Leave plywood bare?

[Inselaffe]

Hallo!
I just got a piece of 1 1/2" (40mm) thick plywood for a new sill for the well where my outboard sits.
The very knowledgeable and helpful guy in the joinery told me that it was what he normally gave people for outboard mounting.
I asked him about varnish and he said that it wouldn't be necessary - although it might be 'kaput' after about 20 years.
I'm just not sure about leaving the wood bare- even if it is cheap to replace, it's a bugger to change over. Also, I was talking to him in German so I might well have missed something...
Are there marine plys that don´t need protection, or was he talking about the glue only?
If I do have to protect it, I thought of giving it a coat of epoxy or polyester, to avoid revarnishing, but are there any problems with oils in the wood or anything else?
The ply is light in colour.

I would go back and ask him again but last time we had a nice long chat about football and how he admired the English team, and I'm not in the mood for that today....




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[Georgio]

it will take a long time to break-down but I would give it a few coats of varnish just to keep it looking clean/tidy, this will also protect it when oil/petrol is spilt.

I have heared a few cases of the wooden pad onwhich an outboard has been mounted becoming rotten from the inside out. Looked fine from the outside but broke when given a suitable wack. Gonna be replacing mine now as it's probably origional (25yrs old).

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[richardandtracy]

The stuff shouldn't delaminate if using a WBP glue [as in marine or shuttering ply], but it may rot. Best to protect it in some way - eg Ronseal 5 year wood stain or varnish. If you just regard it as sacrificial it won't cause you too much grief should the protection flake off or fail.

Regards

Richard.


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[mirabriani]

In addition to Giorgios advice why not edge it in hardwood using West or similar epoxy resin? It will look better and the end grain will be sealed.
Briani

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[Colinl]

Having had mine split in half and the engine go for a swim seal it as Briani outlines

Colin

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[oldharry]

Anyone who has owned and maintained a plywood boat will agree that leaving plywood bare is a big no-no. If the ply has all hardwood laminates, that is OK but the end grains will need protecting as water will seep in. If rot does not start then the next big freeze up will split the ply and cause delamination.

Any timber needs protecting from the elements if it is to last - plywood more so.

If the sheet has softwood interior laminates, which is standard in all WPB grade plys, then these MUST be protected or they will fail very quickly, and you will have the unhappy situation of a ply sheet which looks solid outside, but is in fact rotten inside, and you will be able to insert a screwdriver down the laminates. O/Bs are too expensive to risk falling off!

If you really do not want to paint, then use solid timber. One of the worst ply killers is coating with polyester GRP. Polyester resin does not stick well to wood and will soon detach allowing water to enter and giving ideal rot conditions.

Epoxy coating is fine, but it is essential to ensure the coating is not pierced either by fastenings, or by accidental damage, as the water then enters and rot starts up again.

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[AndrewB]

Absolutely right. It'll look awful after one season and be dead by the end of two if a decent coating isn't applied.

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[oldsaltoz]

G'day Inselaffe,

A little time, effort and dosh now will add many years to the life of your timber.

If you cut and dress it to the required shape and finish, then soak it in one of the water based anti rot brews, let it dry; then apply a coat of epoxy resin thinned with Metho then apply two normal coats. Next trim the edges with hard wood and glue it on with an epoxy glue; you also need to apply a coat of paint to protect the epoxy from UV.

This will last many years, if you have to drill it to fit securing screws or bolts, drill the holes 6 mm oversize, fill them with epoxy resin and a solid filler like talcum powder [not fibres] and redrill to the req'd size, this will provide a seal to prevent water ingress.

Avagoodweekend........



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[Inselaffe]

Thanks for the replies,

But, since the wood is only bolted on and cost about 5 Euros (and because I am a lazy sod) I have just varnished the board repeatedly and will wait till end season to do a proper job.

A couple of Q's to Oldsaltoz,
What is Metho? Is it methylated spirits (brownpaperbagintheparkdrinkingwithabighangover)?
Also why not seal the holes with fibres as a filler to the epoxy? is it to stop wicking or something?

Thanks again

leigh

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