Piper Super Cub (oz13681)

About this Plan

Piper Super Cub. Radio control scale floatplane model for .25 - .40 engines.

Quote: "The J-3 was used for recreation and as a primary trainer but the Super Cub was built for business: agricultural spraying, remote and rough terrain access, mountain rescue, and even some government training. Between 1949 and 1995, 8,525 PA-18's were built. Probably the most popular was the PA-18-150 powered with the Lycoming 0-320. The PA-18A-150 was Piper's workhorse agricultural ship between 1952 and 1960; then the Pawnee took over. Piper delivered 2,560 8A's.

At first glance, the Super Cub doesn't look much different than a J-3 save the engine installation and rounded tail. A closer inspection, however, reveals an enlarged windshield, slotted flaps, frise ailerons, an enlarged horizontal tail, and a narrower fuselage. Of course, numerous structural and system updates were accomplished to handle the increased horsepower and gross weight. While the most popular 65 horsepower J-3C-65 weighed 680 lb empty and grossed 1,220 lb, the PA-18-150 weighs 930 and 1,750 lb empty and loaded, respectively.

Floats certificated for PA-18's vary considerably. Capri and Canadian Aircraft Products floated some models but the most popular are the EDO 1650's and 2000's. Although most J-3's and some PA-18 float installations required stabilizing ventrals, the two EDO installations do not.

Since my PA-18 began as a seaplane, I spent considerable time at the Renton Sky Harbor in Washington State measuring the full-size ship to get the float installation right. I found, however, after drawing up the side view, that the fuselage-to-float distance seemed excessive. But since models don't need this separation, I shortened this distance 15%.

You will notice the plans show both mini-aileron servos or the more standard single servo ball link configuration. I have used both, but since the ship is essentially a powered glider, I installed a single mini-servo to drive both ailerons.

The firewall is positioned for an OS .40, but by using the full length of aluminum 'T' mounts, a .25 will fit. I selected the OS .25 FP due to its good power, low weight, and reliability. I mounted it in the 120° position to completely hide the head and put the muffler directly below for both clean lines and an oil-free lower fuselage. If you plan to fly at high altitude on hot days with floats, you might consider the 40.

CONSTRUCTION: A word first on sequence. Since the wing must be mated with the upper cabin support hold-down pins, both the wing and fuselage must be assembled together. The other components can be built in any sequence. Fuselage: The fuselage is the classic box most of you have built a dozen times before. I will touch on only the areas needing explanation.

The sides are constructed, aligned, and secured in the front before pulling together at the tail Remember to bevel the insides of the rears so that the tail post thickness is only 3/16. Also since the window sill area will tend to bow out as the rears are brought together, hold them in place with a capture stick until the front sides are first filled in with 3/16 and then sheeted with 3/32.

Complete the rear fuselage next and attach the 3/32 square longerons. Drill and install the firewall blind nuts and then the fuel tank. Next, install the control rod sleeves and throttle cable.

Temporarily attach the wing and line up F-11, the 1/8 plywood pin-alignment fuselage plate, and tack it in place, being careful
not to glue it to the wing. Drill through the plate into F-12, the 1/4 in plywood wing joiner. Next, drill down through the edge of D1 with a 1/8 in drill to accommodate the wing hold-down pins... "

Piper Super Cub from RCM, May 1998.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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