Date: 30.06.2004
Manual
Revision: 0
DEMON US
Page: 7
Performance Variable e.K. Am Tower 16, D-54634 Bitburg
Canopy Size
It is important for your safety and enjoyment that you match your canopy with your ability and weight.
PV canopies are built in several models that span a wide range of canopy surface area. Any can-
opy's descent rate and forward speed increases as the weight it is carrying—the so-called exit
weight—increases. The canopy also becomes more responsive as forward speed increases. It also
reacts more radically when it is stalled or turned.
Because of these aerodynamic facts, it is unsafe to put too much weight under any particular canopy.
Safe and comfortable landings will be difficult to obtain, even for experienced jumpers under ideal
conditions. Less experienced jumpers will have even a harder time and be at greater risk.
Determining the
wing loading of the parachute you intend to jump or buy is a good way to compare
canopy sizes.
Wing loading is easily calculated by dividing the total exit weight in pounds by the surface area of the
canopy in square feet. Total exit weight is the weight of the jumper plus all his clothing and gear, in-
cluding the main parachute itself.
The surface area of
Performance Variable canopies is printed on the data panel, on the center cell
rib, or on the center cell top surface near the tail. (Be sure to actually check the data panel—
canopies of different sizes may look the same.)
A typical ready-to-jump sport piggyback (rig and both canopies) weighs 20 to 30 lbs. Add this, plus
the weight of your jumpsuit, clothing and accessories to your body weight to get the total suspended
weight.
For example, a jumper who weighs 165 lbs
.
wearing his jumpsuit and who jumps a packed rig that
weighs 25 lbs. would have an exit weight of 190 lbs
.
Here is an example of how to calculate wing loading of a 150 ft² canopy and the jumper used in the
example above: 190 lbs. : 150 ft² = 1.27 lbs /ft²
Calculate the wing loading now for the
canopy you intend to jump.
It is useful to compare the wing loading of a canopy you intend to jump with the wing loading values
of parachutes you have been jumping. If the difference is great, you should expect the new canopy
to perform very differently
t
han the ones you have jumped before. See the section of this manual
on Introductory Jumps for our suggestions on learning about your new canopy.
Improving the Performance of your Canopy
The most effective methods of increasing performance involve reducing drag or wind resistance. The
following factors will, to a large extent, determine the performance you get out of your canopy.
Three decisions you made at the time of purchase determine the performance of your canopy. (1)
The size was the most important. Smaller canopies are faster but have a noticeably lower glide ratio.
(2) Microline improves the performance over standard Dacron line
.
(3) Large grommets allow you
to pull the slider down below the links, allowing the canopy to spread out more.
