Ventus B, Discus ect aileron connecting rod/slide lube

On Tuesday, February 3, 2015 at 7:15:37 AM UTC-7, Bob Whelan wrote:
On 2/3/2015 5:31 AM, Don Johnstone wrote:
At 23:52 02 February 2015, HGXC wrote:
On Monday, February 2, 2015 at 3:00:05 PM UTC-5, Don Johnstone wrote:
At 15:26 01 February 2015, wrote:

Some judicious snippage...

I own a Ventus and I have mine lubed at the annual, I have the openings
in
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the wing like Dick Johnson suggested. If Schempp Hirth didn't want this
to
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be lubed then they would have used a different bushing when they made the
g=
lider. All gliders have short comings. The glider has been flown over 30
ye=
ars and like all popular gliders over time, pilots find ways of
addressing
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imperfections and every glider has some.

Dennis

Why is it that some glider pilots feel they know better that the qualified
engineers and designers who design and build the machines they fly. Maybe
using an unapproved lubricant on material that you do not know the
composition of, which might be damaged is unwise but drilling a hole in the
structure to do it, that is stupidity of the highest order, such is life I
suppose. I doubt that the "opening" made was properly sealed to unsure that
moisture could not damage the GRP structure which is hygroscopic, my
advice. Do NOT purchase a glider owned by these people.
It is true pilots have a long history of finding incorrect ways of
addressing imperfections, proves the old maxim I suppose, if flying was
difficult engineers would do it.


Evidently, the original question touched upon "a topic of religion." One
church believes that gliders as-received from manufacturers cannot possibly be
improved by mere humanity unassociated with the original design process (and
to attempt improvement places one in the category of the devil's spawn). The
other church believes that use-/age-related issues will inevitably appear, and
might (if not should) be reasonably addressed by subsequent owners. True - at
least in the U.S. - for sailplanes licensed with (see below) an Approved Type
Certificate or licensed Experimentally.

In my view, there's sound reasons for both views, and in an ideal world, both
can peacefully co-exist. Full disclosu I'm a(n aerospace) degreed
(U.S.-based) engineer, but one who's convinced original designers were NOT
(all apply): all-knowing; incompetent. In other words, designers and the
design team are humans like the rest of us, though with (perhaps) some
specialized training, and (definitely) some specialized interests...again
normal human conditions.

The U.S. is fortunate to have a healthy, vibrant, amateur-built aircraft
licensing category, from which - perhaps - some cogent conclusions about this
particular religious topic may be drawn. As I type, approximately 20% of the
U.S. power, single-engine, 4-or-less seats general aviation fleet is licensed
"Experimental Amateur Built" (a presently increasing proportion), the rest
having Approved Type Certificates. Taken as a whole, the EAB category accident
frequency is (statistically and) significantly higher than the ATC category as
measured against fleet/licensing numbers. Unsurprisingly (in my view) the
percentages have a significant first-/early-flight bias (for engine/fuel and
loss of control reasons, mostly); thoughtful readers can probably make
accurate guesses why (an exercise and validation beyond the point I'm trying
to make with this post). Once beyond that bubble, EAB and ATC accident rates
are (arguably) identical. I expect (but am not certain) accident *causes* are
similar as well (when comparing similar classes of pilots/flight, e.g. Visual
Flight Rules piloting).

My conclusions:
1) "Sound airplane design practices" are not limited solely to factories and
their design teams.
2) The weakest link is generally the nut at the top of the stick.

Stated another way, pretty much every form of human design screwup/oversight
possible in general aviation flying machines (e.g. sailplanes) has been made
long, long ago, and "best practices" are pretty much available (and arguably
well known) to anyone inclined to learn from others' experiences. We're well
beyond the "secret guild stage" of aircraft structural design knowledge, and
the "smoke and mirrors" of ignorance-based myths.

That knowledge availability, along with the tendency of those geekily inclined
(most engineers, and many non-degreed people as well) is why I'm OK with
belonging to the Church of Future Improvement is Possible.

On the other hand, the World Wide Web has made it easier for everyone (e.g.
via YouTube) to easily see that Darwinism remains a potent human genealogical
force. Ignorance is potent, often more quickly than knowledge. Hence I'd never
try to convince members of the Church of Don't Mess With Factory Stuff to
change their beliefs.

Clint Eastwood was right: A man's got to know his limitations.

Further, who hasn't heard the truism: All generalizations are
false...including this one. In my view, there's at least one truism that is
NOT false: Perfection is never an option.

True in glider design, too. The trick is to know - or at lest to remain within
- one's limitations.

YMWV
Bob W.

P.S. I believe Dick Johnson was a degreed aeronautical engineer. His entire
working life was spent in the engineering field, and his extracurricular
soaring-and-sailplane-design-and-testing-related body of work was prodigious.
He likely passed on from heart failure in his mid-eighties while flying the
Ventus he owned for decades - the one in which he drilled lube access holes.
Make of all that what works for yourself!

Yes, nice post, Bob

One thing I wonder about is the continued use of Nylon blocks as cable/pushrod fairleads since there are better engineering plastics available today. For example solid UHMWPE is stronger than Nylon and has a coefficient of friction equal to Teflon. It also seems utterly immune to ageing effects. I know a number of Homebuilt/Experimental people who use it for fairleads.