Coating Wood With Epoxy to Prevent Rot

[Roy M]

Greg, I just finished reading the cited article. It, in no way, says anything different than I characterized. I made no claim as to the ability to rejuvenate rotted wood. We used it to stabilize non structural members. It does, however penetrate more deeply and effectively into porous materials, which, I believe, was the OP's question. Of course, straight, unthinned epoxy is superior to thinned resin, but as the report, you quoted, says: " If you elect to modify it, you become an epoxy formulator and need to understand the effects of your changes. Armed with the information in this article, you can decide if thinning epoxy is worth the tradeoff in performance." The article goes on to clarify the benefits of thinned epoxy (as well as possible liabilities) to rotted wood. Shipwrights have a sense of balance based on experience, judgement, and the particular needs of the boat. Not every part must be as good as the day it was fitted, but it must, at least, be safe and stable for the use intended. Sometimes one needs to do the most cost effective solution for a very particular case. I am very happy to read that Gougeon Bros. has clarified this issue. Perhaps boatbuilding and repair should remain in the purview of the professionals, but each owner ends up making the decision (and accepting the consequences, good or bad). As to micro fractures and infiltration of moisture, I don't think anyone here would consider using thinned epoxy as the final coatings, but it can be used in base preparation, where appropriate, as stated in the Gougeon report.

[minaret]

Originally Posted by Roy M

Greg, I just finished reading the cited article. It, in no way, says anything different than I characterized. I made no claim as to the ability to rejuvenate rotted wood. We used it to stabilize non structural members. It does, however penetrate more deeply and effectively into porous materials, which, I believe, was the OP's question. Of course, straight, unthinned epoxy is superior to thinned resin, but as the report, you quoted, says: " If you elect to modify it, you become an epoxy formulator and need to understand the effects of your changes. Armed with the information in this article, you can decide if thinning epoxy is worth the tradeoff in performance." The article goes on to clarify the benefits of thinned epoxy (as well as possible liabilities) to rotted wood. Shipwrights have a sense of balance based on experience, judgement, and the particular needs of the boat. Not every part must be as good as the day it was fitted, but it must, at least, be safe and stable for the use intended. Sometimes one needs to do the most cost effective solution for a very particular case. I am very happy to read that Gougeon Bros. has clarified this issue. Perhaps boatbuilding and repair should remain in the purview of the professionals, but each owner ends up making the decision (and accepting the consequences, good or bad). As to micro fractures and infiltration of moisture, I don't think anyone here would consider using thinned epoxy as the final coatings, but it can be used in base preparation, where appropriate, as stated in the Gougeon report.

I already tried giving him this argument and he wouldn't hear it.

[Roy M]

Minaret, that must be why we ended up doing what we do, and he does what he does. I hereby promise not to practice law, even sea-lawyer law, without a license. And thanks for telling me about your experience.

[ElGatoGordo]

I build wood boats, I don't believe in totally encapsulating anything. My experience is there is ALWAYS going to be a place for water to get in. ALWAYS! So I like to leave the areas that are open to air able to "breath" if you will. I also like Latex paint, so take my thoughts with a grain of salt. (more money and effort has gone into developing latex house paint BY FAR than any other coating on the planet because more of it is sold BY FAR! Ever wonder how they can guaranty a house for 30 years?!!)

If I built a bow sprit like this, the holes and any area out of sight would be epoxy coated and maybe fiber-glassed. Then the whole thing would be treated with a traditional bright work coating or painted.

[Roy M]

For those unfortunates unfamiliar with the term, sea lawyer: "An argumentative, cantankerous or know-it-all sailor. A sea lawyer is adept at using technicalities, half truths, and administrative crap to get out of doing work or anything else he doesn't want to do, and/or to justify his laziness." That, pretty much, has been my dream job. And now, I've forsworn it to make a stupid point. What a waste of my lifetime.

[Cheechako]

Originally Posted by hellosailor

Ah, no, the plastic bag doesn't have to enter the wood. It compresses all the fluid (and gas) in the bag against the porous wood, and since the fluid is incompressible, any gas in the wood is compressed and fluid impregnates it. Basic hydraulics, no magic.

Yeah, I dumped my post when I realized you said "excess material" !

[minaret]

Originally Posted by hellosailor

Epoxy penetrants may be a myth but I've seen GitRot, an epoxy penetrant, go far deeper into rotted wood than epoxy could.

If you have a slow-curing thin penetrant, you can also pressure treat the wood with it. Seal it in a bag with excess material, tie a good ine and weight to it and drop it 50-100 feet into the water. At that point it is under 2-3 atmospheres of pressure and yes, that forces the penetrant deeper into the wood. (This can be done with wood preservatives, not just epoxy.)

Then it is just a simple exercise to haul it back up and clean the excess off before it hardens up.

