Epoxy ?

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Epoxy ?

Postby t4camper » Mon Oct 20, 2008 9:09 am

Can someone please enlighten me when you talk about epoxy coating your wooden Tears am i to assume you are talking of the following...

I would take that to mean you cover it with what we would call here in the Uk anyway fibreglass resin, which i would imagine would totally water seal and wooden parts if done well.

Or have i missed the point completely ???

Also is there anything that is required to do to the wood prior to "epoxying" it then as in prep..

Pressuming it is fibreglass resin you speak of can it be coloured so as not to show trhe wood below as my VW camper which will be towing it is white it would be nice to have it white to match..

Uk stockists of such materials would also be of great assistance.

One last question being pressuming i go for a wooden construction where the roof meets the side walls or front and back walls the top sheet would obvioulsy go over the side wall Yeh ? and then know matter how good you were there would still be a gap of some sort what do you do with this all be it small gap, in order to keep water out !!!!, my thoughts would be to fill it full of seam sealer as used in motor trade or caravans and fibreglass sheet over the top of it, rubbing down until totally smooth, am i right is there an easier way or am i just plain crazy ????

All assistance appriciated of course, bear with me i'm only learning
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Postby madjack » Mon Oct 20, 2008 10:08 am

...the short answer to your questions...there are two types of resin...polyester and epoxy...I don't know about terminology across the pond but over here, something labeled as fiberglass resin would probably be polyester based and is not preferred...epoxy resin is a better choice and easier to work and more effective at repelling the elements...neither resin, in and of themselves is UV resistant and needs a top coat of some sort of UV resistant finish...over here, the choices are usually auto paint/clearcoat or a UV resistant urethane or urethane based(marine topside) paint...be sure to seal all ply edges very well...gap fillers can be wood putty(not preferred because of shrinkage) Bondo(auto body filler) or thickened epoxy...it is not necessary to cover the top with fiberglass cloth/resin combo...the epoxy resin is OK by itself.....
madjack 8)

p.s. here is a good place to start.......MJ
http://tnttt.com/viewtopic.php?t=18512
http://www.steve-frederick.com/index3.html
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Postby t4camper » Mon Oct 20, 2008 10:15 am

madjack wrote:...the short answer to your questions...there are two types of resin...polyester and epoxy...I don't know about terminology across the pond but over here, something labeled as fiberglass resin would probably be polyester based and is not preferred...epoxy resin is a better choice and easier to work and more effective at repelling the elements...neither resin, in and of themselves is UV resistant and needs a top coat of some sort of UV resistant finish...over here, the choices are usually auto paint/clearcoat or a UV resistant urethane or urethane based(marine topside) paint...be sure to seal all ply edges very well...gap fillers can be wood putty(not preferred because of shrinkage) Bondo(auto body filler) or thickened epoxy...it is not necessary to cover the top with fiberglass cloth/resin combo...the epoxy resin is OK by itself.....
madjack 8)



Madjack - thanks for that it seems a little clearer although still not quite sure, the bit about the edges i fully understand and is infact what i had thought.
So epoxy then if i understand now is not fibreglass resin but rather a very hard wearing varnish i take it.
As for excessive uv we dont get anymore than 2 days of moderate sun a year here in Scotland so i doubt i have to worry all that much.
Would it seeing as how we suffer a lot with rain here in gales ridden [today] Scotland be better off at the seams installing some sort of beading to deflect water away from the seams rather than onto them.
One last thing would i then be better searching for yaght type paints etc to finish with... to get colour and for that matter as a high quality undercoating ????
Slanj
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Postby madjack » Mon Oct 20, 2008 10:54 am

fiberglass resins come in two types...polyester and epoxy...epoxy is superior to polyester...polyester is widely used/sold in the big box and hardware stores over here and is usually labeled as "fiberglass resin"...they are BOTH fiberglass resins and it a marketing/terminology thing...fiberglass cloth "tape" can be used to completely seal edges or just multiple coats of epoxy...ever here, we often use an aluminum angle or RV type trim to cover and seal the edges...a marine topside(urethane based) paint is an excellent finish coat, which will give both the color and UV protection you need...it can be applied directly to "scuffed" epoxy...UV rays penetrate clouds and rain...even in the UK or Scotland!!!!!!
madjack 8)

p.s. if you are not familiar with using epoxy resins, I would highly advise reading the manuals I linked to and any info from Steve Frederick or Doug Hodder on this subject is invaluable.......MJ
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Postby Rock » Mon Oct 20, 2008 11:04 am

Check here for info http://www.systemthree.com/index_2.asp

Just finished using their epoxy products to build a boat from 4mm plywood, fiberglass cloth and epoxy. A 17 ft. long kayak that weighs less than 20 kg. See http://www.pygmyboats.com/Construction.htm

The epoxy will seal the seams, the face of the plywood and the edges of the plywood with no need for any other filler. The edge grain of the plywood may take a couple of coats as it will soak up the epoxy.

