Bill Daniels wrote:
If you consult the maintenance manuals, you will probably find the maximum
allowable fore-aft and up-down free motion (play). For many gliders these
are amazingly large figures.

If my Nimbus 2C were at the max tolerance (which it isn't), flight could
then be fairly described as a "loose formation of glider parts".

Form my point of view, there are two types of 'play'. One is true free
motion due to clearances in the fittings. The other involves some
stick-slip action that occurs with alarming violence - this is very
worrying.

Grob 103's are prone to this. The 103's leading edge pins (spigots)
actually protrude through the sides of the rear cockpit into the side
pockets where the rear seat occupant is likely to be resting elbows. These
pins can shift inward with a loud bang numbing the rear pilots arms. Given
the complexity of Grob wing fittings, I think very little play should be
tolerated.

Bill Daniels

"Jack" wrote in message
oups.com...
I have noticed several older sailplanes with some play in the wings.
They don't seem to pull into the fuselage and have a few thousandths
play so that the wings move fore and aft, slightly. Can this be
shimmed? I know from working on L-33's that they come from the factory
with shims. Is this an acceptable fix for older glass ships?

Jack



My personal general considerations on tolerances and play.

There are designed in gaps on most moving assemblies. One that is easy to see is
the little bit of vertical freedom in most gliders rudder.

This tolerance is generally designed in - although sometimes it is simply
production quality or wear.

Thing to know is which applies to whatever you are wiggling.

So - consider the aircraft gattling gun - it has lots of precision machined
parts that rattle around as if they were unable to machine accurately. Take out
the gaps, and it would seize solid as pieces expand when it fires.

Same principle applies to gliders.
If there is excessive free movement in something (i.e.that is not designed to
have it) - ground the thing and fix it.
If you are not sure if it is excessive, find out - the manuals should have the
limits, and if they don't JAR22 or its successors have blanket limits.

Consider - the all moving elevator on my Std Cirrus has around 4mm tramline
movement. This is considered "good" by the agents given the design of the
fitting. Much less and there would be risk of binding at low temperature.
If the Kestrel had the same play it would be grounded.

From my limited experience I would expect there to be procedures for shimming
or replacing the bearing pins on the wings at the leading edge and at the drag
spar. This is a critical connection - it should be right.

One reason for developing the play on long wings is when misguided or moronic
"helpers" manhandle glass ships by the wingtips. This puts very high loads into
the pins and they will get loose.