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Old 10 August 2010, 06:56   #1
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Coating ply - paint/varnish/gelcoat?

Just need some advice please on how best to protect and finish bare marine ply for a couple of small projects - locker and a seat base. Locker will be wet often, seat just splashing rather than immersion.

Doesn't need any addred strength of GRP just the waterproofing. Ideal finish would be grey and possibly non-slip. Simple/budget method preferred.
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Old 10 August 2010, 08:56   #2
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Just need some advice please on how best to protect and finish bare marine ply for a couple of small projects - locker and a seat base. Locker will be wet often, seat just splashing rather than immersion.

Doesn't need any addred strength of GRP just the waterproofing. Ideal finish would be grey and possibly non-slip. Simple/budget method preferred.
This is probably your most cost effective method sealing and waterproofing plywood. You just paint it in, let it dry, sand smooth, prime and then paint.

http://www.marinemegastore.com/produ...AQU_Q05170.htm

Cheers
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Old 10 August 2010, 09:07   #3
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Flocoat with a small foam roller. Two coats will look superb.
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Old 11 August 2010, 01:52   #4
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Thanks chaps.
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Old 13 August 2010, 23:53   #5
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A lot of guys on some of the wooden boat builders websites are big fans of shellac. It dries superfast, waterproofs nearly as well as polyester resin, won't laminate like polyester, and is a great primer for all kinds of paint.
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Old 14 August 2010, 02:52   #6
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As stephen said:

http://www.cfsnet.co.uk/cgi-local/sh...#aUDAG4D_2d001
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Old 14 August 2010, 04:43   #7
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Flocoat with a small foam roller. Two coats will look superb.
Mollers, have you done this? If so, have you had any problems with cracking? When I did my consoles and seats, I coated all the bare wood in 2-3 coats of neat epoxy. I was wondering the other day why I hadn't coated it all in nice thick flocoat but I came to the conclusion that the flocoat, when set is not flexible and so would be prone to cracking under expansion and contraction of the wood. Epoxy allows the wood to breathe and expand. This could be a load of crap, but I'm sure this is what I was advised at the time.

Cheers,

Tim
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Old 14 August 2010, 04:54   #8
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Yeah, I re-made the transom plate for the Searider. It made for a very smart job. There's a big difference between purely coating ply and glassing over ply. If the ply involved is in anyway structral of liable to flex, it'll need to be glassed-in not just flocoated.
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Old 14 August 2010, 04:56   #9
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Mollers, have you done this? If so, have you had any problems with cracking? When I did my consoles and seats, I coated all the bare wood in 2-3 coats of neat epoxy. I was wondering the other day why I hadn't coated it all in nice thick flocoat but I came to the conclusion that the flocoat, when set is not flexible and so would be prone to cracking under expansion and contraction of the wood. Epoxy allows the wood to breathe and expand. This could be a load of crap, but I'm sure this is what I was advised at the time.

Cheers,

Tim
My anchor locker was done like it (2 coats of flowcoat only). It cracks when it flexes (as Mollers said above)-mine is falling off in lumps and waiting for me to fix it. The Bonda G4 works well though but make sure it's in date and properly liquid when you buy it as it goes hard in the can.
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Old 14 August 2010, 06:10   #10
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Wotcha need to preent cracking is 10-20% flexible resin added to your mix and wax to ensure the resin dries tack free. Wipe the ply with thinners to degrease its surface. It's equally possible to use just flexible resin but it's slightly soft, not squidgy soft but just not so hard. None of these surfaces is grippy tho, they're actually quite slippery.
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Old 14 August 2010, 07:31   #11
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JW, are you saying you can mix this flexible resin (by this I assume you mean normal polyester resin?) to flocoat? I would like the inside of my console and bench seat to be white and hard wearing, not wood coloured as they are now with just the epoxy coating. The other problem I may face is coating over the top of the epoxy with a polyester based resin/flocoat, will that cause problems? I assume the waxy residue that rises to the surface when the epoxy cures can just be sanded back.

