So, er, uh, what are you guys sayin' here? My mast beam is going to fall apart? I haven't noticed anything coming undone voluntarily yet. Is 'yet' the operative word in the works here? Crimony! I guess Ebb's lead in holding the beam together is a fix I could apply easy enough, but, I'd rather think it wasn't necessary...crud. Oh well, one step forward and you know the rest.
Resorcinol's rap is that of being harder to work with than epoxy. You can be sloppier with epoxy. Garden variety epoxies may have some trouble with UV and high temperatures but are tested as being stronger than resorcinol. And there are epoxies that perform well at higher temperatures. What are they making the new Boeing 787 from?
I agree that the best strong back is a band-sawed piece of solid white oak. Preferably from an old gnarly hanging tree.
Ben
Well,
Resorcinol is a wood specific 'bonder'.
If you were gluing exterior mahogany rails up from strips and scarf joints there is no other glue. When you glue coaming blocks and winch islands up with epoxy you will have separation at some point. And as I just said if you have an epoxy glue-up like a bowsprit and/or teak anchor roller they are guaranteed to come apart. I don't know how long it'll take, but the more heat and wet/dry cycles they experience the sooner they will come apart.
I'm talking about pieces of wood brought together into a structure.
Epoxy IS definitely more versatile. You can glue wood together and seal it with the same epoxy. You can fill gaps and fillet, you can laminate fiberglass onto wood and foam panels with the same stuff. You could probably do a barrier coat on the hull with it. But, by definition, you only achieve a mechanical bond.
I hesitate to use that term here as the adhesion is mechanical but not a BOND. There is no comparing here with Resorcinol which can only glue flat pieces of wood together FOREVER. It has a bad rap because of its short open time and need for high clamping and controlled temp.
If I had been more comfortable with Resorcinol I might have done A-338's strongback lamination with it. I felt I couldn't do it within the short open time required.
It is entirely possible to put together a new rudder for the Ariel/Commander with foam and glass OR plywood and glass using good epoxy. There is always the chance that the epoxy can separate from the wood or the foam.
You have to take this into account when designing the rudder. But this is not gluing wood-to-wood. The whole intent is to encapsulate the wood - and it sometimes doesn't work. Exposed, varnished wood swells and shrinks. Epoxy glue-line is more or less non-shrink and hard. Wood wins.
If you had to glue wood-to-wood together for underwater use (like the original non-encapsulated rudder) Nobody would spec epoxy. It's possible to butcher-block and pre-bond pieces together into 'planks' with Resorcinol for cutting the shape and use polyurethane or polyether for gluing/caulking edge to edge planks. Most people these days would then SEAL the wood with a thinned epoxy, then attempt to waterproof with a polyurethane coating (or whatever new comes down the everchanging chemical pike.) Or go right to bottom paint. Imco that's conventional wisdom.
In every case epoxy must be protected with another coating. Even a novolac needs UV protection. Pigmented epoxy coatings/paints will chalk and breakdown. There is no comparison with LPU coatings Even polyester coatings will outlast epoxy coatings. On those winch islands use a clear coating with the highest UV rating you can find. That'll help some.
The chemistry keeps changing. There are new combinations appearing: epoxy polyesters. epoxy urethanes and resorcinol epoxies, and ETC for both adhesives and coatings. Quite amazing.
But at the moment everyday epoxies that we buy really have limited use on the exterior of a cruising sailboat.
Please, I work with these assumptions on my Areil. If there are developments or stuff I've forgotten (more likely every day), please clue me and the boat in! We both depend on it.
The limited info about glues and coatings that I work with IS ALL conventional.
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google>
Laminating white oak w/ Resorcinol - The WoodenBoat Forum
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For unstressed gluing somebody by now must have tried using CLEAR polyether or a silyl-urethane. !NOT SILICONE! Also sold as Hybrid Sealant/adhesive.
This is a one-part, low odor, 100% solids, long life, moisture cured, always flexible synthetic rubber in a gun tube.
Worth experimenting - like gluing a stack of mahogany blocks together and boiling them for awhile!!!
Last edited by ebb; 01-29-2010 at 08:10 AM.
Ebb
I really appreciate the time you put into your responses. The epoxy vs. resorcinol question is new to me. I understand what you're getting at. And I'll be sure to put 10 coats of Eplfanes on those blocks.
I think many people including myself get involved with these old boats thinking that with a little repair effort you can have some fun sailing for a few seasons before everything wears out. Of course once you get started and develop attachments to the project you want the dam thing to work right and last.
Ben
It is REAL easy to get really attached to these boats and want to do the absolute best job you can bringing them up to better than new condition.
Furniture I've built since I could reach the top of a tablesaw. But doing the job right on a boat is a whole new learning curve. And thanks to this place I'm getting an education.
google> Have epoxy adhesives improved recently - Sailing with Lin and Larry ...
www.landlpardey.com/Tips/2007/April.html
You can also find discussions on The WoodenBoat Forum
and the boat design forum.
The second site seems to be sat on by guys like me who dog onto every new post and subject. I have a problem with them because what they say, often with something off color, is hearsay and somebody else's opinion - not even their own. They're comedians. And always NOT funny. I don't go there anymore.
The WoodenBoat Forum seems more sane. Inquiries are often by first timers so the experts who answer are likely to be basic and simple.
On the designforum you will find those who put Larry down - for whatever reason.
Larry at one point took at least one epoxy manufacturer to task for making false claims about the product. You no longer will find data sheets that say the epoxy is waterproof. Or stable in a cruising environment.
Lin and Larry have built their own sailboats and taken them around the world. Larry is an amazing observer. With tens of thousands of cruising miles in wooden boats I'll take his prejudice on glues for gospel. They have received recognition and awards (for their convictions and courage I expect.)
I listen to them and ignore the jealous marina rats who can only put them down.
Both Resorcinol and epoxy have their limitations.
The first because it is a technical glue.
And epoxy because its versatility lulls people into ignoring its limits.
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We all labor with what we know - what we think we know - what we would like to know - with modern chemistry and with traditional ways of thinking and working, I don't believe any thread with prejudices and opinion is convincing.
So try this one on for size and follow it through to the end. It's on the www.woodenboat.com forum. And this is a "flog the dead horse" subject for many of these guys. This thread has a bunch of boat builders and amateurs talking about this subject. Not all the bases are covered but the thread is revealing and will help you come to an understanding of the problem.
google: White Oak glued with Epoxy, PL, Gorilla Glue, Resorcinal The....
(incluide the resorcinal (sic) misspelling.)
The thread begins with "few 3" post
Last edited by ebb; 02-02-2010 at 06:46 AM.
My resorcinal will show up here Monday from Jamestown.
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