On Wednesday, August 19, 2020 at 3:02:00 AM UTC-7, jld wrote:
""GP doesn't just claim "lower weight," but "far lower weight" than other gliders, but w/o any evidence to support this claim""
The evidences are in the design and certification choices.

GP15 is about same empty weight as the H301 which was a fiberglass ship, so there is nothing new. Carbon now allows to use lower relative thickness airfoil and higher aspect ratio wings to get to higher performance.

Certification requirements have forced manufacturers to significantly increase the weight of their gliders (e.g. cockpit protection). Because more recent airfoils are tolerant to higher WL, this has not been a significant issue, except for the fact MTM goes up and self launchers need more power!
By using experimental in US and UL in EU, GP has more design freedom. For example, not proposing a heavy 16G cockpit but a rescue parachute instead!

That is more closely akin to wishful thinking than evidence. Since GP isn't going to certify their gliders to EASA standards we do not know anything about their testing process. A ballistic chute is not going to help you unless you deploy it, which you can't do in the landing phase, the most likely time you will need a strengthened cockpit. My idea of evidence is things like the ultimate breaking strength of a wing taken to destruction (which you must do for EASA certification). Ultralights may be exempted from this testing by each member country so we will not even know if GP has done this test unless they produce the test results from an independent testing company.. I am just not willing to take such things on faith if my life depends upon it (which it does).

Tom