Epoxy over the long term

[bcooke]

Hey, didn't there used to be a thread for each of the major brands of epoxy around here? I think I am losing it.

I was just perusing my new copy of a great book "Details of Classic Boat Construction: The Hull" by Larry Pardey and came across an appendix (C)where the long term viability of epoxy/wood bonding was seriously questioned. Apparently wood and epoxy bonds don't stand up to the natural elements too well. There is even a calculation that suggests a wood/epoxy boat would lose 40% of its bonding strength after 5 months at sea. Larry actually went so far as to suggest a conspiracy by epoxy and boat manufacturers. Seems pretty far fetched to me but he does back his arguments up with some evidence and several quotations from epoxy manufacturers.

Anyone heard of this argument before?

-Britton

[Tim]

I have heard of that article. My own copy of that book is an earlier edition that does not include the article, so I haven't actually read it.

It's one source only, of course, but by an experienced and trusted writer. There are many epoxy/wood boats out there, but I am not aware of a rash of reported failures. How scientific is the data that led to the conclusions in the article?

We all know how traditional Larry Pardey is in his boatbuilding construction and sailing experience. Does this skew the conclusions at all? I admire his carvel boatbuilding skills and feel he is highly experienced, but I also sense more than a little of the "stick in the mud" mentality common among traditionalists. Sometimes I have to wonder if traditionalists are so tunnel-visioned in their experiences that they actively look for ways to discredit other techniques. I don't know. I do know that the old-timers, at least around here, tend to lack any real inclination for change, or to embrace anything different.

Also: do we know how much strength a typical boat of other types of construction might lose in its initial days of service? This sort of information seems critical by way of comparison. Do all structures lose a certain amount of their "fresh" strength when placed into service? Frankly, I don't know and don't care, but in order to discredit one thing you have to offer proof that another way clearly doesn't suffer the same effect.

Whatever the true story, the article certainly bears consideration, as collection of information from a variety of sources is always important. However, if I understand correctly, the article deals more with wood and epoxy construction (a true WEST-type boat, that is) rather than composite. As such, it doesn't really apply to what we are all dealing with. Also, the article (again, as I understand it) deals with epoxy/wood bonds submerged in water. This would not apply, once again, to boats built of wood and epoxy and then sheathed in fiberglass, as most larger boats of this construction are.

While I am open to his conclusions and would be interested in seeing the article (and probably should shut up until I have), I also feel that it needs to be taken with a healthy dose of salt grains, at least on the surface. Any article is, by its nature, one-sided. I bet refuting information could be found if one were so inclined. That doesn't automatically discount the conclusions, of course. They may well have merit...but the situation may not be quite so dire either.

Any access to a copy machine or scanner? I won't tell...

Hey, didn't there used to be a thread for each of the major brands of epoxy around here? I

Yes, and all the threads are still here, but some time ago I consolidated some of the topics on the forum. I think the epoxy threads are located in the "Materials, Sources, and Innovations" category now.

I think I am losing it.

Oh, I'm feeling charitable today, so I'll not add any comments! hehe

[bcooke]

How scientific is the data that led to the conclusions in the article?

Not very. The book goes from a tome of educated informed opinion to a rant in the appendix. That said, the rant does use a lot of epoxy manufacturer's literature to hang themselves. My biggest beef is that it doesn't address the fact that I have personally seen many cases of really atrocious attitudes towards mixing the epoxy parts and general lack of informed use of epoxy in general. I have seen "professionals" just dump hardener (no it is not catalyst) into a bucket of resin until it looks "about right". Just the other day someone came to me with a can of WEST adhesive filler in one hand and a can of sandable fairing filler in the other. The question given to me was "Which filler should I use for glueing wood together?..." How do you answer that without sounding like a know-it-all? The same individual conversely used adhesive filler when fairing a surface to be sanded later. He had a full can of sandable fairing filler sitting on his bench but "he had always used adhesive filler before and it worked..."

if I understand correctly, the article deals more with wood and epoxy construction (a true WEST-type boat, that is) rather than composite...Also, the article (again, as I understand it) deals with epoxy/wood bonds submerged in water.

