alternatives to epoxy

Snowbirder - thanks so much for your input (btw you posted it twice I'm not familiar with hotmelt pu - can you tell me more? Do you regard it as better/stringer than ie loctite PL premium - worth the extra trouble?

 

PAR and Sukisolo

thanks for your replies. I understand all the benefits of epoxy, as you've described. I'm just getting leery of toxicity issues (like snowbirder).

PAR, if I wanted to coat interior surfaces with a non-epoxy sealant that was cost effective and bonded well with epoxy - what would you suggest? (I suggested thinning not to extend but to enhance soaking in, if it left a rough surface presumably it would provide more mechanical 'tooth' for epoxy to bond to?

You guys seem to have a disagreement about prices - Sukisolo says weldwood is much cheaper (?).

thanks again

 

There isn't any coating that's as effective on wood as a waterproofing agent other than epoxy. In fact, the I can't think of any other product that is truly effective on wood. This is the reason wooden boats have seen such a revival in the last 3 decades. With the wholesale replacement of wooden boats by production 'glass boats in the early 60's and by the 70's all of the boat manufactures either died off or converted to 'glass. This was because of the maintenance issues associated with moisture and wood. Nothing was waterproof enough as a coating. A number of adhesives where, but no coatings. With the advent of the Gougeon brothers developments in the 70's, wood could be coated, effectively sealing out moisture.

By the mid 80's the testing was completed and long term assurance, could be had with epoxy as a coating. This caused a slow at first resurgence in wood boat building and repair. By the late 80's a boom was in full swing and it's only slowed for the few economic recessions we've seen since. So effective is the coating, new building methods, entirely dependent on epoxy have been developed.

If epoxy is handled with the appropriate precautions, no toxicity issues will present themselves, for the vast majority of people. Some people will, in spite of precautions, but this is true of most chemical combinations. When fully cured, epoxy is inert. It's so inert, they use it in medical implant devices to seal circuitry and other elements. The problem most run into is, a casual regard for liquid and not fully cured (less then a few weeks after cure) epoxy. The most common concerns are breathing freshly cured epoxy and skin absorption. I know several with allergic reactions to epoxy. When forced to make honest answers, they all without exception, admit to be a bit casual around it for a long time. If you swim in a chemical soup, you can bet you'll develop an issue, just ask any production boat laminator about styrene. I've used epoxy since the 70's, but much more so since the 80's and though I'm now slightly reactive around certain formulations, I have no reaction around others. I'm lucky, because I was casual initially with the stuff, which is what likely caused my initial reactions to appear. Since figuring out it was the hardener type, that was affecting me and switching to different formulations, no issues.

WeldWood isn't a coating.

If you insure you don't breath freshly cured epoxy dust and don't smear liquid epoxy on your skin, your chances of a reaction a very slim. Again, some can have a reaction and there's no way of telling beforehand, though most of these folks have other allergic reactions to things, so a clue can be taken from this.

Testing has shown that thinning epoxy (or anything else for that matter) does improve surface penetration, but dramatically decreases it's abilities to waterproof something (a diluted goo isn't as good as a full strength one). Simply put, a waterproof coating is dependent on the quality and thickness of the coating, not how far it has penetrated a substrate.

So, in a nut shell, you can use other adhesives, but in the big picture, the quantity of adhesive, compared to a coating product will be hugely tipped toward the coating side. I used to do this, using several different glues, but now mostly it's just epoxy, to keep supplies simple and retain common techniques and tools used, not to mention I can be a wood butcher with epoxy, but not with the other adhesives. I once intentionally made a 5 sided box, by breaking the 1/4" plywood into the panel shapes over the edge of a work bench. Yeah, the "cut lines" where as rough and ugly as you'd expect, but I duct taped the box together and put a fillet on the internal corners. I then removed the tape, after the goo setup and smeared thickened epoxy on the outside corners. When it was fully cured, I hit it with a DA, touched up some divots and it was just as ready for fairing compound, as if I had used a fine toothed saw to cut the panels. It was no weaker and I still have this box, which I store about 3 dozen spring clamps in. I've yet to find anything that can come close to all the benefits that epoxy can bring to the table. Some adhesives can be stronger and make tighter glue lines, but can't be used as a coating or to bond a fastener into a hole.

I guess what I'm saying is don't be afraid, just cautious and protected.

 

Agree with literally every word PAR just posted.

The PU hot melt I'm using is as an adhesive only, not a coating. There is nothing to replace epoxy outdoors. I hired people to put the epoxy on the few wooden parts i have that I then glued on, after painting them.

