Rust removal?

[noel.wade]

Hi All,

Hopefully a simple quick question:

I pulled my glider out of the trailer after a long winter recently,
and found that I hadn't greased my lift-pins quite well enough. There
are a few small spots of surface corrosion on them, and I'd like to
get rid of it.

BUT, given the importance of the lift pins I don't want to just go
grinding on them. Anyone have any suggestions on the best/least-
destructive way to get rid of minor surface rust/corrosion on parts
like this?

Thanks a bunch,

--Noel

[Craig[_2_]]

On Feb 25, 12:47*pm, "noel.wade" > wrote:
> Hi All,
>
> Hopefully a simple quick question:
>
> I pulled my glider out of the trailer after a long winter recently,
> and found that I hadn't greased my lift-pins quite well enough. *There
> are a few small spots of surface corrosion on them, and I'd like to
> get rid of it.
>
> BUT, given the importance of the lift pins I don't want to just go
> grinding on them. *Anyone have any suggestions on the best/least-
> destructive way to get rid of minor surface rust/corrosion on parts
> like this?
>
> Thanks a bunch,
>
> --Noel

A green scotchbrite pad lubricated with WD-40 or LPS, etc, does a good
job of pulling up surface corrosion without significantly influencing
the parent material.

Craig

[[email protected]]

On Feb 25, 1:53*pm, Craig > wrote:
> On Feb 25, 12:47*pm, "noel.wade" > wrote:
>
>
>
> > Hi All,
>
> > Hopefully a simple quick question:
>
> > I pulled my glider out of the trailer after a long winter recently,
> > and found that I hadn't greased my lift-pins quite well enough. *There
> > are a few small spots of surface corrosion on them, and I'd like to
> > get rid of it.
>
> > BUT, given the importance of the lift pins I don't want to just go
> > grinding on them. *Anyone have any suggestions on the best/least-
> > destructive way to get rid of minor surface rust/corrosion on parts
> > like this?
>
> > Thanks a bunch,
>
> > --Noel
>
> A green scotchbrite pad lubricated with WD-40 or LPS, etc, does a good
> job of pulling up surface corrosion without significantly influencing
> the parent material.
>
> Craig

Good suggestion. But if that doesn't remove it all, try a fine steel
wool. Start gently, then buff and lubricate when satisfied.

Jeff 7JK

[[email protected]]

On Feb 25, 1:12*pm, wrote:
> On Feb 25, 1:53*pm, Craig > wrote:
>
>
>
>
>
> > On Feb 25, 12:47*pm, "noel.wade" > wrote:
>
> > > Hi All,
>
> > > Hopefully a simple quick question:
>
> > > I pulled my glider out of the trailer after a long winter recently,
> > > and found that I hadn't greased my lift-pins quite well enough. *There
> > > are a few small spots of surface corrosion on them, and I'd like to
> > > get rid of it.
>
> > > BUT, given the importance of the lift pins I don't want to just go
> > > grinding on them. *Anyone have any suggestions on the best/least-
> > > destructive way to get rid of minor surface rust/corrosion on parts
> > > like this?
>
> > > Thanks a bunch,
>
> > > --Noel
>
> > A green scotchbrite pad lubricated with WD-40 or LPS, etc, does a good
> > job of pulling up surface corrosion without significantly influencing
> > the parent material.
>
> > Craig
>
> Good suggestion. But if that doesn't remove it all, try a fine steel
> wool. Start gently, then buff and lubricate when satisfied.
>
> Jeff * * 7JK- Hide quoted text -
>
> - Show quoted text -

Naval Jelly, then rinse well

Aerodyne

[JJ Sinclair]

