alternatives to epoxy

For stitch'n'glue building, some (budget) builders are using one part construction adhesives such as loctite PL premium. I looked at the data sheet, it says not for immersion. But if the project is clad in glass and paint, that shouldn't be a problem. I'd be interested in a one-part adhesive that approaches the strength of epoxy but was simpler to apply, and possible cheaper - and of course, appropriately water resistant. Any opinions/advice? thanks.

 

Construction adhesives like PL 400 are waterproof and are mainly used to glue plywood to 1.5" wide floor joist. I have had occasion to tear it off and you will tear some plys off. If you epoxy a 2x6 to a 2x10 and you have a 24" epoxy joint and you try to break that connection with a chisel and 3 pound hammer you will tear off thick pieces of solid wood from both pieces.
Nothing hi teck in my test BUT epoxy is a much stronger adhesive. And we know that it is truly waterproof.....my 2 bits. I would not try to save money on your adhesive. http://www.oneoceankayaks.com/Epoxresl.htm

 

I have used extensive amount of PL Premium poly Construction Adhesive on my underwater seams. I sealed the entire boat with PL and also mixed PL with sawdust 50-50 it creates a real nice tight swelling glue for large gaps. Cover up the mix with cereal bag plastic and you can get a smooth finish.

I buy the large 30 oz caulking cartridge as it is a lot cheaper then.

And also Black PL polyurethane roof flashing, I skim coated under water wood planks and filled above water seams in various places where I wanted a strong rubber like bond. Black PL is a softer rubber than 5200, so I find it yields to the planks when they move.

I experimented with skim coating underwater planks with black PL mixed with 1/32 milled fibers and black PL alone, and I really like it mixed with microfibers.

Now here is a look at the keel minus worm shoe where I sealed up bolt and screw holes with PL and sawdust mix. If your going to go thicker than 3/8 inch, then absolutely mix in some sawdust with the PL. Doing that it will cure in thick layers.


Here is Black PL in some seams at the bow.


And following behind the Black PL, DAP Dynaflex 230 i put in all above water seams.


Aft part of the boat, I skim coated Black PL on the planks with it also in the seams. I did this since a lot of fresh water cascades from the deck back here, and I had to fix some rot.
I also wet and dry sanded it smooth after a weeks cure and filled in any imperfections with Dynaflex 230, got it very smooth and water cant go through this coating.





Doing that was not easy but it was interesting and I think adds to the lifespan of the planks and framing.

Notice the entire keel is coated with Black PL. My entire underwater hull is coated with Sanitred permaflex, and or Black PL. and all underwater seams are locked tight with PL premium and some with PL premium mixed with sawdust underneath those coatings.

the permaflex was on the hull 5 years ago and held up ok except for the oak keel. I did not stick well there, so I pulled it loose and coated with Black PL. So far it has been flawless.

Looks good to me


There is Black PL under that white paint

Link to album with lots more pics
https://picasaweb.google.com/105248...rHauloutJune242014?authuser=0&feat=directlink

Feel free to ask or say anything.

 

Great info and photos. What is it like if you need to grind it or sand it, with or without the sawdust and microfibers? Does it clog up a grinding wheel?

 

sdowney

thanks for your very helpful detailed advice and pics!
I see you're using Pl as filler and PL black as surface sealant.
I'm mostly interested (right now) is structural adhesion.

"I experimented with skim coating underwater planks with black PL mixed with 1/32 milled fibers and black PL alone, and I really like it mixed with microfibers. "

I've found 'food grade' wood flour to be a great wood filler with epoxy. (Yes, 'dietary fibre' is fine sawdust).

"Black PL polyurethane roof flashing, I skim coated under water wood planks"

how do you apply it - thin and brush? - thinned with what? Or with a spatula?

And how did you sand it? It seems it wouldn't take sanding well.

 

This is the product
http://www.homedepot.com/p/Loctite-...e-Roof-and-Flashing-Sealant-1675273/203163733
No thinning. Clean up hands with dish soap, a scrunge and water. No solvents, nothing else needed.

I used a rotary orbital 5 inch sander and those sticky sanding discs, about 80 grit paper. It does not clog the paper.
It actually sands down fine either wet or dry. But wet sanding is easier. I would use a hose, spray then sand.
You need to wait up to a week before sanding to let it cure. It also when sanding may form tiny sticky rubber balls which to remove simply scrub the surface wet with a cotton bath towel.

I spread it on the surface in multiple thin layers using a 6 inch putty knife.
You can actually form a decently smooth flat surface about 1/16 to 1/8 thick this way. Black PL has a very sticky feeling surface for a while so new layers adhere very well to it. For it to lose that stickiness can take couple of weeks. You get extensive working time of many hours with Black PL. You can also after it skims drier on the surface, wet the surface and use your putty knife or hand to smooth it a little more.

