The plywood monocoque car guy

"Morgans" wrote in message
...

"Peter Dohm" wrote

Even if it was "marine plywood", which I think that I may have heard at
some point, I believe that the term "marine" only specifies that the glue
between the plies is not water soluble; so an acceptable grade of plywood
may not be as close as your nearest "Borg".

Marine plywood also has a higher quality standard for the inner plys, with
a higher standard of species allowed in the interior plys allowed, and no
voids allowed, although they are allowed to have plug repairs in the inner
plys, as I recall.

The glue in marine plywood does have to be waterproof, but more
significantly, remain strong while submerged in water for some specified
period of time.

I don't believe that marine would have been specified for the glue
content, most likely. It is probably specified because of the higher
guarantees of strength and consistency.

Any plywood meant for construction that bears an "X" in the name has
waterproof glue, but it will have voids and repairs allowed, varying with
the grade. CDX is a common structural grade of plywood that has plugs on
the C side, and filled repairs on the D side, with the most knots and
defects allowed in commonly obtained grades.

Any plywood the bears a B or A grade will also have waterproof glue,
unless it bears an interior marking in addition.
--
Jim in NC
Thanks for that. I had considered adding "ping Jim Morgan".

Peter

"Peter Dohm" wrote

Thanks for that. I had considered adding "ping Jim Morgan".

You're welcome. Glad to be of help.

There may me some minor nits to pick in my description of the various factors
and such, but I think it hits the major factors in enough detail to get the
general idea.

Thing is, I don't often deal with the more strange types of plywood, unless they
deal with house construction, or cabinet making.

I have one other plywood trivia ditty that I though might be relatively unknown
to most folks, and might be of interest.

There exists a type of plywood that is strangely bendable, in one direction,
only. The other direction is as strong as normal plywood. You can buy a 4' x
8' sheet, rolled up so that it is 4' tall, in a circle (cylinder, to be more
precise) with a diameter of perhaps 28".

Yep, you heard me right! And that was a roll of plywood with around 1/2"
thickness!

From what I recall, it is made by having the outer plys grain running straight
across the 4' width, and the interior plys perhaps only 5 degrees (or so) off of
that alignment; just enough off to keep the layers bound together.

The application I used it for was for one of those fancy bay window roofs that
have a fairly deep bend in the roof structure, and hips (kinda' like a ridge on
an slope) going to a point at the top of each of the sections, then covered with
copper. I was working for a framing subcontractor at the time, and he turned me
on to this type of plywood; available only from "boutique" plywood distributors.

For those looking for unusual plywood, I suggest you do some looking in your
local yellow pages (hopefully in a relatively large population area) under
plywood, and see if you can find a place that advertises a specialty of stocking
unusual types and grades of plywood. There are more plywood types under the
sun, than you can imagine, and I can imagine a LOT ! g
--
Jim in NC

"Morgans" wrote in message
...
snip
For those looking for unusual plywood, I suggest you do some looking in
your local yellow pages (hopefully in a relatively large population area)
under plywood, and see if you can find a place that advertises a specialty
of stocking unusual types and grades of plywood. There are more plywood
types under the sun, than you can imagine, and I can imagine a LOT ! g

Jim ..........

The place in Tacoma where I bought most of the Finnish Birch plywood for the
Emeraude also stocks molded plywood. This is intended for use in rolling
over cardboard with knives imbedded in the wood. The cardboard is cut into
the various shapes, such as for folding into boxes or packing. The plywood
half-cylinders are about 3/4" thick and are not bendable - they're
structural. Real pretty stuff, too with birch outer layers.

They advertise in Sport Aviation. Beside almost all thicknesses of Finnish
Birch for aviation (.5 mm, 1.0 mm, 1.5, 2.0, 2.5, 3.0, etc.) they sell
Italian Poplar bending plywood. Ideal for making single curve windshield
molds, for instance. I was lucky to have a supplier like this only a
half-hour drive away. When you add in the fact that the principal wholesaler
of aircraft spruce in the nation is also in Tacoma, this is an ideal place
to build a wooden airplane, boat, or organ.

Rich S.

On Fri, 18 Apr 2008 22:18:56 -0700, "Rich S."
wrote:

"Morgans" wrote in message
...
snip
For those looking for unusual plywood, I suggest you do some looking in
your local yellow pages (hopefully in a relatively large population area)
under plywood, and see if you can find a place that advertises a specialty
of stocking unusual types and grades of plywood. There are more plywood
types under the sun, than you can imagine, and I can imagine a LOT ! g

Jim ..........

