Eric Greenwell wrote in message ...
Bob Kuykendall wrote:

Many people say they would be delighted to have a glider with the
performance of an LS4. This performance can now be achieved with a
smaller span glider of 13 M or less. Can you guess at the cost reduction
that would be possible with a 12 or 13 meter glider compared to the 15M
LS4? Smaller factory, less materials, less labor (especially if hand
finishing is needed), smaller trailer, lower shipping costs (RO-RO is by
volume, I think).

Eric,

I wonder about this cost issue. Having done some re-profiling and
re-finishing myself, I have to believe that the decrement in labor and
materials involved in a 2 meter reduction in span is insignifiant.
For instance, once you have the 600 grit on the sanding bar and you're
moving right along, the last one meter of a given wing is lost in the
overall effort of setup and cleanup. Although the materials are
clearly incremental, the percentage of material is certainly less than
10 percent since the surface area of the last two meters is likely
less than 10 percent of a modern wing (e.g. 115ft2 for a modern glass
bird vs about 15 ft2 for the outboard 1 meter on each side [3 feet x 2
feet mean chord]). So, maybe we could optimistically see a 5-7%
reduction in per unit construction cost. Throw in tooling and
development costs, and what's the real savings? That's at least how I
would view the numbers if I were setting up shop...

I think 13M is a legacy of the "build it in your garage" movement.
In that case, there was a very practical reason for a 13M span; the
half-span would fit in an average garage (aka "workshop"). But, since
the homebuilders movement is pretty much moribund except for a few
hearty soles, what's the magic about 13M?

Erik