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chris95040 · 11-12-2015, 18:58

Quote:

Originally Posted by Stumble

Chris,

The issue is that there is no advantage to thin epoxy in almost all applications. Unless working with infusion, vacume bagging, or something equally esoteric. The depth that epoxy penetrates into wood is meaningless. Structurally the weak point is the first cellular layer where there is no epoxy. No matter how deep the epoxy penetrates that is where the bond will fail.

From a waterproofing standpoint again it doesn't matter. The epoxy coating the substrate prevents the vapor intrusion. It never gets to the under layer.

It simply does not matter how viscious epoxy is for 99.9% of applications because the viscosity doesn't effect the finished product in any way.

Finally Smith's CPES/gift rot is absolute junk. There is absolutely no good use for it. Unless you need a non-waterproof epoxy that is a terrible glue, and very expensive.

Regarding Smiths CPES, I don't know, you may be right. I used it on recommendation from a friend who gets really great long-term results using it under bristol 2-part poly on his brightwork. Working well for me so far.

I agree most of the time the viscosity doesn't really matter, and you might as well use the strongest thing you can. The low-viscosity epoxy is still pretty strong from what I read though (http://www.epoxyproducts.com/datalowv.pdf), but the stuff with thinners, like CPES, is certainly a lot weaker.

I think there are times when a thin epoxy with the ability to burp out bubbles quickly and flood into every nook and cranny could be helpful. Like half-assed core repair, which people *often*do with CPES, *sometimes* successfully. I don't think CPES is the right choice for that application, though, because when you trap thinners in epoxy it cures up all rubbery and weird. I'd think just the lowest viscosity, unthinned resin you could get would be best.

Bill_E · 11-12-2015, 19:06

I'll add my $0.02 as a retired physical chemist. I think that there are two issues (somewhat related). The first is a question about what happens with epoxies on wet (water wetted) surfaces or materials. The second has to do with the penetration of the epoxy into the porous wood before the chemistry causes it to harden.

I think it's obvious that if the pores of the material are full of water then the epoxy is going to have to displace it in order to penetrate. (It really doesn't matter if the material is wood, wood particulate, or ceramic tile; the problem is the same. Get the pores emptied out before trying to fill them with the epoxy. Chemists have used acetone to dry their materials for years but it's not quite the same problem. Isopropyl alcohol would also work but most easily available isopropanol is already 30% water. The thing that the acetone will do is mix (or maybe you want to call it dissolve) with the water and as the acetone dries out it kind of pulls the water with it. Acetone has a pretty low boiling point. It's not the same as an azeotrope but it does work. I'd spray with acetone and then put a fan on it. Repeat several times. A little heat will help but beware you are dealing with a flammable solvent.

Once it's dry and epoxy is applied the question is the rate of mass transport into the pores of the particulate. There are (more or less) three factors. One is the molecular weight of the epoxies and that is beyond control. Probably low viscosity epoxies are low molecular weight. The second is the surface tension. Materials with low surface tension will tend to "wick" into the particulate faster than materials with high surface tension. And then there is the viscosity, where lower viscosity will move into small pores faster than high viscosity. Oh yeah, there is the issue of time for the epoxy to harden. If it hardens in 5 minutes it's going to be hard before it penetrates, whereas if it hardens in 36 hours it will have a much longer time to wick it's way into the particulate.

Wow! Is that pedantic, or what???

Anyway, if it were me: I'd dry the hell out of it using a fan and occasional heat gun and maybe spraying with some acetone (when cool) to assist the process. Then I'd look for a low viscosity, slow drying epoxy and paint that on every few hours to try to saturate with the epoxy. I don't know anything about diluting the epoxy with acetone or other solvents so I'll stay away from that question. Someone mentioned vacuum penetration...that would be great but probably out of the question here.

Mark, Are you back in St. Martin? If so, the warm temperatures will help but high humidity days are working against you.

Please...Don't flame me for this pedantic and arcane answer. My background just made me do it!!

Bill

**a64pilot** · 11-12-2015, 19:14

Well Bill, I think you summed it up very nicely myself

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IolantheSF · 11-12-2015, 23:48

If you have sodden chipboard on a boat, the problem is obvious. You must have the boat, and boats will get wet. The chipboard, however can be done without. Get rid of it. It was a liability to begin with. Now it is a soggy rotting mess which can never be turned into anything that belongs near water. Replace it with proper boatbuilding materials like marine grade plywood. Coat each piece with epoxy before installing, then seal it in and paint it.

Lepke · 12-12-2015, 00:28

You have to dry the chipboard. Warm dry air works best. Alcohol helps evaporation, but I like medicinal best. You saturate the wet wood and the alcohol seems to mix or draw out the water. If you're trying to dry core, I use an air compressor with a regulator set to a couple pounds, so air is constantly blowing over the wet wood. An air drier in line, like for painting or sand blasting, helps. If it's open wood, a fan works as long as your changing the air and not circulating the same damp air inside a hull. If you used medicinal alcohol, and have any left, you can drink it while you wait for the wood to dry.

**JPA Cate** · 12-12-2015, 00:36

Mark J, fwiw, (and that may be little), go back to Wotname's post of how he worked out to deal with this. It might work, if you are patient enough, and attentive enough.

"Everybody" knows chipboard is POS. However, maybe you can work around that and avoid having to replace the bulkhead. Sorry this is such a difficult problem.

Ann

**GordMay** · 12-12-2015, 02:45

Quote:

Originally Posted by Bill_E

... Wow! Is that pedantic, or what???

... Please...Don't flame me for this pedantic and arcane answer. My background just made me do it!!

Bill

Not at all Bill. I found your explanation clearly enlightening.

Terra Nova · 12-12-2015, 09:49

I would replace the chipboard with marine plywood.

Curious Sailor · 12-12-2015, 12:33

Quote:

Originally Posted by Bill_E

dd ter. The thing that the acetone will do is mix (or maybe you want to call it dissolve) with the water and as the acetone dries out it kind of pulls the water with it. Acetone has a pretty low boiling point. It's not the same as an azeotrope but it does work. I'd spray with acetone and then put a fan on it. Repeat several times. A little heat will help but beware you are dealing with a flammable solvent.

Bill

I agree...

Cheechako · 12-12-2015, 12:37

Underwater epoxy exists!

Curious Sailor · 12-12-2015, 12:38

Quote:

Originally Posted by hsi88

People that say penetrating epoxy is junk haven't used it or they used it for something it was not intended. I restore old boats and its not my wish to spend thousands on a boat that barely has that much value. I drill holes where needed, use antifreeze/borax to kill spores, dry the wood out, use acetone to displace some of the water, let that dry out, then pour in Total Boat Penetrating Epoxy. Its thin, so you have to dam it off where needed. But when it cures, its pretty damned solid. It might not take all of the flex out of a soft deck, but it vastly improves it. Try it for yourself sometime. Works better than you would think. Look at some of the reviews. It would not review well if it didn't work.

MarkJ · 12-12-2015, 12:38

Quote:

Originally Posted by Bill_E

I'll add my $0.02 as a retired physical chemist. ...

Please...Don't flame me for this pedantic and arcane answer. My background just made me do it!!

Bill

Thanks Bill. Great post and certainly worth more than $0.02!
Thanks for taking the time to write it

Mark