This is two boomerang projects in one. The instructions for each are remarkable similar, and you can follow the differences in the notes on the images.
Traditional boomerangs have two forms: there are the straight, hunting boomerangs, crafted to fly in a straight line at the target, and the V or banana-shaped returning boomerang. This is the source of The Robot Returns*
Modern boomerangs have more complex, multi-armed shapes, and that is what we are going to try for in Dark Kite, an attempt at my own personalisation of a Batarang.
* A little browsing on the web reveals that boomerangs designs have to have interesting names. Robot Returns is obvious. Dark Kite is Weissensteinburg's fault, following a throwaway comment comparing me to ... somebody else...
Step 1: Materials and Tools.
For tools, you will need a saw capable of cutting complex curves in your ply (such as a coping saw or scroll saw), a selection of rasps and files and sandpaper to finish the shaping. If you can, get a range of "grits", rough to smooth. Clamps or a vice of some description would also be useful.
- Or you can use what I did, which was a jigsaw and a dremel.
To finish, you will need a tough, waterproof varnish. You may also wish to paint your boomerang, or add your contact details, just in case you lose it.
- I bought a sheet of beech-faced ply from a local hobby store. With careful planning, it should be enough for about four boomerangs, which makes the raw material cost of them at around a pound each (roughly $2).
Step 2: Make Your Template
Most letters will (I believe) work as boomerangs, with one notable exception: if your name is Oscar Obermeir, make a Frisbee.
The easy way to make a template for most letters is to simply print out a very large single letter in a font of your choice. Choose a sans serif font, without sharp corners. In CorelDraw, it is possible to convert TrueType Fonts to curves, and then deform them. Dark Kite began its life as a letter K.
Robot Returns is basically a traditionally-shaped boomerang, but the centre-section was inspired by the Omega style of boomerang.
I printed both designs out on A4 paper - you could photocopy them larger if you wanted a larger boomerang.
Step 3: Cutting and Shaping.
The easiest way to cut the outline is probably to use a scroll saw, but I only have a jigsaw. Failing that, use a coping saw or even a hacksaw. Whichever you do, make sure you are using an appropriate blade for wood, and that the plywood is clamped firmly. If your cutting skills are at all wobbly, make sure you stick to the outside of the outline. If there is too much wood left after cutting, you can always trim it off later, but if you cut too much off it's kind of hard to put it back.
Hold your plywood shape in your hand. Pretend to throw it like a finished boomerang. Decide which way up you are going to throw it.
Which edges lead the wings through the air? Which edges trail behind? Are there any edges that don't lead or trail?
The leading edges need to be more steeply curved (at an angle of roughly 45o), and the trailing edges do just that - trail off and between 20-30o.
If you're not using a dremel, the best tools for shaping the boomerang are rasps, files and sandpaper or glass-paper. A cheap set can be had from a DIY store for a couple of pounds (few dollars). If you can only afford one file, make sure it is curved on one side and flat on the other.
Officially, some files are designed for wood, others for metal. I find that both kinds work on wood, the "metal" files giving a smoother finish after taking off the bulk with the rougher "wood" files. You can then smooth off properly with the sandpaper.
Avoid lumps, steps and corners in the profile, as they ruin the air-flow. Make sure you don't leave any sharp edges or pointed parts on the boomerang, because it will be travelling rather quickly when you catch it.
Be warned: you will be turning something like a third to a half of the mass of the wood into dust and shavings. This won't be so much of a problem with hand-tools, but the dremel generated so much dust, so quickly, that I had to stop and sweep the bench after every wing. Even now, my shed is thick with dust (highlighting every spider's web).
It's also easy to get carried away with the sanding bit, and scorch the wood.
Unfortunately, when I tried using a cutting wheel to trim Robot Returns closer to shape, the wheel kept snagging and whipped around the edge to the back. There are, consequently, several thin cuts in the back which don't look as nice as I'd hoped.
Step 4: How It Works
The gyroscopic effect is provided by the way the boomerang is thrown, but the aerodynamic lift is created by careful shaping of the arms of the boomerang.
To picture the profile of a simple lifting surface, picture a rain-drop shape, cut in half down the middle, and turned on its side, flat side down.
The shape utilises the coanda effect (basically, moving fluids stick to surfaces and follow them) to deflect air downwards. The reaction to the downwards-deflection is upwards lift.
For the coanda effect to work, the surface of the boomerang needs to be as smooth as you can reasonably manage, otherwise turbulence ruins the effect.
As the boomerang spins on its side, the top arms are moving through the air more quickly than the lower arms. This produces an imbalance in the lift, which tries to tilt the spinning boomerang over. Through the gyroscopic effect (described by a hideous set of equations that make my eyes water), the tilting effect is translated into a turning effect, which makes the boomerang loop (hopefully) back to the thrower.
If you have a gyroscope handy, give it a spin and then try and tilt it - that twisting you feel is the same force that bends the boomerang's flight back on itself.
(If you really want to have a stab at the maths behind boomerang flight, have a look at this website, which also has a couple of videos on throwing techniques.)
Step 5: Finishing.
It also needs to be waterproof (you never know what it's going to land in!).
You may varnish or paint your boomerang, but you first need to check it works. If you get your boomerang wet and muddy before finishing, it will never look right. Use a sanding sealant (available from most hobby or hardware stores) to prevent water penetrating the ply.
When you have flown your boomerang a few times (see the next step), and are happy with it, you can finish it properly - paint, varnish, even Sharpies - and seal it.
When painting and varnishing, it is best to apply several thin coats, sanding with a fine-grit paper between coats.
