Wing walk ply question.

"Mustardbuilder" wrote

Dunno, that's what I was asking. I've laminated two pieces of ply
together before, just was wondering if it was practical or advisable to
do it curved.

I would be very surprised if your one ply of 1/4" ply would not conform to
the curve you need. Astonished, even! g

Don't forget that the curve is part of what gives that thin of a piece of
plywood the ability to carry your weight.

Is there any other structure to help out? Extra stringers, or anything?

I would think there should be no more than 6" to a stronger structure as you
measure parallel to the grain of the ply face, and perhaps 9 or 10 inches
between supports as measured across the grain.

Are those types of numbers close to what all of you other wooden
homebuilders have found in your plans?

I am going with these types of numbers based upon my knowledge of being a
woodworker. I am curious if that is what others have found.
--
Jim in NC

wrote

My son and I finished a small boat last year, using 1/4"
Chilean Pine plywood, and we put some impressive curves in it. See this
picture of an identical boat:

http://www.glen-l.com/designs/outboard/dsn-sqtd.html

Nice boat!
--
Jim in NC

Mustardbuilder wrote:
wrote in news:1169135944.927468.166880
@m58g2000cwm.googlegroups.com:



1/4" ply will bend more easily if you orient the grain
across
the bend instead of along it. The grain should be parallel to the
spars.
If it's 1/4" birch ply, that would seem a lot of overkill
for a wingwalk. If it's 1/4" pine or fir, it should bend without any
problem.


Well, I was planning to use birch in fact. hadn't thought about using
anything else but now you have me thinking. My real concern about
bending the stuff in the first place was, in fact, the stiffness of the
Birch ply. I imagined it never reall settling down. The 1/4 birch I have
is 12 ply and is like iron!

What do the plans call for? Any specific type of plywood? What
model of aircraft is it? 1/4" birch is awfully heavy, and if that's
what the designer calls for I'd wonder how overbuilt the rest of the
airplane is. My Jodel has a wingwalk of 1/8" birch and it's good
enough.

Dan

Mustardbuilder wrote:
"Morgans" wrote in news:cZIrh.1221$cZ1.187
@newsfe04.lga:


"Mustardbuilder" wrote

Well, what I was actually asking is if I could laminate the two
pieces
to take the curve in the wing. I realise this is basic stuff for a
lot
of you guyus, but I've never bent realatively thick ply before and I
don't want to make a mess out of the rest of the wing trying..

Reread what I said. That is how to laminate two, without a mold. One
should work, though, no problem


Dunno, that's what I was asking. I've laminated two pieces of ply
together before, just was wondering if it was practical or advisable to
do it curved.

Laminating a curved piece is, if anything, better than laminating
a flat piece, and also better than using a single piece.

If you laminate it on the curve before the glue sets the
laminated plywood will be pre-stressed to the desired curve.

You don't need a mold, you can attach one piece, let it set,
then glue the second piece over it.

Regarding the veneers, the laminated piece should be symetrical.
If the pieces have an A and a B face, they should be laminated
ABBA or BAAB, not ABAB or BABA. The grain on the new front
and back face should be parallel. I'd put the A faces out, ABBA.

But I think aircraft and marine plywood is supposed to have A-grade
veneers front and back, right?

--

FF

"Morgans" wrote in
:


"Mustardbuilder" wrote

Dunno, that's what I was asking. I've laminated two pieces of ply
together before, just was wondering if it was practical or advisable
to do it curved.

I would be very surprised if your one ply of 1/4" ply would not
conform to the curve you need. Astonished, even! g

Don't forget that the curve is part of what gives that thin of a piece
of plywood the ability to carry your weight.

Is there any other structure to help out? Extra stringers, or
anything?

Well, the ribs are truss type., the two that will support the walk I've
covered with 1/16th birch ply. I plan to run a 1/4 inch stip alnog the
length to hold the walk surface fluch with the top of the ribs an glue
some , say 1/2 inch sq spruce betwwn the ribs every 6 " to support them
The whole thing shouldn't be too heavy, I reckon, especailly as I'm only
going to install one on one side.

I would think there should be no more than 6" to a stronger structure
as you measure parallel to the grain of the ply face, and perhaps 9 or
10 inches between supports as measured across the grain.

Yeah, the ribs are 12 " apart, so thats about right. And ther shoud be
no more than that to each cross brace as well.

wrote in news:1169496475.404255.84720
@m58g2000cwm.googlegroups.com:


Mustardbuilder wrote:
"Morgans" wrote in news:cZIrh.1221$cZ1.187
@newsfe04.lga:


"Mustardbuilder" wrote

Well, what I was actually asking is if I could laminate the two
pieces
to take the curve in the wing. I realise this is basic stuff for a
lot
of you guyus, but I've never bent realatively thick ply before and
I
don't want to make a mess out of the rest of the wing trying..

Reread what I said. That is how to laminate two, without a mold.
One
should work, though, no problem


Dunno, that's what I was asking. I've laminated two pieces of ply
together before, just was wondering if it was practical or advisable
to
do it curved.

Laminating a curved piece is, if anything, better than laminating
a flat piece, and also better than using a single piece.

Yeah, that's what I reckoned.

If you laminate it on the curve before the glue sets the
laminated plywood will be pre-stressed to the desired curve.

You don't need a mold, you can attach one piece, let it set,
then glue the second piece over it.

Regarding the veneers, the laminated piece should be symetrical.
If the pieces have an A and a B face, they should be laminated
ABBA or BAAB, not ABAB or BABA. The grain on the new front
and back face should be parallel. I'd put the A faces out, ABBA.

