On Wednesday, September 11, 2019 at 10:11:06 AM UTC-4, wrote:
On Wednesday, September 11, 2019 at 10:00:12 AM UTC-4, Senna Van den Bosch wrote:
I noticed for the first time when flying at speeds above 200 km/h, my wingtips start to bend down a bit, has anyone ever noticed this? Glider is a DG-100.

Yep. The twist that helps provide the very docile handling hurts at higher speeds.
The airfoil is not very efficient above 150 or so. Not much reason to fly very fast.
FWIW
UH

Yup. The wing twists because of inadequate torsional stiffness.
IIRC, as you go faster, the center of lift moves aft, so twists the wing.
And as it twists, it aggravates the situation by further reducing tip AOA.
Later designs use a variety of trickery to minimize this effect.
Carbon wing skins (stiffer) help, hence big reduction in twist from
LS6a to LS6b with corresponding high-speed performance improvement.

Recent designs (eg from Boermans, Antares and later) use tailored airfoils
rather than twist to obtain gentle stall and minimize this.
On open and higher-aspect-ration ships this is quite challenging!
Concordia design worked hard to minimize twist (Dillinger's Phd thesis).
Don't know about Nexis.

Interesting stuff...
See ya, Dave