Come on guys, those pins are 10 times stronger than they need to
be..............sand off the rust with 220 or emery cloth and lube
them next time. I keep my pins in two large plastic tubes with lube
inside (duct-taped together) as I remove them they pick up just
enpough lube to shove them home.
JJ

wrote:
> On Feb 25, 1:12*pm, wrote:
> > On Feb 25, 1:53*pm, Craig > wrote:
> >
> >
> >
> >
> >
> > > On Feb 25, 12:47*pm, "noel.wade" > wrote:
> >
> > > > Hi All,
> >
> > > > Hopefully a simple quick question:
> >
> > > > I pulled my glider out of the trailer after a long winter recently,
> > > > and found that I hadn't greased my lift-pins quite well enough. *There
> > > > are a few small spots of surface corrosion on them, and I'd like to
> > > > get rid of it.
> >
> > > > BUT, given the importance of the lift pins I don't want to just go
> > > > grinding on them. *Anyone have any suggestions on the best/least-
> > > > destructive way to get rid of minor surface rust/corrosion on parts
> > > > like this?
> >
> > > > Thanks a bunch,
> >
> > > > --Noel
> >
> > > A green scotchbrite pad lubricated with WD-40 or LPS, etc, does a good
> > > job of pulling up surface corrosion without significantly influencing
> > > the parent material.
> >
> > > Craig
> >
> > Good suggestion. But if that doesn't remove it all, try a fine steel
> > wool. Start gently, then buff and lubricate when satisfied.
> >
> > Jeff * * 7JK- Hide quoted text -
> >
> > - Show quoted text -
>
> Naval Jelly, then rinse well
>
> Aerodyne

[ZZ]

noel.wade wrote:
> Hi All,
>
> Hopefully a simple quick question:
>
> I pulled my glider out of the trailer after a long winter recently,
> and found that I hadn't greased my lift-pins quite well enough. There
> are a few small spots of surface corrosion on them, and I'd like to
> get rid of it.
>
> BUT, given the importance of the lift pins I don't want to just go
> grinding on them. Anyone have any suggestions on the best/least-
> destructive way to get rid of minor surface rust/corrosion on parts
> like this?
>
> Thanks a bunch,
>
> --Noel
>


Noel

To prevent this in the future try this. Mix some LPS 3 (very waxy) and
white lithium grease into a paste and coat any metal surface that you do
not want to rust. It's very effective, easy to remove in the Spring and
cheap.

Paul
ZZ

[[email protected]]

On Feb 25, 6:26*pm, JJ Sinclair > wrote:
> Come on guys, those pins are 10 times stronger than they need to
> be..............sand off the rust with 220 or emery cloth and lube
> them next time. I keep my pins in two large plastic tubes with lube
> inside (duct-taped together) as I remove them they pick up just
> enpough lube to shove them home.
> JJ
>

Hey JJ - any reason to be concerned about the tightness of the fit of
the pins in the bushings? I'd think you wouldn't want a shimmy in
flight. Is there any risk of that?

Andy

[JJ Sinclair]

> Hey JJ - any reason to be concerned about the tightness of the fit of
> the pins in the bushings? I'd think you wouldn't want a shimmy in
> flight. Is there any risk of that?
>
> Andy

Some will experience what is known as the "clunk". That is the sound
you may hear when rolling into a thermal. It is the fuselage sliding
in the lift fittings and going "clunk". If you hear this you need at
least a 20 thousands shim on one aft lift fitting, determine which one
by measuring from the TE probe on the fin with a steel tape to a
common point on each wing, say the aileron cut-out. Don't be surprised
to find your prize possession is off by close to an inch! This will
tell you where to epoxy the shim onto one of the aft lift fittings.
Some will find their lift fittings are too tight which makes getting
the wing onto the lift fittings a chore. Clean the fittings and scrub
them with magic-marker, then put it together again. Then remove the
wing and observe the magic-marked pins. The shinny spots show the
interference fit areas. My ship showed a problem on the front end of
the forward lift fitting and the back end of the aft lift fitting. It
took months of working these areas down with emery cloth every time I
flew to finally get the wing to slide on easily. Believe me you don't
remove much steel with sandpaper!
JJ

[noel.wade]

JJ -

My fault, I wasn't clear enough - I meant the _other_ "lift-pins". My
spar pins are exactly as you describe: Kept in a set of PVC tubes with
well-greased felt inside so that they "self lubricate" every time I
pull them out or put them back in the holders.

I was referring to the alignment pins on each side of the fuselage
that plug into the root rib sockets and ensure the wing is at its
proper angle of incidence relative to the fuselage. They're a lot
smaller and I don't think I want "variable incidence" wings as I fly
around... ;-)

Thanks,

--Noel

[Andy[_1_]]

On Feb 26, 6:32*am, JJ Sinclair > wrote:
> This will tell you where to epoxy the shim onto one of the aft lift fittings.

