Infant sportster (oz694)

About this Plan

Infant Sportster, a Bill Winter designed 36 in span K&B Infant powered sport free flight model circa 1949.

Update 26/09/2018: Added article, thanks to RFJ.

Quote: "When K & B introduced the tiny Infant glow-ignition engine, they planted the seeds of a revolution in free-flight. For, if you disregard the potency of this sturdy little mill for miniature free-flight and control-line contest designs, you surely will spot the obvious possibilities for the genuine sport-type model that can be turned loose in relatively confined areas. For sport flying, this revolutionary engine can cure all the ills of free-flight.

While the Infant was under development, rumors were heard that excellent contest-type models could be made with wings having 80 square inches of area. It was felt, however, that such an engine should make possible a new kind of model and a new kind of flying. What the sport model is to U-control, this theoretical engine-plane combo would be to free-flight.

As you know, the die-hard contest boys who have made a monster out of free-flight think 100 ounces power loading is pretty high; 120 ounces leads to arguments, and only the wild characters will try 140, or maybe a horrible 160. We went all the way to 210 ounces plus. With a light wing loading of slightly under three ounces per square foot, the test model flew beautifully.

As large as a big CO2 job - the Infant Sportster has about 170 square inches of area - it will make three to six wide power turns to an altitude of 200 to 300 feet, then glide more effectively than any straight contest job you can dream up. There are no complex adjustments; just balance the model, start the engine, and launch.

The rudder tab can be moved slightly for turns in either direction. By this tab alone you can keep the Sportster climbing and gliding directly overhead - or keep it from drifting far in a light wind. Brother, there is nothing like it ! No lost models, no crashes, no patching! Nothing but fun (aside to contest fiends: power loading can be stepped up still higher!).

Construction. The fuselage is made entirely from sheet balsa, with tissue covering the upper portion. This construction is tough and, on the original ship, has not developed a flaw that could be detected with a magnifying glass. There is just one trick: coat the finished, outside sheet surfaces twice with a mixture of clear dope and castor oil. Use a quarter teaspoonful of castor oil, stirred into a one-ounce bottle of dope, for a smooth, tough surface.

The two side pieces and the bottom are cut from 1/16 in sheet balsa. The six main bulkheads are cut from 1/8 in sheet. The upper formers, placed midway between the bulkheads, are 1/16 sheet. Cut out the two side frames and all the bulkheads (leave the small formers until later). Cement bulkheads number 1, 2, and 3 between the side frames. The work is held together with a few straight pins while drying. When dry, pull the sides together at the tail and cement, then position the remaining bulkheads. Place the fuselage on top of a sheet of 1/16 balsa and trace the outlines of the bottom piece with a pencil - this insures it matching the particular curves of your ship..."

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