If you put it in a bag, any solvents will be unable to gas off. Therefore it will have to be neat epoxy and probably not that thin. Further, the temp at that depth will not only retard the cure, it will probably cause it to never cure properly. Even the tiniest pinhole leak will result in water intrusion.

That's a lot of risk (plus you have to take a boat out with a bag of wet lam in it), when you could just vacuum bag it for cheap. There are all sorts of cheap or DIY pumps, I've even seen people pull bag with a shop vac. This idea seems a little crazy to me. Keep the project in the shop where it belongs.

[minaret]

Here's something I've found to work well-proper temp control. Here's the basic idea. On a microscopic level, wood is essentially a bundle of straws (simplifying here). Those straws are full of air. Controlling the temp of that air is crucial to effective sealing. If you seal a piece in the morning which has been sitting in the cold all night (a common error), the air in the wood will be slowly expanding as temps rise through the morning. This can commonly be seen as bubbles forming in the sealer on the surface, particularly at end grain. This is a mistake, as it creates positive air pressure in the interstices of the wood, pushing sealer out.
However, if you have carefully left your timber under heat lamps/with heaters over night, so it is just above room temp, and you shut off the heat just before coating, the air in the interstices will be cooling as the sealer soaks in, creating negative pressure and sucking sealer into the wood grain instead of pushing it out. No bubbles an hour after coating, and much deeper penetration. As long as you don't over reduce (10% max), use a very slow hardener, and use an equally slow reducer (MEK for epoxy, to increase the time the resin stays very thin), you will have no trouble. Let it gas off by itself and slow cure, no heat or lamps, but be sure to catch the bond window for the first coat of neat epoxy. Simple.

[Delancey]

Originally Posted by hellosailor

Epoxy penetrants may be a myth but I've seen GitRot, an epoxy penetrant, go far deeper into rotted wood than epoxy could.

If you have a slow-curing thin penetrant, you can also pressure treat the wood with it. Seal it in a bag with excess material, tie a good ine and weight to it and drop it 50-100 feet into the water. At that point it is under 2-3 atmospheres of pressure and yes, that forces the penetrant deeper into the wood. (This can be done with wood preservatives, not just epoxy.)

Then it is just a simple exercise to haul it back up and clean the excess off before it hardens up.

Hellosailor, smartest idea I've heard all day! Where'd you get that one from? I've vacumn bagged a on a sometimes daily basis, great for about 15psi. Your way capable of much more force and doesn't need a pump. Nice!

I have heard of Explosive forming - Wikipedia, the free encyclopedia before but never thought about what you are suggesting, great idea!

[minaret]

Originally Posted by Delancey

I think Stumble did pretty good job except for one part, The Gougeon Brothers recommend against trying to epoxy encapsulate dimensional lumber thicker than about 3/8" thick.

So if you want to encapsulate a larger piece they recommend it be made by laminating thinner pieces.

I think this is based on the notion that if the wood does move, the amount it will move cumulatively on larger pieces will exceed the elastic limit of the epoxy and cause it to fail.

So in this case they would recommend against trying to encapsulate the bow sprit. Maybe try a good quality paint or varnish and stay on top of maintenance?

Everything you ever wanted to know about wood epoxy construction in the link below-
http://www.westsystem.com/ss/assets/...k%20061205.pdf

I would certainly not suggest building any size able spar from solid timber, laminating is the preferred method. Solid timber will eventually warp and check, even if well sealed and sticker dried. Reclaimed old growth like the OPs is best for this, but it will still check eventually. I usually laminate a timber like a sprit out of 4-1/4", carefully arranging the laminate so that alternating pieces will cup towards each other instead of all one way. This prevents warpage.



How to Fabricate a Laminated Wood Beam | eHow

[LakeSuperior]

Originally Posted by hellosailor

If you have a slow-curing thin penetrant, you can also pressure treat the wood with it. Seal it in a bag with excess material, tie a good ine and weight to it and drop it 50-100 feet into the water. At that point it is under 2-3 atmospheres of pressure and yes, that forces the penetrant deeper into the wood. (This can be done with wood preservatives, not just epoxy.)

Then it is just a simple exercise to haul it back up and clean the excess off before it hardens up.

Really interesting idea (to me.) It would be somewhat analogous to resin infusion of composites using 4000 mbars (4 atmospheres) total ambient pressure at 90 ft. A 4 to 1 pressure gradient. Resin infusion runs 1000 mbar ambient to ~10 mbars, a 10 to 1 gradient.

With resin infusion/vacuum bagging, the part when cured goes from low pressure to high pressure. The underwater approach takes the cured part from high pressure to low pressure. The same as pressure treatment of wood though. However the fluid that is used in pressure treating wood doesn't cure to a hard somewhat non-porous material like epoxy does.

