Plywood

cagey

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In the teams opinion what grade or spec for ply should be used for a structural bulkhead. Original is 22mm, am mainly concerned about ingress of water from bilges as original has to be replaced because of rot. Is it true that all ply nowdays is WBP, if so can I use cheap shuttering ply because both sides will need to be laminated anyway.
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GrahamC

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Hi
The WBP refers to the adhesive sticking the layers together, the BS1088 standard
is supposed to mean that the material has no voids in the laminate, Shuttering Ply is usually Douglas Fir and is fairly resistant to rot providing it is well sealed,
I would go for the best quality your purse will afford, in structural situations don't skimp
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GrahamC
 

Strathglass

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The stuff you get from builders merchants is usually WBP bonded but often has bad voids in it.
Even when you buy stamped stamped 'marine ply BS 1088' from builders merchants it still often has voids.

You can get good marine ply but it is often very expensive.

especially teal faced 22mm or all mahogany.

Good marine ply is available from -

Robbins timber, marine ply.com and Brunzelle.

You should find them all easily using google

You may be able to find some elsewhere. I would say that shuttering ply would not last for long in a marine enviroment.

Iain
 

charles_reed

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I'd personally not use shuttering ply on a boat except as a one-trip disposable application.

For non-load-bearing, hidden, applications I find birch faced ply is OK.

As already pointed out, the adhesive in most ply on sale is waterproof - the real variation is in the laminates used.

For the job you're proposing I'd use good quality marine ply - the best is Bruynzeel - in fact van der Stadt started his career designing ply boats for Dick Bruynzeel.
 

boatmike

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That's actually the reverse of the truth. BS 1088 as iansimpson suggested often has voids in it as BS 1088 only states that the adhesive should be waterproof and says nothing about voids at all. In fact WBP can conform to and indeed exceed the standard set by BS 1088 quite easily! Confusing isnt it?
The things you need to look for are :
1. The adhesive standard where WBP states it should be to a waterproof standard so thats OK as far as it goes
2. The wood used. Without getting detailed Gaboon is best Birch second best. (Incidentally Gaboon is much lighter in weight too) And it should be the same wood throughout not have a fat softwood filler in the middle!
3. The Number of plys. For 12mm for example this can be anything from 3 to 11 ( suggest not less than 7) For 22mm not less than 11 (always an odd no)
4. Where it comes from. Israel is good and there is a lot of it about. Avoid cheap far eastern stuff like the plague.
5. Density (voids) There should be no voids visible on a cut edge.
If you tell me where you live I could suggest a supplier of good quality
 

Steve_N

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WBP ply from DIY stores seems to vary greatly in quality:
- I bought a sheet of 12mm/7 ply from Wickes to make a temporary washboard last Autumn, and it has been absolutely fine over the winter with just a couple of coats of varnish to seal it.
- bought a second sheet from the same pile a month ago to make covers for the deck hatches while they off the boat for refurbishment. Same 2 coats of varnish. Luckily I returned to the boat after 3 weeks as they wouldn't have lasted any longer: de-laminated and curling up at the corners. Complete rubbish plywood but carrying the same certification.
 

boatmike

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Exactly the point I made about cheap far eastern crap. If an 8x4 sheet of 12mm ply costs you less than about £45 it's probably rubbish. All Wickes stuff seems to come from China or Malaysia. You wont buy ply suitable for exterior boat use in a DIY store.
 

cagey

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Hi Boatmike
I live in Newquay Cornwall. Thank you and everyone for the information didn't imagine it would be such an involved subject.
 

charles_reed

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Sheds

You'll not get marine ply from anyone but a real timber merchant - going to any of the sheds is not only expensive but a certain way to disappointment.

the difference between birch-faced exterior grade and gaboon marine ply in 3mm 3-ply for a standard 2.1m x 1.4m sheet last month in Ostia (which is generally much less expensive than the UK) €53 to €155, so I'd reckon the £45 for a sheet of a reasonable thickness is very optimistic. The gaboon was not only lighter but easier to work - trouble was the merchant only had the one sheet of marine ply.
 
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