Design Round 2: Lockheed P-38 Lightning (Part 5)

As I continue designing planes, you'll start to see a pattern emerge.  It's the same pattern that most planes follow.  A fuselage, a pair of wings, and vertical and horizontal stabilizers make up the main features.  And while their design inherently sets them apart from their folded brethren, it is the details which transforms them from paper airplanes into models.  I'll generalize detailing a model later, but for now I'll concentrate on those that makes the P-38 unique.

Looking back at the spotter card, we can see that the P-38 is not squared-off at all.  Its lines are quite typical for the era--everything is rounded for the sake of aerodynamics.  Even the cockpit nacelle and engine booms carry an oval or teardrop shape to aid the flow of air over and around the surfaces.  If I left these details out, it would carry the same layout as a P-38, but would it really look like one?  I think not.

First, in designing the wings, I already accounted for the angles of the leading and trailing edges, making those details easy.  The wing tips won't be.  I could eye-ball it, and it would look acceptable, but I'd prefer to make it acceptably repeatable.  To do that, I'll need to come up with a way to measure the rounding effect of the wing tips.  I believe the spotter card is more accurate with measurements than shapes, so I look to the Internet for other images, specifically overhead views.

P-38 Spotter Card

Based on the images searches, I notice the leading edge corner has a smaller radius than that o the trailing edge, though both curves seem to met in the middle.  Since the tip of the wing is 1 inch wide, I am going to go with a 1/2 inch radius for the leading edge, and a 1 inch radius for the trailing edge.  But how did I determine the trailing edge?  That's a secret.  Actually, it's a guess.  I'll adjust it later if it doesn't look right.  For reference, a US $1 coin is roughly 1/2" in diameter, and the top of a Yoplait yogurt cup is roughly 1 inch.  You can use these or other analog tools to help draw your arced edges.

The tips of the horizontal tail are 1 1/8 inches wide.  I am settling for 1/2 inch radius (my $1 coin), front and back.  If you want to pick nits, the tips on a P-38's tail are fully round.  You can always (carefully) use a compass to get it exact by finding the center line running the length of the horizontal tail, then setting your compass to the trailing or leading edge--that will give you the necessary 9/16 inch radius.  Just draw your lines from the tips, and be careful not to punch your compass through the paper!

The vertical tails are tricky.  Each one is 2 1/4 inches tall.  Measuring the spotter card again, it appears the horizontal tail intersects them about 1 inch from the bottom of the vertical tail.  This means I can once again use my 1/2 inch radius $1 coin for the bottom.  For the top I think I'll try the bottom of the yogurt cup, which has a (roughly) 1 3/8 inch radius.  Once again, if it looks odd in practice, I'll try something different.

Finally, it's time to tackle the taper of the cockpit nacelles and the engine booms.  I'm going to stray a little from the rounded formula here, simply because--as you will see in the construction phase--cutting nice arcs through some of these parts may be more difficult than with the wings and tails.  For the fuselage sections, I opt for straight lines.  Some of them will come from folding, while others will come from measuring and cutting.  I'm going to hold off measuring these until I start planning the construction.  Needless to say, there will be very small measurements coming from the center of the "T" in the aft, leading to points along the edges closer to fore, which will give these parts the nice tapered look of the real thing.

Speaking of construction, that's the next step!  I can go one of two routes: actually build it, paper and all, or virtually build it in Sketchup using the parts I have created so far.  If I do the latter, it allows me to take screen shots which can be used for instructions later.  I'll also be able to use the measure tool to find my new measurements, and fiddle with placement without worrying about glue setting.  This round goes to Sketchup.  So, look forward to a lot of images, and a virtual preview of what the finished product will look like!