PL Construction Glue vs. Epoxy

[andrewmct]

I have been considering a ply on frame spira dory and have been looking at blogs on line about dory building. One builder has been using PL adhesive (polyeurethane I believe) and was wondering if it can be used instead of epoxy for frame building etc. The builder also glued the plywood skin to the wood frames using PL. Is that a big no-no? I thought the frames were best left un-glued. Thanks for the help.

Andrew

[donald branscom]

I really like the PL premium glue. It costs less and it is easy to use and it expands.
I built a plywood boat and glued the skin to the frames.

All the wood boats I have seen attach the ply to the frames.
On a steel boat you do NOT weld the frames to the hull material only to longitudnal stringers.
Also on a steel boat, all finish welding done on the INSIDE first. Then the outside.

On the net there was a test of PL glue joints tested and put in water, and boiling water. All the joints passed.

No amine blush to deal with. Can be used down to 50 degrees.

[Bob Smalser]

As it has a very limited track record to bet your family's safety on, read up on it.

http://www.sawmillcreek.org/showthread.php?t=21822

Some factors that may be limiting are:

1) That PL doesn't stick at all without at least some clamping pressure, and accordingly, the strength of the gluejoint is probably proportional. That means in situations where workpieces to be glued barely touch, you still need epoxy.

2) It was formulated as a convenient construction adhesive, usually used in conjunction with mechanical fasteners. Open times are short compared to traditional marine glues. If in warm weather it skins over before assembly is complete, the gluejoint can fail.

3) Because it glues such a wide variety of difficult materials, PL is probably chock full of cyanoacrylates (superglue). Superglues by themselves are way too brittle to use as general-purpose glues....the joints break easily under shock loads....and you have no idea how PL will continue to perform over time.

[Thorne]

I use PL Premium quite a bit for non-critical joints, and it has worked out OK so far with no cracking or failures (Gorilla glue failed all sorts of applications, for comparison). Nothing quite like it for a quick "grab and glue" job, as you can cut open the tube when the spout finally blocks and glop it on with a knife.

To me the biggest drawbacks are that it never gets hard enough to be sandable, and exposed beads/surfaces will bubble a bit -- making a visual blemish. See the base of the oarlock pad here. Easily trimmed but then some of the bubbles are exposed.

Untrimmed -


Trimmed / cleaned up on another oarlock pad -


But I'm a rank amateur compared to Bob and many others here.

Bob -- a question about open time for PL Premium. I was using it for gluing oarlock pads to the gunwales (backed by mechanical fasteners) during a rainstorm in an open shed. Since PL Premium is moisture-cured, wouldn't those conditions be the worst for open time for that adhesive type?

Since epoxy is heat-cured we tend to think of hot temps as impacting open time, but for PL Premium I wonder if we should be considering other factors?

[erster]

Once the PL construction Adhesive has skinned over, [the thinner the amount the quicker] if you are using the glue to bond parts together and the glue to be structual, you have lost this ability by comparison to almost all over adhesives being sold in tubes. With fasteners, and proper fits of bits and pieces, chewing gun can be used to seal the joints. Think about the standard of bedding, for boats of the past, dolphinite, which did not expand and did not bond and used as a structual glue, only sealed the area to hopefully keep moisture from building up in dead spaces when wicking takes place or when dampness gets caught up in dead spaces.
Expanding glues when used to fill misfits and voids creates air which further reduces structual intergrity.

[ssor]

The methods used by house carpenters make PL Premium very desireable. You lay a bead of adhesive on each joist and lay a sheet of subflooring on top and nail it down. If you are building a girder, you lay out the beam, lay a fat bead of adhesive down and nail down the next layer of 2x12's. boat building isn't quite so easily simplified.
In boat building we tend to cut and fit with great care the frame of the boat. The trim and finish work will be exposed to the eyes and be the subject of pride by the builder and the owner. With house building I do the best I can and move on to the next job.

[andrewmct]

Thanks for the replies so far. One thing that I am slightly confused about now is the makeup of construction PL. I have used Gorilla glue before and didn't like it. It foamed and is moisture activated. The glue I have in mind is the tubes ofconstruction PL used for wood, concrete, etc. It has a goopy property and as far as I can tell, doesn't foam or need moisture content to cure. That is the stuff I was thinking about using. I will not use Gorilla glue because I have found it to be brittle and fussy. The gentleman with the oarlock picutures is using the glue I am considering.

