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

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

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.

It might be like that old rag-top car we've seen tooling down the highway
with the fabric ballooning away from the metal top when the adhesive gave
way. The altered profile might change the lift characteristics of the wing
to some degree I suspect. I read somewhere that anything above 75 should be
rib stitched, but I'm no engineer.
wrote in message
oups.com...
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

wrote:

...

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 )
...


IIRC the explanation runs something like this:

When the fabric is glued to the rib some of the glue extends
slightly down the side of the rib/ribcap forming a sort of
bead or fillet, the rest forms a ribbon of glue between the
fabric and the ribcap.

As the fabric lifts from the rib the bead/fillet is stressed
in shear, while the ribbon is stressed in tension. The glue
is much stronger in shear than it is in tension, so if the
bead/fillet fails, the fabric will then peel away from the
broad flat surface of the rib cap. No matter how wide the
rib cap is, as the fabric peels the stress is concentrated
on a thin line adjacent to where the fabric has already
pulled away.

The bead/fillet is independent of the width of the rib/ribcap
hence the conclusion that the width does not matter.

Another conclusion is that, no matter how wide the rib caps
are, one should make sure the glue extends all the way to the
edge.

This suggests that the bond might be improved by running grooves
circumferentially around the rib caps. Sort of like what is
called 'tooth' in veneer work.


--

FF

"Stan Premo" wrote in message
...
It might be like that old rag-top car we've seen tooling down the highway
with the fabric ballooning away from the metal top when the adhesive gave
way. The altered profile might change the lift characteristics of the
wing
to some degree I suspect.

The fabric lifting off the top of the wing can, and has killed people. This
is still not to say that it has to be stitched.

If loads on the surface are low enough that the correctly glued fabric stays
place, then all is well. Just make sure the correct techniques are used,
and that loads are low enough!
--
Jim in NC

Morgans wrote:


It might be like that old rag-top car we've seen tooling down the highway
with the fabric ballooning away from the metal top when the adhesive gave
way. The altered profile might change the lift characteristics of the
wing
snip


The fabric lifting off the top of the wing can, and has killed people. This
is still not to say that it has to be stitched.

If loads on the surface are low enough that the correctly glued fabric stays
place, then all is well. Just make sure the correct techniques are used,
and that loads are low enough!

What about the 3rd option from the Tony Bengals books, covering the wing
with thin fiber glass cloth and resin?

I know it would make it harder to inspect the condition of the wood
years down the road (sky?) but it sounds like it would last longer in
the first place.

Tony

Anthony W wrote:
Morgans wrote:


It might be like that old rag-top car we've seen tooling down the highway
with the fabric ballooning away from the metal top when the adhesive gave
way. The altered profile might change the lift characteristics of the
wing
snip


The fabric lifting off the top of the wing can, and has killed people. This
is still not to say that it has to be stitched.

If loads on the surface are low enough that the correctly glued fabric stays
place, then all is well. Just make sure the correct techniques are used,
and that loads are low enough!

What about the 3rd option from the Tony Bengals books, covering the wing
with thin fiber glass cloth and resin?

Just in case anyone wants to find his books its _Tony Bingelis.

Fiberglass wings are not fabric wings. You might as well say,
hey, why not cover them with aluminum sheet metal.

Also, I _think_ fiberglass wings will be heavier.

--

FF

wrote:

What about the 3rd option from the Tony Bengals books, covering the wing
with thin fiber glass cloth and resin?


Just in case anyone wants to find his books its _Tony Bingelis.

Fiberglass wings are not fabric wings. You might as well say,
hey, why not cover them with aluminum sheet metal.

Also, I _think_ fiberglass wings will be heavier.

I may have spelled his name wrong but from your answer, I don't think
you've read his books or at least this part.

Tony