Something to measure physical pressure.

Well Roger, I was really just looking for a couple of simple
answers. Seeing how this is an experimental hobby, I thought
that I would compare the strengths of the plywood that the designer
put on the plans (old design) against some newer materials and idea's.
It may cost me a few bucks but I want to measure strength and breaking
points against each other.
Lou

In article . com,
Lou wrote:

Well Roger, I was really just looking for a couple of simple
answers. Seeing how this is an experimental hobby, I thought
that I would compare the strengths of the plywood that the designer
put on the plans (old design) against some newer materials and idea's.
It may cost me a few bucks but I want to measure strength and breaking
points against each other.
Lou

You should be able to find that information in the materials handbooks.

I would start with a Google search for "Forest Products Laboratory",
which is the central source of information on wood products. They test
materials and publish the results.

On Oct 31, 10:02 am, Orval Fairbairn
wrote:

You should be able to find that information in the materials handbooks.

I would start with a Google search for "Forest Products Laboratory",
which is the central source of information on wood products. They test
materials and publish the results.

That's true as far as it goes. However, the design and development of
sport aircraft occasionally demands that one innovate beyond the
boundaries of what established laboratories and institutions have
deigned to test and approve.

Consider the practice of using cellulose fiber composite panels for
the reinforcement of truss junctions in chordwise wing members. First
developed in the 1930s, this practice was validated in a successful
glider design and is currently under evaluation for at least one light
sport aircraft.

However, it would never have seen the light of day of some poor guy
hadn't snipped a bunch of wing rib gussets out of cereal box cardboard
and tried them out. Necessity is the mother of invention. Theory often
follows practice.

Thanks, Bob K.

"Lou" wrote in message
ps.com...
That will break it, but will it measure?


What kind of measurement would you like to see?

What kind of measurement would you like to see?


Well, I'm not sure how to put it. I want to see how other materials
and
combination of materials measure up to the original design. I probebly
will
stay with the original, but while I'm at this part, it would be, in my
opinion,
pointless not to venture down other paths while I can. The
measurements
don't even need to be a real measurement such as psi. As long as I can
have a comparible measurement. In other words, if it takes 50lb of
force
with a fish scale to break a certain peice of wood. I would compare
another
material with the same fish scale set up to have a comparable
measurement.
Lou

"Lou" wrote in message
oups.com...


What kind of measurement would you like to see?


Well, I'm not sure how to put it. I want to see how other materials
and
combination of materials measure up to the original design. I probebly
will
stay with the original, but while I'm at this part, it would be, in my
opinion,
pointless not to venture down other paths while I can. The
measurements
don't even need to be a real measurement such as psi. As long as I can
have a comparible measurement. In other words, if it takes 50lb of
force
with a fish scale to break a certain peice of wood. I would compare
another
material with the same fish scale set up to have a comparable
measurement.
Lou


The problem is that if you want to compare two materials for a particular
application - you need to match the way you measure the strength of the
materials with the kind of loading that will be applied when they are in the
stucture.

Example - heavy fabric and thin plywood may have similar tensile strength as
measured by your fish scale, but the fabric won't work for gussets and the
plywood will.

So, before you can decide what kind of test you should use to compare, you
have to determine how the material is loaded.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

Sounds reasonable to me. So, if I where comparing wing loads of
plywood
and fabric, how would you suggest I measure this against composite or
other materials? I'm open to suggestions.
Lou.

Lou wrote:
Sounds reasonable to me. So, if I where comparing wing loads of
plywood
and fabric, how would you suggest I measure this against composite or
other materials? I'm open to suggestions.
Lou.



Maule fabric punch?

Sounds reasonable to me. So, if I where comparing wing loads of
plywood
and fabric, how would you suggest I measure this against composite or
other materials? I'm open to suggestions.
Lou.



Maule fabric punch?

I don't think so.

The punch test tells you if your fabric is rotten, or not. The load it puts
on the fabric is a result of testing to know how much force the punch should
be able to apply, and not have the system of fabric and attachment fail, or
not.

If your punch test fails, you could develop a long rip , or a rip at a
stitch and/or glue by the rib, or in the middle of the fabric, and it could
let you fall out of the sky.

A point load like a punch is not the kind of load the (lets say) top fabric
will see. It will be an evenly distributed load, pulling up, with the glue
or stitching (on the ribs) resisting the upward lifting forces. The load at
the ribs would be a long attachment, or lots of small point loads from the
stitches, but still, the dope should be gluing the fabric to the ribs, also.

So, if there is two feet between the ribs, and the bay is 3 feet long, you
have 6 square feet of area. If you have a 20 pound per square foot wing
loading, you could have 120 pounds of force pulling at the attachments of
the ribs and spar caps. (front and rear spars) You want to know if the
fabric will fail or hold at those pressures.

You could make an airtight box with an open top, of 2' X 3', which would be
864 square inches area of the top. Glue and stitch the fabric on the top
flange (same sizes as the ribs or cap, and spar caps) of the box and put
120 pounds of force on the fabric, which would be 864 sq inches/120 lbs per
sq ft = 7.2 psi air pressure inside of the box. If it holds, you might not
fall out of the sky. g

You could then substitute the material you want to test for this application
(plywood, fiberglass, fiberglass/foam sandwich, aluminum foil g, or
whatever you want to test, and whatever holding method you want to use, and
test it.

That's my thinking in/out of the box, so to speak. Right, or wrong. I
don't know. It is how I would likely go about it. I'm not an aeronautical
engineer. I did stay at a Holiday Inn last night! ;-)
--
Jim in NC

Morgans wrote:
Sounds reasonable to me. So, if I where comparing wing loads of
plywood
and fabric, how would you suggest I measure this against composite or
other materials? I'm open to suggestions.
Lou.



Maule fabric punch?


I don't think so.

The punch test tells you if your fabric is rotten, or not. The load it puts
on the fabric is a result of testing to know how much force the punch should
be able to apply, and not have the system of fabric and attachment fail, or
not.

If your punch test fails, you could develop a long rip , or a rip at a
stitch and/or glue by the rib, or in the middle of the fabric, and it could
let you fall out of the sky.

A point load like a punch is not the kind of load the (lets say) top fabric
will see. It will be an evenly distributed load, pulling up, with the glue
or stitching (on the ribs) resisting the upward lifting forces. The load at
the ribs would be a long attachment, or lots of small point loads from the
stitches, but still, the dope should be gluing the fabric to the ribs, also.

So, if there is two feet between the ribs, and the bay is 3 feet long, you
have 6 square feet of area. If you have a 20 pound per square foot wing
loading, you could have 120 pounds of force pulling at the attachments of
the ribs and spar caps. (front and rear spars) You want to know if the
fabric will fail or hold at those pressures.

You could make an airtight box with an open top, of 2' X 3', which would be
864 square inches area of the top. Glue and stitch the fabric on the top
flange (same sizes as the ribs or cap, and spar caps) of the box and put
120 pounds of force on the fabric, which would be 864 sq inches/120 lbs per
sq ft = 7.2 psi air pressure inside of the box. If it holds, you might not
fall out of the sky. g

You could then substitute the material you want to test for this application
(plywood, fiberglass, fiberglass/foam sandwich, aluminum foil g, or
whatever you want to test, and whatever holding method you want to use, and
test it.

That's my thinking in/out of the box, so to speak. Right, or wrong. I
don't know. It is how I would likely go about it. I'm not an aeronautical
engineer. I did stay at a Holiday Inn last night! ;-)

He was asking about test samples, not finished product.

For a replacement for fabric skin?

So f it punches good, it's ok, right?

My only question is how much weight is added replacing fabric.


Richard