[Bob Smalser]

... I have used Gorilla glue before and didn't like it. It foamed and is moisture activated. The glue I have in mind is the tubes of construction PL used for wood, concrete, etc. It has a goopy property and as far as I can tell, doesn't foam or need moisture content to cure.

Study the cured gluelines of PL and liquid poly after following the manufacturer's instructions for moisture content, clamping pressure and temperatures, and you'll find they are almost identical.

PL is the same stuff with the addition of ground limestone to thicken it and additional cyanoacrylates to make it stick to almost anything.
It is equally moisture activated, and even foams in its own way. All that ground rock simply tones down the foaming in reaction to moisture.



Keep in mind when boatbuilding that in the glue manufacturer's jargon, you are doing structural work. And that there is no such thing as an unimportant gluejoint in a boat two miles offshore in 40-degree waters containing my grandchildren.

[andrewmct]

Interesting stuff, Bob. Thanks and I will do some more research on this. I had no idea about tube PL. Thanks

[Breakaway]

And that there is no such thing as an unimportant gluejoint in a boat two miles offshore in 40-degree waters containing my grandchildren.

This quote is going above my bench!

[erster]

Lots and lots of little boats have been built with PL. Blue water cruisers are a different story. Besides you will be backing the glue with mechanical fasteners.

Lots and lots of plywood on frame boats which incorporates fasteners for a sound hull are built using PL as the glue of choice for two main reasons, ease of use and readily avaliable. Is it cheaper than epoxy and will it do what epoxy does for a wider array of jobs, mainly structural for the diverse builders these days? No way.. Do not get lulled into the notion that the PL construction adhesive is a structual glue exclusively for small craft given the wide array of skill levels by comparison for boats under 20 foot especially, either.

[Cuyahoga Chuck]

This little boat was built with epoxy and glass.
http://gallery.bateau2.com/displayim...lbum=333&pos=8
From a distance it looks like a lot of S&G plywood pirogues. But up close it looks like it's made from 12 different pieces of plywood. That isn't quite correct. It's made from four half-sheets of plywood (the material only comes in half-sheets) that have been scarf-jointed together.
I built this boat ten years ago when I had very little experience making scarfs. For this job I cut a total of 16 feet of scarfs. That 's 4 feet more than necessary because one scarf had to be recut and done over. The glue-up was very difficult because I had to prop up the panels on the basement floor which was not very level. But in the end I epoxied the whole mess together and it has stayed together and been in use ever since. There is only one screw in it. One of the breasthooks didn't fit so I pulled the seam together with a screw.
In ten years only one epoxied joint popped. It was at the intersection of the inwale and the breasthook. And it only failed because the boat came off my roofrack while on the Turnpike.
This boatbuilding project was a success because of epoxy. No other adhesive could have filled all the necessary stick-um and encapsulation required to put this thing together.No other adhesive would have tolerated all the screw-ups and inconsistancies I generated.
Epoxy is my friend. I am not going to engage in any hair-tearing or teeth-gnashing trying to find a cheap substitute.
Instead, I'm going to take this pirogue for an 8 mile run down a local, rather rocky, scenic river on Saturday.

[erster]

Stitch and glue boats are being built with PL as well. There is a funny attitude here, let me try and sum it up: Traditional wood and construction methods plus modern epoxy are the only acceptable way to build a boat- everything else is black death.
Reminds me of the back to the 1800's progressives that love their mac products...

Yep, you are correct on all accounts, this thread is filled with a bunch of closed minded meatheads gathered in front of their computer screens sitting in their wheelchairs awaiting their kids to push them off a cliff. Carry on.........

[pipefitter]

In construction uses, nearly everything these days is done with pneumatic fasteners at a very fast rate with multiple installers, also. The construction adhesive also becomes a semi-hard adhesive shim gasket that takes up space in the joint between fasteners which helps keep plywood decking from squeaking, fasteners from popping etc, along with the addition of glue coated fasteners and as an aid in situations where glue coated staples are used and as a redundant necessity in the eyes of the code enforcers and insurance industry.

Epoxy becomes somewhat expensive 'initially' as a coating and a laminating resin, not expensive when used as an adhesive.

[Thorne]

Can we leave the BS in the Bilge where it belongs? Some of us are trying to discuss glues and boats here...

If I was building a glued lapstrake boat with minimal overlap between strakes, I'd use epoxy if at all possible. Same thing for edge-gluing narrow pieces of wood, and covering wood with a cloth/fabric overlay. Ditto for fillets used to join stitch & glue designs.

