"Eric Greenwell" wrote in message
...
Bill Daniels wrote:

Snip--(A pretty good history)

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


Since this is early January we can knock this one around a bit. The "sweet
spot" argument for 18 meters ignores all but weather and wingspan.

It seems to me that the Skylark 4 was 18 meters as were several 1960's
vintage wood and metal gliders so 18 meters could and was done then, albeit
with a bit more effort than 15. I have never been too comfortable with the
idea that cost and wingspan had a high correlation. Most designers I have
talked to say that adding wingspan is the cheapest way to add performance.

For a decision made in the early 1970's, 15 meters was arguably not a bad
choice. The error, if there was one, is not too have allowed for
improvement in aerodynamics and materials. (Not too sure how they would
have done that.) The "low cost" goal for the Standard Class doesn't seem to
have worked out too well though.

Bill Daniels