The Double Dangerous Book for Boys. Conn Iggulden

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       FLYING MACHINES

      Rubber-band aeroplanes are as old as, well, rubber bands. You could use the skills in this chapter to make a simple one, with a propeller. That’s part of the reason why we’ve put this in the book: it’s astounding what you can do with balsa wood, superglue and ordinary thread. The other reason is that an ‘ornithopter’ flaps its wings. They’ve been around since the 19th century as toys, but they’re still impressive. You can buy a kit or a complete plastic one easily enough, but it is immensely satisfying to make. At the time of writing, the world record for indoor rubber-band-powered flight is 21 minutes, 44 seconds, held by Roy White of America. Our ornithopter will fly for just a few seconds, but it’s still worth it.

      YOU WILL NEED

       Needle-nose pliers

       Superglue

       Thread

       Elastic bands

       A razor blade or art knife

       Tissue paper or a supermarket plastic bag

       Wire. Paperclips will do, but we used 1/16in brass rod, because it felt a little stronger

       Electrical wire (for the plastic covering)

       Oil or grease

       ⅛in aluminium tubing

       A few coffee-shop wooden stirrers (or ice-lolly sticks)

       A hard plastic bead

       Spars of balsa wood

      Note: ‘Super’ or ‘crazy’ glue refers to the group of fast-setting cyanoacrylate glues. Although it is apparently a myth that they were developed to close battlefield wounds, they are sometimes used in that way today, to seal cuts where it would be difficult to stitch. In other words, superglue sticks well to balsa wood, but it sticks amazingly well to skin. In the course of making this ornithopter, we stuck our fingers together many times – and our fingers to other things, including the tube of glue itself. Acetone is your friend when it comes to removing superglue, but please try to avoid pulling your fingerprints off. They do grow back, however. There is clearly potential for injury here, so find a dad and make him help, but don’t let him do all the tricky bits. Remember: scars are fine. Having to go through life attached to a superglue tube is not.

      In balsa wood, you’ll need a couple of spar pieces to act as the body and a couple of thin spars to form the backbone of the wings. Hobby shops sell balsa in all shapes and sizes. It’s not expensive stuff, so you should be able to get a selection for a few pounds. The point of having more than you need is (a) for when you tread on a wing spar and snap it, and (b) because, as you’ll see, balsa is really useful. It won’t be wasted.

      We formed the main body with four pieces. The thin spars are ⅛in thick, ½in wide and 7in long (4mm × 13mm × 17.5cm). The thick ones are ½in × ½in square and 2in long (13mm × 13mm × 50mm). We added blocks of ½ × ½in batten beneath as well, to hold the rubber band later.

      Up to this point, it’s all symmetrical. Choose an end to be the front and cut three pieces of aluminium tube. You could use brass or plastic. It should be the right size to allow your wire to pass through.

      With a razor blade or a hacksaw, we cut all three tubes the same length – ⅝in (16mm). As a general principle, it’s worth sanding the rough edges. Two tubes go on the top, parallel to one another, while the third goes at the bottom. It’s vital they don’t come loose, so we cut a groove for the bottom one, glued them all in place, then wound cotton thread around the entire assembly. Cyanoacrylate glues essentially form a hard plastic as they set, with a little heat given off. The result is impressive and incredibly strong. Honestly, the application of superglue on balsa was very satisfying. Once or twice when fiddling, a crack was heard. A dab of glue on the hairline crack, good as new.

      The crank is the only tricky part of making this, so here it is. The rubber band will be held by one end and wound at the front. (We did try a rear-winder on the first attempt, with a cork attached. That actually worked pretty well, but we’ll keep this simple.)

      The problem is how to turn that rubber band rotation into an up-and-down motion for the wings. A spinning disc doesn’t work – it’s impossible to get the wings to act together. What works is a staggered crank, which lifts two rods at slightly different times.

      The wire comes out of the bottom tube, leaving enough room for a plastic bead (fake pearls work well). With the needle-nose pliers, make a 90-degree bend to the left, looking at it from the front. It should be as sharp as you can make it – you do not want that bead to work its way around the corner. After ¼in (6mm), make another 90-degree bend, heading away from the main body. Leaving enough space for a small wooden batten – say ¼in – turn back in a 90-degree bend, parallel with the first bend.

      So far so good, but that upside-down ‘U’ has to be twisted to create an angle of 60 or 70 degrees.

      Looking down the crank, it will look like this:

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