Rib stitching vs glueing

I was reading some information on Fisher Celebrity builders websites
and saw that one builder did not like the idea of glueing the fabric to
the ribs as per the plans. The ribs on the Celebrity are very thin and
he didn't think there was enough glue area for a satisfactory bond, so
he rib stitched.

I also recall reading somewhere that the glue area doesn't really
affect the strength of the bond between the fabric and wood rib ( which
I can't believe )

I know the wing loading of the Celebrity is low compared to some of the
more high performance bipes, but if the glue area is such a concern,
wouldn't it be OK to just increase the rib capstrip width slightly to
give more glueing area? Might only increase the whole airplane weight
half a pound.

Thoughts? Thanks

Neal

On 12 Oct 2005 14:33:47 -0700, wrote:

I was reading some information on Fisher Celebrity builders websites
and saw that one builder did not like the idea of glueing the fabric to
the ribs as per the plans. The ribs on the Celebrity are very thin and
he didn't think there was enough glue area for a satisfactory bond, so
he rib stitched.

I also recall reading somewhere that the glue area doesn't really
affect the strength of the bond between the fabric and wood rib ( which
I can't believe )

I know the wing loading of the Celebrity is low compared to some of the
more high performance bipes, but if the glue area is such a concern,
wouldn't it be OK to just increase the rib capstrip width slightly to
give more glueing area? Might only increase the whole airplane weight
half a pound.

Thoughts? Thanks

Neal

of course!

btw dont be beguiled by the semantics.
the glue strength doesnt change with the glue area since it is a force
per unit area measurement.
the glue area directly changes the amount of total force that the rib
fabric join can stand.
a pound per square inch strength applied to a square inch can hold a
pound
a pound per square inch strength applied over a square foot can hold
one hundred and fourty four pounds.

Stealth Pilot
Australia

In article ,
Stealth Pilot wrote:


btw dont be beguiled by the semantics.
the glue strength doesnt change with the glue area since it is a force
per unit area measurement.
the glue area directly changes the amount of total force that the rib
fabric join can stand.
a pound per square inch strength applied to a square inch can hold a
pound
a pound per square inch strength applied over a square foot can hold
one hundred and fourty four pounds.

Stealth Pilot
Australia

I'll bite into this topic from an intellectual curiosity perspective.
What are the forces acting on a rag plane that would tug against the rib
bond? Source? Direction? Magnitude? How common are such bond failures?
What is the cause? Poor surface prep or other application shortcomings?
Deterioration of the glue or fabric over time? Other?

If I take a 3" long piece of tape and stick it on my desk, and a 12"
long piece and stick it next to it, does it take more force to peel the
longer one, or just more time? I'd say a wider one would stick more
assertively, but not a longer one. Is this at all analogous to what's
going on in an airplane, or way off?

Has this been studied like wing loading, with safety margins built in?
Does an airplane fall out of the sky if the fabric starts letting go? I
guess eventually it would, if pieces started tearing and departing the
airplane. That would disrupt the airflow, I imagine. There was a
discussion of punch testing a short time back. Is there also a "pull
test" to see whether the glue bonds are getting ready to fail?

These are the things that I think about while I struggle valiantly to
smash two rivets to the same shape and size.

On Thu, 13 Oct 2005 09:13:37 -0700, Smitty Two
wrote:

In article ,
Stealth Pilot wrote:


btw dont be beguiled by the semantics.
the glue strength doesnt change with the glue area since it is a force
per unit area measurement.
the glue area directly changes the amount of total force that the rib
fabric join can stand.
a pound per square inch strength applied to a square inch can hold a
pound
a pound per square inch strength applied over a square foot can hold
one hundred and fourty four pounds.

Stealth Pilot
Australia

I'll bite into this topic from an intellectual curiosity perspective.
What are the forces acting on a rag plane that would tug against the rib
bond? Source? Direction? Magnitude? How common are such bond failures?
What is the cause? Poor surface prep or other application shortcomings?
Deterioration of the glue or fabric over time? Other?

I'll reply for the other guys benefit. I dont know what you'll read
into this :-)

glue bonds fail over time from the stress rise at the edge of the
joint.

air pressure will create a force perpendicular to the surface.
have a look in a text at one of the manometer photos of a wing section
under test to get an idea of the pressure distribution.

the predominant cause of failure in fabric bonds is the reversing
loads created by turbulence from the slipstream off the prop. outside
of the slipstream competently bonded fabric seldom fails.
the fabric bond fails from the edge and slowly the failure creeps
inward across the joint. ribstitching in the area of the slipstream
works to correct the problem because it doesnt have stress risers
occurring at the edges of the thread.

my method of checking the stits fabric on my tailwind is to look
inside the tailcone out in the bright sunlight and pick the areas
where the uv opaquing was poorly done. I then make the "bird" with one
hand and walk along those areas banging the finger into the fabric as
hard as my hand will allow. If I ever get a puncture I'll initially
repair it. If I get areas of punctures then it is in for a refabric.
I've wanted to refabric the aircraft for a few years now but the stits
seems to have an infinite life. I cant detect any deterioration other
than in the visual appearance of the paint.

not a complete disertation but then the other guy wasnt asking much.
Stealth Pilot

On 12 Oct 2005 14:33:47 -0700, wrote:

I was reading some information on Fisher Celebrity builders websites
and saw that one builder did not like the idea of glueing the fabric to
the ribs as per the plans. The ribs on the Celebrity are very thin and
he didn't think there was enough glue area for a satisfactory bond, so
he rib stitched.

The Celebrity is a biplane with a top speed of 95 mph, right? Has it
been a problem? Have any of the Celebrity's that had the fabric glued
had the fabric come unstuck? Ever?

