Wing Flex System.
The Wingflex system was first developed by Bruce and the Airwave paraglider
design team in late 1996. The system improves canopy stability at speed, and it
was on the first ΠWingflex & Mac226; competition prototypes that Peter
Brinkeby lead the PWC for most of the 1997 season and that John Pendry won the
Paragliding World Championships the same year. Now approximately half the
paragliders manufactured worldwide incorporate wingflex. In 1998 Bruce received
the ΠSaloman Trophy&Mac226; from Price Andrew on behalf of the Royal Aero
Club in recognition of the technological advances that helped John become World
Champion.
The name wingflex is actually rather misleading. It is really a system that
reduces the flex in the wing by distributing that line attachment points (tabs)
in an unconventional way on the bottom surface of the glider. The traditional
way of designing a paraglider is to fix the positions of the tabs at percentage
positions along the cord of the profile. Typically the A tabs will be at 10%,
the B tabs at 30%, the C tabs at 55% and the D tabs at 80. These same relative
positions are then maintained for all the ribs with lines on across the whole
span of the glider. The lines are then linked to the risers and the speed system
on the risers then speeds up the glider by changing the relative lengths of the
risers. Because the cord is much longer at the center of the glider than the
tip, the tips of the glider will be accelerated much more than the center. The
faster tips then collapse too easily limiting the top speed attainable.
With the Wingflex system the tabs are kept the same distance apart across the
whole wing. This means that if the distance between the A and the B tab at the center
of the wing is 50cm, then it should also be 50cm in the tip. This means that
when you accelerate the wing, the whole wing is accelerated uniformly, providing
more stability. An offshoot of the wingflex system is that the D lines fall off
the back of the wing about half way across the span and thus the total amount of
line lengths is also reduced.
This diagram shows one problem with the wing flex system. If you use pure wing
flex then not only do the D tabs fall off the trailing edge but also the C tabs.
Having only 2 tabs is too little to support the wing properly so most glider use
a kind of modified wingflex where this problem is avoided as shown below.
As you can see the tabs do not stay exactly the same distance apart, but get
slightly closer together towards the tip, but the general idea is still there.
Wingflex is useful on not only competition gliders but all gliders benefit from
increased stability without any penalty at all, from DHV1 gliders up. This is
why this system has become so uniformly adopted across the paragliding world.