Scale
One of the things I didn't like was the size of some of the pieces. The smaller the pieces, the harder the folds, and the less surface area for glue. The first thing to consider is the use of paper. I could use legal (B/ledger) paper, but it's pretty uncommon to have that lying around, and I don't want to go to the store just to get paper for airplanes.
So, the maximum length of a part is 11 inches. Lucky for you, I forget the various scales of the plane, so I have to measure them again! Lucky for me, many decks of playing cards made during World War II featured a variety of planes from several angles*.* These were called "spotter cards," and served a dual purpose. First, it provided entertainment for troops and civilians alike. More importantly, it helped educate both on the silhouettes of friendly and enemy planes, making them easier to identify and determine if the flight of incoming planes were returning home, or were the start of an air raid.
Using the center image, I measure the length of the engine booms in an image editor: 245 pixels. Because my intent it to make the wings out of two separate parts, I measure from the center of the plane to the tip of the wing: 175 pixels. Applying this ratio to my 11-inch maximum, if I were to design the plane with a 22-inch wingspan (impractical, but not impossible), then the booms would have to be more than 15 inches long! Legal (B/ledger) paper is only 14 inches long--that's not going to work for a second reason. The choice is obvious. I can now measure the rest of the parts in pixels, and convert those measurements to inches. Hint: The new wingspan is just under 16 inches--a big step up in scale!
Two-Part Wings
The part that will change the most from the original design is the wings. Designing wings from a single piece of paper is inherently simple--it is already structurally linear, so all that is needed is a leading edge and maybe a little folding. Designing a wing with two parts becomes more challenging. While they are essentially mirror image of each other, one must keep in mind how the leading edge is presented with respect to the flight vector (the direction of travel), as well as how the wings attach to the fuselage (in this case all three fuselages), and possibly how they attach to each other.
In Sketchup, I make an 8-inch by 11-inch plane (a flat surface, not an airplane). Half of the wingspan is 7 and 7/8 inches, so I mark this point. This is from the tip to the center of the wings, though not the end of the part. I want to add some material to fold down into the cockpit nacelle. This will add some weight, as well as some structural integrity, making it harder for the wings to separate from each other and/or from the body (which is one of the many ways to obtain the "catastrophic failure" achievement).
Based on my measurements from the spotter card, the distance from the top of the wing to the bottom of the cockpit nacelle is 25 pixels. (I trust this measurement because I took the measurement from the top image, which has the same wingspan as the center image.) This means the cockpit nacelle is about 7/8 of an inch tall. While it would be nice to round it up to a full inch, the original design was only 3/8 inches tall, so for now I'll accept it and roll with it. If this design suffers from the same tail-heavy attitude, I'll increase it to a full inch, which will help increase weight in the nose.
Back to the wings, I add an extra 7/8 inches of material to the end of the wing part. Remember, this extra material gets folded into the cockpit nacelle, so it doesn't attribute to the wingspan.
Now to give the wing some shape. First, using the center image from the spotter card, I estimate and measure along the center line, from the leading edge to the trailing edge. From this, the maximum width of the wings is 3 inches. But I'm not going to mark this in Sketchup yet.
Good paper wings resemble actual airplane wings. That is, they create an airfoil by forming a thicker leading edge than trailing edge. I accomplish this by having more material along the leading edge. To get this extra material, the paper will be folded several times so that the wing is 4 inches wide, and a half-inch mass of folded paper rests along the leading edge. Some trimming will be necessary due to the rounded wing tips, but this can be handled later.
Accounting for the angle of the edges of the wing is a snap with Sketchup's compass tool. After finding that the edges are 15° apart, I just need to mark the angles, and provide numbers for easier measurements. Luckily, the numbers were very close to eighths already. Because the leading edge is also angled (5°), I need to account for the piece being folded into the cockpit nacelle. Once again, marking from the angle and measuring gives a usable number in 3/8 inches.
In the end, we're left with very little paper actually being used for the wing. The yellow areas in the image above are the area I will use for the wing. Knowing this allows me to rearrange the parts on the paper, which lets me fit more parts onto a single sheet. By an eyeball estimate, it looks like I might still be able to make both wings out of a single sheet of paper, and still have some material to spare. I'll verify this later.
With this little bit of fudging to make measuring and marking the parts easier, the wingspan for the new P-38 will be just over 15 1/2 inches. Right on target. As I've said previously, the rest of the plane won't change much, but that isn't going to stop me from covering it. The next entry will probably cover the fuselage(s).
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