The forces that affect a parachute are invisible, but not incomprehensible.
Learn what makes a parachute fly well and you will know what makes it fly badly.
There are two basic ways for parachutes to slow our descent - lift and drag.
A round parachute creates drag by simply grabbing as much air as it can,
putting on the brakes for us.
But a square parachute creates lift, which forces an air foil in a particular direction determined by
the design of the foil and its presentation to the fluid it moves in.
Controlling the flow of air over the foil is the art of the canopy pilot.
Quote from www.bpa.org.uk |
Usually parachutes will swing wildly because of air spilling from alternating sides of the canopy.
This swinging can be reduced by cutting a hole in the parachute's apex (crown),
or altogether eliminated by cutting a large number of holes all over the canopy.
But remember that adding vents will increase the descent speed. In the case of apex (crown) venting,
the area of the apex (crown) should be about 1% to 10% of the parachute's flat surface area,
depending on the desired trade off between a slower descent speed and improved stability.
Remember! The larger the hole, the faster the descent speed, since the value of the drag coefficient, CD, will decrease in the process.
Quote from
www.pcprg.com/rounddes.htm |
The statement HIGH LIFT LOW DRAG as you can see from above is not possible, especially with a large apex (crown) opening on their parachutes.
See comparison charts below on sizes.
Our crowns are smaller, offering more lift for their size.
Bigger parachutes will give more lifting power of course,
BUT WHY PAY FOR A BIGGER SIZE WHEN A SMALLER SIZE AND COST WILL ACHIEVE THE SAME RESULT. |
