Monday, 16 September 2013

More on boomerangs - the making of them.

Once I got into the subject of boomerangs I was soon fascinated by the scope of the topic. Combining the skills of technology, craftsmanship and creativity,  the making of boomerangs is more art than science, but no less alluring for that.

The first art to boomerangs is that of actually throwing them, and in the absence of any expertise in my neighbourhood I had to resort to the internet for some help.

Of course the easy path is to go buy one; even boomerangs have their mass-produced commercially available models.
The Aussie Magic, a typical A-pattern sport 2-blade boomerang

But since when did I choose the easy way? Attempting to achieve a good returning boomerang by building them at the same time as I learn to throw them has definitely complicated the whole exercise, but hey, I have the time, so why not.


One issue I have struck early on is that of the suitability of materials. Ideally the material should be light enough to fly well (weight can always be strategically added), durable, adequately rigid in narrow thicknesses, and easily worked.

Another self-imposed criterion is that the material should be readily available and easily affordable, to avoid my research becoming too expensive.

Plastics of various sorts are an obvious option. My first problem is understanding what material I am using; for example one of my first boomerangs was made from a 4mm kitchen chopping board. It is a waxy translucent material, fairly dense and therefore a little heavy, but easily worked; I think it is polypropylene. PVC (polyvinyl chloride) is another possibility. I have also used ABS (acrylonitrile butadiene Styrene). Polystyrene is a little brittle, melamine even more so.

I also intend to experiment with creating my own reinforced resin laminates, so I can achieve the required attributes.

I also intend to explore the use of aluminium extrusion, as aerofoil-shaped sections are available quite cheaply. I believe that metal boomerangs are not used for safety reasons in competitive boomerang events, but that is not an issue for me at the moment.


There are a myriad of designs to draw inspiration from. the early design decision is the number of effective blades the boomerang should have; four and three-bladers are general suitable for short fast accurate flights; I personally find the two-bladers,  traditional or otherwise,  for long range slower flights, more intriguing.


The first design I attempted to build was an A-shaped 2-blader similar to those pictured above, called Aussie_Round, as the plan showed appropriate airfoil cross-sections.

I built two, one in 3mm pvc, the other in 4mm pp; The latter I got flying fairly well, until a recent careless throw landed it firmly in a treetop, where it hooked over a branch and will need a decent storm to dislodge.


I found construction to be a quite straightforward:
  • download pattern and scale to required size
  •  print on A4  paper (make sure print size is a full 100% ),  and cut out paper pattern  (paste together several sections if larger than A4)
  • tack pattern to material and transfer outline
  • cut out outline with jigsaw
  • carve aero profile with surform file, and scrape smooth with craft knife

The scraping is used because trying to smooth these plastics by sanding produces a furry mess, whereas scraping works well.



Insolite - 3mm abs version
  Insolite (a small weighted 2-bladed design by P Boillot - see my index of his plans) in 3mm abs - this version of abs was a bit brittle, and the rang broke on a crack introduced while fabricating.
Insolite mkII - 1.5mm polypropylene

A version in 1.5mm polypropylene proved too flexible, and unstable.

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