tray.

This is not a difficult process by any means and the measurements provided in the manual were spot on to achieve a straight linkage to the control arms. The provided control rods are threaded on one end and require soldering the clevis on the other end. I am not the best at mechanical soldering but was able to achieve a good connection in both attempts without any major issues.

The choice of power for this build is the O.S. 46AXII engine with a Pitts style muffler. The manual is written mainly from the perspective of using a 4-stroke engine and mentions that a spacer has to used to set the proper distance of the engine from the firewall if a 2-stroke engine will be used. Do not blindly drill holes in the firewall using the template provided in the back of the manual as I found that the hole locations were incorrect as shown above. I used two pieces of 1/4 aircraft ply to achieve the required spacing and bolted the engine in place. The throttle servo was then installed and the push rod and guide tube installed in place. There is ample space to the side of the gas tank to route the push rod and there is no need for complicated bends as the control arm on the O.S. 46AXII was almost directly in line with the hole that was drilled on the firewall.

With the engine installed, I moved on to marking and cutting the fiberglass cowl for installation on the nose. I had to cut three openings for the cylinder head, the carb and the high speed needle. What is not shown in the above picture (which I neglected to cut during the assembly) is another small hole right in front of the high speed needle for the low speed needle adjustment. I cut that with a hobby knife later at the field when I realized I had to make a small adjustment to the low end. The mock cylinder heads are then cut from the molded plastic sheet and can be painted and glued to the other side of the cowl. The use of the Pitts muffler on the O.S. 46AXII makes the overall installation look very clean.

To secure the gas tank in place, I drilled two small holes on each side of the plate that it rests on and used a long zip tie to make sure it could not move. The picture above shows the servos for the elevator, rudder and throttle all installed. Small pieces of balsa are provided to route the push rod guide tubes through to make sure that they do not flex and cause unwanted movement on the control surfaces. The side window panels are then cut and glued in place followed by the canopy which needs to be trimmed and glued in place as well. You might want to paint the inside of the fuselage black to match the looks of the real J-3 Cub. I used some Tamiya black and made quick work of adding a touch of black with a small brush.

About the only complaint that I had during the assembly was during the installation of the struts. The manual recommends a complicated procedure to make sure the installation of the struts do not inadvertently warp the wing and to use an incidence meter to check for proper wing incidence during the installation of the struts. I found this process to be a bit unnecessary as the struts themselves do not really exert too much bending pressure on the wing when they are installed with the model upside down on the table. Plus there would be little I could do to correct for minor incidence offsets so I just placed the plane on its back, made sure the struts were laying flat with no force exerted on each side and drilled holes in the hardwood locations of the wings and installed them in place. All screws used in this process are self tapping screws and I was not really pleased with the bottom screws being of this type as they will regularly be removed and inserted causing the wood to give over the long run. I later replaced these with blind nuts on the inside of the fuselage and 4-40 bolts with washers on the outside.

To complete the assembly, I installed a 11×7 wood prop and a black Dubro spinner nut before applying the stickers and the J-3 Cub was ready for the field.


FLIGHT REPORT

Even though the J-3 Cub has a single piece wing, I was able to easily fit it in the back of my SUV and transport it to the field without any major issues. Once at the field, the single servo connection to the Y-connector of the ailerons is made, the wing attached with two nylon bolts and the struts are affixed to the bottom of the fuselage with two self tapping screws. Some time was then spent at the starting station to break in and tune the brand new O.S. 46AX and it went without a hitch. It was here that I realized that I had neglected to open a hole for the low speed needle which was easily remedied with a small blade.

Once the O.S. 46AX was transitioning and idling reliably, we placed the J-3 Cub on the ground and taxied to the runway for its first flight. The steerable tail gear performed quite well on the ground and within no time, we were already lined up and ready for the first take off. As I advanced

the throttle, the J-3 Cub was quick to respond by rolling for a few feet before the tail lifted off and almost immediately followed by a very short roll and take off. The O.S. 46AX was at full throttle and the J-3 Cub was climbing at a respectable rate with a nice stream of smoke coming out of the muffler when I started to trim the airframe out and noticed that it did not require much to achieve neutral flight conditions. After a few short circuits, I was immediately comfortable with the Cub to start performing slow and low passes for the camera and the Cub behaved in a predictable manner throughout.

After we decided that we had enough shots of the Cub, I started to explore the capabilities that the Cub had to offer. The first thing that I noticed was that while the power provided by the O.S. 46AX would pull the airframe around fairly quickly, I would still considered it to be more on the scale end of the spectrum as pulling vertical maneuvers and trying to perform large loops were limited on

the top end by the power available from the engine. The roll rate of the Cub was actually quite good considering the long wing and in no time I was performing four point rolls with nice and crisp hesitations in between. Flying the Cub inverted requires a touch of down elevator and poses no great challenges. The biggest surprise that I got from flying the Cub was its capability to perform very controllable knife edge passes with very little coupling from the rudder. It really is a sight to see a scale looking J-3 Cub perform a full runway length knife edge pass low to the ground which pleased many onlookers. The rudder also performed quite well when it came to stall turns as I was able to perform reliable stall turns without any issues.

The flight time allowed by the O.S. 46AX engine and the provided gas tank was around 10 minutes of close to full throttle flying. This was very pleasing as the J-3 Cub is very enjoyable to fly. Before I ran out of fuel and had to land, I started to drop the speed to see how the Cub behaved on the other end of the spectrum only to find that there were no surprises and the Cub continued its predictable flight envelope as it slowed to crawl like speeds. A few touch and goes were

attempted before approaching landing pattern and each time I felt like I could just cut the throttle and the Cub would just land on its own. On final landing pattern, I had to apply a bit of throttle to line the Cub straight with the runway and once I was pleased with the descent rate, I chopped the throttle and was able to gently come in for a mains first landing. A bit of wheel hop was observed from the foam landing wheels but nothing that was uncontrollable. I found that the Cub really likes to swerve to the left right after it touches down which has to be compensated with the rudder. With the limited throw from the rudder, I found myself struggling at times to be able to keep the nose straight after touch down so trying to get the tail gear on the ground as quickly as possible was the goal of the day for smooth landings.

 


SUMMARY

From its great scale looks to quick assembly process and fantastic flying characteristics, the J-3 Cub from Tower Hobbies is another gem that will have beginner and expert pilots alike looking for more time behind the sticks. About the only minor issue that I had was the use of self tapping screws to hold in the flying struts which was easily remedied by using blind nuts and bolts for long term durability purposes. The power offered by the inexpensive O.S. 46AX provides the J-3 Cub with enough grunt to make it an exciting flight however I would almost recommend using the O.S. 55AX if you have the choice. As I rushed to get the J-3 Cub ready for flight, I did not have the time to dress up the cockpit area and add a pilot but I certainly believe that this would push the looks of the Cub over the top and is on my to do list going forward. I certainly have enjoyed my time with the Cub every time I brought it out to the field and look forward to many more flights.
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