Replace fabric with glass

Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth with a paint "epoxy".

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

"Ernest Christley" wrote in message
m...
Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth

Most cloth like Polyfiber's and Ceconite's is polyester, trade name Dacron.
Nobody uses cotton any more because it can't hold a candle to polyester. I
don't know of any use for nylon on aircraft wings.

with a paint "epoxy".

The coatings are nitrocellulose or vinyl base, not epoxy,afaik. Paints for
Polyfiber are vinyl based or polyurethane with a flexitive.

much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

One of the covering processes uses fiberglas cloth. I remember Ray Stits
badmouthing it on his videotape. It has at least one desirable quality ---
resistance to deterioration from UV rays.

On Thu, 08 Apr 2004 20:01:51 +0000, Ernest Christley wrote:

Most of the fabric covered aiplanes I've seen didn't seem that hard. That
is, you could walk up to them and push the fabric in with your hand. The
way I understand the fabric process, it is basically a composite
structure. You have a nylon cloth with a paint "epoxy".

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping it
around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?

The fabric must be quite taut so that the external surface of the aircraft
maintains the correct shape, even when subjected to the force of the
airflow. How would you achieve this with fibreglas without having
excessive weight?

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

Ernest Christley wrote:
Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth with a paint "epoxy".

You have a cloth material coated with a doping silver compound to
reinforce the material and make it taut, on top of which paint is
applied. The former does not penatrate the material but is on one side.

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

Keep in mind that fabric covered structures are not Load-bearing in
the structural sense of the term. The fabric is there to keep the
aerodynamic shape and provide an area for the pressure to act on. It
is not a stressed skin structure in that the fabric takes pressure
loading, especially on the wings, but does not contribute to the
strength of the underlying framework as in metal skined designs. As
such, the extra strength is not really required on existing fabric
covered structures. You could maybe argue for a weight saving factor
in the days of lead based paints, but now... There is the advantage of
better UV resistance and not cracking or pealing over the lifetime.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?

This is where there is some skin loading required. Stressed skin
designs can make the use of very thin aerofoil sections possible by
taking some of the load off the spars and ribs making for lighter and
stronger structures.

Cotton (rare these days) is not worth a hoot. Probably no better lasting than
say....15 years. Linen is only good for maybe.... 20.
GA

In article ,
Ernest Christley wrote:

Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth with a paint "epoxy".

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?



There have been some fibreglass/dope coverings around for at least 45
years. I remember a couple of Stearmans that the University of Illinois
had that were covered in glass/acetate dope. They looked like wrinkled
shirts whenever theweather was coll & humid. I understand that CAB dope
works bettere here. The shrinkage of the butyrate dope provides the
taughtness that the fabric needs.

Another disadvantage of this process is weight -- glass weighs more than
Dacron.

The glass process is also more susceptable to "ringworm" -- little
ring-shaped cracks in the finish.

As others have posted, fabric provides very little in the way of
structural loads -- all it really does is help to provide aerodynamic
shape.

On Thu, 08 Apr 2004 19:01:51 GMT, Ernest Christley
wrote:

Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth with a paint "epoxy".

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?

Not sure that the fiberglass cloth plus the resin would be lighter
than the cloth plus the paint. For one thing, you left out the paint
on the fiberglass, or were you going to leave it the opaque look that
the fiberglass gets after wetting out and curing?

The other thing is that the fabric covered wing was designed for a
fabric covering. In some cases where a wing was "metalized" the
airplane ended up with a performance that was not as good as the
fabric covered wing.

Finally, as was pointed out already, there is no benefit to putting a
stiff panel around the wing. You don't save weight because the wing
is structurally designed for a fabric covering so it's internally
braced. If you wanted to use a stiff skin to cover the wing, you
should redesign the wing such that it gets it's stiffness from the
covering, not the internal bracing, and save weight.

For instance, the wing I built is fabric covered. The spars are wood,
and the ribs are wood. The wing is braced with drag and anti drag
wires that are actually 1/4" drill rod. Because they tend to try to
draw the spars together, the spars need to be held apart with steel
tubes called compression tubes. There are around six of them.

There's also a diagonal brace at the wing root to prevent the wing
from swaying back and forth, or in my case, a plate of sheet aluminum
instead. All this is to make sure the wing is stiff enough to
withstand the forces it's expected to encounter in flight. It's the
result of many years of aviation experience and engineering.

If I were to cover the wing with metal instead of fabric, I could do
away with all of the braces mentioned above.

Corky Scott

On Thu, 8 Apr 2004 15:32:43 -0400, " jls"
wrote:




One of the covering processes uses fiberglas cloth. I remember Ray Stits
badmouthing it on his videotape. It has at least one desirable quality ---
resistance to deterioration from UV rays.


that is razorback. it's weakness is that it will fret away where it
goes over a former or stringer. the glass vanishes over time and you
are left with glass panels joined by just the finish.

polyfiber is nothing to be afraid of. it is the best system going so
far. if you use polytone paint it is permanently repairable.
Stealth Pilot

Orval Fairbairn wrote:
In article ,
Ernest Christley wrote:


Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth with a paint "epoxy".

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?




