Andreas Maurer wrote:
Or maybe: "Is the Diana 2 crash protection as good as the ASW
27 (for example)?"


Indeed.
The 27 is a good example because its dimensions are very similar to
the Diana 2.

I know how long it took for Schleicher to squeeze only 20 lbs out of
the forward fuselage from the ASW-27 (which then became the 27 SL with
an empty wight of 230 kg). Hard to see for me how someone is able to
save another 48 kg on a glider of similar dimensions without
sacrifying anything (the empty weight of the Diana 2 is 182 kg).

I can only speculate, because I am not familiar with the Diana 2. I know
from speaking to Gerhard Waibel that some structure on the Schleicher
gliders is much stronger than required by the flight loads. I learned
about that when I had a problem with an aileron push rod at the root of
my ASW 20. Gerhard told me I didn't have a problem, because those rods
were three times stronger than the flight loads required, due to ground
handling issues (pilots would grab the rods to keep the wing from
tipping in a wind). Similarly, the wings are much stronger in the
horizontal direction than needed in flight, because pilots and crew put
a lot of force on the wing tips when pushing the glider around on the
ground.

If a designer believed the owners of his glider would be very careful
when moving the glider on the ground, he could save weight in these
areas (and others). Of course, there are other ways to save weight: the
SparrowHawk is an extreme example of this, and one factor is the use of
pre-preg carbon fiber instead of wet lay-up. Or, perhaps, pultruded
carbon rods instead of a roving spar cap, as some gliders use.

I don't know how the Diana does it, but if I wanted a Diana 2, I would
ask questions like "How did you achieve this weight reduction without
sacrificing strength needed for ground handling or crashworthiness?".

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Eric Greenwell
Washington State
USA