If not, why should it be considered an issue?

On the other hand, if the guy just cannot live with attaching the
fabric with glue, even if nothing bad has ever happened, he can
certainly rib stitch. It won't hurt anything but his wallet, a bit,
and add to the length of time building.

Corky Scott

wrote:
On 12 Oct 2005 14:33:47 -0700, wrote:

I was reading some information on Fisher Celebrity builders websites
and saw that one builder did not like the idea of glueing the fabric to
the ribs as per the plans. The ribs on the Celebrity are very thin and
he didn't think there was enough glue area for a satisfactory bond, so
he rib stitched.

The Celebrity is a biplane with a top speed of 95 mph, right? Has it
been a problem? Have any of the Celebrity's that had the fabric glued
had the fabric come unstuck? Ever?


I vaguely remember reading in the FAA/NTSB archive about such an
incident. It was a while ago, so I may be a bit off. What I remember
was that the pilot was killed on impact and apparently he was aware of
some minor seperation and continued to fly the aircraft until it failed
catastrophically. Might have been another bird, but I think it was a
celebrity. I'm not 100% sure though. You might try searching the
accident database for the celebrity if you haven't already.

-Matt


If not, why should it be considered an issue?

On the other hand, if the guy just cannot live with attaching the
fabric with glue, even if nothing bad has ever happened, he can
certainly rib stitch. It won't hurt anything but his wallet, a bit,
and add to the length of time building.

Corky Scott

wrote:
wrote:
On 12 Oct 2005 14:33:47 -0700, wrote:

I was reading some information on Fisher Celebrity builders websites
and saw that one builder did not like the idea of glueing the fabric to
the ribs as per the plans. The ribs on the Celebrity are very thin and
he didn't think there was enough glue area for a satisfactory bond, so
he rib stitched.

The Celebrity is a biplane with a top speed of 95 mph, right? Has it
been a problem? Have any of the Celebrity's that had the fabric glued
had the fabric come unstuck? Ever?


I vaguely remember reading in the FAA/NTSB archive about such an
incident. It was a while ago, so I may be a bit off. What I remember
was that the pilot was killed on impact and apparently he was aware of
some minor seperation and continued to fly the aircraft until it failed
catastrophically. Might have been another bird, but I think it was a
celebrity. I'm not 100% sure though. You might try searching the
accident database for the celebrity if you haven't already.


That sounds pretty much like what happened to Steve Wittman.
He put off fixing the problem until after he got to Oshkosh.

--

FF

wrote:
wrote:
On 12 Oct 2005 14:33:47 -0700, wrote:

I was reading some information on Fisher Celebrity builders websites
and saw that one builder did not like the idea of glueing the fabric to
the ribs as per the plans. The ribs on the Celebrity are very thin and
he didn't think there was enough glue area for a satisfactory bond, so
he rib stitched.

The Celebrity is a biplane with a top speed of 95 mph, right? Has it
been a problem? Have any of the Celebrity's that had the fabric glued
had the fabric come unstuck? Ever?


I vaguely remember reading in the FAA/NTSB archive about such an
incident. It was a while ago, so I may be a bit off. What I remember
was that the pilot was killed on impact and apparently he was aware of
some minor seperation and continued to fly the aircraft until it failed
catastrophically. Might have been another bird, but I think it was a
celebrity. I'm not 100% sure though. You might try searching the
accident database for the celebrity if you haven't already.


That sounds pretty much like what happened to Steve Wittman.
He put off fixing the problem until after he got to Oshkosh.

--

FF

wrote in message
ups.com...

That sounds pretty much like what happened to Steve Wittman.
He put off fixing the problem until after he got to Oshkosh.

--

FF

Ok, I'm curious, since I haddn't heard this before, and it doesn't seem
to be part of the report (ATL95FA092) in the accident database.

That's really not too surprising, since the folks I knew who rushed off
to take part in the investigation regarded Steve Wittman as roughly
equal to Jesus of Nazareth...

At least hypothetically, delamination could have been detected in the
same manner on the O&O Special as on a composite aircraft--by
taping with a coin, or even a fingernail. However, Mr. Wittman was
not tall enough to do so on a plane larger than a Tailwind, and this
would appear far beyond the scope of a pre-flight inspection unless
one had some cause for suspicion; whether visual, hearsay, or some
anomoly on a previous flight.

Sooooo, tell us more...

Peter

Peter Dohm wrote:
wrote in message
ups.com...

That sounds pretty much like what happened to Steve Wittman.
He put off fixing the problem until after he got to Oshkosh.

--

FF

Ok, I'm curious, since I haddn't heard this before, and it doesn't seem
to be part of the report (ATL95FA092) in the accident database.

...

At least hypothetically, delamination could have been detected in the
same manner on the O&O Special as on a composite aircraft--by
taping with a coin, or even a fingernail. However, Mr. Wittman was
not tall enough to do so on a plane larger than a Tailwind, and this
would appear far beyond the scope of a pre-flight inspection unless
one had some cause for suspicion; whether visual, hearsay, or some
anomoly on a previous flight.

Sooooo, tell us more...


I read, but do not recall where, perhaps you should DAGS in this
newsgroup, that someone who helped Mr Wittman prepare the
O & O for that last flight noticed a problem and tested the
fabric by pulling on it with a suction cup. Even though some
pulled loose, Mr Wittman did not think it was that serious
and the helper deferred to Mr Wittman in the matter.

That is not reflected in the NTSB report, but it may be that one
person helped him prepare the plane and a different person helped
with the pre-flight inspection per se.

--

FF