Scale VS Original
Most everyone has noticed that replicas vary widely in the closeness of their resemblance to the aircraft they’re patterned after. Generally this is because of the problems scaling an airplane that’s a fairly tight fit (at best) for the pilot even in it’s original form. The larger the airplane, obviously, the easier to scale. A perfect example is the WAR series of replicas. Most of them are patterned after radial engined fighters (FW 190, F4U Corsair, Sea Fury) and even at ½ size, they look quite good. The P 47 belonging to Russell Myles is a perfect example. The shape of the fuselage and canopy allow size reduction without overly distorting the lines of the airplane. The detail added to this airplane in simulating the sheet metal lines and panels of the original and choosing a color that is close to aluminum completes the illusion that you’re looking at a P-47.
Another good example is the Jurca FW 190 of David Spencer. With the proportioning allowed by the radial engine (actually an opposed Lycoming in this replica) , and the very nice paint detailing it is almost indistinguishable from the original.
This FW 190 is designed by Marcel Jurca.
The inline engine fighters bring more problems to the table. The ME-109 has to be the most difficult, due to it’s size and the relatively small cockpit canopy. The Spitfire seems to scale well, at least down to .7 or so, and the Mustang isn’t too bad as long as they aren’t parked next to a real one.
Below are drawings of a full size P-51 and the same drawing altered to the proportions of the SAL. It’s apparent that the SAL fuselage is a bit deeper (actually almost a perfect .75 scale of the original) and the length is between .66 and .7. This isn’t obvious unless they’re directly compared. The canopy and windshield of the SAL is a little larger than scale, but there’s not a lot to be done about that except to minimize the effect with contours, since the pilot still has to fit in.
This is where the two seater fuselage shows an advantage over the single seater in that it’s the same depth, but is longer. This makes it a little closer to .75 than .66, but no problem there, since the length and depth now match. By positioning the windshield in the scale position instead of placing it about 13 inches forward of the single seater’s windshield position (per plans) and building the canopy to as close to scale size and shape as possible, I believe it’s possible to have a very good looking airplane and still have a back seat. The pilot position would still be moved forward, since he sits quite far back in the canopy of the single seater. The final piece of the puzzle would be to extend the cowling over the front of the fuselage so the dividing line falls in the scale position, as was done with the FEW Mustang. The best of all things: two seats, scale appearance, shorter engine mount, and leg room. I haven’t actually seen the two seater plans, but I wish they’d been available when I built my fuselage.
Details
Scaling an airplane like the P-51 requires overcoming or working around some problems. Unfortunately, one of the most obvious simply can’t be ignored, that being the size of the pilot. All fighter replicas have this problem, but the slim, sleek inline engined P-51, Spitfire, and similar airplanes are the hardest to scale. No matter what, there must be room for a pilot to (more or less) comfortably operate the airplane and have an adequate view. It wouldn’t be much fun to fly looking through a periscope, even if it was possible, so usually the most obvious departure from scale is the windshield and canopy
The above picture shows the resulting canopy and windshield. The windshield is a three piece unit with 1/2 inch plexiglas center and 3/8 side panels.
The cowling was a little too short, so I have converted it to a plug for new cowling to be vacuum bagged, which should save quite a bit of weight. After lots of fiberglass work and a few gallons of bondo, the results are below. I still need to do a bit of fine sanding and shaping to get the plug in shape to make molds from.
It'll look a lot better primed one color. The spinner is a Stewart S51 unit and it fits perfectly, the airplanes are almost exactly the same size. I THINK the Stewart cowling would adapt easily, too, sice it comes a little oversize and the panels are trimmed and fitted by the builder.
This winter I hope to make the molds and finish a set of cowlings.