However you apply colour, make sure that at least the last coat is waterproof.
- Dark Kite was just finished with two coats of clear varnish.
- For Robot Returns, I used model paint* to paint in the details of Robot, then varnished over the top of the whole boomerang.
Step 6: Flying Your Boomerang.
Whichever shape of boomerang you have made, they are all thrown the same way. The "making" instructions in this project have assumed you are right-handed, and so will these throwing instructions.
The best weather for boomerangs is still air, or a light wind. Stand facing into the breeze.
Hold the boomerang vertically in your right hand, between finger and thumb, with the curved surface towards you (your thumb will be on the curved surface, and your forefinger will be on the smooth surface).
Lean the top of the boomerang slightly outwards, swing your hand back over your shoulder, and then flick it forwards rapidly.
It is vital that the boomerang is released with a powerful flick - if it doesn't spin fast enough, it will not return.
It may sound silly to say, but boomerangs don't fly in straight lines. When they fly properly, they fly in loops.
As you are facing into the wind, you are facing the furthest point your boomerang will fly. Throw your boomerang out to the right, about 20-40o from the way you are facing (if you are facing "12" on a clock-face, aim between one and two).
Hopefully, the boomerang will come back. As it flies, it will tilt, and be almost horizontal be the time it gets back to you. It will still be spinning quickly, though, so the safest way to catch the boomerang will be the clap it - smack two flat hands together to trap the boomerang as it passes.
Boomerangs are fun. They are cool. They let you show off when there's not enough wind for kiting. They can, though, be dangerous - spinning rapidly, moving quickly, they can cause potentially-serious wounds to the unsuspecting passer-by. Make sure your flying area is clear, or at least that everybody in it knows you are hurling unpredictable missiles around the place.
Throwing advice from Australia
Throwing advice from the USA
(There are also plenty of videos on YouTube. I have not made a "how to throw" video of my own because I am really bad at throwing boomerangs.)
But, above all, have fun.
Step 7: Tuning, and Advice From Experts.
In the first test-flights, Robot Returns didn't actually return. After some extremely helpful advice from Adam McLaughlin of the British Boomerang Society, I rounded the ends of the arms and added an airfoil profile to the inside of the boomerang's "elbow" (Robot's
Adam also pointed me towards the simply beautifulboomerangs of Jay Butters, another respected BBS member, as examples of what the ends of my boomerang arms should look like.
I am indebted to Adam (and indirectly, Jay) for their help in making RR fly.
Other Advice Culled from the web:
Are you throwing it properly? Most especially, are you using enough snap at the wrist to give the boomerang plenty of spin? Also, try leaning the boomerang out at a flatter angle, or lifting it nearer to the vertical. Are you holding it the right way round, so that the leading edge is leading, and the curved side faces you?
If the fault lies in the boomerang itself, then we move into the realm of suck-it-and-see, as well as facing the real possibility of having to start again.
- Maybe the whole boomerang is too heavy - try shaping the wings to be narrower (and hence lighter) near the centre or elbow. You may end up narrowing the whole length of the arms. You could be (very) adventurous and drill holes in the wings, which will also give extra leading and trailing edges to shape.
- Maybe the wing profile is wrong - try a bit more shaping, as guided by this image from Greg Courts' excellent photographic tutorial on making boomerangs..
- Maybe you got your leading and trailing edges mixed up, in which case you will probably have to start again.
However, it is possible to add weight, typically by taping small weights such as coins or washers near the tip of the arms (and at the "elbow" of a two-winged boomerang). The weight will make the boomerang fly further, but you will probably need to adjust the way you throw the boomerang as well, leaning it flatter as you throw, and aiming higher or lower depending on the exact positions of the weights you add.
I am sure boomerang enthusiasts will be able to suggest other ways of modifying your new toy, so keep an eye on the comments.
Step 8: The Aftermath: a Few Disordered Points and Thoughts.
- Wear goggles - my rotary tool is the only power tool I have where I always wear goggles. As well as flying sawdust, one of the sanding bits I used flew apart quite dramatically, peppering my face with flying pieces of grit. It stung, and rattled on my goggles.
- Give the various paints and varnishes plenty of time to dry between coats, and especially before adding details.
- Seal before you paint details - if you are planning to paint or draw draw details on your boomerang, use sanding sealer to stop the paint soaking into the wood and going all blurry along the grain.
- Be aware of compatibility - the acrylic paint worked well on Robot Returns, but the silver dots in the eyes dissolved in the solvent-based varnish, and had to be wiped off, re-applied and re-varnished with dabs instead of strokes.
- Dust, dust and more dust. You will make lots, and it gets everywhere. I should probably have worn a dust-mask, but I didn't have one and I was, frankly, too lazy to go and get one. After making these two boomerangs, I made a third as a gift: I used an extension lead to take my dremel outside, and the breeze took most of the dust away quite effectively.
- I used a cut piece of (clean) dish-washing sponge to apply the varnish, hoping to avoid brush-strokes in the surface. It seems to have worked well, and I just threw the sponge out instead of having to clean a brush.
- If I make many more boomerangs, I will get one of those dremel bits that can cut sideways through things - it will make it a lot easier to follow close to outlines.
- Consider printing your template on card, or glueing it to a piece of cereal box - the thin paper templates I used were a bit awkward to draw around without moving or creasing them. Heck, if you've got a laser cutter, use that to cut your template out exactly.
- After Adam's advice, I came across this database of plans - eighteen pages of them! If you don't want to design your own boomerang, there must be something there you can use. There's even an "O" boomerang!