PL and Epoxy on the same project?

I have not experienced PL Premium foaming. For $7 buy a tube and try various configs.

 

I plan on trying the economy epoxy from duckworks next time, while I like the MAS it is expensive + shipping and not to many dealers near me.
link: http://www.duckworksbbs.com/supplies/epoxy/marinepoxy/index.htm

 

Note the bulge at the back of the skeg and along the seam(s). I cleaned this off and then did it again and once again later. I think the warmer it is the foamier it can be. This was within the last week of August.

 

Polyurethane glues are expensive and no better than a good water-based glue in a well-fitted joint, and useless for boat building purposes in a gapped joint. Used in a gap or fillet it turns into insulation foam with no structural value, except maybe to keep out draughts. I would not wish to trust my life to a boat built with it.

I use Titebond III and epoxy in my chine boats. Titebond III is used where I can easily get a perfectly fitted joint that is not exposed to water below the waterline. Epoxy is used for gap-filling and exposed locations. Titebond is faster, cleaner, cheaper and easier to use than epoxy.

Typically I use chine logs which are glued to the ply planks at the same time as the inwales. This is done with the plank laid flat if the chine log is thin enough to bend easily; that way it supports the thin ply during handling. The logs have more volume than the fillets but lower density so there is little weight difference, and the wood is as strong as the ply which is as strong as it needs to be. I prefer the look of the chine logs to the epoxy fillets in S&G construction and they require no sanding.

Once the sheer and bottom planks (odd planks) with chine logs attached are bent around the station forms the garboards (even planks) are added between them to complete the hull using epoxy. The Titebond joints on the chine logs are only exposed along one edge inside the boat, which is an inside corner so the protective varnish or paint doesn’t get rubbed off.

I use epoxy in this way because my tests suggested Titebond loses some adhesion strength when the wood around it is wet. Although it recovers once dry there is the risk that it will let go if stressed while wet. Epoxy retains its grip on wet wood. My theory is, epoxy makes a chemical bond to the wood; I suspect Titebond merely keys into the grain and is less effective if the wood has been softened by water. In addition the last seam joints are the hardest to fit exactly and the epoxy fills any gaps.

The 2-part epoxy in a caulking gun tube (West Systems and System Three) is very convenient and effective, and available is several formulations, but more expensive than regular epoxy. That’s OK for me since I don’t need much and a tube will do a small boat or two, and I don’t want to bother with pumps, filler, micro-balloons, mixing sticks and pots, and long-term storage.

 

PL Premium and the PU's like Gorilla Glue are similar, but not the same. Both have the same base, but are quite different in physical construction on a molecular level, as well as formulation. TiteBond III is a PVA and a product I use fairly often. Personally, I have no use for either type of previously discussed polyurethanes. Polyurethanes have considerable difficultly remaining stuck to wet wood in testing, unless under fairly high clamping pressure during the full cure period (a few weeks) or use a very high cyanoacetate activation, which none of the discussed polyurethanes do.

As Terry mentioned TiteBond III (the only PVA I'd recommend near a boat) is pretty good, but has it's own issues, such as creep, tremendous lose of stiffness with the mere mentioning of moisture, high clamping pressures if used in a structural environment and the disclaimer from the manufacture, that it's not to be considered a structural adhesive. If you can live with this, then go for it. This said there are uses for TiteBond III, but keep it out of the bilge or any likely to get wet locations. It's fine for interior work, furniture, cabinets, light spars, etc. I've just made a cradle with it.

Epoxy packaging that places cartridges in a caulking gun, is way more costly then just buying epoxy in a jug. You pay over twice the per ounce amount packaged this way, but it can be handy. The mixing tips have gotten better over the years, but I still remember the first generation tips that didn't give you a complete mix, which was enough to really piss you off.