But for wide joints backed by fasteners, and in particular for boats built at shows, schools and other places that have to meet regs for VOC and toxic materials, PL Premium is a good alternative for many (not all) applications where epoxy is often recommended.

[erster]

Thorne, there has been legitimate replies from real to life users of the PL products no matter how some folks choose not to accept the replies from certain people.

I use all three types of their products and have years of success using their flex caulks under structural conditions. Window, Door, and Siding sealant used in real to wooden boat hulls, Roofing and Flashing sealants gluing down hardwood flooring and wooden rail laminates, and untold amounts of additional bits and pieces and if I need a quicky product in many hidden positions to seal a seam I also use the Construction Ashesive. One thing that I do know if that it does not replace epoxy fillets and finish cloth tabs, and and does not replace thickened epoxy for gap filling either


As current as today, you will see that I carry all three of their main caulks and so far understand limits of each from using all three unless I happen to be out, such as the screw driver with the cured white product.



Accept it or discount any and all if wish. But accompanying photos will provide supporting evidence that at least two here including your photo will support certain testing of individual products.

[Thorne]

Interesting! I've only used the PL Construction product. Do you find the Window and Door to level better, stick better, or ? I used one tube of it around the house and yard, wasn't impressed but may not have tried it in the correct application. I've read good stuff about it on the Oregon Coots list also.

[Michael D. Storey]

Yep, you are correct on all accounts, this thread is filled with a bunch of closed minded meatheads gathered in front of their computer screens sitting in their wheelchairs awaiting their kids to push them off a cliff. Carry on.........

What a terrible thing to say.

[erster]

What a terrible thing to say.

Terrible is promoting the notion that PL Construction Adhesive used exclusively by itself to build a boat will be as good as a lot of other proven products. Highlighting reasons that PL is suggested in the use of building simple hulls is not a derogatory post either.

While doing so addtional elements are indeed in play for long term sucess rates. If it was worth the effort I would also provide you real boats operating in real life situations that are still going strong using big box glues that has been used for years in the home setting. The savings to the wallet is ten fold too. This will be my last post on this issue. Believe what you wish. There are some that will never accept enough evidence.

This is window door and siding which has some issues with painting when green but can be worked around, and far suppassed any "marine" adhesive for quicker drying, flexibility and even removable down the road when some form of adhesive and in turn structual product is called for. This product has numerous advantages over any tube of Construction Adhesive ever manufactured in the marine industry as long as you yourself become familiar with the products.

[Eric D]

I will say I have used PL roof/flashing on bilge plug on an alum boat that was in need of a quick fix. Slapped some on a chunk of wood and some on the plug and....it worked. So well in fact that 4 years later the boat still has that same patch job in place. One of those, yah, I should change that but...

Still doesn't mean I would not use epoxy for fillets. Still doesn't mean I might not use PL premium in certain applications.

[JimConlin]

I note that the pics show the boats very near land. That's prudent.

PL isn't better than epoxy, but someday, something will come to market that is better than epoxy. Hope I'm around to watch.
I believe this book talks about building with PL http://search.barnesandnoble.com/Ult...0071477925#TOC
Gasp it is in a book. Yeah I know the guy designs dinks and only a few hundred of them have been built. There are other ways folks.

[ssor]

One of the problems that keeps showing its face is that so many have a well defined opinion of what constitutes a proper marine adhesive without having defined the requirements of such an adhesive. Stitch and glue works because it involves large surface areas and so much redundancy. In the video thread of the construction a traditional bark canoe. The proper selection of all of the materials and the application of proper technique was foremost in the content of the effort. Are there better materials available in a wilderness camp? Probably but these have been proven.

[andrewmct]

Thanks for the help. There is obviously some strong thoughts on this. I want my boat to last so I think I will go the epoxy encapsulation route when it comes time. I re-read the stuff in the glen l book about fastening plywood to the frames and it said don't fasten to the frame (not glue to the frame) I guess it has to do with poking holes in stressed plywood. I may use the PL here and there, but I guess I will stick with epoxy. Thanks for the help.

[gert]

I guess I will stick with epoxy

Good for you

Make sure you wet both surfaces to be glued twice with plain epoxy,then apply the thickened epoxy (peanut butter consitency) and don't over clamp; you just want to see nice even squeeze out (this can be your fillet).

Now about "encapsulation" ; theres another hot button topic here...