ASW 20 Handling Issues?

On Sunday, November 5, 2017 at 2:23:24 PM UTC-5, wrote:
...I heard a story/rumor/speculation that the fabric tape used to cover
the flap/wing joint might be to blame if it bulged out into the airflow
during slow flight and triggered separation.

IIRC that tape bulging caused aileron flutter, but not other problems.
Regardless, the tape should have been replaced with mylar on all 20's.
Hank???

On Sunday, November 5, 2017 at 2:44:28 PM UTC-5, Dave Nadler wrote:
On Sunday, November 5, 2017 at 2:23:24 PM UTC-5, wrote:
...I heard a story/rumor/speculation that the fabric tape used to cover
the flap/wing joint might be to blame if it bulged out into the airflow
during slow flight and triggered separation.

IIRC that tape bulging caused aileron flutter, but not other problems.
Regardless, the tape should have been replaced with mylar on all 20's.
Hank???

Flutter was associated with seal tapes. Flaps fluttered more than ailerons if I remember correctly. Mylar is a good improvement and was standard on B and C. Flaps on A go down far enough to be tough on Mylar on bottom when in full landing flap.
UH

A few 20's were produced with slightly different incidence angles in the wings..........yep, the wings were not hooked on straight! I'm sure those ships liked to spin when flown too slow. Schleicher had several "eccentric" rear lift fittings to solve the problem. I'd bet they are all fixed by now, but if your 20 always seems to turn one way, your wings may not be true!
JJ

On Sunday, November 5, 2017 at 10:28:45 PM UTC-5, wrote:
A few 20's were produced with slightly different incidence angles in the wings..........yep, the wings were not hooked on straight! I'm sure those ships liked to spin when flown too slow. Schleicher had several "eccentric" rear lift fittings to solve the problem. I'd bet they are all fixed by now, but if your 20 always seems to turn one way, your wings may not be true!
JJ

Errata:

Interesting. I recall that a few ASW 19s had the same problem...and solution: i.e., eccentric rear lift pins from the factory. My memory might be playing tricks but the guy who told me about it had a '19, not a '20. I've always wondered how the wing was twisted after that since the spars and main pins weren't altered.

My memory might be playing tricks, Part II, but regarding flap flutter, I also recall hearing that some early '20s had a slight amount of "slop" in the flap drive that was fixed by smearing epoxy on the end of a long wooden stick or dowel, jamming it into the wing root at the appropriate point, waiting for it to harden up, then breaking off the stick/dowel. Apparently a bunch of owners had theirs done on a rain day at a big contest (late 70s/early 80s?). That seemed to address the flap flutter.

I believe Rudy Mozer's ASW 20B was one of four brought over for the Worlds (Hobbs, 1983). When I saw it that spring, it had lower flap seals that were beryllium copper (to accommodate the landing flap deflection?). Pretty nifty looking. Beryllium copper dust is toxic so that might have killed any enthusiasm for using this material.

Chip Bearden

On Sunday, 5 November 2017 23:45:19 UTC+2, wrote:?

Flutter was associated with seal tapes. Flaps fluttered more than ailerons if I remember correctly.
UH

Mine had aileron vibration (it is not flutter) twice with pristine teflon/mylar seals, so it might not be that simple. I did change flap hinge bearings and new seals just to be sure and never experienced vibration again. (Control play was well within limits before change).

Talking about 20 handling, you would probably compare it to gliders similar vintage. LS4, Discus or Ventus with aft c/g will spin as eagerly and drop wing in most cases in similar fashion. 20 is no different in that respect. I flew 20 for over 1000hrs with few wing drops after mishandling the glider in thermal but I wouldn't call the glider anything but extremely well-behaved. It is the safest glider to land in tight spot. One of few gliders that truly were well ahead of it's time.

Krasw, I've been thinking the same.
This was a period of pushing performance without as much consideration for things like handling, cockpit ergonomics and safety as there is in current models. Seems there was always something missing. Perhaps Gerhard did better with general handling than Klaus achieved in the Ventus A/B, but the Ventus had auto hook ups while the early 20s required connecting 7 L'Hotelliers.. The elevator became auto hook up in late 20B and all C model, or modification using Tech Note 29.
Rick Wagner had some mods for 20s that improved performance, including shortening of the flap at the root and aileron at the tip, a better wing root fairing, and a wingtip that looked like an LS4. His work was before we had winglets.
Sorry that the earliest Ventus I've flown was the C, which had lovely handling. The A/B without winglets seemed to have a reputation for needing to be flown all the time. The 20 A- B- and C- models I've flown all had great handling (pilot-glider relationship much like any other Schleicher) and personally didn't have any spin entry threat. One of them was a "Hobbs Special", but the high red line was only for the duration of the Worlds. None had winglets, which seem to improve characteristics near to stall speed.
I've been on both sides of this equation: ASW20 flying alongside ASW27. In the midrange there was no difference! One mistake in a 20 and you won't catch up, though.
The LS6 was the easiest to fly well of this vintage in my experience. Climbs full of ballast and outruns a 20. Not enough time alongside Ventus A/B or C at 15m. Once ran all day at Ely with a 15m V2 at the same wing loading.
Once swapped an original LS6B for one with the Flying Nun tips for a few days. Thought the biggest difference was in blocked visibility.
Jim


On Sunday, November 5, 2017 at 11:28:19 PM UTC-8, krasw wrote:

Talking about 20 handling, you would probably compare it to gliders similar vintage.

On Monday, 6 November 2017 19:44:45 UTC+2, JS wrote:
I've been on both sides of this equation: ASW20 flying alongside ASW27. In the midrange there was no difference!

27 is overrated, that tiny wing needs 18m span to work as intended as 29 has shown. I've flown 20 against 27 and sure it runs a little better at very high speeds but you can basically fly all day long side by side and arrive home 5 minutes later. When you put glider price into that equation...