Bill,
I think you have a solid point. i've been re-reading for the 8th or 10th
time Fred Thomas' book on sailplane design and some of the information on
cross country speed vs span mskes it look like the sweet spot is somewhere
in the 18-20 meter range, just as you say.
Cabon makes the wings lighter and easier to rig that's for sure and maybe
more stable dimensionally.
Thirty meters seems excessive but we would all like to experience "wretched
excess" for the pure fun of it once in a while and 13 meters seems just
excessively limiting (at least to me).
Cheers!

"Bill Daniels" wrote in message
news:ff4rd.181115$R05.60069@attbi_s53...

"David Bingham" wrote in message
...
Hi Gang
For approximately 30 years the performance of gliders has hardly
advanced at all and yet we now have the tools (computer programs) and
much stronger materials (carbon composites) to surely advance the
state of the art of gliders. Has this happened? Yes there are marginal
improvements but so small. What's the reason for this slowdown in
innovation? I believe in no small part it is due to the sailplane
classes. With the establishing of the classes that are so rigid and,
in my mind, so restrictive, innovation has suffered.

(Snip------)

Yep.

The first class, (Standard Class) was intended to reduce glider costs by
virtually eliminating innovation which, it was felt at the time, was
leading
to ever larger and more expensive gliders.

The flap enthusiasts insisted on splitting off as the 15 meter class.

Both classes became successful at the expense of the open class where
carbon
composites make the most difference. In a 15 meter design, the main
benefit
of carbon is lighter wings for easier assembly.

Manufacturers were forced to produce special gliders for two similar 15
meter classes. Designers were forced by the same class rules to pursue
ever
more expensive ways to improve performance such as extremely smooth
surfaces. They wound up producing expensive gliders anyway because of
short
production runs.

It's interesting to speculate what would have happened if the competition
organizations had resisted creating competition classes. Innovation would
have run free. It's even possible that large span, ultra-high performance
gliders would be priced the same as 15 meter gliders are today because of
much larger production runs.

I've heard interesting speculation that there's a 'natural best span'
around
18 - 20 meters that would be the best compromise for all conditions. If
the
market had settled on that, we might have had innovation AND low costs.
We'll never know.

Bill Daniels

p.s. I recently listened as a 'pundit' was holding forth on the reasons
for
the demise of the open class. He was saying that they were just too hard
to
rig. A short distance behind him an ASH-25 owner was whistling softly to
himself as he rigged solo using simple aids.