Is Marine Ply real?

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richardabeattie

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I'm about to replace my clapped out and delaminating cockpit seats which are some sort of faced ply with hard wood edging and nearly 40 years old. (So I am not going to send any complaint to the builders, MarCon!) But is modern marine ply really sea proof? If not then what does the panel advise? I do not want to make the seats from planks or from synthetic material. And what should I use to seal them - Woodskin?
 
Proper marine ply is - but there's a lot out there which is not what it claims to be.

Robbins Timber in Bristol will supply you the right stuff, at a price, if you let them know what it's for.

Pete
 
richardabeattie said:
I'm about to replace my clapped out and delaminating cockpit seats which are some sort of faced ply with hard wood edging and nearly 40 years old. (So I am not going to send any complaint to the builders, MarCon!) But is modern marine ply really sea proof? If not then what does the panel advise? I do not want to make the seats from planks or from synthetic material. And what should I use to seal them - Woodskin?
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Yes it is real but you need to buy it from a decent supplier rather than the rubbish sold at B&Q/Wicks/etc.

Do yourself and your boat a favour and browse the Robbins Timber website and catalogue. Top quality Plywood and almost any other type of wood. Yes, decent marine ply is expensive, but it lasts. Robins will deliver and supply 1/2 sheets if necessary.

http://www.robbins.co.uk/
 
richardabeattie said:
I'm about to replace my clapped out and delaminating cockpit seats which are some sort of faced ply with hard wood edging and nearly 40 years old. (So I am not going to send any complaint to the builders, MarCon!) But is modern marine ply really sea proof? If not then what does the panel advise? I do not want to make the seats from planks or from synthetic material. And what should I use to seal them - Woodskin?
Click to expand...

Oh is it a Trident by any chance, they were MarCon built, and from experience their ply (or the ply that they used) lasted very well, but then Boats and Yachts were really built to last :)
 
I'm still skeptical as to whether there is really any difference today between 'marine ply' and any other GOOD quality ply of similar specification (number and grade of ply, type of timber, etc). The 'marine' description was in use long before modern synthetic glues, and may have had relevance back then.
 
I think the enemy is "voids" not the particular glue. My experience is that all ply will fail pretty quicky if not edge-sealed, and lots of fairly cheap ply will last if edge-sealed. You can edge-seal by lashing on epoxy or varnish. Epoxy will degrade with UV and any coating like this will chip. You can do better by lipping the edges. If you bore a hole and put in a screw water will get into the edges created, so you have to dip the screw in sikaflex or equivalent. I have a hatch that was made from cheap far-eastern ply 12 years ago and shows no signs of degradation. I think that once water has got in, the voids in cheap ply make degradation much more rapid. Of course it goes without saying that the surface must also be sealed.
 
Use synthetic materials, why people insist on using wood (or metals) when far more economical marine appropriate materials are available is beyond me. Wood is pretty and easy to work I agree but still....
 
Ok, I am ready to be shot down, but I looked into this when I built a stitch and glue canadian style canoe.
The only difference between good exterior ply and marine ply is the glue used.
Marine glue resists water.
There is no guarantee about voids being less prevalent.
Cockpit seats are neither structural nor constantly immersed in water so I personally don't feel the expense of exterior ply is justified.
 
I'd heard a variety of things regarding mystical Marine ply.

1. all ply glue is waterproof
2 the guarantee of voids is the difference
3 Marine ply is made of hardwood.

No idea if any one of the above are actually true, but it's what people have told me at various times in the past.
 
Slight thread drift but what would you use to build the carcasses for the galley. I think carpenter was talking about Robbins Elite which i thought was OTT?
 
Let me start by stating that I have spent the 40 years devising ways to get out of using ANY timber in or on a boat.

Having said that I can assure you that timber can be utilised but at a cot and with lots of maintenance.
I'd rather be sailing thanks.

The project you have on hand is very strait forward but there are a number of very important items that MUST be correct to perform at their best.

