Aerodynamics
There are three principle features to be aware of, they are: Effects of the angle of attack.
The effect of air resistance and direction.
Types discus
Air resistance cause the discus to follow a flight path that is other than a simple parabola.
many potentially along throws are lost by athletes not considering the Aerodynamics
qualities of their discus or understanding their ability to throw different types.
A negative angle of attack in the early flight path is essential since the gyrating discus will
at some stage present a large surface area to the approching air. as long as the surface,
is spinning the surface area will be small. as it slows the edge to the thrower drops and
this cause an increasingly larger area to be prearnted. the sail like qualities of the surface,
will cause the implement to be retarded and it will slow more rapidly and lose height.
with a negative angle of attack the discus will have a porlonged flight path this increase in
distance indicated from the second curve. the inner curve will represent a neutral angle of
attack, become closer to the parabolic path.
Coaching point: Observation of novice throwers should verify this as a discus with a positive
angle of attack as is so often the case form a standing throw will present a very large underside,
surface to the on coming air and visibly stall.
The negative rake angle
Diagram from the science of track and field A.H and R Payne.
hear the angle of release is inside the angle of the flight path or negative. the discus will travel further in the
oncoming air with smaller surface presented. contrast that with the opposite of a higher angle of release than
the flight path and the 'sail effect' produced such that in a moderated.
Wind direction
Diagram From Discus Throwing, Max Jones,BAF.
A Headwind increases the velocity past the discus in much the same way as would a higher realease speed.
it will give the discus more aerodynamic lift.A thower unaware of this or how to use it is not goiing to improve,
just by getting stronger.
It remains important to give the discus a 'nose down' approach and there is same sence in a right handed thrower
throwing towards the right hand sector line as the wind will draw it in to sector.doing a left of center throw might
see a strong wind take it out of sector.
Negative wind condition (all throwers) is from behind.the discus does not elevate easily and a thrower with good
control will usw a nise up technique.this is achived by throwing up with the arm much like a standing throw.
Distance usually suffers in such wind condition,however,with good technique somebody will use them best.
it should be apparent that a toppling discus,one thrown with a wobble will have a similar effect to a discus thrown,
with a positive rake angle until the wind get under it and it falls.the poverty of hte throw will also be compounded
by poorer gyration characteristics than wereoriginally intended.
Coaching point: Noboay does this deliderately be very positive in criticism.point out the reasons for stabiliasing the
discus flight.spend some time on release techniques.
The types of discus
Centre weighted.cheap club style discoi with a mild steel or drass centre weight and a duralumin edge.although they
appear to spin quickly these hane low internal momentum characteristics as the majority of the weight is close to
the centre.they lose their stability fairly quickly edge weighted these are the discoi good throwers buy.
the edge is brass and much higher proportion of the weight is close to the edge.the redius of gyration is larger and
although they need more effort to spin them they do not lose rotation easily.they stay stable longer.
These differing type do effect the distance thrown.
A good thrower can work the edge of a discus and generate more release momentum of the gyration characteristics
of the discus.the effect is marginally more total momentum and a much longer period of stability.
A club thrower wiil not begin to generate enough momentum to stabilise an edge weighed discus so the centre
Of the mass in much closer to the centre.in this way same fairly quick spin is possible which helps the stability.
it is however esily gained-esily lost so the overall period of stability is quite short.
The overall effect can be quite staggering perhaps 10 meters. A good thrower will throw 5 metres further whilst a
poor thrower not able to drive the rim might throw 5 metres less than they would with a 'normal' club discus.
