Piper J-3 Floats (oz15977)

About this Plan

Piper J-3 Floats. Sport-scale floats, designed to fit onto Piper Cub J-3 (oz256) at wingspan 70 in. Scale is 1/6.

Quote: "Piper J-3 Semi-Scale Floats. Scale 2 in = 1 ft. Floating cap 3 - 4.5 lbs. Designed and drawn by Chuck Hollinger. Published Feb 1955 Air Trails. Re-drawn & revised by Dick Gleason 1-14-82.

Quote: "Semi-Scale Floats For RC Models. By Chuck Hollinger. What say we go for a short hop in the Cub before discussing seaplanes? Here, you take the transmitter and I'll have the motor going in a jiffy. There she starts! Give three beeps and it will drop to idling speed. Now I'll set the Cub in the water and you taxi her out to that clear spot - see how nicely she controls with that water rudder operating? Check the wind. All clear? Okay, give three beeps and there she goes! Look at the wake - there now, it's much smoother because it's on the step - another fifty feet and she's off! How about a 180 turn now and cut the motor back to low speed for a power-on landing. Here she comes taxiing up to the beach - now three more beeps, hold, and there the motor has stopped.

This is only a sample of the fun that is in store for you with an R/C seaplane. Looked easy, didn't it? Well, a lot of work and a good many dunkings preceded this flight.

Here, for instance, is a short, sweet history of some of the things tried. First off, two stationary rudders were mounted for scale appearance. Result - no control over direction on the water as the air rudder wasn't effective enough. No take-offs. Next we tried to make one water rudder steerable using pulleys and Nylon thread. This didn't work because the Nylon had too much stretch, so a pushrod system was devised using aluminum tubing. This functioned perfectly on the bench, but with the motor running it created so much static that the receiver was unreliable.

The solution to that was to substitute plastic knitting needles as pushrods. Now the steering both at low speed and high was licked, but try as we might she still liked the water too well and wouldn't get off. In the process, however, we soon learned that water can really chew up the tips of a prop so now we fiberglass them, resulting in a practically indestructible propeller and one that has more fly wheel action, which means increased reliability on low speed.

A hook (slight droop) was added to the step of the floats. This resulted in quite an improvement, but still no take-offs. The only thing to do then was to move the steps forward one inch from their present location. But in the rush we didn't bother to build up the hooks as we were sure it would make it now! Well, it didn't. Another thing learned, however, was that water was getting into the cabin, so as a protection for the receiver we enclosed it in a small plastic bag and applied rubber cement around the plug to make the radio unit absolutely waterproof.

While it didn't quite take off on those last tries we noticed that it apparently had enough flying speed but there was just too much suction. Back to the shop and the 'hooks' were added again. This time she made it after a run of about 150 feet! Since then we have experimented with the angle of floats relative to the fuselage, and with about a 2 deg. angle she now consistently takes off in about 100 feet. This could be shortened even further if we wished to sacrifice its landing characteristics by putting them at 0 deg. angle. This would be okay for an R/C job with elevator control to level her off on the approach. One inch has been added to the aft end of the floats for increased buoyancy.

Now for the construction. Let's start by cutting out of 3/32 sheet the formers a for both floats and mark their centers with a light pencil. Formers number 5, 9, and 14 are to be cut from 1/8 ply. Cut out tops of floats from 3/32 sheet and mark a light line down the center. Cement formers in their respective places.

Cut out sides to the outline shape as shown on the drawing, bevel the top edges and cement them in place. It is recommended that Weldwood glue be used for attaching the sides and bottom. Cover the bottom of the floats from former No.3 forward, with the grain of the sheet running crosswise. Cut nose blocks to shape and cement to the No.1 former..."

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to DPlumpe.

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