If you have bubbles present in the epoxy they would be compressed to a quarter their surface volume. You may have exploding epoxy bubbles when you bring the wood up.

Also, the air in the voids of the wood are at 1/4 the pressure of ambient, so 1/4 volume and the voids are filled with epoxy. I speculate that the epoxy and compressed air would share the void unless the air was displaced out of the void. I don't understand what would happen to this air and epoxy in the void when the wood is brought to the surface. I guess in one scenario the air would simply remain under pressure in the voids and slowly diffuse into the remainder of the part and out through epoxy over time.

Anyway, just some random thoughts on a neat idea.

[minaret]

Originally Posted by Delancey

Hellosailor, smartest idea I've heard all day! Where'd you get that one from? I've vacumn bagged a on a sometimes daily basis, great for about 15psi. Your way capable of much more force and doesn't need a pump. Nice!

I have heard of Explosive forming - Wikipedia, the free encyclopedia before but never thought about what you are suggesting, great idea!

I pull 29.92 inches of mercury all the time. Perhaps some of the wizards around here could tell us the depth you would have to submerge an object to (and the necessary salinity of the water I bet ) to get this pressure?

[minaret]

Originally Posted by LakeSuperior

Really interesting idea (to me.) It would be somewhat analogous to resin infusion of composites using 4000 mbars (4 atmospheres) total ambient pressure at 90 ft. A 4 to 1 pressure gradient. Resin infusion runs 1000 mbar ambient to ~10 mbars, a 10 to 1 gradient.

With resin infusion/vacuum bagging, the part when cured goes from low pressure to high pressure. The underwater approach takes the cured part from high pressure to low pressure. The same as pressure treatment of wood though. However the fluid that is used in pressure treating wood doesn't cure to a hard somewhat non-porous material like epoxy does.

If you have bubbles present in the epoxy they would be compressed to a quarter their surface volume. You may have exploding epoxy bubbles when you bring the wood up.

Also, the air in the voids of the wood are at 1/4 the pressure of ambient, so 1/4 volume and the voids are filled with epoxy. I speculate that the epoxy and compressed air would share the void unless the air was displaced out of the void. I don't understand what would happen to this air and epoxy in the void when the wood is brought to the surface. I guess in one scenario the air would simply remain under pressure in the voids and slowly diffuse into the remainder of the part and out through epoxy over time.

Anyway, just some random thoughts on a neat idea.

And the temps at that depth? Must we plumb in an electric blanket to this bathymetric vacuum bag? Or just take the boat to the tropics and find a hot water jet on the sea bottom?


How often do you pull pressure on a bag and have zero leaks from the outset? I bag a lot, and for me it's not often. Usually takes at least a few minutes of careful leak detection to find every pinhole leak and seal them for a perfect bag. One pinhole and the deep sea bag would be done for. You'd almost have to bag it the usual way first to make sure it's leak free before submerging it. Then you'd want to do it in deep clean clear water, because if it gets one hole poked in it it's kaput. Seems like conditions are easier to control on the shop bench to me.

[Delancey]

Originally Posted by minaret

I pull 29.92 inches of mercury all the time. Perhaps some of the wizards around here could tell us the depth you would have to submerge an object to (and the necessary salinity of the water I bet ) to get this pressure?

Um, yeah, like I pull 29 inches of mercury too. It's equal to you know, like about 15psi.

Atmospheric pressure - Wikipedia, the free encyclopedia

To get this pressure you need to be like above the water, 15psi is all around you and you don't even realize it. It's pushing on your skin right now but since you grew up on earth and not in outer space you aren't aware of it. Go walk out in space at zero psi and you blood boils and eyes pop out all Total Recall-style.

It's what the measurement unit called an atmosphere is. Hellosailor is talking about what 3 or 4 atmospheres? So what 45-60psi worth of clamping? Nice! No pump, even nicer!

[Delancey]

Originally Posted by minaret

And the temps at that depth? Must we plumb in an electric blanket to this bathymetric vacuum bag? Or just take the boat to the tropics and find a hot water jet on the sea bottom?


How often do you pull pressure on a bag and have zero leaks from the outset? I bag a lot, and for me it's not often. Usually takes at least a few minutes of careful leak detection to find every pinhole leak and seal them for a perfect bag. One pinhole and the deep sea bag would be done for. You'd almost have to bag it the usual way first to make sure it's leak free before submerging it. Then you'd want to do it in deep clean clear water, because if it gets one hole poked in it it's kaput. Seems like conditions are easier to control on the shop bench to me.

Since he is talking about a hydraulic bag instead of a vacuum bag the leaks you're thinking of aren't really a concern. Since the bag isn't being evacuated there isn't anyplace for the leaks to go.