As jack says the epoxy is not UV proof and will weather and turn chalky over time. In Scotland that may be a lifetime, however. Still a varnish with UV blockers is a good idea. Just make sure to contact the epoxy manufacturer for recommendations - not all finishes are compatable.

Hope his helps.
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Postby vrooom3440 » Mon Oct 20, 2008 11:05 am

The major difference with respect to fiberglass resins, is in how they are cured.

With epoxy you generally mix ratios of a resin and hardener which chemically combine as the resin sets. The ratio of the parts is actually rather critical as too much of one or the other just leaves soft gooey excess stuff. Further epoxy can be chemically engineered to provide different cure times. The real beauty of epoxy is that it cures all on it's own and NO AIR IS REQUIRED. Epoxy tends to be less odorous but can cause allergic reactions with repeated exposure.

The most common and least expsensive, at least in the US, fiberglass resin is polyester based. In this case the cure process is heat-based. Some very small by volume catalyst is mixed in to trigger a chemical reaction and generate heat to cure the polyester. Thus cure, and by inference working, time can vary by temperature and amount of catalyst mixed in. It can also vary based on the radiation of the generated heat and cooling affects. Since the resin does not radiate heat well on it's own, resin mixed in a container will cure MUCH faster than resin on a project. It can even generate enough heat to melt plastic containers.

Note that there are two different kinds of polyester resins: laminating and finishing. The difference is finishing resins contain some amount of wax. The function of the wax is to rise to the surface and protect it from air. This has the affect of keeping heat at the surface and allowing it to fully cure. It also causes adhesion problems between laminations if the resin cures between laminations. Which is why there is a laminating resin. But note that laminating resin will have a tacky surface because of the slight layer of uncured resin.

Note that the two types of resins are generally NOT COMPATIBLE with each other. Polyester tends to not cure over epoxy but you MAY get away with epoxy over cured polyester.

Note that, as previously stated, fiberglass composites do not last with sun/UV exposure. They also can have problems with heat from sun exposure and thus should be painted with lighter reflective colors.
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Postby Mini Renegade » Mon Oct 20, 2008 3:58 pm

Dougie, the epoxi these guys are talking about is really good stuff. The only down side is 1L is £90!!!!
I spoke to a boat builder who suggested mixing varnish and white spirit 50:50 and applying in liberal coats witha sand in between. It soaks in and sets hard as well as filling in the grain.
I coated an offcut of 5mm bendy ply (luan) twice, let it dry then split it. It had soaked right throughthe top ply (2mm)
thats my 2p :)
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Postby madjack » Mon Oct 20, 2008 7:29 pm

Mini Renegade wrote:Dougie, the epoxi these guys are talking about is really good stuff. The only down side is 1L is £90!!!!
I spoke to a boat builder who suggested mixing varnish and white spirit 50:50 and applying in liberal coats witha sand in between. It soaks in and sets hard as well as filling in the grain.
I coated an offcut of 5mm bendy ply (luan) twice, let it dry then split it. It had soaked right throughthe top ply (2mm)
thats my 2p :)


OMG...90pounds forra litre..I paid 150USD for a 3 gal setup...and I thought that was expensive......... 8)
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Postby angib » Tue Oct 21, 2008 3:26 am

Yep, we just don't have access to cheaper epoxies over here - I don't know why.

Scotland does definitely not have low enough UV that you can leave epoxy unprotected - sure, it'll take twice as long to fail as it would in the Mediterranean, but it'll fail just the same.

If you want a painted finish, the expense of epoxy is hard to justify unless you want the trailer to have a twenty or thirty year life. If not, going with a full marine paint system as used on a boat would be a good alternative - and you could get it from a local supplier who might offer you decent advice too.

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Postby glider » Thu Oct 30, 2008 2:42 pm

Hi dougie.

I dont realy know what it is that you are looking for but I think that this may be what you mean. http://marinestore.co.uk/Merchant2/merc ... tems-epoxy
I think, though i may be wrong that this is the same as CPES (clear penetrating epoxy sealer) a solvent-based, low viscosity epoxy primer.
worth a look I think.

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