Which plywood

mrangry

mrangry

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Ok I know this has been discussed before but after searching the forum I am still unsure.

I am rebuilding the galley area, cabin sole and saloon under seat supports (timber sheets under cushions) on my Moody 33 mk1 and trying to decide on whether I need marine ply or would exterior ply suffice?

I am also looking for somewhere to buy locally (Glasgow area) and I understand that the B&Q stuff is of poor quality and should be avoided.

Has anyone any suggestions?
 
Marine ply is for building plywood boats, which will spend a lot of time immersed in water. I hope that is not true of your bunk fronts! So exterior ply will be more than up to the task.

Pete
 
I agree

prv said:
Marine ply is for building plywood boats, which will spend a lot of time immersed in water. I hope that is not true of your bunk fronts! So exterior ply will be more than up to the task.

Pete
Click to expand...

marine ply has no voids in it - which are only a problem if the ply gets wet

exterior ply has good quality on the outer layers but may have some voids

the glues are exactly the same

so go to your local timber yard and look for sheets that have a nice grain

Dylan
 
As someone has already pointed out, the difference between BS1088 Marine ply and exterior grade is the guaranteed lack of voids in the marine version. The glues are the same. Our local builders merchant (not B&Q!) had some very nice ply which they said had come from Eastern Europe, exterior grade and very reasonably priced. I've yet to find a void in a sheet I've cut... Nice hardwood laminates as well, with very few knots.
 
There is a Dutch marine ply that is guaranteed for fifty years. We had it under our teak decks and cabin sole with oak panelling on top. I don't know where you can buy it because the previous owner fitted it. A company specialising in marine ply may know.
 
Have you tried George Hulley at Dumbarton, situated in the old McAllisters boatyard on the Leven, did have good stocks of marine ply
George is one of the last wartime boatbuilders, built clinker lifeboats for the war effort on piecework after he finished his day job. longest serving member on the LIBS committee and builder of the ARDEN 24.
Gilmour & Aitken used to be situated in Pollokshields in Glasgow where they had multi level storage facility to condition logs brought in from their own timber stocks in Africa, huge logs of teak and mahoghany would be cut, kiln dried and stacked to await customers orders. You bought the log by the cube! and hoped it would be suitable for boatbuilding purposes however the yard foreman would suggest that the first cut be taken through the centre of the tree and depending on what he saw with regard to the grain made the difference between it being cut for planking or joinery.
 
dylanwinter said:
marine ply has no voids in it - which are only a problem if the ply gets wet

exterior ply has good quality on the outer layers but may have some voids

the glues are exactly the same

so go to your local timber yard and look for sheets that have a nice grain

Dylan
Click to expand...

I am afraid its not quite as simple as that: Marine ply has (should have!) laminations of the same thickness throughout and of hardwood of similar quality to the external veneers, except in the case of a 'faced' ply which has a decorative veneer. Also, voids are present, but may not be greater than a specified width. Glues are also to a specified standard. The difference between a cheap Marine ply and the better grades like Brynzeel will be in the quality of the wood used.

WBP may have a similar grade glue, but there is no specification for the maximum void size making it unsuitable for any strcutural component. There is no specification for the thickness, number or quality of the internal veneers, and it is not unusual to find softwood cores, often birch. Even in thicknesses up to 8 mm or more it is not unusual to find a single thick softwood core, sandwiched between two hard(ish)wood veneers of as little as 1.5mm thickness. If there is a substantial void, then the strength of the board can be seriously compromised.

In any case WBP MAY be glued using the same glues as marine ply, but with the cheapest far eastern imported boards (and how do you know where it came from?) they seem to use something akin to baked cow dung! Unfortunately there are a number of companies also selling cheap imported far eastern manufactured 'marine ply', which often has 'BS1088' stamped on it: A simple 'BS 1088' stamp is meaningless unless it is kitemarked. Even that is not 100% guarantee that it complies, and there is a lot of rubbish being sold as BS1088 marine ply, even by reputable suppliers.

Cheap BS1088, or good quality WPB is OK for internal furniture if it is reasonable quality, and you can GUARANTEE that it will NEVER get soaked! In a boat? There ARE good quality WPB boards around, some of which are better than cheap BS1088 boards, but forget cheapo domestic grade stuff. And even with quality Marine ply make 100% sure the end grains are properly sealed. The cheaper core boards will soak water up like a sponge, then disintegrate within a few years.
 
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If you take a look at any old plywood-1960s and before it always consists of a layer of veneers of equal quality whether exterior or interior quality.
Much of the current mass produced rubbish only has the outer layer of proper veneer with the interior being off whatever cheap and cheerfull rubbish that can be got away with.
Firm in Alexandria looks really good
 
Trying to find reasonably quality/priced plywood seems very difficult and there seems to be some good suggestions. I would look at using an exterior ply and then adding a layer of veneered ply, our builds merchant keeps a good range of 4mm veneered ply. the thing I wanted to add was whatever ply you use make sure you seal any unseen edges, ideally with a wipe of epoxy, or at least a couple of brushes of quick drying satin varnish or primer if going to be painted.

Good luck with it.
 
john_morris_uk said:
As someone has already pointed out, the difference between BS1088 Marine ply and exterior grade is the guaranteed lack of voids in the marine version. The glues are the same. Our local builders merchant (not B&Q!) had some very nice ply which they said had come from Eastern Europe, exterior grade and very reasonably priced. I've yet to find a void in a sheet I've cut... Nice hardwood laminates as well, with very few knots.
Click to expand...

Birch plywood from eastern europe is pants
 
G & A Timber in Alexandria, Jamestown actually, Is good for most wood but the marine ply is not top quality. I live on the opposite side of the river Leven from the yard and buy most of my stock from them except ply. Having said that I bought some 12mm boards a couple of weeks ago and they are ok for the under bunk lids but that is about as far as I would go. Although they are stamped BS1066 they are not equal thickness ply's so the boards warp. That goes for 18mm as well. I had to go to Robbins for the good stuff to refit the boat and had to try to get it all in one order as there is a £40.00 shipping fee ex VAT.
George Hulley has retired and although Hulley Marine is still in business it is a shadow of it's former self. It is still in Sandpoint Marina but in the newish sheds, his old one having gone to landfill.
 
Given the variable quality of any ply, whether or not it is stamped (easy to fake, anyway), would not a good coating of West epoxy and/or two pack varnish overcome any difficulties with water-induced delamination? If it is also non-structural, do we care too much about its provenance?
 
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