Wing walk ply question.

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