I used maybe 30 to 40 tubes on the boat which is 37 foot. I thought it gives real good coverage, so perhaps $250 to $300 is what I spent.
I also skim coated the rudders and the struts to seal them from salt water. I coated from bow back 10 feet, the entire transom below waterline, the entire keel, and about 5 feet forward from the stern the entire area. And topsides the bow. I rescrewed the forward planks where it meets the stem, and cleaned out all old caulking and used Black PL in the seams, totally seals this from water. This gave it a lot more strength and will absolutely keep fresh water out. The black PL being a resilient rubber it wont ever crack. I coated aft the sides going forward 10 feet. I only used milled fibers on the bow underwater area.

When I used the 1/32 milled fibers, (they are fiberglass), I did this on the forward underwater part of the hull going from bow back about 10 feet. Mixed in about 30% fibers which act as an extender and also a toughener to the rubber.
I really liked the surface it created. Having fibers in stiffened the mix and so made the surface coating a little thicker. It also sanded ok, and on some ridges I used a steel wire wheel in the drill and it came out beautifully smooth, no water needed, do this dry.
I tried a wire wheel on Black PL without milled fibers and it created some small craters in the surface, was very hard to wire wheel without the milled fibers. With a wire wheel and the milled fibers mixed in, it worked extremely easy to smooth out the surface, not that it was really needed. To mix in fibers, I used plywood, squeezed out Black PL spread out on the board, then put the milled fibers on top and worked it in. It reminds me of working with bread dough like when rolling flour. abut 30%to 40% is what I used of fibers to 70% to 60% black PL.

I found filling the seams with black PL to be easy except I did one side with the sun beating on it and some entrapped air caused some areas to bubble out which is hard to fix if you want a certain look like seeing the seams. So the best thing I found for filling seams above the water is the Dap Dynaflex 230. Very easy to fill seams and fix them. Can be hand wet sanded or power wet sanded the next day or if real hot, same day. After a few days it dry sands too. Then over top skim coated Black PL.

Another interesting think about Black PL, after it sets a day or two, if you heat up a tool like a small screwdriver with a torch, you can melt it, I did that in some of the seams to remove material to show the seams, because sanding seams is almost impossible with Black PL. Not fully cured, heating Black PL turns it into a black grease, then you use dish soap and a scrunge and can scrub it off. If you wait too long, the heat method no longer will melt the Black PL.

When black PL is cured, it is a softer rubber than 5200.

There is one odd thing about black PL on pine wood but not all spots, just some, the sap I think interferes with the cure or the adhesion. The fix is to scrub the pine with dish soap and a scrunge, rinse and let dry then coat. Seeing most of the boat is mahogany and oak, no trouble with that at all.
Some few pieces on the hull, I used some pine and noticed it did not cure in a few small areas on the pine wood So scrubbed with dish soap and a stiff brush or a scrunge, it will remove the uncured Black PL, and whatever chemical was causing that problem, then recoated and it cured fine. It might be that some of the problem was it was pressure treated pine loaded with odd chemicals.

 

Here is a good picture showing Black PL coating the rudders - struts - bottom aft view.

 

thanks for the update sdownwey - very helpful.

I found this link - very useful primer on glues (no pun intended, heh)

http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=smalser&file=articles_737.shtml

 

Have not had much troubles with PL Premium anywhere.
Of course my boat is bronze screwed and glued. Adding sawdust to the glue has a marked effect on the properties. It makes it swell up a lot more and cures in any thickness. I found it to be a good wood filler and it will take wood stains. I have fixed some rot by wire brushing the rot and filling with a mix of PL and sawdust and never has rot reappeared. In 1998 I replaced the transom planking and in 2005, noticed rot was developing under that SS trim. I cleaned it all out, bleached it, then filled with PL mixed with sawdust, packed it in there and put a cereal bag (HDPE plastic) over to keep it flat. It expands aggressively and fills up any cavities so keeps out water. Perhaps PL also kills rot as it never comes back.

If you get PL premium CA on your hands about the best solvent is E10 gasoline. Gas quickly dissolves the glue. Seems like any other solvent leaves behind a residue of glue which will make your skin turn black, I guess it picks up dirt. then it has to wear off over couple of weeks. I tried dish soap and rubbing alcohol but nothing works perfectly as gasoline.

I have an upper cabin board to board issue which I tried using the PL, but it developed a crack again along the glue line, too much stress between those boards. I plan to remove my repair and use the black PL there which has a lot more resiliency, will yield and snap back, just like a rubber tire, so that should resolve the issue. It is basically 2 large one inch thick boards rabitted together and was glued. when the OEM glue line broke free, those two boards started to work along their edges, edge to edge, so any paint there would always crack and show the seam. I will have to take my circular saw and remove a small section= sliver of wood and fill up with Black PL and maybe a long squared piece of mahoagny. Nothing will show on the inside of the cabin.

 

SDowney -
thanks again! Love the anti-rot aspect! And the gas-as-solvent tip.

