Speaking of building, let’s talk a bit about just how much of an old time building project this particular model airplane is…or is not. The Top Flite Stinson kit is designed around what experienced model builders usually refer to as a traditional, built-up structure, which means that the engineering, the shape and function of the individual parts and the way they work together closely follows full scale practice. For example, the wing panels are built of lots of ribs assembled around multiple spars, and the fuselage consists of a series of formers (bulkheads) joined by longerons and faired (shaped) by stringers. This is quite a bit different from the way lots of more “modern” models make use of things like molded foam wings and fuselages based on big, flat sheet balsa side panels. Neither way is best for every case…but the built-up approach has been proven to work very well for scale models of vintage airplanes, at the expense of being more demanding of time and effort.
Take a close look at the image above. The two parts sheets on the left are from a contemporary laser cut kit. The two in the middle are from a ’50’s vintage Berkeley die-cut kit, and the three on the right are from a ’40’s vintage Cleveland printwood kit.
In the case of our Stinson, all the parts that are shaped specifically to create the shape of the airplane are die cut from sheet balsa or plywood using custom formed lengths of steel cutting rule mounted in a press. Die cutting became very common during the 1950’s owing to the time and effort it saved over printwood kits which provided sheets of balsa with parts outline printed in ink for the builder to cut out one by one using a sharp blade. The problem with die cutting is the expense of making all the dies necessary to produce a kit, and the tendency of those expensive dies to get dull over time. This meant that you might get nice, accurate, crisply cut parts sheet in, say, kit number 43 that came off the line, but by the time kit number 2043 came along you would discover die crushed parts that might or might not be much use in building a model airplane. (That’s one of the factors that had a big hand in the disappearance of the Berkeley models I mentioned a while back.)
There have always been good ways to avoid the problem of poor quality die cutting. In fact, it is possible to fix sloppy, die-crushed parts sheets, but I’m going to save that lesson for another time. The simplest way around the problem is also the oldest, but it’s not easy. If you create the parts outlines yourself, or transfer them from printed paper patterns by tracing or gridding, you can keep the entire cutting process under your own control…if you don’t mind all that extra work before you get to see any model airplanes parts at all. The next step came along in the years before World War II. Printwood kits include balsa sheets of the necessary size and thickness with all the parts outlines printed in ink right on the wood. You got to cut them out, one at a time, with a sharp model knife if you could afford one, or more likely an old razor blade. Those outlines were usually pretty accurate. Getting accurate parts was up to you, and not everybody could do it. More recently, a few larger, more elaborate kits appeared featuring band-saw-cut parts. As such kits could only be produced one at a time, they also tended to be expensive.
Today’s standard for balsa wood model airplane kit production is computer controlled laser cutting. A digital parts file is a whole lot easier, quicker and less expensive to create than a set of steel cutting dies. The lasers never get dull, and there are very few model builders anywhere who can hand cut balsa as accurately. (I can’t, even though I enjoy the challenge of building an occasional printwood kit.)
Based on the example I have seen, the Top Flite Stinson is a good example of a die cut kit done right. The wood you will find in the box is of appropriate weight and quality and the actual die cutting is as accurate as any I have ever seen. Knowing all this may not make any difference in the actual materials that find their way onto your work table, but I think it helps to understand just how this kit fits into the history of balsa model airplane building technology.
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