View Full Version : ply on top of ply...

05-31-2012, 05:40 PM
I have just stripped back to the wood, a ply deck on a 20 ft runabout. the intention was to simply strip, sand, revarnish, but as the wood is so scarred and discoloured and with so many little defects and I have decided to 'laminate' a new 4mm marine ply layer on top as the cost of three 8 x4 s is a lot less than hours of sanding and prep ...starting from scratch so to speak..... I intend to screw the new sheets down as well as glue, and my question is, what glue..? water resistant PVA is available and cheap, poly ureythane is almost impossible to find and 20 beerbtokens for 250 ml or something crazy, when you do find it... cascamite / urea/ wetmix casein glues I used when I built the boat twenty years ago, and they have failed..... any ideas ... epoxy ? expensive no? go to it guys...

05-31-2012, 05:51 PM
thickened epoxy

05-31-2012, 05:55 PM
Yup, epoxy. Forget the screws and weight the new deck down with sandbags. You'll get more even contact than with screws.

wizbang 13
05-31-2012, 06:24 PM
same answer

05-31-2012, 06:26 PM

05-31-2012, 07:11 PM
So it looks like Poxy... I can get resin and hardener as sold for glassing up stuff with matting or weave, quite cheaply, car shops etc but once I start off down to the boatyards its crazy money even for only a few square metres, in epoxy resinglue..'araldite' for instance..
Can I use the fibreglass resin mix without the matting, as a glue...??. should I prep the two mateing surfaces first with some kind of primer.... tanx guys

05-31-2012, 08:28 PM
The new plywood should get a coat of neat epoxy, let it tack up and then glue on with thickened epoxy (I like woodflour about like catsup) However, if the hull has paint, and I guess it does, you need to grind that off and probably give it a coat of neat epoxy too before assembly. If you do not there is a likelyhood that the bare wood will suck the epoxy out of the mix and you will have a poor joint, if you leave the paint you will have a poor joint too I am afraid.


05-31-2012, 08:37 PM
If you are getting resin from a car place make sure it is epoxy not polyester.

05-31-2012, 09:06 PM
"If you are getting resin from a car place make sure it is epoxy not polyester."

Yep, the terminology is f^c^#d& up. Pl Premium with a notched trowel, fastenings you can remove after a week! / Jim

05-31-2012, 09:19 PM
Use thickened West System epoxy. Do not use Polyester car or general purpose epoxy resin.

+1 on the sandbags...maybe use a few screws to orient things and then press with sand bags...

06-01-2012, 02:51 AM
thanks for the advice everyone, just one question ....why not polyester, as there's no exposed edges just maybe 2-3 sq mtrs of flat raw ply on totally cleaned old bare ply....

06-01-2012, 02:57 AM
I like the sand bags idea, sounds like a good way to get a decent even pressure without having to think about hundreds of little staple holes.

06-01-2012, 03:24 AM
thanks for the advice everyone, just one question ....why not polyester?
Polyester does not work well as a glue, epoxi on the other hand works very well.
It's all about surface adhesion...

John Meachen
06-01-2012, 04:50 PM
Be glad you didn't find polyurethane glue.With thin skins it foams and bulges unless you can apply a lot of even pressure.Epoxy will do the best job even if it is a bit expensive.Polyester is ok for holding moderately heavy glass laminates together but is no glue.

wizbang 13
06-01-2012, 11:10 PM
polyester is not an adhesive, it just gets hard