Plywood, again: Red Cedar face and Poplar core can be Marine grade?

[Éric Bouvéron]

Hi,
I received today an offer for plywood, as follows:

item : Marine plywood
size: 1250x2500mm
thickness: 6mm 15mm
finish: satin finish
glue: WBP
core: full poplar core
F/B: red cedar face and back
grade: A/A

A few concerns about this:
Satin finish. What can it means?
Core: Poplar is not a very durable wood, as far as I know. Is it suitable for boatbuilding?
Face and Back red cedar. I asked for Mahogany or Okoume, but it seems that they don' t have it. Does epoxy sithks on red cedar?
Once again, thank you for your answers and advices,
Éric

[Blanc Jean-Paul]

Hello
sorry for my accent.
Did you have a Notice or the origin of these plywood?
It's must be for decoration ( satin finish)
Is the plywood classified to lloyds for example?
You must have the garantee of this by the manufacturer or the tarder.
For me red cedar can't be used for plywood. And poplar (peuplier en français? ) is just good for decoration.
marine plywood is also defined by the quality of glue. For example resist to hot vapor during 72 h without delaminate,
y hope that you understand my english.
Good luck.

[Éric Bouvéron]

Your English est as terrible que le mien. :-) mais pas plus.
Origin is China. I note that they use "WBP", water boiled proof glue. But, yes, except this point, I don't feel confident about the quality.
Red cedar doesn't work with epoxy?
I will search again,
Merci,
Éric

[Blanc Jean-Paul]

En français dans le texte.
Desolé mais je n'ai pas voulu parler du collage du red cedar avec l'epoxy. Le red cedar est au contraire un bois qui va bien avec l'epoxy. Par contre il faut des sections plus fortes.
je vais rechercher dans ma documentation pour la classification marine des contre plaqués.
Personnellement, pas de classification aux lloyds, je n'achète pas.

[Omar M. Rashash]

Using a waterproof glue and labeling it as "Marine Plywood", doesn't make it so. By definition, Marine Grade Plywood not only uses WBP glue, but all the interior plies are of the same species as the face plies. The interior plies may be of a lesser grade, but will be free of voids. The only exception to this is Marine Grade Teak plywood, which may use another rot-proof wood as the core. The plywood you've been offered sounds like it's intended for interior architectural work and has a pre-applied factory finish.

HTH,

Omar

[Éric Bouvéron]

Merci à tous, Thank you everybody! I will try to find something better.

[Robert]

Hi Éric,

I found this: http://wood28.com/en/index.php

They seem to do BS1088 marine ply and have manufacturers certificates for the wood, which is a good sign.

R

[Éric Bouvéron]

Thank you Robert, I have made contact with them.
However, they re in Hong Kong, and I intend to build in China, where I have a sheltered place. I will check how to bring the sheets there, if I do not find anything else.
For information, here is what they offer:

BS1088 Meranti (with PEFC) -pefc is a certificate about sustainable forest management- is mostly used in interior structure where mechanical strength is of importance and building standards such as BEAM or LEED require full documentation of the chain of custody of the timber source.

BS1088 Keuring is for exterior application with damp environment. Keuring is a tropical hardwood of density 800kg/m3 or above. It is used as railway sleeper and fixtures built in seafront.

Both options use Phenol WBP glue and passes WBP test.
Also, no 15mm available, but that's already something. Price for a 2440x1220mm sheet, 6mm thick is HK$230, say US$30.
Thanks again.
Éric

[Éric Bouvéron]

.

[dennis schneider]

Eric: having built a Tangaroa 35 yrs ago with insufficient epoxy, but Brunzeel ply I can tell you that you do not need to buy a fancy marine grade ply, IF you sheathe underwater with 18 oz biaxial cloth and epoxy. The topsides (i.e. sides, not deck) ply need to be saturated with 5 or 6 coats of epoxy( no cloth)then a two component polyurethane white, without primer, , applied coat upon coat while still tacky, while sides are positioned horizontally...The deck should be done as the underwater area was. This is my experience after working in the boat trade since 1976. The interior surfaces can be given two coats of polyurethane clear in the bilges, one coat everywhere else. Fasteners should be any coated steel screw designed for exterior construction, as long as they are under epoxy. For a 40 ft Wharram figure about 100 gal epoxy (part A&B together). I am glad you have a sheltered shop; that is of very high priority. Wow, building in China - that reminds me of Bernard Moitessier!)

[Tam Dl]

I wouldn't trust much in the way of certification unless there is someone that one knows who is trustworthy behind it.  It is a standard, Loyds isn't wandering the world making sure ply meets the standard.  All you have is a promise.  Marine ply is designed to be edus painted or unpainted in water, with similar durability to solid wood, though with the panel characteristics of plywood.  Since that is not how one builds boats today the standard is broadly irrelevant.

I would wonder where the red cedar and poplar are coming from.  Not chinese woods to my knowledge.  Though we export plenty of wood...A great deal of wood that is used in boats these days is pine (luan) but it gets called mahogany in some circles.  The mahogany that gained the reputation came from SA.  However since that wood is likely to be cites certified some day, and not importable or exportable after that (a problem in a boat) not having real mahogany is probably a plus.  Basically people shouldn't buy boats that are part of this kind of process.  I have no problem making boats out of dodgy materials, but I wouldn't buy one.  Most of the boats I see for sale are " made of 1088 mahogany and WEST system epoxy) but the boards I surf have so far never had that project.