Pazmany PL-4A (oz12630)


Pazmany PL-4A (oz12630) by Leon Bennett 1978 - plan thumbnail

About this Plan

Pazmany PL-4A. Jumbo rubber model. Wingspan 56-1/2 in. Scale is 1:5.6

Quote: "Before the limits were lowered, four-foot-span-and-over Jumbo Scale rubber models were the glamerous and colossal 'big guns' of rubber scale. This 56-1/2 inch span ship represents that category.

OK, why build it? The drawbacks are obvious; a lot of work, a lot of materials. But stay with it; the virtues are just as real. Here is a machine whose flight pattern is stately, even lordly. She climbs slowly to about seventy feet and cruises for about twenty-five seconds. When the prop folds, she drifts downward for another twenty-five seconds. None of the usual dips and lurches in response to turbulence or motor run kinks. The glide is the flattest I have seen in forty years of rubber-powered scale work. Those big wings really help. The overall scale-like quality of flight is awesome; Peanut fliers actually stop in the middle of winding to watch this one go by.

The Pazmany PL-4A was designed for the basement builder by Ladislao Pazmany, a California engineer. By using a boxy design, he helped us keep the model's weight down (260 grams, ready to fly). The constant chord wing (370 square inches; better than fifty-six inch span) means that the stall starts at the dihedral break and slowly moves outward, instead of starting at the tip and then developing violently as it does on pointy-wing machines. Pazmany's use of a VW engine forced him into a belt drive reduction system. While a nuisance for him, it gives us a nice high thrust line which easily accommodates a fourteen-inch propeller.

Pazmany has also done us the favor of scorning fillets and wheel pants, and finally flew his full-scale machine before mounting a blown canopy. This means that only a bent windshield is required on the model, hence there is no vacuum forming to struggle with. Even Pazmany's color choice (red, white, and black) fits in with standard tissues no spray painting is required.

In short, Pazmany had done us the favor of designing a machine well-suited for large scale modeling. And this one is large. How large? Well, lees put it this way. You're familiar with the usual hassle involved in getting the rubber motor on the rear peg; the wires, bits of string, etc. On this model, you reach into the cockpit with your fist and then thrust your entire forearm into the fuselage, simply carrying the motor to the rear peg in your hand. Now that's large!

With the test motor you can expect a flight of about thirty seconds. With the contest motor, she will do a rock-steady fifty seconds at 85% allowable turns. At last October's Connecticut FAC meet, held in a light drizzle, I was able to get an official forty-three seconds. Considering the enormous weight of water the model carried, that s not bad.

Interested? Start by getting your scale presentation material together. Sport Aviation (March 1973, Vol.22, No.3) has an excellent article, including three-views and thirteen photos, of which two are in color. Private Pilot (Feb. 1973, Vol. 8, No. 2) has no three-views, two black and white photos, and one in color. As an alternative to the old magazine road..."

Direct submission to Outerzone.

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Pazmany PL-4A (oz12630) by Leon Bennett 1978 - model pic

  • (oz12630)
    Pazmany PL-4A
    by Leon Bennett
    from Model Builder
    November 1978 
    56in span
    Scale Rubber F/F LowWing Civil
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 11/11/2020
    Filesize: 1148KB
    Format: • PDFbitmap
    Credit*: MB2020
    Downloads: 631

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