Well, the don't really. This stuff is so fine it's beyond belief. For
instance the 1/4 birch IU have is 12 ply and is one direction on one
side and the other on the other side, so it doesn't much matter which
way you put it on.

But I think aircraft and marine plywood is supposed to have A-grade
veneers front and back, right?


This stuff has a grade all the way through..

wrote in news:1169163273.789874.240970
@l53g2000cwa.googlegroups.com:


Mustardbuilder wrote:
wrote in news:1169135944.927468.166880
@m58g2000cwm.googlegroups.com:



1/4" ply will bend more easily if you orient the grain
across
the bend instead of along it. The grain should be parallel to the
spars.
If it's 1/4" birch ply, that would seem a lot of
overkill
for a wingwalk. If it's 1/4" pine or fir, it should bend without
any
problem.


Well, I was planning to use birch in fact. hadn't thought about using
anything else but now you have me thinking. My real concern about
bending the stuff in the first place was, in fact, the stiffness of
the
Birch ply. I imagined it never reall settling down. The 1/4 birch I
have
is 12 ply and is like iron!

What do the plans call for? Any specific type of plywood?

no, he pretty much leaves the whole thing up to the builder. Not much
more than a mention that there is one!

What

hatz..

model of aircraft is it? 1/4" birch is awfully heavy, and if that's
what the designer calls for I'd wonder how overbuilt the rest of the
airplane is. My Jodel has a wingwalk of 1/8" birch and it's good
enough.

Well, it's a pretty strong airplane. He calls for Mahogony or birch
throughout but I've got a good supply of aircraft birch so that's what
I'm using (there's not a lot of ply in it anyway) They come out
reasonably light if you don't go nuts on things, though. I have a good
idea what I want to do with the wing walk, but I just didn't want to
make a mess with the ply top.

Mustardbuilder wrote:
wrote in news:1169496475.404255.84720
@m58g2000cwm.googlegroups.com:

...

Dunno, that's what I was asking. I've laminated two pieces of ply
together before, just was wondering if it was practical or advisable
to
do it curved.

Laminating a curved piece is, if anything, better than laminating
a flat piece, and also better than using a single piece.

Yeah, that's what I reckoned.

If you laminate it on the curve before the glue sets the
laminated plywood will be pre-stressed to the desired curve.

You don't need a mold, you can attach one piece, let it set,
then glue the second piece over it.

Regarding the veneers, the laminated piece should be symetrical.
If the pieces have an A and a B face, they should be laminated
ABBA or BAAB, not ABAB or BABA. The grain on the new front
and back face should be parallel. I'd put the A faces out, ABBA.

Well, the don't really. This stuff is so fine it's beyond belief. For
instance the 1/4 birch IU have is 12 ply and is one direction on one
side and the other on the other side, so it doesn't much matter which
way you put it on.

Aha, I bet that is exactly why they make it that way. Plywood with
the grain on the front and back parallel is 15% stronger (or is it
stiffer, I don't remember) vs bending across that grain. Made as
you describe, it is more omnidirectional in stiffness.

If I were to laminate it for the wing walk, I'd do it with the
outer face grain (outside and inside) parallel to the spar
It should curve better that way and be a bit stiffer--like the
way plywood is laid over joists.


But I think aircraft and marine plywood is supposed to have A-grade
veneers front and back, right?


This stuff has a grade all the way through..

Over on rec.boats some people say they have found marine
ply with voids in the interior plys.

--

FF

wrote

Over on rec.boats some people say they have found marine
ply with voids in the interior plys.

And I have had a video card fail on a brand-new laptop, in less than a
month. Manufacturing defects occur, in everything under the sun.
--
Jim in NC

wrote in news:1169587980.886995.205400
@s48g2000cws.googlegroups.com:


Mustardbuilder wrote:
wrote in news:1169496475.404255.84720
@m58g2000cwm.googlegroups.com:

...

Dunno, that's what I was asking. I've laminated two pieces of ply
together before, just was wondering if it was practical or
advisable
to
do it curved.

Laminating a curved piece is, if anything, better than laminating
a flat piece, and also better than using a single piece.

Yeah, that's what I reckoned.

If you laminate it on the curve before the glue sets the
laminated plywood will be pre-stressed to the desired curve.

You don't need a mold, you can attach one piece, let it set,
then glue the second piece over it.

Regarding the veneers, the laminated piece should be symetrical.
If the pieces have an A and a B face, they should be laminated
ABBA or BAAB, not ABAB or BABA. The grain on the new front
and back face should be parallel. I'd put the A faces out, ABBA.

Well, the don't really. This stuff is so fine it's beyond belief. For
instance the 1/4 birch IU have is 12 ply and is one direction on one
side and the other on the other side, so it doesn't much matter which
way you put it on.

Aha, I bet that is exactly why they make it that way. Plywood with
the grain on the front and back parallel is 15% stronger (or is it
stiffer, I don't remember) vs bending across that grain. Made as
you describe, it is more omnidirectional in stiffness.

If I were to laminate it for the wing walk, I'd do it with the
outer face grain (outside and inside) parallel to the spar
It should curve better that way and be a bit stiffer--like the
way plywood is laid over joists.

OK, that makes sense. This stuff is pretty stiff as it is which is why
i'd prefer to make it out of two laminated pieces.



But I think aircraft and marine plywood is supposed to have A-grade
veneers front and back, right?


This stuff has a grade all the way through..

Over on rec.boats some people say they have found marine
ply with voids in the interior plys.


Yeah, i think that's allowed in marine. This stuff is aircraft grade and
I've cut up quite a bit of it into small pieces. I've never found even
the tiniest spot in it. Bit of sworl on the outer faces from time to
time, but nothing even approaching what you'd call a knothole..