Part III. BOTH FEET IN THE 21st CENTURY
You might be reading this and thinking to yourself, "Wood from Amish store? Carving? How is that 21st century technology?"
And you might be right. So read on.
It was right around January when the fuselage molds were finished, and the first successful fuselage was produced. It had good glossy finish, and was stiff and light enough to give us hope that this technology is viable enough to continue working on.
The next large part of the airplane, of course, is a wing. Some would say it is the most important part, because that's what is carrying the plane through the air. After all, that was the foundation of the sheeted foam wing cottage industry: consistently straight, dimensionally stable wings. Everything else can be built.
So I breached this subject with Gabe. My thinking was that we could hotwire the wing bucks out of blue foam, cover them in fiberglass, sand and finish, and then pull the mold off that. There was one limitation, though...
Gabe's ears perked up.
- What is that?
- Well, I can only hotwire a straight tapered wing...
There was some silence for a moment, and then I heard:
- No. It has to be elliptical, just like Skittles.
"- Gabe", objected I, "how am I supposed to hotwire an elliptical wing? It's impossible. The wire is straight."
Again, silence, and then "No".
Have you ever had a 4-year old stop in his tracks at the sight of an ice cream shop on a stroll through town, and refuse to leave until he got a cone? "Johnny, you can have a popsicle when we get home..." -- "No!"
That was Gabe at this moment. He dug his heels in and would not budge, which is not very typical of him. Usually my technical arguments are convincing enough, but this was not the case that day.
In retrospect, I'm glad he stood firm. The composite elliptical wing turned out to behave very well (something that we actually knew from the original, built up Skittles), but I'm skipping too far forward.
We started brainstorming how to make a buck for an elliptical wing. The only method that I knew of was learned by me from an RC boat modeler about 30 years ago; he was making bucks for racing boat hulls. Not too long ago I came across Bob Hunt's TruForm molding method description, and it is very similar. The idea is to install several plywood bulkhead-like templates at predetermined stations along some sort of a building reference board, fill the spaces in between with a material that can be carved (blue foam, basswood, etc), and carve until the surface reaches the bulkheads. This way the cross sections are both known and guaranteed (as opposed to me eyeballing the fuselage cross sections when carving from a single block).
I outlined the process to Gabe, and warned that something this involved could cause our build schedule to slip severely, but it did not seem to move him. You know, this generation of kids just doesn't understand what it's like to operate within constraints (technical, budgetary, etc) - they reach for the sky and worry about the costs later. Maybe it's a good thing, I don't know.
And then he said something that almost made me laugh:
"I'll 3D print the wing buck".
It is true, he just got a shiny new 3D printer for Christmas, a $500 Creality CR-10 Pro V2. But wait, kid... It will take you up to a year to learn how to use it! And then you need to learn CAD, which is probably another year. I took CAD in graduate school.
"Nah", was Gabe's response, "it won't take that long. I'll have the buck printed before you can make your foam wing. Bet!"
The word "bet" was a challenge thrown my way, and in such a cocky tone, that I just had to teach this kid a lesson.
I said the following:
"If you can produce a useable elliptical wing buck before I make mine, you will get a fast gaming laptop for your birthday".
Needless to say, I was absolutely confident that I'll win this bet. After all, how long does it take to hotwire a wing! Piece of cake, huh?
Instead of cake, I ended up eating crow. Before I had my templates made out of formica (again, thanks Joe!), Gabe presented a fully rendered 3D model of the Skittles wing, done in Fusion 360 (and Autodesk product). He downloaded the Fusion 360 hobby version (free), watched a 10-minute tutorial on Youtube, and declared, "I got it". At that time, I chuckled to myself, thinking "good luck, kid". By the end of the day, he was lofting straight wing sections. Next day, he had a crude prototype of an elliptical wing, which got refined better and better every day. Things were looking both promising and more sour for me.
Here's a 30-second animation of his design process in CAD: