PT-108 (oz14716)

About this Plan

PT-108. Free flight model for CO2 power.

Quote: "PT-108. A neat little design for CO2 power from the drawing board of Jack Headley.

THE ARRIVAL of the new generation CO2 engines in the model shops coincided with the arrival of myself in England for a summer holiday visit, so after recovering from jet lag, and remembering to drive on the 'wrong' side of the road, I lost no time in scurrying to the nearest purveyor of balsa wood and purchasing one of those items.

Later on, back at home in California, and after recov-ing from reverse jet lag, and remembering to drive on the right side of the street, I gut around to opening up the box and admiring my new toy for a while, after which the question arose, what to build for it ?

Clearly, a lightweight model would be required to use the engine to its best advantage, so I sketched out a smal-lish model, but before beginning to cut balsa 1 decided to do a few engine runs first, to really see what the power felt like. I bolted the engine to a block of wood, clamped this in the vice, and ran a few cylinders of gas through it. This turned out to be very instructive, if like myself you have never run a CO2 engine before. It is good experience in filling the tank, and setting the throttle, which, as Eric Coates writing in AeroModeller noted on the Telco, was better done with a pair of pliers than the tool supplied.

These bench runs showed the power level to be higher than I expected, and thus a more robust model could be used, so the initial design scribbles were revised, and the result is the model you see here. The shape is based, very loosely, on the Livesey DL5.

Wings: Construction begins with the wings. The plans show the starboard (right) wing, so start by building this one. Cut and sand the leading and trailing edge pieces, plus the wing lips to roughly the final shape, then pin one set down to the plan. Try to make both sets of LE and TE pieces of equal weight by using similar pieces of wood initially.

Glue into place all the wing ribs except the two inner ones, and leave to dry. When dry, remove the frame from the plan and repeat for the port (left) wing. You can do this on the same plan by reversing the position of the leading and trailing edge pieces, ie pin down the leading edge where the trailing edge should nhe, and vice versa.

When both basic wing panels are finished they can be joined together. Bevel the ends of the LE and TE to the angle shown on the template, then pin one wing down to the building board (flat), and prop up the end of the other panel 3 in, and check that the bevel joints are good. If not, sand as required, then glue the two panels together, together with the 1/32 plywood wing brace, and the remaining wing ribs..."

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