Stearman PT-17 (oz6579)

About this Plan

Stearman PT-17. Radio control scale model biplane, for .60 power.

Quote: "A magnificent 2in = 1ft model of the venerable lady of yesteryear, Charles Litzau's scale version of the famous WWII trainer flies exactly like its full-size counterpart.

During the winter of 1964, I was bitten by the bug to build a scale PT-17 for R/C, since this has always been one of my favorite airplanes. I will not go into detail about the history of the PT-17 as there has already been much written on this subject. I will only say that a great many WWII pilots were trained in the Stearman and, today, it is a much sought after collector's item.

In order to get started on my project, I sent away for some of the existing plans on the PT-17 that were designed for U-control, having considered enlarging a set of plans to a scale of 2 in = 1 ft. However, after I obtained several different sets of these plans, noticed that they did not agree in many major respects. The question was - who was right?

Since there was little information available on how to design and fly an R/C biplane, I had to find a method of determining proper CG, incidence, dihedral, airfoil, etc. I searched back through the model magazines to see what the average non-scale R/C biplane utilized. As a result of this study, I evolved a pretty good average of the statistics I needed to know. At least, it was a place to start!

The next step was to lay out the plans. I was able to obtain a set of AIR PROGRESS plans of the PT-13. These plans are of the real aircraft and it is from these that I worked. In order to blow them up to the chosen scale I took my 35mm camera with a telephoto lens and took colored slides of the plans. I then projected them onto the wall to where the scale was 2 in = 1 ft.

It was at this point that I decided to build a test model to make sure that everything worked before going 'all-out scale'. Since strength was of prime importance to me, I decided to experiment with styrofoam wings and elevator. On this first model, I did not bottler to duplicate the wing ribs. Also, I held the wings in place with rubber bands, while the 'N' struts were secured with toothpicks acting as shear pins.

Then came the day for the first flight and I was suddenly quite happy that I had proportional radio! The plane took off by itself and started into a stalling attitude. (By the way, I was flying the plane with a Veco 45.) After managing to get it back for a reasonably good landing, I made adjustments to the elevator and added weight to the nose. This corrected the situation, but it was still a little under-powered. At this point I changed to a .60 engine.

To date I have over 400 flights on the prototype model with only four major crashes - all four occurring during gusty winds, dead stick, and going down-wind. From these crashes, I was able to locate the weak points in the fuselage and correct them in the final design. In all these major crashes, neither the wing nor elevator was even damaged or broken. There were only a few dents even though the wings were torn from the fuselage!

I was now satisfied with the design and quite happy about the way the Styrofoam wings worked out, so I decided to get started on my 'all-out scale' PT-17. The question was - how scale is scale and how far did I want to go? The main objectives for this design were:

1. Strength - be able to take bad landings, ground loops, and minor mishaps and still be able to fly.
2. Styrofoam wings - but still be able to duplicate all ribs and details.
3. Solid landing struts with workable shocks.
4. Scale 4 in tires - made from two sets of Trexler (4-1/2 in) tires, giving tire and tube, and inflating them to 4 in for scale.
5. Wings to be fastened on exactly like the real aircraft.
6. Model was to be built without having to have a machine shop.

With these points in mind, I began to build. I finished it (other than interior detail) in the summer of 1967 and you can imagine what a blow it was when I read that Sterling Models was coming out with a kit of the PT-17 in the same scale! I thought to myself - If they had come out with it a few years earlier, it would have saved me all this work! After thinking it over, however, I was glad they came out when they did with their kit for two reasons: their dummy engine of the Continental solved a big problem for me since I could use it as a mould..."

Update 30/11/2015: Replaced this plan with a much clearer copy, thanks to theshadow.

Supplementary file notes

Article pages, text and pics. Also, previous scan version.

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