Actually, the article also uses many examples of joinery work using epoxy above the waterline too.

Any access to a copy machine or scanner? I won't tell...

I think Larry would have wanted you to have a copy :-)

I haven't heard of any epoxy built boats falling from the sky - or rather dissapearing under the waves - so I am not going to go switch all my adhesive work to resorcinal as the article is suggesting. It really does sound like the rant of an old Stick-In-The-Mud but it does come from a very knowledgeable and experienced person with a proven track record. I think overall the information was not enough to convince me that the problem is real but it does raise some suspicion and I will pay more attention in the future.

Oh, and thanks for being charitable.

-Britton

[Tim]

Britton,

Your yard scares me!

I do agree with the theory (or fact?) that wood and epoxy bonds are not the end-all. Resorcinol has definitely been shown to create stronger and absolutely waterproof bonds, whereas epoxy, as water resistant as it is, can indeed sometimes fail.

You are right in that the way epoxy (or any product) is handled and applied probably has the largest effect on its ultimate performance. The kind of lackluster attitude you see at your boatyard is frighteningly common. For that matter, Resorcinol can fail miserably if its specific application guidelines are not followed (particularly ambient temperature).

We all know, or should know, that epoxy degrades in UV exposure. Could the failures reported in these above-waterline bonds between epoxy and wood be the result of UV degradation from improper coatings maintenance (or the entire lack thereof)?

I think the best aspect of this article is that it raises cautionary flags in the face of the "epoxy is infallable" race. Certainly it is not perfect, and we should all use care in its application. Epoxy has important limitations and is not a "wonder" product. All epoxy is not created equal, either; different formulations make different product brands act differently. All industrial epoxy is not ideal for the marine environment. The basic makeup of all epoxy brands may start the same, but each specific brand modifies their product significantely--and in different ways--to increase one attractive benefit or another. Pretending that it doesn't matter what brand of epoxy you choose, or from what source, is like pretending that all cars are exactly the same because they all start with steel. They may all ultimately get the job done, but there will be certain compromises along the way.

I can't (and am not trying to) discount what Pardey reportedly says, because he has a lot of experience and generally is very well informed. He has real credibility, and the workmanship shown elsewhere in that book (which, for those of you who have not seen it, details--exhaustively--the construction of the hull and deck framing of Talesin back in the late 70s or early 80s, whenever it was) is outstanding and second to none from what I can tell.

[Figment]

Modulus of elasticity
Coefficient of thermal expansion
Porosity or permeability

That's three key issues off the top of my head which will cause problems whenever two different materials come together. Wood and epoxy have very different material properties, and as the composite assembly is exposed to dynamic forces ("worked"), a certain amount of degradation of each is inevitable. The thing is to engineer enough reserve into the assembly to withstand the strain over time.

The same holds true of concrete and steel, but bridges generally last decades.
The same holds true of WOOD and METAL (traditional boatbuilding) as well.

[rshowarth]

As I have been researching my Rhodes 19 renovation and rib replacement, I have been told it may be better to use a polyester resin, rather than epoxy. I was told the Polyester would adhere better to the wood and the fiberglass.

Your thoughts?

[Figment]

One man's thought: that's crap.

For my money the ONLY time to ever use polyester is in an application where gelcoat is the final finish.

[dasein668]

I agree with Figment. Polyester is OK for laying up new glass (and arguably still not the best choice), but if there needs to be a secondary bond, I prefer something with adhesive properties. Epoxy fits that bill nicely.

[CharlieJ]

I agree - that's crap. Epoxy is well respected as a MUCH better adhesive to old glass than polyester resins are. Most boat builders or boat repair people who work with both will agree. Polyester resin DOES NOT adhere well to wood by the way. One of the reasons old tabbing to wooden bulkheads is often found to have come loose.

