Saturating Epoxy on Plywood

[the1much]

try it on a scrap,,,half 1 way half the other,,then after curing, cut it in half and see which way worked better,,, then let me know so i can pick the right side,,hehe

 

[Landlubber]

at the end of the day, the pores are sealed, dry rot (actually wet and living), cannot survive without heat, moisture and oxygen, like a fire (fuel, oxygen heat) remove one of them and the others do not exist.

 

[Meanz Beanz]

All I can say is Everdure works... maybe not for the reason's I thought but damn it, it works

 

[PAR]

The coating must do two things to work, stay stuck and limit moisture vapor ingress below levels where rot and movement from moisture gain can become issues.

Several manufactures and plenty of outside sources including myself have preformed these "penetration" tests. The net results are not the amount of penetration, but the ability for the coating to resist moisture vapor penetration and remaining stuck to the substrate.

Keeping an intact coating is the real test of any product. In this vain diluting epoxy with solvents, in an effort to increase penetration, just decreases the epoxy's ability to resist moisture vapor penetration.

In other words, all the major brands of regular epoxy produce a 100% solids product, when cured. This has been found to be the best at resisting moisture vapor penetration, so long as it's not breached. If you thin epoxy, the grip is weakened and the epoxy isnt's as able to resist moisture vapor as it was when it was unthinned.

Of course this had to piss off all the CPES and similar products folks, who have for years used a thinned epoxy as a base under paint and in restoration work. I learned this on my own, but recent tests by West System confirmed what I've know for some time.

If using epoxy as a moisture barrier, then don't thin it, the penetration thing doesn't matter, just how intact the coating is matters. If you keep the wood sealed with epoxy, it should last for many generations.

If you want to increase penetration of epoxy, then use the "hot on hot" method, which will increase penetration a fair amount, but you'll still have a 100% solids cure, which resists mosture.

 

[the1much]

makes perfect sense to me,,,,,,,,,,,,,,,,Ya what he said
hehe

 

[Landlubber]

yes, except the solvent evapourates and leaves 100% solids anyhow, just further in, and a thinner layer than you put on.

That is common knowledge , the reason 100% solids are used is so that there is less (no) shrinkage of the wet layer, put on 100microns, you get 100 microns (on a piece of glass anyhow), the solids are what remains after the solvent has evaporated when not using solventless resins.

 

[Butch .H]

Thank you PAR

 

[Blastoff]

I was just going to say BE CAREFUL with heating epoxy it will go off on you.
I am going to fiberglass the the hole project when I start so now My question is:
Do I just put the cloth and epoxy on the plywood or should I coat the wood first with something else ???
What I am trying to say is would the first coat of fiberglass stick to some kind of treatment first or do you just go ahead and fiberglass the raw plywood ???
I would like to use carbon fiber for the top deck just for looks.

My last project went Mach 3.1 until it glitched
http://www.rockethigh.com

 

[PAR]

Solvents added to epoxy to decrease viscosity also decrease the molecular cross link during the reaction. This dramatically weakens the epoxy, which in turn lessens it's moisture vapor penetration ability.

Please, don't believe me, most of the major brands have conducted tests and the results didn't surprise any of the chemists, but did piss off the advertising departments of several "penetrating" products. Try the West System web site, www.westsystem.com (industry leader).

Better yet, get a couple of balsa blocks, say 4" square. Scallop out a few tablespoon size chucks from one side to make a depression. Coat the thing in your favorite thinned goo, then coat the other in regular laminating epoxy (unthinned of course). Let them cure, then weigh them carefully. now fill the coated depression with water and keep it full for a month. Empty them, dry any drips or drops, then carefully weigh them again. This is a reasonably accurate assessment of how much moisture gain you can expect in a comparative measure of the two.

I used a similar test and a "vessel" test, which is a captive method. Both proved much higher moisture resistance with unthinned laminating resins. How much higher? Some brands where 20% lower in moisture resistance, meaning that they were about the same as varnish and a little worse then shellac at preventing moisture vapor penetration.

Blastoff, you should coat the plywood first, sealing it. There are many previous threads on this subject, you may want to employ the search tool. You can do this all at the same time, if you proceedures are right.

Carbon fiber is lovely, but doesn't like to be exposed to UV for very long, before it starts breaking down and changing color (a sure sign it is). It will need UV protecting topcoats (varnish or one of the polyurethanes).

Use slow or super slow epoxy when using the hot on hot method. West System 105/209 will give you 20 - 30 minutes of pot time at 100 degrees.

 

[Blastoff]

Priceless !!!
Thank you PAR
I have not started my build yet, Just collecting info.

 

[Meanz Beanz]

I would consider the Glycol trick, I mean its cheap enough for added protection.