I don't doubt JJ knows this but the Schleicher approved method of
shimming the lift pins is to remove the lift pins and put the shims
behind them.

When I did this job on my 19 I found it best to do a trial fit by
putting the shims on the outside face of the lift pins. A little
grease will hold them in place. When the right additional shim
thickness is found the lift pins are driven out, the shim stack
adjusted, and the lift pins driven back in. I set mine up so there
was no detectable fore/aft motion at the wing tips but the main spar
pins could still be easily inserted.

Andy

[Andy[_1_]]

On Feb 26, 9:42*am, "noel.wade" > wrote:
> Kept in a set of PVC tubes with
> well-greased felt inside so that they "self lubricate" every time I
> pull them out or put them back in the holders.

If you mean that you put the "self lubricated" pins stright into the
spars I think that's a really bad idea!

I never assemble without completely cleaning the main spar pins and
the spar bushings and lubricating them with fresh grease. Any other
way risks the bushings and pins being scratched by accumulated dirt.
The lift pins and the horizontal stab pins get the same treatment.

I fly in a very dusty environment. I might be less picky if it was
clean.


Andy

[noel.wade]

On Feb 26, 11:50*am, Andy > wrote:

> I fly in a very dusty environment. *I might be less picky if it was
> clean.

Andy -

My spar bushings definitely get cleaned regularly. The pins are
either in the wing or in the "holders" (they get pulled from the wing
and go straight into the tube) - so they are not exposed to the air
(dirt) for any length of time. The felt lining also acts as a "wiper"
as they go in and come out. Finally, I fly near Seattle for about
half the year - and the rain keeps the dust out of the air up
here. ;-)

Thanks, take care,

--Noel

[[email protected]]

On Feb 26, 11:50*am, Andy > wrote:
> On Feb 26, 9:42*am, "noel.wade" > wrote:
>
> > Kept in a set of PVC tubes with
> > well-greased felt inside so that they "self lubricate" every time I
> > pull them out or put them back in the holders.
>
> If you mean that you put the "self lubricated" pins stright into the
> spars I think that's a really bad idea!
>

You know, I don't think I will take the time to share a few things I
have picked up over the last 35 years of repairing these glass toys.
Ras has a wide range of posters, some have vast experience and
knowledge, others share their ignorance, suspicions, rumors and
incredible lack of common sense. We have posters that think knocking
the rust off lift fittings will somehow change the wing incidence or
make the wings loose! Another thinks storing the main wing pins in a
greased holder will somehow gouge the pins when the greased holder
protects them from just that.
So long,
JJ

[brianDG303[_2_]]

On Feb 26, 10:42*am, "noel.wade" > wrote:
> JJ -
>
> My fault, I wasn't clear enough - I meant the _other_ "lift-pins". My
> spar pins are exactly as you describe: Kept in a set of PVC tubes with
> well-greased felt inside so that they "self lubricate" every time I
> pull them out or put them back in the holders.
>
> I was referring to the alignment pins on each side of the fuselage
> that plug into the root rib sockets and ensure the wing is at its
> proper angle of incidence relative to the fuselage. *They're a lot
> smaller and I don't think I want "variable incidence" wings as I fly
> around... ;-)
>
> Thanks,
>
> --Noel

Noel, I don't think those are alignment pins, those are the studs the
fuse hangs from. They do align things of course but I was the longest
text realizing that those little studs are the weight bearing points.

[noel.wade]

I'm going to have to come up with a way to better signify when I'm
making a sarcastic or tongue-in-cheek comment...

JJ - C'mon you gotta admit that if you tweaked those pins/studs, you
could get the wing to fly at a different angle of incidence! ;-) For
the record, I appreciate all your info and tips.

Brian - I am aware of what the "studs" do - which is why I've always
heard them referred to as "lift pins" (they "lift" the fuselage along
with the wing)... but JJ's response sounded like he was talking about
the big pins that we use to fasten the spar roots to one another so
that the spar forces are transmitted through from one wing to the
other. So I deliberately described them using "alternate" means. :-P

OK, maybe my efforts fell flat; but there were good intentions!

