Bob Kuykendall wrote:

This performance can now be achieved with
a smaller span glider of 13 M or less.


I consider that an extremly debatable proposition. I'll wait to see a
stub ship consistently beat an LS-4 in unhandicapped, nationals-level
competition before I abandon my grain of salt.

There seems to be something about having a little span that always
makes you want a little more...

I think this is one big barrier to lower cost gliders, all right:
incremental additions seem like a good value, and after a few of them,
the complaints start coming about how much the glider costs! You know
how it goes: retractable gear doesn't add that much in cost; water
ballast is only a few layers of glass to stiffen the wings; winglets are
pretty cheap; another meter or two of span hardly adds to the price; and
so on. At the end of these "it doesn't cost much to ..." additions, we
have a significantly more expensive glider.

It's the same way we turn an $18,000 car into a $25,000 car, then
complain about how much cars cost.


snip

less materials,


Theoretically so. But in order to bring that 13m ship closer to your
goal of 15m-type performance, you have to make it lighter per unit of
area than a 15m ship. And that means more costly materials and
processes. That's one of the reasons why Sparrowhawks go for $193 per
pound versus about $100 per pound for a new-run LS-4.

But, at 150 pounds versus 500 pounds, the SparrowHawk would still be
cheaper! I don't know what the economic comparison of pre-preg carbon
versus wet lay-up fiberglass construction is, but it would be an
interesting one to read. The pre-preg is more $ per pound, I'm sure, but
you need less pounds of it for the same strength, and laying up the
pre-preg is easier than wet lay-up.

In any case, a 13 meter ship would not necessarily need to be pre-preg.
THe SparrowHawk uses it to meet it's 150 pound weight goal.

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Eric Greenwell
Washington State
USA