On Tuesday, February 2, 2016 at 3:41:35 AM UTC-5, BruceGreeff wrote:
The very long wing open class gliders have a bad record on spin recovery.
They will generally transition to a spiral dive quite early in a spin,
but will accelerate very rapidly on the exit.
If they do get into a stable spin, the momentum in the wings is a problem.

If you have water in the wings, or fuel, then you are a test pilot.
Certification is done dry.

There are at least five Nimbus 4D accidents I am aware of where recovery
was past Vne and the glider broke up on recovery. Ash25 - same story.

Bruce

Bruce Greeff
T59D #1771

"Certification is done dry..." No. Current CS-22 Amendment 1:

"CS 22.221 General
(a) Compliance with the following requirements must be shown in all configurations and, for a powered sailplane, with the engine idling.
For sailplanes equipped to carry water ballast, the demonstrations of sub-paragraphs (b) to (g) must also be made for the most critical water ballast asymmetry that might occur due to any single malfunction or due to lateral accelerations during a spin."

Then, in spin testing (later in CS22 AL1):
"AMC 22.221(b)
Spinning
General
It will normally be sufficient to conduct a number of spins of about two turns in each of the conditions of CS 22.221(b) and subsequently to conduct spins of five turns in the most adverse cases."

You may recall the ETA spin test with one wing full/one empty led to a crash. Both CS-22 AL1 and the ETA test are available by mr. google.