--Noel

[Papa3]

On Feb 26, 6:07*pm, wrote:
> On Feb 26, 11:50*am, Andy > wrote:
>
> > On Feb 26, 9:42*am, "noel.wade" > wrote:
>
> > > Kept in a set of PVC tubes with
> > > well-greased felt inside so that they "self lubricate" every time I
> > > pull them out or put them back in the holders.
>
> > If you mean that you put the "self lubricated" pins stright into the
> > spars I think that's a really bad idea!
>
> You know, I don't think I will take the time to share a few things I
> have picked up over the last 35 years of repairing these glass toys.
> Ras has a wide range of posters, some have vast experience and
> knowledge, others share their ignorance, suspicions, rumors and
> incredible lack of common sense. We have posters that think knocking
> the rust off lift fittings will somehow change the wing incidence or
> make the wings loose! Another thinks storing the main wing pins in a
> greased holder will somehow gouge the pins when the greased holder
> protects them from just that.
> So long,
> JJ

JJ,

Please please please don't stop posting. I have a special folder of
"Tips from JJ" that I refer to all the time. Just the other day I was
looking at blending a repair and went back to your post from about 6
months back.

You need to write a book one of these days. You could make millions
(of pennies, if you're lucky).

Regards,
P3

[Brad[_2_]]

On Feb 26, 4:19*pm, Papa3 > wrote:
> On Feb 26, 6:07*pm, wrote:
>
>
>
>
>
> > On Feb 26, 11:50*am, Andy > wrote:
>
> > > On Feb 26, 9:42*am, "noel.wade" > wrote:
>
> > > > Kept in a set of PVC tubes with
> > > > well-greased felt inside so that they "self lubricate" every time I
> > > > pull them out or put them back in the holders.
>
> > > If you mean that you put the "self lubricated" pins stright into the
> > > spars I think that's a really bad idea!
>
> > You know, I don't think I will take the time to share a few things I
> > have picked up over the last 35 years of repairing these glass toys.
> > Ras has a wide range of posters, some have vast experience and
> > knowledge, others share their ignorance, suspicions, rumors and
> > incredible lack of common sense. We have posters that think knocking
> > the rust off lift fittings will somehow change the wing incidence or
> > make the wings loose! Another thinks storing the main wing pins in a
> > greased holder will somehow gouge the pins when the greased holder
> > protects them from just that.
> > So long,
> > JJ
>
> JJ,
>
> Please please please don't stop posting. *I have a special folder of
> "Tips from JJ" that I refer to all the time. *Just the other day I was
> looking at blending a repair and went back to your post from about 6
> months back.
>
> You need to write a book one of these days. *You could make millions
> (of pennies, if you're lucky).
>
> Regards,
> P3- Hide quoted text -
>
> - Show quoted text -

Polyprime.....................need I say more?

Brad

[Andy[_1_]]

On Feb 26, 4:07*pm, wrote:
> Another thinks storing the main wing pins in a
> greased holder will somehow gouge the pins when the greased holder
> protects them from just that.

Any pin storage system that does not clean the pins before each
insertion has the risk of dirt transfer. The pins can pick up dirt
while they are installed in the spars both at the far end and at the
gap between the spars. Any dirt picked up here may be transferred to
grease in the storage tubes.

Whether that is a problem is left to the individual owner to decide.
Since I have found grit in my storage tubes more than once I'll
continue to clean my pins and use fresh grease before every insertion.

Andy

[Doug Hoffman]

noel.wade wrote:
> On Feb 26, 11:50 am, Andy > wrote:
>
>> I fly in a very dusty environment. I might be less picky if it was
>> clean.
>
> Andy -
>
> My spar bushings definitely get cleaned regularly. The pins are
> either in the wing or in the "holders" (they get pulled from the wing
> and go straight into the tube) - so they are not exposed to the air
> (dirt) for any length of time. The felt lining also acts as a "wiper"
> as they go in and come out. Finally, I fly near Seattle for about
> half the year - and the rain keeps the dust out of the air up
> here. ;-)

Noel,

Did you store your glider-in-trailer outside for the winter?