The ply or timber MUST be dry, any moisture trapped inside after treatment WILL cause problems.

The design should include sacrificial edges and the fixings for the edges MUST be into anything but the timber, by this I mean any fixing screw, bolt or whatever must no contact the timber, holes MUST be predrilled oversizr and re-drilled after setting and a sealant used when securing.

I personally have had very good results with solvent free Epoxy resins. Taking great care to ensure the timber is very dry and the timber is warm to hot when the epoxy is applied. The end grain or ply edges need a lot of attention to ensure the edges/ ends are well soaked and sealed. Best to apply wet on tacky to avoid sanding between coats and for an improved bonding.

Finally, it's critical that the epoxy coating is well protected against UV light exposure. Only Varnishes with a very high UV rating should be used and lots of it.

I take my hat off to all you lovely people who have the most beautifully maintained timber on their boats. Beautiful hardly describes how fantastic they look.

Keep up the work, meantime that's me on the horizon.

Replaced some timber on the foredeck of the cat about 8 years ago, using that enviro' stuff, recycled rubbish. Gave it coat of average paint and till looks great.

Good luck and fair winds. :)
 
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stu9000 said:
Ok, I am ready to be shot down, but I looked into this when I built a stitch and glue canadian style canoe.
The only difference between good exterior ply and marine ply is the glue used.
Marine glue resists water.
There is no guarantee about voids being less prevalent.
Cockpit seats are neither structural nor constantly immersed in water so I personally don't feel the expense of exterior ply is justified.
Click to expand...
Quite the reverse, unless completely covered with some sort of tent, cockpit seats are constantly wet from rainwater and bombarded by that other destroyer, UV light.

I had this problem with a Trapper 500, the cockpit seats, made from teak frames, had teak-faced plywood tops that eventually delaminated. I replaced with high-quality, exterior grade, 6mm ply, epoxy sealed with emphasis on all edges. I then covered with Tek-Dek simulated teak, adhesively secured to the entire surface, that no one would believe wasn't real teak planking. It was still perfect many years later when I sold the boat.

BCHCMBR6.jpg
 
chrisbitz said:
I'd heard a variety of things regarding mystical Marine ply.

1. all ply glue is waterproof
2 the guarantee of voids is the difference
3 Marine ply is made of hardwood.

No idea if any one of the above are actually true, but it's what people have told me at various times in the past.
Click to expand...

1. is not true. Plenty of ply out there which will delaminate if it sniffs water.
2. Marine ply should have below a certain % of voids. The last lot I bought had none at all, and was not expensive.
3. Marine ply should have durable inner laminates

And good exterior and marine use the same glue.
 
I agreeto some degree about the scepticism and uncertainty regarding marine ply. I wanted a couple of sheets to reinforce my detatching rear bulkhead but baulked at paying Robbins prices circa £150 a sheet and I looked around. Some I looked at a large suppliers had obvious voids at the edges although marked with all the suitable markings andnsome even showed early signs of delamination in the shop. I eventually went for a reputable wood supplier at £60 a sheet who gave a detailed wood spec on their web site as Eucalyptus, which is used extensively in the east and Australia for marinme purposes. When I went to collect the wood I spoke to the people in the sshop who did not know what the wood was and appeared unaware ofthe website details. Anyway it looked ok at the edges, felt hard to probe and was suitably flat and without obvious blemishes. Having boiled a piece for a few days and then left it out int he rain for a couple of months it seems to be coping ok so I am reasonably happy but I do understand the concern and uncertainty. I think the advice about sealing all surfaces and edges and holes with epoxy and using bolts rather than screws is good advice.
 
Bruynzeel plywood is some of the best. Can be obtained from Timbmet, but there are others - I managed to get a local supplier buy some in without any trouble at all; you just need to know what it is you want in order to have an intelligent conversation with them....

With regard to Robbins - from personal experience their stuff is disgustingly overpriced and no better than the Bruynzeel (maybe in fact not as good). I would never use them again.
 
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