Sailplane Classes - a different perspective

Bill Daniels wrote:

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.

And it worked! Standard class gliders were a lot cheaper!


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.

Wait a minute - these classes came into being years before carbon was
used. The first really successful Standard Class glider, the Ka-6, was wood!

In a 15 meter design, the main benefit
of carbon is lighter wings for easier assembly.

Also a higher aspect ratio leading to better L/D, and thinner wings,
leading to higher cross-country speed.


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.

Baloney! Far more gliders in EACH class were produced than ever would
have been produced for even a single Open class. THe classes weren't
popular because they were FAI classes, but became popular because they
were such an outstanding combination of cost and performance. That
magical "sweet spot" some people talk about.

snip

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.

The market is moving there, to some extent. Remember, the 'natural best
span' is _very_ dependent on the materials available (and their costs),
and will be different for wood, metal, fiberglass, and carbon. There is
nothing magic about 18 meters, because it depends on a value judgment
(performance versus costs). So, the market couldn't settle on 18 meters
sooner, but had to wait for technology to advance, material costs to
come down, and for pilots to decide that they were now willing to pay
for a certain level of performance.

A lot of ras pilots seem to think 15 meters is the 'natural best span',
when embodied in a low cost LS4.


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.

And taking far longer than an ASW 27, which cost far less. If your
pundit talked only about putting it together, he hasn't been around one
enough to know what a bloody pig it is on the ground, and how much real
estate they need just to be tied down, or pushed around on a ramp, or
taken down a taxiway, and how wide the runway needs to be to take off or
land on, the size of the towplane, and how many people had better show
up if he ever hopes to get it out of a field! Shucks, just trying to
push the empty trailer around to hook it up is more than my crew can
handle. It's not ignorance that keeps people from falling all over
themselves to get a 25 meter glider.

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Eric Greenwell
Washington State
USA