PL Premium and Gorilla Glue are also more costly then epoxy, if you compare price per ounce and avoid paying $100 dollars or more a gallon for epoxy. I pay about $40 a gallon for name brand epoxy and much less for "less refined" epoxy formulations. Here's a tip folks, buy 3 or more gallons of epoxy. Okay, some of you will now have a life time supply, but keep in doors, out of sun light and sealed up, it'll last several years without worry. 3 gallons is the usual "price break" and you can save in the neighborhood of 35%+ over a half gallon or gallon price. Yep, that's right 3 gallons for less then the price of two. Hummmm . . . Also check for local formulators. They're everywhere and I have one just a few miles from me, who's making special "PAR" batches (no kidding that's whats on the label) at a fraction of the cost of West System.

Gorilla Glue is about $.50 per ounce in the 4 ounce bottle ($64 a gallon) and about a $1.05 per ounce in the 18 ounce bottle. PL Premium is $.45 per ounce in a 10 ounce cartridge ($57 a gallon). My $40 per gallon (includes hardener) epoxy is about $.31 per ounce. Even if you pay full retail for your name brand epoxy (about $100) it's still $.78 per ounce.

Given what epoxy can do, compared to the other adhesives and the real costs associated with these products, it's tough to complain about epoxy costs. I have an experiment going this summer. I've sheathed a plywood shape with TiteBond III and 6 ounce cloth. I couldn't fill the weave with TiteBond (I tried twice), so I just primed and painted it. Well see how well it works, but don't hold your breath, partly because it cost more to laminate with TiteBond then epoxy, but mostly because I know the moisture vapor percentage it'll permit. Though this percentage is good enough to just barely pass the short term type 1 test, it will not last in time trials.

 

Epoxy is great. But something that you could just squirt out and stick it together would be handy. Has anyone considered polymide hot melt glues? The sellers claim "working characteristics of epoxy but without the mixing". It looks like it cost about $0.73 per ounce.

http://www.glu-stix.com/shop/page/product_detail/Product/67136cccf00d511637cd2e7ece2b38b7.html

 

A minute of working time doesn't let much adjustment. Creep will be a big problem. It's sensitive to chemicals and UV. It works great for sticking a well glittered star onto a paper angel's back for a Christmas present from your 10 year old, but I wouldn't trust it to hold a boson's chair 30' off a deck. If it's a HMW version it'll be fairly strong, but nothing near the strength or stiffness of the epoxies we usually employ in boats.

 

Seems like we are going in circles here. Let's summarize:

1) Epoxy resins mixed properly and used according to manufacturer's specifications is an optimal proven adhesive for marine environments.

2) Polyurethane resins mixed properly and used according to manufacturer's specifications is a lower cost alternative. This cost advantage has to be weighed against composite structures that may be higher weight / lower strength than comparable epoxy structures.

3) Water resistant glues like Titebond III are suitable for use where they are not exposed to immersion and sustained water contact. They may be suitable for dry-sailed low cost boats with acknowledgement that the resulting boat may not last as long as the same boat executed in epoxy or polyurethane resin.

4) Construction adhesives and other bonding formulations may be used to construct low cost, reduced lifespan boats with acknowledgement that the resulting boat will have a far lower lifespan than any of the above.

5) Traditional plank on frame designs caulked with oakum or similar are out of reach for the entry level skill builders and although modern adhesives aren't used, they are viable boats.

6) Sub-optimal adhesives produce lower strength and lower reliability structures. Construction techniques need to be matched to the adhesives used. Stitch & tape works with epoxy fillets - but does NOT work with less capable adhesives. The lower performance the adhesive, the larger the bonding surface required and more help (screws etc.) it may need.

From my point of view, the effort required to build any boat is pretty much the same, regardless of the choice of adhesive. Since the "labor" component of the build well exceeds the "material" portion from a financial point of view, if the objective is a long lasting boat with resale value, adhesive choices are best optimized for performance, not lowest cost. If the builder places no value on their time, the cost of the adhesive becomes a much higher proportion of the overall investment, therefore in some cases optimizing low cost may be practical. I feel this may be appropriate at the very low end of the marketplace where the choice is between "no boat whatsoever" versus a "short life, minimal cost" home build.

