Introduction: Multi-Blade Bomerang
I have always wanted a really good boomerang.
The reason I haven't had one in the past is that I haven't seen them in the shops.
I know some things about aerodynamic and gyroscopic forces and have done a little research into boomerangs and their design. Even with this research I still taught it would be best to do a little experiment to make sure I had the best shape for my boomerang.
I didn't want a 2 winged boomerang so discounted this as a possibility.. (this is mostly because I don't like the shape as much as a multi bladed boomerang).
Did you know: Boomerangs are associated with Australia but examples have occurred in Egyptian tombs and other places independently.
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Step 1: Designing the Experimental Boomerangs
I started out with the idea that I would create a fair experiment to identify the ideal shape for a boomerang.
In hind site for my experiment to have been more accurate I should really have used a 3D printer or CNC milling machine to reduce the amount of variables I introduced whilst crafting
So I designed each boomerang to have the same length from its center. have the same circle to the globular part at the end (the glob part was part of my design and is not needed for the boomerang to work) and the thinnest parts were all the same width.
I did some fancy things with the compass to work out the angles but this is most likely easier to do using a protractor. (I used the compass because I have miss placed my protractor)
Step 2: Cutting the Shapes
I designed 5 shapes (Mainly because they fit nicely on the plywood I had spare for this project)
I had some 3mm plywood left over from a project.
The best plywood for boomerangs is aircraft birch ply. It is light and strong. It is also very expensive and would have taken some time to get to me. I am happy enough with using my scraps for now but If a client was to commission a boomerang from me I would defiantly go for the best stuff.
I used spray glue to attach cutouts of the boomerang shapes to my plywood and used my band saw to cut out the shapes. (If you don't have a band saw you should be able to cut out your shape with a saw of your choice. Scroll saw, coping saw, jigsaw) Pleas if you are using power tools be safe use the proper safety equipment and as always if your not feeling focused hold back until you are.
Step 3: Shape the Aerofoil
The easiest way to think of how a boomerang works is thinking of it like an airplane wing. The same type of shape is needed.
I used a small grinding tool with a sanding head on it to help with the shaping of the wings. (I also used a wolfram carving burr which seeded up the process a lot.)
If you don't have the tools I have don't worry. You could shape your wings with rasps, files, sanding paper, carving tools or whatever you find works best.
The lair's of the plywood work as a handy guide showing how far down you have carved. try to make the patterns on each wing match as well as you can.
Step 4: Dihedral or Not
Dihedral is the slightly upwards angle in an airplanes wing.
(When I was looking at boomerang physics alot of focus was given to having positive dihedral in your wings. In my experiments I didn't find it made a huge difference. When I gave an extreme positive dihedral the effect was to send the boomerang on an extreme lift before returning. If you were to watch this flight path from the side it would look similar a J shape)
To give your wings positive dihedral put it in a microwave on full power for around 4 seconds (this will soften the glue in the ply and possibly soften the ligneum in the wood) then place the boomerang on a surface where its wings can be held above its center. weight the center and as the boomerang cools the new dihedral shape will be retained.
Step 5: The Day of the Test Flights
I could have been a little more scientific with my test flights. Possibly collecting some data ect.
But instead a few of us headed out to play with boomerangs and decided on the ones we liked the most.
All the boomerangs were super fun and flew in really fun ways but for me the one I liked the most was the straight 3 winged boomerang.
It consistently came back almost to my feet and on one occasion hit the person trying to take photos of the boomerangs in flight for me. He was stood right next to me. The flight pattern was also a pretty C shape as viewed from above.
The weather conditions were unusually good with a slight breeze coming towards where we were throwing. (I suspect given different conditions the favorite boomerang could have been different.)
We threw the boomerangs with the blunt end (leading edge) cutting into the wind and the thin sharp edge trailing. we gave the boomerangs as much initial spin as possible and tried to throw them with an approximate 90 to 120 degree angle towards towards the horizon.
Did you know the record for a boomerang to stay in the air is over 6 minutes?
The longest distance is 427 meters. My boomerang doesn’t hit these records but I am still very happy with it.
Step 6: The Paint Job
I designed a fun little skull, heart and Celtic knot line art design (I did this by tracing around the boomerang shape sketching one wings design and then scanning and manipulating the orientation to allow the design to exist on each wing. Interestingly the skull looks towards the direction the boomerang should be thrown.
I used some ebonising lacquer to make the boomerang black as a base coat. I then hand sketched the design with a stabilo carb0thello pencil. this is a chalk like pencil which allowed my to get an idea of where to paint whilst being wipe off able.
once I had a sketch of the design on the boomerang I over painted this with a thin paintbrush and some slightly watered down acrylic paint. Parts of the acrylic needed re painting.
I have finished the whole thing with some gloss lacquer.