Introduction: Airplane Covering-With Plastic Wrap!
So, you spent six months finding five-minute breaks to glue in struts and bend longerons. Finally, the kit instructions say something along the lines of, "use our magic tissue and overpriced dope to cover up that beautiful balsa sculpture on your bench." What? No way are you going to cover it up with boring tissue! A white plane? This ain't no Cessna!
This Instructable will detail the simple steps involved in covering a balsa structure with plastic wrap (or cellophane, or food wrap, or Saran wrap--whichever name you prefer). No, it's not as strong as Monokote or Ultracote, and probably not as strong as tissue. It certainly isn't as easy to patch as tissue. However, it's much lighter, cheaper, easier to find, and better at showing off the underlying structure.
My original attempt was to replicate the look of the SIG Rascal, which I find to be one of the nicest-looking covering jobs on a sport flyer. I wasn't sure how well I could combine tissue and plastic, so I went for a more basic approach. Pictured is my SIG Tiger, which has a similar design, but a longer nose (since there's no engine to balance it).
Some of you may remember the forum topic I posted quite awhile ago on this subject.
Step 1: Materials
There isn't much here.
-Frame The balsa aircraft, sans covering. Or with any tissue trim, if you want.
-Plastic wrap Plastic, Saran, food, or cellophane wrap. Call it what you want, find something in pretty colors. I raided this from the kitchen drawer a year ago, and I don't think Mom knows that it's gone yet.
-Glue stick Nothing fancy here. I raided this from the office. Aren't raids fun?
-Heat gun That is a manly-looking piece of equipment. The one in the basement didn't look nearly manly enough for me to photograph it, so I raided this from a garage. Raid!
-Scissors and razor blade (not pictured) Some scissors work better than others. I don't know why.
Step 2: Build Your Airframe...
...and do a darned good job! Remember, you have transparent covering, so any and all mistakes will be visible. I admit, I'm not showing the covering of an airframe for this Instructable--I already covered it! I figured it would take at least two tries, so I didn't take any pictures. With the exception of a tiny triangle that only taught me whether the glue stick would work and how far away to hold the heat gun, my wing was the very first structure I covered with plastic wrap--In fact, it was the first time I'd ever used a heat-shrinkable covering!
This image shows the little frame I built to demonstrate this technique. It's just some scrap balsa I had, so don't start bugging me about the rhombicosidodecahedron I could have built instead. I also have a picture of the horizontal stabilizer of that SIG Tiger-I recovered one side of it at the same time (I...um...dropped a Dustbuster on the plane and tore it. Yeah, really.), but since the other side was already covered, it's harder to see.
Step 3: Prep the Frame for Covering
This step is fairly simple. First, cut the plastic wrap to the general shape you need, leaving plenty of room to hold on to it. Then, cover every surface that you are about to attach film to with glue. It takes a surprisingly small amount, so just smear on a thin layer. Try not to scrape off big blobs of glue, as you can see them through the film and it looks bad.
You'll notice that I'm using a blue glue stick. That allows me to see what I've already covered, and the color won't be visible because I'm also using blue film.
Step 4: Place the Film Covering
I had originally planned to glue some sticks to the edges of the sheet of film to create a frame to pull it tight, but I discovered that I didn't really need it. Lay out the piece of film over the frame much like you would do with tissue. Don't pull it tight enough to stretch it out, but be sure to remove any wrinkles before you let the glue dry. If you leave a wrinkle in, it WILL show up, even after you shrink it down. Once it's down, gently run a finger over all frame pieces to attach the glue.
See Step 3 of this Instructable for another rundown on how to lay it out.
Step 5: Shrink It Down...you're Done!
I shall say this straight out: this step is the reason to build a test frame before you cover an airplane. Plastic wrap is thin stuff, and it's very easy to melt a hole through it.
As the film shrinks, you will see it stretch tight, and the texture will become shinier. As soon as you see this change, stop heating that area, because that's as shrunk as it gets. Don't even think about using an iron on this; all you'll get is dented covering. I used a big industrial-type 1700W heat gun, just because it's huge and awesome-looking, and made me feel like a lumberjack, but a hair dryer is plenty, and will probably work even better because of the lower temperature. Keep the heat gun/hair dryer fairly far away from the covering as you can, because it is so easy to melt through before you get used to it. With the big heat gun, it shrank nicely from about 18 inches away.
Once it's shrunk, place it covering-side-down on a smooth, clean surface (I used the glass top of my desk) and carefully run a razor blade along the edges of the frame to trim off the excess.
Step 6: Maintenance
This is an easy-to-apply covering, but it is delicate. If you poke it, it will dent. If you poke it harder, it will tear. Patching a section will be much more noticeable on film than a patch on a bit of tissue, so try not to fly this somewhere where it might be mistaken for a pheasant or a Soviet bogey. If you do get a tear, it might be easier to just replace the whole sheet, rather than trying to fix a little patch.
Congratulations! You've just finished a nice-looking aircraft, and at the same time, you cheated Top Flite out of a $18 roll of Monokote.