Here's and article from the Gougeons Epoxyworks Mag they did as a result of exactly the sort of stuff Larry says in his book- Take a look.

http://www.epoxyworks.com/17/longevity.html

The trimaran I build - started in 1976, launched 1981, lived aboard full time and cruised for several years- has been continuously in the water ever since. Has passed NUMEROUS insurance inspections and has NEVER had any problems with degradation of any part of the boat. With the exception of one place on the transom where the second owner llet it ram a dock and didn't repair it for some months- THERE he had a problem.

I'm a fan of Lin and Larry but on the subject of epoxies I have come to believe he "doth protestoth too much" He's made it obvious in other writings that he doesn't like the stuff, which is fine. But I've been building boats using WEST Sys since 1976 and I disagree. And I'm currently building my ninth boat using wood /epoxy.

[rshowarth]

Figment-

He did recommend finishng the bilge with gelcoat.

With epoxy, would you recommend a paint instead? Interlux Bilgekote?

[Tim]

As I have been researching my Rhodes 19 renovation and rib replacement, I have been told it may be better to use a polyester resin, rather than epoxy. I was told the Polyester would adhere better to the wood and the fiberglass.

Your thoughts?

Here's why so many people (often under the guise of "professionals") will suggest this: cost.

Simple fact: people are cheap. Polyester is much, much cheaper than epoxy, so it's natural for people to want to use it. What's worse is when certain "professionals" tout the use of polyester as if they have good reasons for it: you'll hear a bunch of phony-baloney about how using polyester for repairs keeps the repairs "homogeneous" with the original construction of the boat, that sort of thing...hogwash. It's about cost, cost, cost, and cost. Oh, and did I mention it's about cost? A "pro" recommending polyester for repair work is looking to pad his repair estimate by using an inferior product that costs him less.

What's really too bad is how many times I have read the same advice being given: polyester is the choice rather than epoxy. The level of misinformation out there is sometimes startling. Quality repair work just isn't done using polyester resin. Period. (That goes for vinylester also, which is just a modified polyester and still doesn't have the adhesive qualities of epoxy.) I don't know where the current spate of advice suggesting that polyester is a better product with wood began, but it's like a boat repair urban legend in the way it has spread itself insidiously over the web. I've read this in any number of places, and can only shake my head in disbelief at the wrongness of it all.

For ALL repairs on any fiberglass boat, especially where wood is involved, epoxy is the only choice if you want a quality job. Quality isn't always the cheapest way out. It's important here to remember that epoxy is an adhesive first, laminating product second. Epoxy such as WEST System was engineered and conceived to be used with wood (WEST stands for Wood Epoxy Saturation Technique), so perhaps that is telling. Polyester is not an adhesive and requires chemical bonding to bond even to itself. Since all repair work needs to be essentially "glued" (secondary bonded) to the old surface, how could anyone ever suggest that a nonadhesive product is what should be used?

Epoxy does not accept gelcoat over the top, but I don't know why one would use gelcoat here anyway. Gelcoat, when it's not installed in a female mold, is not a smooth, shiny product, but is a rough, lumpy, non-curing, brush stroke-filled mess that has no benefits over quality paint. Some people have the same fascination with using gelcoat instead of high quality paints that they do with using polyester resin instead of the clearly superior epoxy.

Instead of gelcoat, use any quality paint designed for the environment in which it will be used. This means just about any of the excellent solvent-based marine paints on the market, including Bilgekote, which is a fine, durable product.

Here's the crux of this issue: boats are (let's face it) luxury items for us. As such, they cost money to maintain and repair. Those who seek to own boats without spending a dime might as well be from Mars as far as I'm concerned; I might even understand the Martians better, were I given the opportunity. Doing shoddy work will only cost more in the long run; do the job correctly, once, and you'll be set for the life of the boat.