I have noticed, and I believe JJ has commented, that winter storing the
glider-in-trailer inside (such as in a heated or unheated pole barn or
whatever) makes a big difference in preventing surface rust.

Has anyone had luck storing their glider-in-trailer outside in a winter
climate like Washington state or Michigan? If so, did you do anything
special (sealing the trailer? other?)?

Regards,

-Doug

[[email protected]]

On Feb 26, 5:32*am, JJ Sinclair > wrote:
> > Hey JJ - any reason to be concerned about the tightness of the fit of
> > the pins in the bushings? *I'd think you wouldn't want a shimmy in
> > flight. Is there any risk of that?
>
> > Andy
>
> Some will experience what is known as the "clunk". That is the sound
> you may hear when rolling into a thermal. It is the fuselage sliding
> in the lift fittings and going "clunk". If you hear this you need at
> least a 20 thousands shim on one aft lift fitting, determine which one
> by measuring from the TE probe on the fin with a steel tape to a
> common point on each wing, say the aileron cut-out. Don't be surprised
> to find your prize possession is off by close to an inch! This will
> tell you where to epoxy the shim onto one of the aft lift fittings.
> Some will find their lift fittings are too tight which makes getting
> the wing onto the lift fittings a chore. Clean the fittings and scrub
> them with magic-marker, then put it together again. Then remove the
> wing and observe the magic-marked pins. The shinny spots show the
> interference fit areas. My ship showed a problem on the front end of
> the forward lift fitting and the back end of the aft lift fitting. It
> took months of working these areas down with emery cloth every time I
> flew to finally get the wing to slide on easily. Believe me you don't
> remove much steel with sandpaper!
> JJ

I guess I was wondering what happens if, due to sanding, the lift pins
end up smaller in diameter than the bushings. Then it seems to me that
no matter how much you shim you could end up with a clunker since the
distance between opposing lift fittings is fixed by the main pins so
you can't really push the wings further to get the (usually tapered)
lift pins to snugly engage with the bushings all the way around the
circumference.

If I recall correctly my 1980-vintage LS-4 was put together such that
you could pull straight up on the trailing edge of the wing right near
the root and feel the lift pin "clunk" from resting on the bottom of
the bushing to the top. It was only a fraction of an inch, but you
could feel it. The glider was a mix of wings and fuse from two
different S/Ns so this could also just be rigging rather than wear,
but it's what raised the question in my mind.

9B

[[email protected]]

On Feb 27, 1:12*pm, wrote:
> On Feb 26, 5:32*am, JJ Sinclair > wrote:
>
>
>
>
>
> > > Hey JJ - any reason to be concerned about the tightness of the fit of
> > > the pins in the bushings? *I'd think you wouldn't want a shimmy in
> > > flight. Is there any risk of that?
>
> > > Andy
>
> > Some will experience what is known as the "clunk". That is the sound
> > you may hear when rolling into a thermal. It is the fuselage sliding
> > in the lift fittings and going "clunk". If you hear this you need at
> > least a 20 thousands shim on one aft lift fitting, determine which one
> > by measuring from the TE probe on the fin with a steel tape to a
> > common point on each wing, say the aileron cut-out. Don't be surprised
> > to find your prize possession is off by close to an inch! This will
> > tell you where to epoxy the shim onto one of the aft lift fittings.
> > Some will find their lift fittings are too tight which makes getting
> > the wing onto the lift fittings a chore. Clean the fittings and scrub
> > them with magic-marker, then put it together again. Then remove the
> > wing and observe the magic-marked pins. The shinny spots show the
> > interference fit areas. My ship showed a problem on the front end of
> > the forward lift fitting and the back end of the aft lift fitting. It
> > took months of working these areas down with emery cloth every time I
> > flew to finally get the wing to slide on easily. Believe me you don't
> > remove much steel with sandpaper!
> > JJ
>
> I guess I was wondering what happens if, due to sanding, the lift pins
> end up smaller in diameter than the bushings. Then it seems to me that
> no matter how much you shim you could end up with a clunker since the
> distance between opposing lift fittings is fixed by the main pins so
> you can't really push the wings further to get the (usually tapered)
> lift pins to snugly engage with the bushings all the way around the
> circumference.
>
> If I recall correctly my 1980-vintage LS-4 was put together such that
> you could pull straight up on the trailing edge of the wing right near
> the root and feel the lift pin "clunk" from resting on the bottom of
> the bushing to the top. It was only a fraction of an inch, but you
> could feel it. The glider was a mix of wings and fuse from two
> different S/Ns so this could also just be rigging rather than wear,
> but it's what raised the question in my mind.
>
> 9B- Hide quoted text -
>
> - Show quoted text -

