waterproof Plywood

   Our club Wayfarer needed new bottom boards. It's on a drying mooring on a slope so the aft end of the boards are often wet and also when we don't pump it out. 

We brought 10mm ply from local builders merchant and coated it with 4 coats of this:
https://www.screwfix.com/p/no-nonsense-water-repellent-seal-clear-5ltr/57474

They had an extra coat each year and apart from looking rough there is no delamination.

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Riv Send Private Message Find Member's Posts Far too distracted from work Joined: 23 Nov 13 Location: South Devon Online Status: Offline Posts: 353	Post Options Post Reply Quote Riv Report Post Quote Reply Topic: waterproof Plywood Posted: 15 Mar 19 at 5:11pm
	Our club Wayfarer needed new bottom boards. It's on a drying mooring on a slope so the aft end of the boards are often wet and also when we don't pump it out. We brought 10mm ply from local builders merchant and coated it with 4 coats of this: https://www.screwfix.com/p/no-nonsense-water-repellent-seal-clear-5ltr/57474 They had an extra coat each year and apart from looking rough there is no delamination.
	Mistral Div II prototype board, Original Windsurfer, Hornet built'74.

ColPrice2002 Send Private Message Find Member's Posts Far too distracted from work Joined: 25 Nov 08 Location: United Kingdom Online Status: Offline Posts: 222	Post Options Post Reply Quote ColPrice2002 Report Post Quote Reply Posted: 15 Mar 19 at 7:47pm
	A couple of coats of epoxy resin, couple of coats of good varnish, last coat sprinkled with granular sugar. Allow to set/dry between coats, then wash the sugar off. You'll have a non-slip coating, and it will last - it's worked on our Wanderer floor boards for many years. Colin

davidyacht Send Private Message Find Member's Posts Really should get out more Joined: 29 Mar 05 Online Status: Offline Posts: 1345	Post Options Post Reply Quote davidyacht Report Post Quote Reply Posted: 15 Mar 19 at 9:55pm
	Robbins Timber for marine ply. On a previous boat I edge sealed with epoxy, then coated with Deks Olje which worked fine.
	Happily living in the past

pij27 Send Private Message Find Member's Posts Groupie Joined: 27 Jul 10 Location: Ryde / Tilbury Online Status: Offline Posts: 44	Post Options Post Reply Quote pij27 Report Post Quote Reply Posted: 18 Mar 19 at 8:55am
	Thanks, will look into the sealant from Screwfix. Sounds like sensible thing to do first is to seal the edges and then either paint and varnish or epoxy then paint.

snowleopard Send Private Message Find Member's Posts Visit Member's Homepage Groupie Joined: 02 Oct 17 Location: Cornwall Online Status: Offline Posts: 66	Post Options Post Reply Quote snowleopard Report Post Quote Reply Posted: 18 Mar 19 at 10:30am
	The big problem with ply these days is it's hard to know what you're getting. Cheap ply with inferior glue, made in China, has flooded the market. It disintegrates in a year or two. It is often marketed as 'waterproof', 'exterior' or 'marine' but is all the same stuff and it doesn't match up to the old BS1088 standard. Don't touch 'exterior' ply from builders' merchants. Go to a reputable supplier of marine ply such as Robbins and ask them to guarantee that it meets BS1088. In order of quality/durability, varnishes are : Epoxy 2-pack polyurethane 1-pack polyurethane Genuine marine varnish DIY store varnish. The big joke these days is stuff bought in DIY retailers labelled 'Yacht Varnish' with small print saying 'not suitable for marine use'!
	One hull good, two hulls better.

pij27 Send Private Message Find Member's Posts Groupie Joined: 27 Jul 10 Location: Ryde / Tilbury Online Status: Offline Posts: 44	Post Options Post Reply Quote pij27 Report Post Quote Reply Posted: 19 Mar 19 at 7:54am
	Thanks for the advice, will look at the ply and if not right will change it, looks like seal it with epoxy and then use a decent yacht paint, maybe bilge/locker paint?