Sorry to hijack the thread, but its all relevant I guess
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Old 14 August 2010, 07:40   #12
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Wipe the ply with thinners to degrease its surface.
I'd opt for acetone which leaves no residue after evaporation. I tend to blow the area over with a hot airgun to get rid of the acetone.
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Old 14 August 2010, 13:45   #13
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JW, are you saying you can mix this flexible resin (by this I assume you mean normal polyester resin?) to flocoat?
It's not normal laminating resin, it's flexible resin. You can cast a lump of it and it will bounce if you drop it. You could actually throw it at a concrete floor and it'll bounce. It is softer, as you can imagine and it doesn't hold a shine as well as a normal gel coat but it has it's uses. I don't buy flocoat, I make it up to suit the job. Mollers I respect your choice of acetone but personally I've stopped using it long ago. Spirit wipe and standard thinners depending on application for me.
Slimtim, if the resin is well cured it will be necessary to sand it to achieve a key.
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Old 14 August 2010, 15:06   #14
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After starting this topic and back-searching dozens of others there seemed to be so much conflicting advice. I range cfs about this a few times, also resin-supplies.co.uk and another supplier too - all agreed that the only pro way to do it is to:

1: seal the ply (bondaclear G4 etc)
2. glass with at least two layers of csm
3. flocoat on top (with non-slip additive if required - for top of anchor locker in my case).

Preferably all done wet on wet for the best result.

I pressed them on short cuts, ie is glass really needed as the structure itself provided the strength but all said as above without this it will be short term and crack up.
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Old 14 August 2010, 21:04   #15
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If you want a quick but very durable solution then use neat epoxy. Coat it on like varnish and the first coat will soak into the first bit of ply sealing it. After an hour or so (check with CFS, it might not be that long) you can re-coat again (repeat 2-3 times). If you leave it too long, the epoxy will cure and you will get a waxy coating on top that will need to be removed with acetone and a quick rub with sand paper. I've used it on seat bases and inside my consoles and its stood the test of time very well. For your application I think glassing is over kill, I did this on the outside of my console, but I wanted a bit of extra strength and durability.

JW, thanks for the tips, helpful as always
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Old 15 August 2010, 01:50   #16
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I should edit the advice I was given and say that it was wet on wet until the last glass which should be allowed to fully cure then sanded back to remove any fibres sticking out before the flocoat.

Slimtim - thanks for the advice. So is epoxy more flexible then and unlikely to crack?

I thought about just using a few coats of G4 sealer on the ply and then a few coats of non slip deckpaint on top of this. Is this likely to last? Does the deckpaint need an undercoat or another primer or will it go straight on top of the G4?

And what would be the best G4 product to use that can be used as a sealer and top coat varnish if necessary?

CFS recommended pond sealer at first but out of these?

http://www.cfsnet.co.uk/acatalog/CFS...Clear_527.html
http://www.cfsnet.co.uk/acatalog/G4_Damp_Seal.htm
http://www.cfsnet.co.uk/acatalog/CFS...aler__519.html
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Old 15 August 2010, 06:30   #17
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The epoxy works just like a varnish, being flexible and allowing the wood to expand and contract but its much more durable. It would be perfect for the seat bases.

As for the locker, are you making like a wooden box? If you want it grey in colour rather than wood/varnish type finish then you could use some sort of international paint. I used Brightside on my console. Can be quite time consuming to get a nice finish though. The other option as discussed previously is to glass the outside. Check out the first post (and there are some other posts later on) on my thread here:

http://rib.net/forum/showthread.php?...student&page=7

Hope it helps.

Cheers,

Tim
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Old 15 August 2010, 06:51   #18
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Quote:
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As for the locker, are you making like a wooden box? If you want it grey in colour rather than wood/varnish type finish then you could use some sort of international paint. I used Brightside on my console. Can be quite time consuming to get a nice finish though. The other option as discussed previously is to glass the outside. Check out the first post (and there are some other posts later on) on my thread here:

http://rib.net/forum/showthread.php?...student&page=7

Hope it helps.

Cheers,

Tim
Thanks Tim, yes, a top and front piece, sikaflexed with SS screws and a batten inside and the whole thing Sik'd to the inner side of the hull so plenty of strength there. Finish needs to be non-slip grey.
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Old 15 August 2010, 12:00   #19
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Another product (more expensive) but definitely more bullet proof is SP Systems EpoSeal.

If one was to go down the road of sheathing the plywood then I would use SP106 and some glass cloth.
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