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Epoxy vs resorcinol or other adhesives for boat building Answered

I've been a big fan of epoxy for a long time. It's been recommended to me as the best glue ever, and lately as a great/durable coating to be used like paint. It's so popular that companies are starting to market things as epoxies that might be related but, really are something else. FYI anything sold as a "one part epoxy" is not an epoxy at all. it's something else. Epoxies must be 2 part.

My father started building wooden model sailboat, and wanted to use Resorcinol. What?? Never heard of it. can't be good. must be toxic. use epoxy, Dad. Lately, I've heard differently, with some caveats.
This was mentioned on www.woodenboat.com forums:

http://www.cpadhesives.com/media/ClassicBoatAppendix.pdf

The upshot is that epoxy bond strength weakens dramatically with exposure to heat or (maybe?) saltwater or UV light. Additionally, epoxy's bond is not as fatigue resistant as wood. So using it as a structural bond is questionable. Using it in hot (120F+) environments is questionable. Using it in saltwater environments is questionable.

Since boats sit in the sun, tend to flex, and are often exposed to saltwater, how can we possibly use epoxies in long term situations.

I had to search hard to find any info on Resorcinol, but it's cheaper, supposedly lasts longer. But, as far as I can tell, it's really hard to find.

Comments?

Discussions

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ThomasS468
ThomasS468

10 months ago

When I was in my mid to late teens, 1953 to 1960, I worked in a smallish boat yard in Westport, Connecticut. We were a Lyman - Evinrude dealership. When I first started there were only wooden boats. Lyman boats were built in Sandusky, OH and they were originally designed for boating on Lake Erie. Since Westport is on the Long Island Sound, they were a good fit for us, the type waves and rough water being similar. Earlier Lymans were similar in construction but used cedar planking instead of the marine plywood used in the '50s and later. Construction of both was "lapstrake" type. My recollection is the strakes varied in width from about 2" in the bow to about 5" at the hull center. Since the strakes were all longer than the marine plywood available at the time, they were made in sections, pressure-glued using scarfed joints and resorcinol glue. Then cut to the correct shape for the strake location. I performed many of the common tasks at the boatyard because although I was young, I was a very quick study and once shown how to do something I could easily repeat it. Because boats were not unlikely to sustain damaged strakes, I learned to repair them using the techniques recommended by the Lyman factory. We would order a strake from Lyman shaped to fit in the exact location and I would scarf the ends of the replacement strake and the strakes remaining where I had removed the damaged strake, apply the sealer used between the strakes and glue the repair in place with Elmer's resorcinol glue. Since it wasn't possible to apply to use the pressure technique used in producing the factory joints I would apply the necessary clamping by using 5 clinker nails, 2 close to each end of the scarfed joint and one in the center. During my 8 years working at the boatyard, I never saw even one of the scarfed/resorcinol joints fail. Neither the factory joints or the approximately 24 joints(12 repairs) I made in the field. The resorcinol glue had no failure modes in my experience! Above or below the waterline, in the primarily fresh water of the river where the boats spent most of their time at moorings or the salt water of the sound. Many of the boats we sold were moored at other locations where the water was salty with the same results. When I was younger and worked on many projects of my own design, I always tried to use the Elmer's resorcinol glue but it became more and more difficult to buy because the demand was low and most individuals had switched to simpler, cheaper, premixed formulations. During my lifetime, I am now 81, I have seen many glued joints fail, where virtually all the other glue formulations were used but never resorinol! Properly done, a wood joint using resorcinol glue, becomes essentially one piece! Use it and, if the joint and glue are prepared properly, you won't be disappointed. One of the things mentioned here by others is the odor of the glue. I have thought things over carefully and can't remember having any problem with the outgasses produced. This may be due to the fact that I mostly worked in warm weather in buildings with doors and windows open because of the hot summers in Connecticut and no airconditioning back then! Or maybe we were just more tolerant of working conditions back then!

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Lroy_RC
Lroy_RC

7 years ago

Boys & Girls,
Maybe if you tried Resorcinol you might know its merits. First of all, next time you are at the lumber yard, look at the edge of waterprood or exterior plywood. Notice the black or reddish glue line . That glue is Resorcinol or a cousin. It has the mots guts / longevity for wood when exposed to moisture for a long time. Epoxy will fail when subjected to same wet or heat conditions . I guarentee..

Also Resorcinol is about the only glue that can bond teak or other waxy or resenous woods.. If you prep a waxxy surface with a toothing plane and wash with thinner you can not beat the bond of Resorcinol.

Try it you will turn your back on epoxy wor severe conditions!

Lroy_RC

2-part epoxy works fine for me on wood because 1. it bonds well with minimal clamping 2. you can get it in many forms: paste, syrupy liquid, quick-curing, slow- curing 3. it's waterproof. Resourcinol has one trait I've found impossible to beat, however - it bonds those oily exotic woods such as teak and rosewood where other adhesives fail. you can get it in a small kit labeled, "Elmer's Waterproof Glue," but it is hard to find and is nasty stuff to work with, consisting of a liquid resin and a formaldehyde powder that you don't want to inhale. another adhesive with a fantastic bond on just about any surface (and another old wood boat product) is 3M 5200 adhesive in a caulking tube. this is only good for surfaces that can be somewhat flexible after being joined.

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lemonie
lemonie

11 years ago

I think that the Resorcinol product is something like the trademarked products "Bakelite" and "Formica". The phenolic and formaldehyde precursors of which are not nice. Then again epoxy two-parts aren't exactly pleasant either. Think about this: what is "marine" or "yacht" varnish? has it been developed for exactly this sort of application? Also, are you planning upon berthing the model sailboat outdoors for most of the year- how much sun is it actually going to get? L

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danlocks
danlocks

Reply 11 years ago

heh. well, I wasn't exactly worried about the model boat; I think for that purpose almost anything reasonably waterproof will work. I was thinking about my aging fiberglass catamaran, and wondering if the failing repairs the previous owner made are due to materials (epoxy) or workmanship. I've had to redo a number of epoxy based repairs which were probably on the order of 7-10 yrs old. I can see weakened bonds in the form of easily flaked fairing compound on other repairs that are in low stress, mostly protected from direct sunlight areas of the hulls. The boat is dry stored, but since it has a number of slow difficult to detect leaks, it's subject to repeated wet/dry cycles. It's not delamination.... yet.

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lemonie
lemonie

Reply 11 years ago

I answered this yesterday (comment dissapeared) Fibre-glass different, use more fibre-glass? was essentially it L

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caitlinsdad
caitlinsdad

11 years ago

http://www.chemical-supermarket.com/home.php?cat=14

Lots of hits when you search "resourcinol glue". Saw that wooden boat forum topic which says the DAP one is "summer grade" whatever that means and it is found at your local ACE hardware store. The link above may have the super industrial kind some prefer. Good luck.

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danlocks
danlocks

Reply 11 years ago

I saw the same thing. There's not much breadth of product availability. I'm curious about the functional merits of the two, mostly.

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gmoon
gmoon

11 years ago

I have three or four 16 oz. cans of DAP "Weldwood" Resorcinol downstairs, and I doubt they will ever be used.

My bet is that urethanes have completely supplanted Resorcinol for almost all production use (plywoods, etc.) They are the common choice when epoxies are too expensive.

Resorcinol is pretty poor at gap-filling, too. Much worse than modern marine adhesives.

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Tool Using Animal
Tool Using Animal

11 years ago

Wow resorcinol is old school, yep almost impossible to find and leaves a purple glue line, that's all I can tell you. As for epoxy, yes it UV degrades, that's what paint and varnish are for, the temp and salt water problem I have no info on.