 

True PAR,but the OP asked for water resistant glue(s). Though I have a bit more faith in UF resins especially on small boats like racing dinghies. There are an awful lot of 40 to 60 year old Fireflies still out there, moulded with it. Collar's who still make wooden masts (S Spruce and D Fir) use it along with resourcinol. Certainly I've been offshore in 30'+ cold moulded hulls laminated with it but sheathed with epoxy and Dynel or similar. IMHO quite a sensible approach.

In fact Fairey Marine buried a bare Firefly hull in the mud between high and low water somewhere - probably the Hamble. After a year, they took it out, cleaned and dried it and finished it off (rest of the wodwork, paint, varnish etc) and it went racing at the next Championship.

Generally I've found the joints on loaded spars will give up - after 30+ years use or so. One good thing is, they tend to give warning and then you can simply split the joint, plane off the hard residue and reglue....
Worst thing is when someone squeezes PVA into the warning crack.....

These guys have a good range of adhesives, but availability in the US I have no knowledge of.

http://www.alansonsuk.com/urea-and-resorcinol-adhesives.html

But please note the joints MUST be tight for most of these other glues - UF, resourcinol etc to work at their best. Epoxy is very tolerant of er er gaps in the joinery. This is one of it's many properties, but for immaculate topside work with invisible glue lines it is not quite so good.

 

I have a related question. I am thinking about making some removeable boards with 1x6 tongue and groove softwood lumber. I want to avoid using epoxy for all the usual reasons, but mostly to keep the time and cost down while I test out the idea.

So if I use polyurethane and later decide I would like to add epoxy and glass reinforcement, should I start over or just sand and epoxy over the polyurethane? Do I need to get it all off or just most of it? Would it be simpler to start over? Alternatively, if I use the lumber bare for a few weeks, and that way I can still use them for firewood if they get broken or I decide to go a different way. The area I am covering is about 8 feet by 30", so six 8 foot 1x6 cut into thirds, for about 18 slats. Thoughts on using them untreated for a few days or weeks?

p.s. If I like the look and functionality I want to find a way to reinforce them for strength and have them still be removeable. Will also find a way to make them semi-watertight and still be removeable, but until I add some automatic bailers as scuppers I don't mind if any water makes its way down to the bilge.

 

^^^ You've got to go back to bare wood to switch to epoxy.

 

Thanks snowbirder. I think I will start with bare wood, maybe 6 cut from two 8 footers, and see how it looks and feels. Then start over once I decide what to do. Worst case I have some untreated kindling.

 

Epoxy will stick to most things, though does have trouble with PVA's. This said, if you do put epoxy over something else, you're dependent on the peel strength and adhesion of the underlying whatever.

Often times, grinding back to bare wood will work, but also sometimes, unless you grind down a lot, the previous adhesive has sealed the wood pores and prevents epoxy, from getting as good a grip as it can.

Yes, agreed Suki, water resistant, but to me water resistant means, you'll have a little time before it lets go. There's lots of water resistant glues and adhesives. I use to use resourcinol exclusively on spars, but now very rarely. I repaired too many old boats with this stuff and it does work well, but doesn't age as well as epoxy. I had to redo a transom I replaced a core in. I did this job back in the early 90's and damn what a pain in the butt. No deterioration of the goo at all and it was still stuck like an ugly girl to a good looking boy friend.

 

Be careful Jamie, epoxy does not like bonding to wet timber. The drier the better, which is why I opt for a more moisture tolerant adhesive in certain situations on repair work. New build or 'bone' dry and epoxy is excellent. A lot of people underestimate the time to really dry some timber out, which then leads to epoxy not bonding and the dreaded black mildew appearing under it - then even harder to remove.

Agreed PAR, well worth clearing of any adhesive residue prior to rebonding. You can guess my pet hate is the so called water proof PVAs'......

 

Thanks SukiSolo.

 

"Agreed PAR, well worth clearing of any adhesive residue prior to rebonding. You can guess my pet hate is the so called water proof PVAs'"

right, bad stories about TitebondIII - nothing sticks to it.

"This said, if you do put epoxy over something else, you're dependent on the peel strength and adhesion of the underlying whatever."

Good point PAR. Obvious, but good to remember. Same goes for paints, etc.

But on the subject of "The drier the better, which is why I opt for a more moisture tolerant adhesive in certain situations on repair work."

I'm still kicking this around. PAR's KISS principle - just one kind of adhesive - make good sense. But if, say you went with a PU for scarfs and skin-bulkhead joints, then fillet epoxy and glass, would there be benefits htat outweigh the added complexity? Thinking out loud here - I think PAR and Sukisolo have really addresses this already.