Even the worst modern adhesive and plywood can produce a functional boat that may last a season or two if dry sailed and well painted with a good barrier paint. Compare this to the build technology of a couple generations past (hand caulked, plank built boats) and the difference in basic skill levels required quickly make it clear that a dirt cheap "new" technology home build is viable at low skill levels if carefully maintained.

Boats produced with sub-optimal adhesives should NOT be used where their failure may endanger lives. What is acceptable on a small mill pond close to shore is not acceptable offshore or out of easy swim range. Basically if you like the people using the boat at all, better materials will give you some assurance you will see them again alive.

--
CutOnce

 

So I guess I take the Ex out on Superior in a cardboard boat glued with Elmers... I'm right on that!

 

A dry-moored boat doesn't get a lot of stress from mere day sailiing. I built my small sailboat primarily with Titebond III except for one exterior joint exposed below the waterline that has epoxy. It was finished with latex house paint and water-based varnish, the plan was to store it under cover but it has been stored outside all year round, now into its third season.

The paint looks OK but the varnish already looks like it needs refinishing. The "BS1088 marine plywood" has a split in the face veneer which doesn't speak well of its quality - I suspect only the BS part was accurate - and I'd guess the house paint is not keeping the wood dry either.

Despite a harsh environment there is no sign of any joint failures. It hasn't had much use due to health problems now hopefully gone, but I will refinish it and check it thoroughly before it goes back into the water next year.

 

Is you BS-1088 Okoume or Meranti? The latter can check if permitted to moisture cycle. This is why plywood boats get the "please sheath" disclaimer from their designers. Also check the face split and see if it wasn't a surface defect filled by the manufacture, which can often fall out with movement. Okoume is well documented as not especially tolerant if exposed. Under paint is exposed, unless it's a pretty thick layer of LPU. Under an acrylic (latex) house paint, you've just applied a sheet of news paper on a pile of puppy poop. Eventually it'll let you down and probably leave a stain.

 

Took a couple of minutes for me to get off the floor for that one!

 

I had a Piver Nugget.
It was made of 1/4" Douglas Fir sheathed in fiberglass/ polyester resin.
It was just fine externally, but rotted out internally due to fresh water in the bilge, even though it was soaked with green cuprinol.
My subseqent boats, a Buccaneer 24, and 28, were built with 1/4" mahogany marine ply, which was coated with two coats of Epoxy inside and three coats outside. Fiberglass tape set in epoxy, only on the panel seams. Painted with no undercoat in polyurethane paint for a hard gloss finish. Resisted abrasion well. The only gouge I did get was quickly cured with a dab of epoxy filler smoothed out with a spatula.
Worked well for me.

 

Par: good one! I thought ply that would take boiling for 48 hours or whatever would laugh at an occasional bit of rain. Of course I did not plan to store the boat outside, I just never gave storage a thought . . .

 

Sorry for the visual I must have imbedded into your brain Steve. I hope it's not the last thing you remember as you lay down to sleep tonight.

The Type 1 WBP test is fairly short term and has a very quick cycle, compared to reality. Naturally, it's supposed to simulate the environment, just at an decelerated pace, but what it's really good at doing is separating the boys from the men in the WBP department, not real world conditions.

So, how many feet (meters?) of snow laid on top of this puppy (Dace?), how many times during how many winters? And you have just a single split showing. Sounds like it's faired surprisingly well . . .

I'm now at a point where I can repair boats that I've built or repaired many years previously and can attest to the effectiveness of epoxy on plywood. The Gougeon brothers are fanatical in many regards, but they've learned these same things sooner then I, which is likely why I'm now becoming as much of a nut job about it. At $30 to $40 a gallon and considering all that it does, it's often difficult to bother opening another container of something else.