Drag
Drag is an important part of hang glider operation.
Drag is the resistive force that opposes the motion of the glider.
It, along with gravity (which will be discussed later), are the forces
that must be overcome by lift in order for the glider to fly. Every
object moving through the air experiences some amount of drag. In the case
of a glider, the air that the glider is moving through exerts this resistive
force and is sometimes known as air drag.
There are a few factors that influence the amount of drag experienced by a glider. These are the shape of the glider, the velocity, and the density of the air. The density of the air can generally be considered constant unless flying at very high altitudes, and is accepted as about 1.29 kg/m3. There is an equation that can be used to calculate the resistive force on objects moving at high speeds through the air. It is R = 1/2CDþAv2, where R is the resistive force, CD is the drag coefficient, þ is the density of air, A is the cross-sectional area of the glider, and v is the velocity of the glider. The drag coefficient varies depending on the object and ranges from about 0.5 for round objects to about 2 for irregular objects.
Aerodynamics is another factor influencing the amount of drag on a glider. By making a glider more aerodynamic, you are reducing the drag force experienced by the glider. Newer models of hang gliders are becoming more and more aerodynamic. This is done partly with better wing shapes, but mostly by getting rid of the wires that support the rider. In older models, the drag on the wires and supports was far greater than the drag produced by the wings alone. Below is an example of an older glider compared to a newer one.
Newer glider
Photo courtesy of: Seattle's Museum of Flight
There are a few factors that influence the amount of drag experienced by a glider. These are the shape of the glider, the velocity, and the density of the air. The density of the air can generally be considered constant unless flying at very high altitudes, and is accepted as about 1.29 kg/m3. There is an equation that can be used to calculate the resistive force on objects moving at high speeds through the air. It is R = 1/2CDþAv2, where R is the resistive force, CD is the drag coefficient, þ is the density of air, A is the cross-sectional area of the glider, and v is the velocity of the glider. The drag coefficient varies depending on the object and ranges from about 0.5 for round objects to about 2 for irregular objects.
Aerodynamics is another factor influencing the amount of drag on a glider. By making a glider more aerodynamic, you are reducing the drag force experienced by the glider. Newer models of hang gliders are becoming more and more aerodynamic. This is done partly with better wing shapes, but mostly by getting rid of the wires that support the rider. In older models, the drag on the wires and supports was far greater than the drag produced by the wings alone. Below is an example of an older glider compared to a newer one.
Newer glider
Photo courtesy of: Seattle's
Museum of Flight
Older gliderPhoto courtesy of: Seattle's Museum of Flight