Sunday, November 30, 2008

Advanced Halloween Construction Techniques

I had been anxious to try my hand at some "cool" Halloween costumes since my now four year-old daughter was born. My aunt had made me and some of my cousins a series of costumes when we were kids - like airplanes, helicopters, robots, etc. Now it was my turn.

Using some model RC airplane techniques that I'd learned along the way, I set out to build a costume from corrugated cardboard. I wanted to build a replica of my all-time favorite plane, the Fairchild PT-19.

Here is a photo of a fine looking model of John Hooton's PT-19.

I started by taking measurement's of my my daughter, and sketched an airframe around that. I used old corrugated cardboard boxes to cut the pieces from, which mainly consisted of several formers, and a wrap-around fuselage.

After some careful bending, and plenty of carpenters glue, I had a 3-dimensional airframe taking shape.

I wanted the nose and tail to slope downwards, like a real plane does. I suppose that I could have mocked up the exact cuts using a paper model or even CAD, but I found it simple enough just to cut a triangle shape from the side of the fuse, and then glued the sides back together with a cardboard doubler on the inside. The final step was to trim the bottom side flush.

In the tail, I scrounged together some Styrofoam blocks to make the final former. Next, I cut the fail feathers out of cardboard. I cut one of each the horizontal and vertical stabs, and then used it as a template to cut a second. The pairs were glued together on top of each other to double their thickness, thereby adding strength.

Using the actual parts as a guide, I cut slits into the Styrofoam blocks in the rear of the fuse that my tail feathers would slide into. It was very important to have a nice tight fit, and to not cut ALL the way through the Styrofoam block, so that it retained some of it's inherent strength. The block gave me plenty of gluing area, and I used Gorilla Glue to secure them in place.

To build the wings, I first cut a single piece of cardboard to the size and shape. Using that as a template, I cut three more corrugated wings. I bought a 4x8 sheet of pink Strofoam from a big-box home improvement store. Note, I used the denser pink board as opposed to the white bead board.

I peeled the plastic backing off of both sides of the foam (that backing is one of the few things that I've found that Gorilla Glue won't stick to - I saved mine for later as I needed to keep the wings from being glued to the fuselage). I smeared the glue all over the cardboard wings, and very carefully laminated the foam with cardboard on either side. I had pretty good luck having the top and bottom line up. After it dried, I cut the excess foam away from the cardboard, and wound up with two extremely strong wings.

Unfortunately I didn't take any photos of the mechanics of the wings, but I took one of those ~6 foot fiberglass rods from the home improvement store (I think they're used for marking your drive way for the snow plow), and cut it in half. I drilled holes through either side of the fuse, and threaded the rods across - one in front and one behind the pilot. This gave the wings something solid to lay on, but was still narrow enough that it would fit through most doorways.

Because there's no way that the wings would make it through doorways, I bought a couple pairs of cabinet hinges and glued them onto the edge of the wing. Some 3 inch drywall screws along with plenty of Gorilla Glue made a good attachment point. I then propped the wings in place, and glued the other side of the hinge to the side of the fuselage. I used some of that plastic film from the Styrofoam board to keep everything from sticking together. Now, when it came time to get through a narrow area, the wings could be pulled up to a vertical position, and the costume was only about 30 inches wide.

Once the glue was dry and I knew exactly where the hinge needed to be, I was able to drill through the fuse and, using some scraps of aluminum sheet metal, I bolted the hinges to the fuselage.

It was time for a test flight!

I spent the next several nights putting drywall primer and latex paint of the rought fuselage. Admittedly, I got a little lazy, cheap, and quite frankly, short on time, and just painted blue and yellow. It took several coats brushed on rather heavily to cover.

I ordered a geared motor from All Electronics and bolted it to the front of the fuselage. I used some more cardboard for the propeller, and with a handful of odd parts from the hardware store, I glued the prop onto the motor shaft.

Next, I glued a green LED on the right wing tip, and a red LED on the left wing tip. I also put a red LED on the top of the vertical stablizer. I just used some old flat telephone wiring to supply power, and wound up using Gorilla tape to hold the wiring in place. I wired up a little 555 IC timer to make the tail blink on and off. An old 7.2V NiMH battery pack that I had laying around supplied power, and I put some old toggle switches on the control panel so that the pilot could switch the motor and lights on.

Finally, I used some fairly wide nylon webbing material from the hardware store and wrapped either side around those fiberglass rods fore and aft of the pilot. This served as the "seat belt", which really let the plane rest on her shoulders. I doubled the strap back onto itself, and secured it with a pair of heavy-duty safety pins so that I could adjust the length easily.

A trip down the the local space museum scored us a military flight suit to complete the outfit.

All in all it was a great costume. Coming in at over 11 pounds, it was quite heavy for a 4 year old, but she managed long enough to wow her friends, her classmates, and the judges at the costume contest at the local mall. Next time I would focus more heavily on the weight. I could have easily put lightening holes in the formers. Also, I would have used thinner foam in the wings. Size was also a larger factor than I had anticipated. The folding wings worked well, but it was awkward to maneuver in, and it ALMOST didn't fit into the van.

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