There have been some fibreglass/dope coverings around for at least 45
years. I remember a couple of Stearmans that the University of Illinois
had that were covered in glass/acetate dope. They looked like wrinkled
shirts whenever theweather was coll & humid. I understand that CAB dope
works bettere here. The shrinkage of the butyrate dope provides the
taughtness that the fabric needs.

Another disadvantage of this process is weight -- glass weighs more than
Dacron.

The glass process is also more susceptable to "ringworm" -- little
ring-shaped cracks in the finish.

As others have posted, fabric provides very little in the way of
structural loads -- all it really does is help to provide aerodynamic
shape.

There have been a lot of very informative responses in this thread, but
they don't seem to address the question I have; therefore, my
conclusion is that I didn't ask the question very clearly.

Razorback has been mentioned several times. Everyone seems to agree
that it's heavy, the glass will last forever...IF it is supported
properly, and that the dope which makes it taught needs some care.

Corky and several others make the point that the fabric doesn't need to
be strong, it's just there to catch the wind.

So let's take an example. I have an aileron that was designed for a
medium weight fabric (which is 4oz/sq yard?). A 2oz FG woven finish
fabric would still be much stronger by far, but it will be much thinner.
Being thinner, it won't need as much "filler" (whether that be epoxy,
dope, or paint).

The process would go like this. I cut a piece of fabric the dimension
of my aileron with an inch or so overlap. I wet out the glass on a
sheet of 6mil plastic, set the aileron on top of it and bring the
fabric/plastic up around the aileron sides...just wrap it over. The
fabric is bonded to the ribs and around all the edges. No shrinkage
necessary, since it will be the exact size. Once that cures, I repeat
the process for the other side. The FG will add no more to the
structrual integrity than the fabric did. It's bonded to the ribs, so
no more attachment work or possibility of fretting. It has the smooth
FG look, and even with an exterior coat of paint will be thinner and
hopefully lighter than the medium weight fabric. Concerning Corky's
excellent point about the aerodynamics, a suitably flexible epoxy will
allow the fabric to have just a slight amount of give just like a fabric
covering.

This seems like a way to make a stronger, lighter skin without as much
work. But on the other hand, I'm dreadfully afraid of falling out of
the sky. How could this technique be safely tested?

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

On Fri, 09 Apr 2004 14:59:24 GMT, Ernest Christley
wrote:

So let's take an example. I have an aileron that was designed for a
medium weight fabric (which is 4oz/sq yard?). A 2oz FG woven finish
fabric would still be much stronger by far, but it will be much thinner.
Being thinner, it won't need as much "filler" (whether that be epoxy,
dope, or paint).

The process would go like this. I cut a piece of fabric the dimension
of my aileron with an inch or so overlap. I wet out the glass on a
sheet of 6mil plastic, set the aileron on top of it and bring the
fabric/plastic up around the aileron sides...just wrap it over. The
fabric is bonded to the ribs and around all the edges. No shrinkage
necessary, since it will be the exact size. Once that cures, I repeat
the process for the other side. The FG will add no more to the
structrual integrity than the fabric did. It's bonded to the ribs, so
no more attachment work or possibility of fretting. It has the smooth
FG look, and even with an exterior coat of paint will be thinner and
hopefully lighter than the medium weight fabric. Concerning Corky's
excellent point about the aerodynamics, a suitably flexible epoxy will
allow the fabric to have just a slight amount of give just like a fabric
covering.

This seems like a way to make a stronger, lighter skin without as much
work. But on the other hand, I'm dreadfully afraid of falling out of
the sky. How could this technique be safely tested?

Ernest, from what I've read and seen in the world of fabric covered
airplanes, it's really hard to substitute something for the fabric
itself and do any better in the weight saving department.

I've heard of people laying up fiberglass as a sheet and applying it
to fuselages, but the airplane ended up being heavier than when it was
covered with just fabric.

Fabric works fine by the way, it was used right through WWII on a
number of airplanes including bombers and fighters. The Corsair, one
of the most powerful fighters to fly originally had a portion of the
wing covered with fabric and even during the Korean War still flew off
carriers with a fabric covered rudder. The P-51 Mustang, one of the
fastest fighters of the war had a fabric covered rudder.

Are you trying to save money or weight, or both? When you wet out the
fiberglass fabric, it sometimes takes a lot of primer to fill the
weave, depending on the weight of the cloth. That could make for a
looonnnnggggg time of finishing to make it look good.

So what's the thought process you're going through? Why are you
interested in making the substitution? If you are looking for
additional strength, you don't really have to. Here's why: When a
friend of mine was covering his biplane, he thought it would be
interesting to test the fabric for strength, just for fun. He had a
metal stool with two loops on either side so he glued fabric across
the loops and taughtened it with the iron just like he did with the
wing. He then reached into his toolcabinet and pulled out a 16oz
ballpeen hammer. He made a half hearted swipe at the fabric and the
hammer bounced off without a mark. He swung harder and got bounced
off harder. So he stepped back and lunging forward, put every ounce
of his strength behind the swing. He hit the fabrice right in the
middle and was rebounded so hard he almost hurt himself. The fabric
was undamaged. Try that with an aluminum wing. ;-)

Corky Scott