Praktikus (W.E. Mittelstaedt)

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1958 freeflighter from Germany.

The design is 1200 mm span and the plan offered the option to construct a rubber-powered or diesel driven version.

A diesel version had a much shorter nose and shorter undercarriage legs with appropriate wheels.

This plan is still available on the web (January 2017) but mine was found on the back of another plan, around 1978.

Praktikus fulfilled several desires: I had always wanted to experience a large rubber-powered vintage model and hoped that this one could double as a slow park flyer that would not sacrifice a valuable diesel engine in the case of mishap.

For the sake of fidelity a huge old school airscrew was carved, but the intention to use it was never there – 9-inch commercial plastic props were presumed to be a more viable solution. Just think of the rubber needed to drive the big prop! Enough to injure you and destroy the fuselage in the event of some failure.

Because the enormous balsa prop is such an effective brake when it stops, a clutch allows it to spin freely once the rubber is unwound. That is the theory, of course. The nose block has to be retained by rubber bands.

Bamboo undercarriage legs with wire end pieces hinge in the fuselage and can deflect backwards. They are sprung and have a flexible spacer.

Tiny bushed wheels complete the U/C. All very authentic but best removed before flight!

Another original design detail is the rear rubber peg mounting. It is far better moved forward a bay or three in order to save nose ballast.

Resting on such a tiny surface, the stabilizer is poorly attached to the tail – a platform should be added.

Built in the 90's, this Praktikus never made it to the flying fields, but it's structure is so light that it might well be worthwhile to replace the heavy tissue covering with a lighter quality and fly it indoors instead.