Nov 21, 2005, 11:26
Here is a short guideline to contemporary LD airfoiling, to be used
for boomerangs of the MegaQuirl, Voyager, Buzz Whip, Backdraft, etc. type.
If we think about what LD booms are supposed to do, i.e. go out far
and come all the way back, we can identify two airfoil characteristics:
1. low lift
2. low drag
The boom must have a little bit more lift than required to keep it in
the air. Because of the small forces and moments, inertia dominates the
motion and the boom will go out far. The boomerang must be launched almost
flat, so that the small lift force may counteract the weight of the boom.
Of utmost importance is low drag to maximize the conservation of energy,
which the boom needs to come back to the thrower eventually.
Here is an airfoil, not too aggressive, for you to start with: I use
it on the
which is not a top performer, but a steady boomerang with range 100-120
m. Compared to airfoils of shorter flying boomerangs, e.g. booms for Aussie
Round, the leading and trailing edges are more pointed, reducing thereby
lift and drag. An important feature is the undercut, meaning material is
removed from underneath the trailing edge, which reduces lift dramatically.
Be careful with undercuts - too much and your boom will just fly straight
out and won't return.
Booms with airfoils like the one shown above (Offspring) fly considerably
far, while still being quite forgiving and stable in flight. For throws
going out much farther, the airfoils need to be more AGGRESSiVE. The Backdraftis
my competition boom with a distance 120-170m. Compared to the previously
shown airfoils, the faces are carved much further into the wing, with smooth
transitions. Also, the leading edge is rather pointed. These features let
the boom travel out much farther, but also render it less stable and prone
to crashing on the way back. You have to give the boomerang as much forward
velocity and rotation as possible to keep it in stable flight.
Here is the airfoil Manuel Schï¿½tz uses for his Voyagers.
It seems less aggressive than the Backdraft airfoil. But maybe he showed
here a bit of a conservative airfoil, not his most aggressive one. Anyway,
we can see that the undercut reaches up to half the material thickness,
giving very low lift.
A special feature Manuel introduced is the concave trailing edge. He
has booms with concave carving only on the top, and such where both sides
are shaped concave. Manuel points out that this brings about a further
reduction in drag, and judging from flights I have seen of Manuel's boomerangs,
it appears that the ones with the concave trailing edge return with higher
In conclustion, it can be said that in order to attain a maximum distance,
you have to go to the boundary of the stable to the unstable flight regime.
The last bit of tweaking to approach this limit may be effectively achieved
by tuning. Reducing drag is of primary importance. So use the thinnest
material available that is still stiff and strong enough to withstand your
throw without getting deformed or warped.