The point under discussion is how to remove corrosion from a slightly
rusted lift fitting. I just measured (with a micrometer) a rusted rear
lift pin on a G-102 left wing and locked the micrometer at this
reading. I then polished the lift fitting to bright steel using medium
grade emery cloth. The locked micrometer went back on the lift fitting
with the same force it took to remove it when rusted. There was no
measurable difference between the rusted reading and the bright steel
reading, meaning the amount of steel removed by the above process
could not be detected. I ask again; How much steel do you think you
can remove by scrubbung off light rust with sandpaper? To me this is
nothing more than common sense!
JJ

[[email protected]]

On Feb 28, 9:25*am, wrote:
> On Feb 27, 1:12*pm, wrote:
>
>
>
>
>
> > On Feb 26, 5:32*am, JJ Sinclair > wrote:
>
> > > > Hey JJ - any reason to be concerned about the tightness of the fit of
> > > > the pins in the bushings? *I'd think you wouldn't want a shimmy in
> > > > flight. Is there any risk of that?
>
> > > > Andy
>
> > > Some will experience what is known as the "clunk". That is the sound
> > > you may hear when rolling into a thermal. It is the fuselage sliding
> > > in the lift fittings and going "clunk". If you hear this you need at
> > > least a 20 thousands shim on one aft lift fitting, determine which one
> > > by measuring from the TE probe on the fin with a steel tape to a
> > > common point on each wing, say the aileron cut-out. Don't be surprised
> > > to find your prize possession is off by close to an inch! This will
> > > tell you where to epoxy the shim onto one of the aft lift fittings.
> > > Some will find their lift fittings are too tight which makes getting
> > > the wing onto the lift fittings a chore. Clean the fittings and scrub
> > > them with magic-marker, then put it together again. Then remove the
> > > wing and observe the magic-marked pins. The shinny spots show the
> > > interference fit areas. My ship showed a problem on the front end of
> > > the forward lift fitting and the back end of the aft lift fitting. It
> > > took months of working these areas down with emery cloth every time I
> > > flew to finally get the wing to slide on easily. Believe me you don't
> > > remove much steel with sandpaper!
> > > JJ
>
> > I guess I was wondering what happens if, due to sanding, the lift pins
> > end up smaller in diameter than the bushings. Then it seems to me that
> > no matter how much you shim you could end up with a clunker since the
> > distance between opposing lift fittings is fixed by the main pins so
> > you can't really push the wings further to get the (usually tapered)
> > lift pins to snugly engage with the bushings all the way around the
> > circumference.
>
> > If I recall correctly my 1980-vintage LS-4 was put together such that
> > you could pull straight up on the trailing edge of the wing right near
> > the root and feel the lift pin "clunk" from resting on the bottom of
> > the bushing to the top. It was only a fraction of an inch, but you
> > could feel it. The glider was a mix of wings and fuse from two
> > different S/Ns so this could also just be rigging rather than wear,
> > but it's what raised the question in my mind.
>
> > 9B- Hide quoted text -
>
> > - Show quoted text -
>
> The point under discussion is how to remove corrosion from a slightly
> rusted lift fitting. I just measured (with a micrometer) a rusted rear
> lift pin on a G-102 left wing and locked the micrometer at this
> reading. I then polished the lift fitting to bright steel using medium
> grade emery cloth. The locked micrometer went back on the lift fitting
> with the same force it took to remove it when rusted. There was no
> measurable difference between the rusted reading and the bright steel
> reading, meaning the amount of steel removed by the above process
> could not be detected. I ask again; How much steel do you think you
> can remove by scrubbung off light rust with sandpaper? To me this is
> nothing more than common sense!
> JJ- Hide quoted text -
>
> - Show quoted text -

