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Why does the paraglider fly? The answer is given by the aerodynamics.
Every flying apparatus, including the paraglider obeys the laws
of aerodynamics.
The earth attracts the glider vertically with force G. G is the
gravity of the pilot and all the equipment (hook in weight). It
is completely compensated by full streamline force T. It is the
resultant of the elevating force and the resistance.
Elevating force
Elevating force A lifts the paraglider up and forward. It works
perpendicularly to the direction of the stream. It is the elevating
force that makes the difference between a paraglider and a common
parachute. The streamline is the basic premise of the elevating
force. The air particles and the paraglider glide over each other.
The air particles glide in the glider with a certain speed, called
air speed.
The formula of the elevating force is:
A = cA.p/2 .v2.F
cA = elevating force coefficient, depending on the form of the section,
the form of the wing and the angle of attack.
p = the consistence of the air.
v = own speed.
F = area of the surface
Resistance
Resistance stops the paraglider and lowers the energy. Despite this
fact, the resistance is very important for a proper operation and
landing. There are three types of resistance: drag (caused by the
air particles creating the elevation force), inductive resistance
(appearing at the edges of the carrying surfaces) and the resistance
caused by the particles that do not take part in the creation of
the elevating force (the pilot and the lines, for example).
The formula of the resistance is:
W = cw.p/2.v2.F
cw = resistance force coefficient, depending on the form of the
section, the form of the wing and the angle of attack.
p = the consistence of the air.
v = own speed.
F = area of the surface
Controlling the Speed
Pulling the lines pulls the trailing edge towards outer parts of
the cupola. Thus the angle is lowered and the section is altered.
If the lines are loose the glider flies at its top speed. The angle
of attack is small and the elevating force - moderate.
When the lines are slightly pulled the glider slows down. The elevating
force and the resistance are in such ratio that the angle of planing
is the best. The more the lines are pulled, the more the angle worsens
and the resistance increases. The stream slowly starts departing
in great surfaces. The speed comes to its lowest. The best speed
of flying is from 30 to 40 km/h
Closure of the cupola
If the angle of attack is too small, the leading edge is being streamed
from above. The rigidity the wing filled with air is not enough
to hold the aerodynamic forces. The canopy turns downwards.
Axes
The paraglider performs all the aerodynamic turnings round the three
aerodynamic axes that cross the center of gravity of the wing-pilot
system.
· The parachute bends round the cross-axis. The pilot rocks
backwards and forwards.
· The parachute turns round the longitudinal axis. The pilot
bends left and right.
· The parachute twists round the vertical axis. The pilot
spins.
In case of a static turn, it is necessary to define the radius
of the curve, the slope, the speed and the weight. In order to go
into a turn, the pilot pulls the brake line at the wanted side.
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