" Adding sawdust to the glue has a marked effect on the properties. It makes it swell up a lot more and cures in any thickness. I found it to be a good wood filler and it will take wood stains. I have fixed some rot by wire brushing the rot and filling with a mix of PL and sawdust and never has rot reappeared. In 1998 I replaced the transom planking and in 2005, noticed rot was developing under that SS trim. I cleaned it all out, bleached it, then filled with PL mixed with sawdust, packed it in there and put a cereal bag (HDPE plastic) over to keep it flat. It expands aggressively and fills up any cavities so keeps out water. Perhaps PL also kills rot as it never comes back."

why HDPE? Is it the same as what is sold as 'peel ply'?

"If you get PL premium CA on your hands about the best solvent is E10 gasoline. Gas quickly dissolves the glue. Seems like any other solvent leaves behind a residue of glue which will make your skin turn black, I guess it picks up dirt. then it has to wear off over couple of weeks. I tried dish soap and rubbing alcohol but nothing works perfectly as gasoline."

have you tired latex/nitrile gloves?

 

Cereal bags are handy as our family eats a lot of it I suppose. Those cracker bags are also same stuff, the glue just does not stick to it. It will peel right off after it cures.
Peel ply I guess is an HDPE type plastic.

Gloves would work, but never bothered.

The milled fibers dont work as well with the PL CA, I may have mixed in too much.

What does work ok is the open weave FG duct tape meant for seams.
I happened to have a lot of rolls here so thought to use it up. I laid in multiple layers of it mixed with PL and as it sets uses a putty knife (or fingers) to squeeze it down.

I repaired a broken formed plywood chair botton doing that, it worked great.
I coated a rusted metal electric grill drain base.
Right now I am repairing a formed plastic cover for an old electric anchor winch which was cracked and missing a few pieces. It is working great. I can take a photo show what I mean.

Here it is
Added a SSteel reinforcing bar under the FG tape. Plastic had cracked. It is a naturally weak area. It is now quite a lot stronger.


Plastic top had cracked due to someone dropping something on top.
And something whacked a small hole in the front. Likely due to the anchor.



I plan to put some more reinforcing layers on the inside. PL sticks very well to this kind of plastic.
And I first roughed it up with some sandpaper.
The squeezed out some PL.
Cut some FG tape strips.
Laid them in the glue, used putty knife to smooth it out.
After 5 to 10 minutes put some cereal bag plastic on top and smoothed it flat.
After a few hours, pulled off the bags.

Plan to spray paint gloss finish the outside, maybe a hammertone finish paint.

 

"The milled fibers dont work as well with the PL CA, I may have mixed in too much. What does work ok is the open weave FG duct tape meant for seams.
I happened to have a lot of rolls here so thought to use it up. I laid in multiple layers of it mixed with PL and as it sets uses a putty knife (or fingers) to squeeze it down."

Not quite sure what you mean by "open weave FG duct tape". I've looked at the open weave fibre tape used for drywall work with similar intentions.

So those pics are PL with open weave tape? I'm assuming the adhesive on the duct tape does not compromise the PL bond?

 

The anti-epoxy crowd

I found this online - a strenuous argument against epoxy by Larry Pardey.
The doc doesn't list an author - but the reference to Taliesin gives it away.

 

I've avoided this thread for a few reasons, but damn, Pardey showed up, so . . .

Larry Pardey thinks epoxy is a fad and will go away someday. His comments and opinions don't have any science, documentation or even logic behind them. He's simply an old school sailor, that thinks all sailboats need to be slow, cumbersome, leaky and without basic amenities, like GPS, or A/C, let alone a flushing toilet.

PL adhesives have two basic drawbacks: modulus of elongation properties and creep. On small boats, you can live with these short comings, but on highly loaded, dynamic structures, you should choose something else. Construction grade adhesives are designed to work with static loads, so they don't need a very good elongation modulus and creep can be controlled with metal fasteners. So, if it's used as intended, to hold plywood to a floor joist for example, it's great stuff.

Now, if you take the same floor joist and plywood combination and start twisting and flexing the assembly (like a boat underway will), this is where the downfalls of this combination start to show up. PL is fine for a cheap, not expected to last very long, down and dirty type of build. In fact, I've developed a skiff design that uses no epoxy, just PL, so the whole boat can be built from big box stocks, but it's not going to be as strong or as durable as other adhesive and materiel choices.

 

Yes, the drywall FG tape. It has an open weave compared to a FG cloth meant for epoxy resins. The adhesive on that tape has no effect.



In past I tried PL Premium with tight woven cloth, problem is it gasses off a lot during the cure and tends to lift the FG cloth. So you have to keep forcing it down. I found that does not happen with drywall tapes. All I am doing here is strengthening and repairing this plastic cover. It costs me very little to do this and is very effective and durable type repair. You can add many multiple layers to build strength if needed. I did that to a cracked 1/2 inch thick plywood chair bottom a few years ago and it has not failed. I use this chair everyday. On the chair, I layered 2 to 5 crisscrossing layers on both sides of the plywood.

I bet Black PL would work great with FG cloth since it does not gass off during the cure and is thin enough to work into cloth and has many hours of open time even at 95* . But your could not saturate a FG mat with it.

You would spread a layer down, then press in the cloth and spread in more Black PL on top.