The place in Tacoma where I bought most of the Finnish Birch plywood for the
Emeraude also stocks molded plywood. This is intended for use in rolling
over cardboard with knives imbedded in the wood. The cardboard is cut into
the various shapes, such as for folding into boxes or packing. The plywood
half-cylinders are about 3/4" thick and are not bendable - they're
structural. Real pretty stuff, too with birch outer layers.

They advertise in Sport Aviation. Beside almost all thicknesses of Finnish
Birch for aviation (.5 mm, 1.0 mm, 1.5, 2.0, 2.5, 3.0, etc.) they sell
Italian Poplar bending plywood. Ideal for making single curve windshield
molds, for instance. I was lucky to have a supplier like this only a
half-hour drive away. When you add in the fact that the principal wholesaler
of aircraft spruce in the nation is also in Tacoma, this is an ideal place
to build a wooden airplane, boat, or organ.

Rich S.

Isn't aircraft ply made with the plies on a 45 degree bias for
bending?
** Posted from http://www.teranews.com **

In article ,
clare at snyder dot ontario dot canada wrote:

On Fri, 18 Apr 2008 22:18:56 -0700, "Rich S."
wrote:

"Morgans" wrote in message
...
snip
For those looking for unusual plywood, I suggest you do some looking in
your local yellow pages (hopefully in a relatively large population area)
under plywood, and see if you can find a place that advertises a specialty
of stocking unusual types and grades of plywood. There are more plywood
types under the sun, than you can imagine, and I can imagine a LOT ! g

Jim ..........

The place in Tacoma where I bought most of the Finnish Birch plywood for the
Emeraude also stocks molded plywood. This is intended for use in rolling
over cardboard with knives imbedded in the wood. The cardboard is cut into
the various shapes, such as for folding into boxes or packing. The plywood
half-cylinders are about 3/4" thick and are not bendable - they're
structural. Real pretty stuff, too with birch outer layers.

They advertise in Sport Aviation. Beside almost all thicknesses of Finnish
Birch for aviation (.5 mm, 1.0 mm, 1.5, 2.0, 2.5, 3.0, etc.) they sell
Italian Poplar bending plywood. Ideal for making single curve windshield
molds, for instance. I was lucky to have a supplier like this only a
half-hour drive away. When you add in the fact that the principal wholesaler
of aircraft spruce in the nation is also in Tacoma, this is an ideal place
to build a wooden airplane, boat, or organ.

Rich S.

Isn't aircraft ply made with the plies on a 45 degree bias for
bending?
** Posted from http://www.teranews.com **

Some is 45; others are 90 -- you can specify when ordering.

--
Remove _'s from email address to talk to me.

On Apr 19, 8:26 pm, Orval Fairbairn
wrote:

Isn't aircraft ply made with the plies on a 45 degree bias for
bending?
** Posted fromhttp://www.teranews.com**

Some is 45; others are 90 -- you can specify when ordering.

I think it's the face plies that are either 90 or 45 to the cut
edges, and the core plies are at 90 degrees to the face plies. I
haven't seen plywood with the cores at 45 to the faces.
45 degree faces are for places where the design calls for
angled grain across some structure (like a box spar) to closely align
with the stress forces, while avoiding so much waste.

Baltic birch (or Finnish birch, if you prefer) will bend most
readily across the face grain (grain 90 degrees to the bend line) if
it's dampened. I used to spray water on the faces and run a hot
clothes iron across it, turning that water to steam and driving it in.
Doesn't hurt the resorcinol ply glue. I once cut a 3/4" wide strip of
1.5mm ply, face grain running the long way, steamed it, and wrapped it
around a pencil spiral-fashion without it buckling or breaking. Tied
it that way and when it was dry it pretty much held that shape.
Trying to bend it with the grain (grain parallel to the bend
line) will usually fracture the core plies, since it's pretty hard to
get moisture that deep.

Dan

On Apr 19, 8:05 pm, wrote:
Trying to bend it with the grain (grain parallel to the bend
line) will usually fracture the core plies, since it's pretty hard to
get moisture that deep.
-------------------------------------------------------------------------------------------

Try adding two ounces of household ammonia and ONE DROP of liquid
detergent (or a drop of Kodak 'Photo Flow') to each GALLON of water.
Soak over-night then heat the soaked wood to 165 to 185F degrees.
Bend to the desired shape and allow to dry. For extremely deep
curves, do the bend in graduated stages, keeping the plywood moist
until the desired shape has been achieved.

Thinner is better; make the part as two shells if needed to achieve
the desired thickness.

This procedure does not work with all plywoods.

-R.S.Hoover