Plywood - signs of delamination (?)

[Pelle]

Hi!

As some of you know, I'm currently struggling to renew the decking of my 47' wooden motorboat "Dreggen".

All the beams has been faired, and I'm currently adjusting the first layer of 1/2" ply (7-layers) to go on to
those beams. The weather here from a deck-laying point of view) has been hell. Twice as much rain the first
week in July compared to average. How about June ? How about it ??......... and no sign of change to the
better the next few days.....

Well, to the point. Of all the rain, some of it has managed to lure through my tarp. The result ?? Some of the
upper layer of ply has "buckled" at the newly cut edges. Also has happened around some of the screw holes.
The dealers pushing this ply (said to be WBP) does not seem concerned at all to what they're selling. Knowing
this, I myself went to a wholesaler to make sure that I got what I needed, explaining that I were to use it as
a strucural fundament for a wooden decking (5mm thick). I even made the wholesaler call the importer to
make sure that it really was WBP. The pile of plywood had WBP made up on the side, but apart from this there
is no print or anything else on the plywood itself to identify what it is (pine). This wholesaler, by the way, is
making a point of saying that the glue is WBP, not the wood itself.....

(I have previously built a dinghy using the same ply, although this beeing only 1/4" thick. Some scrap of this
has been laying around outside exposed to the local weather without showing any sign of local delamination.)

I have taken (1/2" ply) some offcuts and boiled the for a couple of hours without any delamination happening.
The ply has however digested water to the extent that it is no longer bouyant. This problably is bad news ??
Can I feel confident in the ply despite the local delaminations, or can it blow up in my face should water get
past the epoxy barrier ?? I'm doing the decking after the "west-system" method, although I'm using a
different norwegian brand epoxy.

I surely can get "marine quality" from another part of Norway and this is Lloyds approved with a 20 years
warranty. This has A/A sides, but - all things considered, I don't need that. I just need something
("exterior-grade") that will do the job and keep together. The never ending struggle between quality and
money......

Help?????

Per Olav

PS I'm going on a needed vacation borrowing my in-laws 30' something in a couple of days. We'll be cruising
up in northern Norway (Lofoten/Vesteraalen), so I'm not in a hurry that way. I'll be back in about 3 weeks and
will be happy to hear your views/comments up to when I'm back. Hopefully I'll get my sleep back by then(!).
This really stresses me....(the ply, that is...)

[ 07-10-2002, 04:46 PM: Message edited by: Pelle ]

[Scott Rosen]

It sounds like there's something wrong with that ply. I wouldn't use it on a deck. If there is buckling of the laminations when wet, then there is a failure somewhere, bad glue, voids, who knows?

The stress of spending more money now and replacing the plywood will be much less than the stress of finishing the entire job with questionable plywood and then discovering that you have to redo it in a couple of years.

[thechemist]

Something sounds very wrong.

When you look at a sanded edge, do you see the different layers of wood with no particular lines between them, or do you see dark brown lines? It has to do with the kinds of glue that may be used. Some are merely water-resistant, and others really do not soften or decompose at all upon water-exposure.

Then there is the question of what kind of wood it is.....some being more resistant to water absorption than others. Is it off-white in color, such as spruce or birch, or is it dark brown in color , such as mahogany, meranti or other woods might be?

I do not recognize the term WBP. Can you tell me what it stands for?

[Donn]

WBP = weather and boil proof

[stan v]

Boil proof is a rating I've not heard before. Sure that's correct?

[wolfietuk]

Sam Devlins book talks about testing wood by boiling it. Cut a couple squares about 4"x4", put them in boiling water for 10 minutes then into the freezer, then back in the boiling water. Repete this 4 times, if the ply comes apart you do not want this ply.

Rick

[Tom Dugan]

It seems to me that the real issue is that Per has lost confidence in his plywood, and he's already stressing over it. If you look ahead to the first time your boat is in rough weather I think the answer is clear. Do you want to stress the boat with a plywood you have no confidence in?

-T

[Alan D. Hyde]

If it's delaminating, it's not strong enough to do to job for which it was intended. Therefore, it must be replaced.

Unpleasant, but unavoidable.

I'd talk to the manufacturer and supplier about making some appropriate adjustment with respect to the defective plywood. Let us know how they treat you. Tell them that your wooden boat friends world wide will hear about their honest response--- or the lack of it.

Have a pleasant holiday.

And, once more, good luck on a great project.

Alan