I have spent hours taking off 1 thousandth of an inch from an oversize
pin.
JJ is absolutely right. You can't go wrong by sanding off the surface
corrosion to bright and then protecting it.
That said- if you see pitting, that is another matter.
And NEVER be tempted to save a little time time by picking up a file.
32 years doin' it.
UH

[[email protected]]

On Feb 28, 12:48*pm, wrote:
> On Feb 28, 9:25*am, wrote:
>
>
>
> > On Feb 27, 1:12*pm, wrote:
>
> > > On Feb 26, 5:32*am, JJ Sinclair > wrote:
>
> > > > > Hey JJ - any reason to be concerned about the tightness of the fit of
> > > > > the pins in the bushings? *I'd think you wouldn't want a shimmy in
> > > > > flight. Is there any risk of that?
>
> > > > > Andy
>
> > > > Some will experience what is known as the "clunk". That is the sound
> > > > you may hear when rolling into a thermal. It is the fuselage sliding
> > > > in the lift fittings and going "clunk". If you hear this you need at
> > > > least a 20 thousands shim on one aft lift fitting, determine which one
> > > > by measuring from the TE probe on the fin with a steel tape to a
> > > > common point on each wing, say the aileron cut-out. Don't be surprised
> > > > to find your prize possession is off by close to an inch! This will
> > > > tell you where to epoxy the shim onto one of the aft lift fittings.
> > > > Some will find their lift fittings are too tight which makes getting
> > > > the wing onto the lift fittings a chore. Clean the fittings and scrub
> > > > them with magic-marker, then put it together again. Then remove the
> > > > wing and observe the magic-marked pins. The shinny spots show the
> > > > interference fit areas. My ship showed a problem on the front end of
> > > > the forward lift fitting and the back end of the aft lift fitting. It
> > > > took months of working these areas down with emery cloth every time I
> > > > flew to finally get the wing to slide on easily. Believe me you don't
> > > > remove much steel with sandpaper!
> > > > JJ
>
> > > I guess I was wondering what happens if, due to sanding, the lift pins
> > > end up smaller in diameter than the bushings. Then it seems to me that
> > > no matter how much you shim you could end up with a clunker since the
> > > distance between opposing lift fittings is fixed by the main pins so
> > > you can't really push the wings further to get the (usually tapered)
> > > lift pins to snugly engage with the bushings all the way around the
> > > circumference.
>
> > > If I recall correctly my 1980-vintage LS-4 was put together such that
> > > you could pull straight up on the trailing edge of the wing right near
> > > the root and feel the lift pin "clunk" from resting on the bottom of
> > > the bushing to the top. It was only a fraction of an inch, but you
> > > could feel it. The glider was a mix of wings and fuse from two
> > > different S/Ns so this could also just be rigging rather than wear,
> > > but it's what raised the question in my mind.
>
> > > 9B- Hide quoted text -
>
> > > - Show quoted text -
>
> > The point under discussion is how to remove corrosion from a slightly
> > rusted lift fitting. I just measured (with a micrometer) a rusted rear
> > lift pin on a G-102 left wing and locked the micrometer at this
> > reading. I then polished the lift fitting to bright steel using medium
> > grade emery cloth. The locked micrometer went back on the lift fitting
> > with the same force it took to remove it when rusted. There was no
> > measurable difference between the rusted reading and the bright steel
> > reading, meaning the amount of steel removed by the above process
> > could not be detected. I ask again; How much steel do you think you
> > can remove by scrubbung off light rust with sandpaper? To me this is
> > nothing more than common sense!
> > JJ- Hide quoted text -
>
> > - Show quoted text -
>
> I have spent hours taking off 1 thousandth of an inch from an oversize
> pin.
> JJ is absolutely right. You can't go wrong by sanding off the surface
> corrosion to bright and then protecting it.
> That said- if you see pitting, that is another matter.
> And NEVER be tempted to save a little time time by picking up a file.
> 32 years doin' it.
> UH

That's a good enough answer for me. Get some 40 grit and go to
town. ;-)