There are some other discussions along these lines here on the forum, should one care to search for them. I'm not sure which keywords will bring them up, but this is one of those recurring topics that is worth rehashing time and again.

[JetStream]

There is another myth along these same lines. You have been told that gelcoat will not adhere to epoxy and thus every epoxy repair would have to be painted. Hogwash. Since it is only a mechanical bond anyway after the first layup, gelcoat will adhere to epoxy as well as it would adhere to polyester. The "Epoxyworks" magazine did a special test to prove just that and found that for secondary bonding, the gelcoat actually adhered better to epoxy than it did to the polyester. The chemical bonds only work when the original polyester is still "green". Even the so called "activating" by applying styrene to the polyester will not really make any difference for the chemical bond.

Last year I did a repair to my Boston Whaler Outrage. I used epoxy for the repair and then used a "Preval" sprayer to apply the original gelcoat color (Still available from Minicraft http://www.minicraft.com/). I then went through the wet sanding grits up to about 1200, followed by rubbing compound and wax. I'd defy anyone to find the repair.

[dkall]

Funny that the material they used on Spaceship One (or whatever it's called) as reported by 60 minutes awhile ago is put together with epoxy. I don't know the details. Just remember that as I was listening to the show they mentioned how they bonded all the panels together.

[Tim]

There is another myth along these same lines. You have been told that gelcoat will not adhere to epoxy and thus every epoxy repair would have to be painted. Hogwash. Since it is only a mechanical bond anyway after the first layup, gelcoat will adhere to epoxy as well as it would adhere to polyester.

Interesting! Thanks for the info--I did not know that. I'll have to try and look through the Epoxyworks stuff online to see if I can find that article.

There is also a method in new construction to use a sort of "tie coat" between a gelcoat layer in a female mold and an all-epoxy laminate. I don't know much about this, but it is done in certain boats.

[Allen]

Funny that the material they used on Spaceship One (or whatever it's called) as reported by 60 minutes awhile ago is put together with epoxy. I don't know the details. Just remember that as I was listening to the show they mentioned how they bonded all the panels together.

SpaceShipOne was constructed of a graphite epoxy laminate by Scaled Composites. http://www.scaled.com/



http://www.scaled.com/projects/tierone/ ... ip_one.htm

[A30_John]

... considering the kind of exposure to the elements these spaceships get, I'm suprised they didn't opt for plank on frame construction.

[Allen]

Why not...

[JetStream]

I'll have to try and look through the Epoxyworks stuff online to see if I can find that article.

The Epoxyworks article is Number 22, Winter 2004, Page 18-19

[westsail42]

I didnt see anyone mention vinylester resin. This is often used for repairs that require secondary bonds. Yes it has it's pros and cons over epoxy as well.

Pros:
cheaper than epoxy
easier to work with than epoxy
flexes a bit more, not as brittle as epoxy (if that is appropriate for your repair, see con)
stands up to the elements better than polyester: blistering, osmosis, etc. etc. (though not as good as epoxy, see con)
You can laminate over it within 24 hours or so without needing to sand (you need to sand epoxy). Note, you need to use the "laminating" version of vinylester resin to do this.

Cons:
not as hard as epoxy
flexes more than epoxy
not as impermeable as expoxy

In any case, it is much better than trying a secondary bond with polyester. Polyester shrinks slightly when fully cured essentially "popping off" the secondary bond you sought in the first place.


The big problem with using resin or epoxy to bond to wood is when the wood absorbs moisture and then dries and repeats. The wood swells, then shrinks, weakening the bond. This is very common with bulkheads/floor timbers that have become wet near the bilges. This is why it is best to thru-bolt bulkhead tabbing to help reduce bond separation

[dasein668]

Epoxy is actually quite flexible in thin layers. Its just big blocks of the stuff that exhibit a brittleness. A thin coat of epoxy over a flexible wood strip, for example, holds up extremely well.