Ben Philpott <<press.bhgc>> writes:

I think the issue comes down to adjustable ribs which allows the
pilot to flatten the wing profile. These differences were visible to the eye
from glider to glider at the Pre Worlds when looking along the trailing edge
from the tip towards the root. Some "factory" pilots had adjustable ribs that
created a very flat profile.

Please see below a selection of comments from our hang gliding comp forum here
in the UK. I can not add anything else to this, but clearly illustrates the
level of concern for a level playing field. If you visit my old blog address
pressbhgc.blogspot.com and look at the July entries you will see my
posts during the comp.

"So AIR had some 'tunable' gliders at the pre-worlds? From what I've seen of AIR
and Felix, I would like to think they are doing this in a safe/controlled manner
- it's not necessarily dangerous. Are we jumping to conclusions?

"There is simply no adjustment possible to the profile of 'most*' V series
profiles. However, the early production VR's do differ, in that the outer 2 ribs
are not fixed to the LE extension, hence the angle of incidence can be changed
by how you position the velcro during assembly.

"Making the tips flatter gives a more neutral pitch feel, and as far as I know
has not resulted in any incidents. In 'flatter tip' mode the pitch is neutral
(much like an aerobatic aircraft) plus at speed it can start to 'hunt' - its
very subtle and barely noticeable. A trait of flying wings I believe, and I only
got to know about it when XXXXXXXX replayed his filming of my low passes.

"I can understand Felix wanting to release production gliders in 'softer' mode,
but perhaps encouraging that in the future we may be able to tune within limits
(assuming this is what he is going for).

"AIR and Felix got bit with the original Atos C (pre-tail) that seemed to take
the tailless aircraft past the limit of what is safe. There were numerous
spinning incidents and Davis Straub's infamous 'blown up' glider. The
introduction of the V tail solved all issues overnight (i.e. bullet proof pitch
stability and unspinnable). I'm sure Felix wouldn't risk what seems to be an
unblemished safety record for at least a decade.

"Ben is right, although 99% of people don't and can't 'tune' their Rigid wings,
all three pilots on the podium in the Pre-worlds had altered gliders (and then
everyone noticed the difference in glide).

"I'm sure more will be turning up with lowered ribs in the worlds.

"Two of them were test pilots for AIR which meant they had fitted threaded tips
on their ribs to adjust them easily. Something should really be done to make it
a level playing field. As XXXXXX says though, all the VR's or VQ's that you will
buy can't be tuned except moving your hang point and adding lead or cutting down
on the pies!"