Thread: marine ply

Construction ply uses the same glues as marine ply but is made from non rot-
resistant species - radiata or slash pine - and is allowed all sorts of strength reducing
& rot inducing flaws in the veneers. It also typically has fewer & thicker veneers than
marine ply. Treated & sealed, with excruciating attention to detail, it would
probably last quite well as a floor in a runabout. Untreated, you would need to fix
every nick & scratch reasonably promptly.

If you buy Australian made, you have two choices of marine ply - hoop pine or treated
radiata.

The hoop pine ply may be 2 or 3 times the cost of structural, but it will be a superb
quality ply made from a naturally rot-resistant (*not* rot-proof) timber which is
intrinsically stronger than radiata or slash. Your floor can be made lighter and/or
stronger.

Treated radiata marine ply made to the aust standard (I can't remember the AS
number) will be far better quality than construction ply in terms of voids, splits, knots
& durability, but it will be the same pinus crapiata for strength vs weight. I think
boatcraft pacific carry it. Not sure. Cheaper than hoop, more expensive than
construction. Treated radiata lasts for decades as jetty piles, so there would be no
worries about rot. Just don't suck on it for long periods... !!

A reasonable quality asian made "pacific maple" marine ply, nominally made to
BS1088, will be about the same price as the construction ply. BS1088 allows more
imperfections than the AS, and is only enforceable in Britain. Outside Britain, anyone
can stamp any old garbage with it with impunity. But if the ply has genuinely been
made to BS1088, & you get it from a reputable dealer, it will be good ply. It will
probably also be lighter & stronger than construction ply of the same thickness.

Whatever you do, make sure you provide for plenty of under-floor ventilation.

cheers
AJ

Wot 'e said.

Construction and other cheapo ply has really cr@p durability. Hoop pine exterior grade can be a very nice board indeed.

No comparison.

MIK

Do ring around. I've always been amazed that careful buying can really bring down the cost. I'm interested in multihulls so the ply of choice is gaboon which isn't as durable as hoop and some others, but I have from time to time been able to find marine grade gaboon for only about 10% more than structural. It's 1088 but legitimate 1088 not junk. You can save a lot by not insisting on A grade faces. If your going to paint it or something lower grade faces won't rot faster but can save you money. In my experience marine suppliers aren't the cheapest place to buy ply. I find reputable ply specialists to be cheaper. There area couple of excellant specialists here in brisbane who are helpful and offer great prices.

If all you are doing is putting a floor in a runabout surely you are only talking about a small amount of ply?................use good quality marine ply the cost difference for a small amount (even a full sheet) won't be much and the floor will probably outlast the life of the boat.

we jsut baught english standard merianati? marine plywood for the interior of out 21'er and it was about a quater of the cost of the ausie stuff. normaly i wont buy timber products form outside aus but i could not afford the amount in the aus stuff.

Meranti or luan isn't very durable. Make sure you protect it properly or it'll rot.

1088 is the british standard and as stated above not all the ply supplied out of SEA actually complies.

http://www2.dpi.qld.gov.au/hardwoodsqld/12458.html

Meranti is a complex beast.

The deep red stuff (probably heartwood) is rated as reasonably durable.

The pink sapwood ... well ... the less said.

So paint it really carefully and make sure it has good ventilations on the underside.

You could consider epoxy sealing .. but sounds like the budget is not there. So go for paint.

MIK

we are using it on the interior and supperstructure of the boat so its not in the watter all teh time. we use asu standard marine ply on the hull. everything is painted both sides so it should be no problems.

for your floor cut teh sheets out and paint it both sides and on the edges with a few coats of exterior paint or even better 2 pot marine paint.

From someone who has done it I say get a structural ply.
Reason - costs much less , is not immersed in water , going to get kicked and scratched and gauged etc so whatever you use will need repeated attention.

Ask for a waterproof glue firstly ,then ask for a few sample pieces ,of your available choices , number them, then boil them in water for 1 hour and see how they hold up .
If its waterproof glue it will not separate (and some will ).

Then as it will be removable or make it so , use only an epoxy based paint both sides and particularly coat the edges well , and the screw holes . All water entrance points should be coated . I use R180 epoxy and mix it and brush it on thinned with acetone first and then a second coat of either epoxy or epoxy based paint . Don't use polyester resin as it is porus as are most of the paints. If painting I use a polyurethane primer ,fill imperfections with micro-spheres and epoxy filler and then paint again with an epoxy based paint .

yep ... polyester resin is porous and does not stick to wood well.

i got mine form australian wood pannels.

they had a sighn on teh wall that said that the marine ply used teh same glue and everything but it was made from all clear sheets free from knots making it a lot stronger and no gaps in the side when cut. dont know how tru this was but it look good to me.

the merianati sheets were $38 each.

My choice would be pacific maple/ luan/ meranti rape & pilliage ply.

Particularly if you get a decent sheet of it. generaly it is pretty solid on the faces without knots or voids and if you paint it up properly it will be fine.

I've seen this stuff left out in the eliments for ades unprotected and as long as it can dry and isnt in contact with the ground it survives quite well.
certainly better than radiata.

to seal it up use a good solvent bassed primer thined out runny so it get in and give it several coats.......make sure the surface is well choked before you top coat.

cheers

I've had a lot of luck with pacific maple for the Mouseboats, far better quality than any 'exterior ply' I've come across for about the same price. It's more than just the glue, the timber is sort of important too.

Richard

I'm a little lost here on exactly which timber pacific maple is.
If it is Meranti (Shorea spp. Parashorea spp. in the references I have) then it is durability 4 , the worst for boat work. I used it in my house as architrave and its very soft.
Lauan is another sale name for Meranti I think

Its also durability4 if its Qld Maple.

You can look them up here
http://www2.dpi.qld.gov.au/hardwoodsqld/7680.html

This is the info for Meranti

Durability above-ground. Balau (other than red Balau) class 1 - life expectancy > 40 years. Red balau class (4) - life expectancy less than 7 years. Philippine mahogany (light red) class (4) - life expectancy less than 7 years. Philippine mahogany (red) class 3 - life expectancy 7 to 15 years. Meranti (dark red) class 3 - life expectancy 7 to 15 years. Meranti (light red) class 4 - life expectancy less than 7 years. Meranti (white) class (4) - life expectancy less than 7 years. Meranti (yellow) class (4) - life expecancy less than 7 years.
Durability in-ground. Balau (other than red Balau) class 2 - life expectancy 15 to 25 years. Red balau class 4 - life expectancy less than 5 years. Philippine mahogany (light red) class 4 - life expectancy less than 5 years. Philippine mahogany (red) class 4 - life expectancy less than 5 years. Meranti (dark red) class 4 - life expectancy less than 5 years. Meranti (light red) class 4 - life expectancy less than 5 years. Meranti (white) class 4 - life expectancy less than 5 years. Meranti (yellow) class 4 - life expectancy less than 5 years.