Re: best materials for constructing boomerang

Hi Jim,
The 'best' material for a boomerang will depend on several factors:

1)The material should be strong enough to survive the flight, and be 
something that can be formed into the right shape with a smooth finish.

2) The material must have a low enough density (mass per unit volume)so 
that the 'lift' produced by the boomerang is greater than its weight.

3)  The material must have a HIGH enough density to give the craft enough 
mass and momentum to keep it moving for the length of flight needed.

There must be an optimum density to meet both conditions 2) and 3). 

First some definitions to help explain the "optimum density": 
"Lift" is the upward force that is produced by the air moving over the 
boomerang that keeps it in the air.  The lift of a boomerang is much like 
that of an airplane wing.  The top surface (when flying horizontally) has 
a more rounded, bulging shape compared to the flat bottom surface.  When 
moving through the air, an air particle on top has a longer path to follow 
than the air on the bottom, and therefore moves faster.  The faster 
flowing air produces a lower pressure on top than the air on the bottom.  
This difference in pressure causes a net lifting force. The amount of lift 
depends on the velocity that the 'wing' is moving through the air and the 
density of the air itself.  (For more details on this type of lift, do a 
web search for "Bernoulli lift").  

The lift of a boomerang is produced by the rotating motion of the blades, 
as well as the forward movement.  When the boomerang slows, the amount of 
lift decreases to the point where its weight exceeds the total lift.  At 
this point, it will start do decend to the ground.  So far, the less 
weight, the better..

Now consider point 3): "Momentum" is a physical term defined by an 
object's mass times its velocity.  After a boomerang leaves you hand, it 
has a certain momentum, determined by the release speed and its mass. This 
can be thought of as the "fuel" to carry it through the flight.  If the 
boomerang were made from a very light material (low density), such as 
balsa wood, its mass, and therfore its momentum would be very low.  

The ideal density for a boomerang could actually be calculated, based on 
the concepts described above, but it would be extremely complicated.  

The bottom line is that the best material would appear to be hardwood that 
has been used for hundreds of years, or modern plastics (with a density 
similar to hardwood).

I hope that this helps!

Best Regards,
Jay Shapiro


Note to Moderator- I attemped to answer this question last week, and has a 
more detailed response.  When I attemped to 'send' it, the web site went 
down, and I lost the entire response!