Bill Daniels wrote:

I recall a technical discussion a long time ago asking whether there was a
"natural best wingspan" imposed by the nature of soaring weather. The
question was this: "Ignoring competition classes, is there a single best
wingspan that is suited for the widest range of soaring conditions? The
answers converged around 18 meters. Larger spans were considered too slow
in strong conditions and smaller spans suffered in weak conditions. It's
interesting that the "most cost effective wingspan" is about the same.

This makes me wonder if eventually the 18 meter class will become dominant.
It also makes me wonder if the selection of 15 meters for the two most
popular classes was an error.

Here's my recollection of the genesis of the 15 meter class. Real
historians please fill in the gaps and correct errors.

In the beginning, there was only One class, and it became Huge and
Expensive, so the World Gliding Body (IGC?) made the Standard Class in
1960. It was Small and therefore Cheap, and it's Leader was the Ka-6. It
was Wood and it was Good.

But then, Dick Schreder rose up and Said, "Spoilers are a False god",
and he Made a Standard Slass glider with Flaps, and it was Better.
Better enough, that the World Gliding Body became concerned, and there
was also Pressure from Libelle H301 owners, so that a New class was born
in 1974 (or thereabouts): the 15 Meter class.

And it was Very successful, and spawned Many designs, and Thousands were
built, and the Contests were full, and it was Good. But then came Carbon
fiber, and new airfoils, and Pilots that knew nothing of Wood, and they
said "the World Gliding Body made a Mistake!" And they were Right..

Whoa! Not so fast. Back then 18 meter wasn't so easy to do. The choices
are different now, and it's a mistake to revisit the decision as if the
materials and aerodynamics we have now were available then, and as if
the pilots would accept the same trade-offs for cost and size that they
are willing to do now.

I think the 18 meter class has been driven by motorglider considerations
much more than any natural "sweet spot" in performance/$. And frankly,
to even claim that 18 meters is the "sweet spot" is a subjective
judgment. Lot's of people prefer smaller gliders, and many prefer bigger
gliders; for many people, it's the cost, not the L/$, that counts;
most people, I believe, don't fly in a wide range of conditions, but fly
during the heart of the day and don't visit locations that vary much.

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Eric Greenwell
Washington State
USA