Its not all in the wrist! Read below
for the why of
the where your disc goes because "Whither thou throwest so there will your
disc lie." The more you know, the better you throw!
The Physics of Disc Flight
A flying disc is a little like a cross between a gyroscope and a wing.
A wing works by having the top and bottom sides of different lengths. The air
flow moves over the longer surface faster, creating a low pressure region on top
of the wing. The higher pressure region underneath the wing tries to move toward
the low pressure region, and as a result lifts the wing.
A disc is like a gyroscope in that it uses gyroscopic inertia, the tendency of a
gyroscope to keep spinning in the same plane without twisting and turning.
With no spin, a disc is inherently unstable, and with no speed, no lift is
generated, so a combination of these factors is needed for a disc to fly. The
exact combination varies significantly from disc to disc, since different discs
have different "wing" shapes. Combining the wing and the gyroscope also
introduces other factors, as the two are not mutually independent.
The most obvious one is a torque on the disc. If the disc is spinning clockwise
and moving forward when viewed from the top, then the left side of the disc is
moving faster than the right side. There is a corresponding pressure drop over
the left side and that side will produce greater lift, and the disc will try to
twist clockwise when viewed from behind. As mentioned above, the gyroscopic
inertia acts to counter this, and the greater the spin, the higher the inertia.
Spin
There is almost never any reason for not trying to put as much spin as possible
on a disc, all other factors being equal. Spin provides stability, so that the
disc will continue to fly in the direction it is already flying. A disc that is
lacking in spin will tend to "turn over", that is, twist about the axis of
flight, and will generally not go as far as one which has more spin. Lack of
spin is probably one of the two major problems encountered when trying to throw
accurately over any reasonable distance.
One time when too much spin is possible is when throwing some golf discs. Their
flight characteristics are such that they have a very narrow window of
stability. Too much spin and they can twist one way, and too little spin and
they will twist the other. In general, however, too much spin is better
countered by other factors in the throw, such as speed and angle of release,
rather than by simply spinning the disc less.
Particular discs are termed "overstable", "stable", and "understable" depending
on how they to spin and speed. A disc which needs a lot of spin to be stable at
a given speed is called "understable", while a disc which needs little spin to
be stable at a given speed is called "overstable". "Stable" generally refers to
discs which are stable at a wide range of speeds for a given spin.
Most discs can be thrown "understably" or "overstably" by decreasing or
increasing the amount of spin put on the disc.
Speed
The speed of a disc is a major (but not the only) factor in determining how far
a disc goes and how quickly it gets there. Unlike spin, it is possible to put
too much speed on a disc. The stability of a disc changes as it gets faster, and
the stable range of the disc is determined both by the shape of the disc and its
spin rate. Most discs used for throwing to other people are stable, that is,
they fly flat at a range of speeds. Golf discs on the other hand are usually not
very stable - they tend to fly flat only for brief periods during their flight.
The rest of the time they are banked either one way or the other.
A generally stable disc thrown with too much speed in relation to the spin will
act understably. That is, it will turn over. For this reason, hucking the disc
requires plenty of spin and speed. Not enough speed results in the throw landing
short, while not enough spin results in the throw diving into the ground.
Most inexperienced players find it easier to get more spin on their backhand,
and as a result most inexperienced players will huck on their backhand side.
Rotation Angle
The title does a poor job of explaining what this section is about. Apart from
amount of spin, the other major factor in lack of accuracy and distance is the
difference between the angle of spin of the disc and the angle of the plane of
the disc. The disc often wobbles at the start of its flight, and this is the
problem. Ideally, the disc should be spinning flat and wobble-free. If the
thrower puts spin on the disc at an angle to the flat plane of the disc, it will
wobble and lack control.
This is usually most obvious when teaching beginners the air bounce. For an air
bounce, the disc is being thrown downwards, and at release the thumb is dragged
across the trailing edge of the disc. This results in a slow upward flight. The
thrower’s wrist is at a sharp angle to their arm, and beginners often find that
getting the arm to move one way while spinning the disc with their wrist in
another direction entirely is very difficult.
The end result is a wobbly throw that lacks spin in the right direction, and
hence lacks both stability and the ability to get much distance. Similar
problems usually result when teaching the high release backhand.
There is often no easy solution. In the case of air bounces and high release
backhand the cure is generally practice. The wrist needs time to learn that it
can impart spin at a different angle to that of the arm. In the case of normal
throws, the thrower may be swinging the disc in a loop instead of straight back
and then straight through. The trick may be just to get them moving the disc
straight back on the backswing and straight through on the follow through. This
is often harder to do than it sounds. Also, it may not be the problem. Plenty of
good players use a slightly loopy backswing, but they are able to get their
wrist and arm in the right line just before release, usually just through
practice.
Attitude (Pitch)
Here we are borrowing a term from aviation to describe one of the angles of
release. Pitch refers to how steeply an aircraft is pointed, rotating about an
axis through the wings. For a disc, it refers to the angle of release where the
front edge of the disc is pointed up or down. Basically the pitch helps
determine how far the disc travels, and more importantly, along which path. By
keeping the front edge well up the disc will travel well into the air, but will
probably stall and float down at the end of the flight. Keeping the front edge
down results in a low trajectory, relatively fast flight.
Roll (Bank)
Roll, or bank, refers to the angle of the disc rotated about the direction of
travel. This means whether the outside edge of the disc is held up or down. The
amount of bank on the disc mainly determines the flight path, and can be used to
good effect to throw around players who are between thrower and target. The disc
will curve in the direction of the lowest edge of the disc.
Wind
Wind can have a marked effect on all of the five factors mentioned above,
depending mostly on which direction it is coming from. An important point to
remember is that regardless of how much wind there appears to be, there is no
wind at ground level, and there is less wind the closet to the ground you are.
This means that to avoid the effects of the wind as much as possible it is a
good idea to release and keep throws as close to the ground as practicable.
A headwind increases the apparent air speed of the disc. This means that the
amount of spin necessary to keep it stable becomes greater. A headwind also
reduces the distance possible, and lifts under discs that are pitched with the
leading edge up, sending them into the air.
A tailwind conversely decreases the air speed of the disc, but can increase
ground speed. While distance may increase there is a drop in lift, which means
that the disc needs to be thrown at a higher angle of attack to counteract the
wind that tends to push the disc into the ground.
Crosswinds have the most effect on banked discs, either by pushing the raised
edge up and lifting the disc, or by pushing down on a lowered edge and possibly
making the disc dive into the ground. Crosswinds also make it difficult to keep
the disc flat on release, and even experienced players may find it difficult to
keep the angle of spin in the plane of the disc.
This article was taken "whole hog" from: http://www.afda.com/skills/physics.htm
Back to top
