| How to Alter the Flight of a Boomerang (General Tuning Tips) | |
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Altering a ‘finished’ boomerang is tuning. This type of experimentation on one or two boomerangs will lead to more understanding than making hundreds and not altering them. Six broad methods are...
Weighting
Weights are added to increase the range, and so require more initial layover in the throw. Because coins change the shape of the whole aerofoil, watch out that you are not increasing the lift at the same time, which would tend to decrease the range, or make the boomerang fly too high. Adding weight to the lifting arm where it will decrease lift is what I most often do. A coomon tip is to tape a coin to the underside of the end of the lifting arm, near the leading edge, like shown: Remember the picture on the left is looking at the underside of the boomerang, so the lifting arm now appears on the opposite side for a right handed boomerang. People virtually always add the weight to the lifting arm as this will generally stop the boomerang from ‘laying over’ too much and give a lower flight. A bit of weighting can make a lot of difference so remember to give yourself extra space after any changes. One penny coins are good, but people also use lead strip. Sometimes the range can be usefully increased by a few layers of tape with no coins / lead. Adding Flaps to increase drag Strangely, more drag can be beneficial at times. Most often this technique is used to stop boomerangs drifting downwind or to slow them down for an easier catch. Use a bit of sticky tape with a ‘pinch’ in it so that it sticks out from the surface. The more area sticking out, the more drag. I usually add the flaps to the top surface, as shown, but this is just a personal preference. The position of the flap is important ; nearer the tips will do the most to reduce spin, whilst nearer the centre / elbow will slow the boomerang down with least reduction of spin.
Bending Changing the shape by bending is a very useful method. Some plastics and plywood can be bent temporarily, and slowly ‘relax’ to their old shape, or can be more permanently altered by warming / heating them first. I use a microwave oven, a disposable lighter, or steam from a kettle for thick ply.
Dihedral means bending the arms ‘up’ and anhedral means the opposite. Dihedral is usually desirable in small amounts (eg arms are a few mm ‘up’ from resting flat on a table) for most boomerangs. It makes the flight stable and increases lift. I find that a bit of extra dihedral on the dingle arm does wonders for a boomerang that dies on the way back just before it gets all the way home. Anhedral (sometimes called negative dihedral) is rarely needed. It is sometimes used to keep a fast catch boomerang low. Twisting alters the angle that the arms push on the air with (angle of attack). Twist the tips up at the leading edge to give a greater angle (i.e. positive twist as shown above). This will increase the lift (and the drag a bit). Increasing the lift will reduce the range of the boomerang. You can also use twisting to alter the relative amounts of lift from the arms of a two blader, and thus gain some control of how rapidly the boomerang lays over (or not) in flight. The secret with tuning by bending is to try small changes with many throws in between to see the effect. A lot of bending is done in tuning an MTA boomerang but it is a complex issue. Drilling Holes This is a more permanent way to add drag and very commonly used. Holes are usually about 3-5mm. Lots of fast catch and high wind boomerangs have holes. Holes near the tips do most to reduce spin, while near the centre they reduce speed. A Different Profile Removing more material from the leading edge, as shown will reduce the amount of lift. This is useful because the boomerang will fly further, if you can throw it hard enough. (Throwing the same boomerang harder usually does not increase the range significantly: it just goes around faster). Very long distance boomerangs have a cross section / aerofoil that is virtually the same for the leading edge as the trailing edge, and also as much material is removed from the bottom as the top so they are virtually the same on top and bottom surface. Combs These are slots cut into the boomerang's edge. They give lots of wind resisitance and also increase range. They have more effect on the leading edges, near the tips. Summary – Tuning Tuning boomerangs can give a lot of insight into how boomerangs work and controlling their flight, but take it slow. Change one thing at a time and make many throws to fully see the changes. Be prepared to alter your boomerangs after they have been made. Even if you ruin one, you can always make a new better one with what you have learned.
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It is often particularly useful to alter the lifting arm in this way to reduce the amount of ‘laying over’ that the boomerang does in flight. Reducing the tendency of the boomerang to lay over will keep the flight lower, and may make it more circular. A boomerang with less lift will need more initial layover, when it is thrown. Basically, the less lift, the longer the range, the more initial layover. Having less lift from the lifting arm stops the boomerang laying over more and climbing too high as it flies.