 

[kengrome]

probably like getting the wood wet with water,,,,opens the pores up so they can be "filled" with the resin

Jim, you may not realize just how right you are! According to Dave Carnell, Ethylene Glycol's exceptional ability to penetrate deeply into the wood is exceeded only by water itself ... so it 'makes sense' that it opens the pores much like water does as it soaks in. Opening the pores means others chemicals (epoxy for example) might get deeper into the wood too, although I think the value of this is rather limited myself. Nevertheless if it helps even a little bit then it's probably a 'good thing' ...

All I can say is Everdure works... maybe not for the reason's I thought but damn it, it works

Meanz, I'm not posting to argue with you because I've heard from others that it works well too, but here's an opinion suggesting that other solutions might work even better:

http://www.storerboatplans.com/Faq/Saltpreservative2.html

yes, except the solvent evapourates and leaves 100% solids anyhow, just further in, and a thinner layer than you put on.

Landlubber, this is way different from what I've been told. Maybe what's left is 100% epoxy, but it is certainly not 100% solid epoxy. Instead the epoxy that remains in/on the wood after the solvents have evaporated is riddled with hollow tube type structures (some refer to them as 'worm holes') where the solvents have flowed through the epoxy matrix to the surface before evaporating.

No I have not looked through a microscope and seen this myself, but I saw a report with pictures online somewhere that showed this to be the case ... and man it's a hassle getting old when I cannot remember to bookmark every little tidbit of info I come across on the internet. I'm guessing it is still online wherever I found it the first time, so if anyone else finds it again can you *please* post the link here? I'm going to add it to my scrapbook pages *and* my bookmarks the next time I find it since this topic seems to keep coming up again and again.

Personally I do not want my expensive epoxy perforated by thousands or millions of hollow tubes that help water vapor and oxygen get into the wood -- not when I'm using epoxy to exclude them! That's why I think a better way to thin epoxy is to 'heat the boat' ... and when you apply the epoxy it will heat up and become thinner naturally as it comes in contact with the warm wood. Robb White built his boats this way and he had good success with it.

But you know something? When all is said and done, I don't think most of these epoxies need any help adhering to the wood even when they are not thinned. In fact I think it may make a whole lot more sense to just use the stuff without thinning it at all.

We seem to want to believe that epoxies are going to stick better if we can somehow get them to soak into the wood deeper. This is probably because we have learned that some paints stick better when the first coat or two is thinned and soak in better. But even though they both come in cans and are applied in a similar manner, epoxy is dramatically different from paint -- and it probably should not be assumed that thinning it will help -- especially thinning with solvents.

 

[Meanz Beanz]

We seem to want to believe that epoxies are going to stick better if we can somehow get them to soak into the wood deeper.

Hi Ken, thanks for the contribution!

For my part its not the idea that epoxy sticks better, I'm using the epoxy for protection against rot so the idea is that the deeper the epoxy saturates the timber the less likely that the protective layer is going to be breached. Any surface layer, no matter how good, runs the risk of physical damage but if I can somehow bind that layer further into the timber (saturate?) then the protection should be better?! If Glycol can achieve that then great... actually they sound like a great duo, the glycol itself will kill rot and allow the epoxy to get a better key on the timber and the epoxy will prevent the Glycol from being "washed" out of the timber over time. They seem like they are perfectly complimentary treatments..... now I am just waiting for some chemisty expert to pop in and point out the gotya... we are talking boats here, there IS ALWAYS a gotya

Thanks all... its been enlightening.

Cheers
MBz

 

[Meanz Beanz]

Meanz, I'm not posting to argue with you because I've heard from others that it works well too, but here's an opinion suggesting that other solutions might work even better:

http://www.storerboatplans.com/Faq/Saltpreservative2.html

LOL no worries Ken... I was just having a little "pouty"... You know, like when you have thought you got how something works and then along comes Mr Reality and stuffs up your nice neat explanation of the phenomena. The fact that Everdure works well probably says about epoxies abilities, even in a technically degraded condition, than anything else.

Cheers
MBz

 

[PAR]

Getting epoxy to bury deeper makes a lot of sense, but the best method is "hot on hot" to improve viscosity, not the use of thinners.

Make a 20% thinned mixture of regular epoxy (which is 12% less then CPES's solvent content) and coat a piece of plastic, several coats thick. Do the same with unthinned epoxy, then peel both off the plastic and see which one you'd prefer protecting the wood. The thinned one will be rubbery, much like cured caulk and it resists only 70% or so of the moisture vapor. The unthinned stuff will be rigid and resist 95 to 99% of the moisture vapor it meets.

The information Michael has on his web site is directly from the West System test results page on this subject and a well documented set of events in the industry.

Anti freeze (Ethylene Glycol) is a fine preservative in timber builds, not so much in plywood (the glue lines prevent penetration). There is some debate on the ability of some adhesives sticking to these treated surfaces, unless well dried prior to gluing.

If using the hot on hot method, the best way is to warm the piece and the epoxy, but apply in an area that is distinctly cooler then the parts and goo. This is only important on the first few coats over raw wood as it prevents out gassing and the contracting wood (as it's cooling) literally sucks in the goo. This trick also works well with the first coats of bright finish on raw wood.