Bill Daniels wrote:

I think gliders are just as strong as the manufacturer says, but no
stronger

Most Gliders are built in JAR country and are certified by JAR rules.
For the utility category, JAR requires an allowed load of 5.3g at Vne
and 4.0g at Vm. JAR further requires that the break load be no lower
than 1.5 times the allowed load.

Since every extra strengh comes at a price in weight and money, the
break load of most gliders acually *is* 1.5 times the allowed load. This
is when the glider is new. Take some turbulence, and the safety cusion
is rather small.

As for the Eta, this may turn out to be an intriguing case. At 31 meters it
is certainly pushing the limits.

Actually this is the whole idea of the Eta project: pushing the limits.
Remember that the first prototype was too heavy and extra work was
required to bring the take off mass down to 850 kg! (The 850 kg limit is
again required by JAR as well as by contest rules.)

Stefan