Forest Products Lab Glue Test

[Venchka]

STRENGTH AND DURABILITY OF ONE-PART
POLYURETHANE ADHESIVE BONDS TO WOOD
FPL Glue Test (http://www.fpl.fs.fed.us/documnts/pdf1998/vick98b.pdf)

Without brand names, this is kinda useless. On the other hand, the wet performance of all of the polyurethanes is eye opening. Bob has been telling us that all along.

Wayne
In the Swamp. :D

[Popeye]

"In a test of resistance to deformation under static loads, polyurethane bonds to yellow birch withstood extremes of temperature and relative humidity for 60 days without deformation, thereby exceeding structural requirements of ASTM D 2559-92 (4)."

[ 06-28-2005, 12:42 PM: Message edited by: popeye ]

[Bruce Hooke]

It should be noted that this is a 7 year old paper, so the state of the art may have changed quite a bit in that time. I think this paper, or the information it contains, has come up in the past here...

I did not read the whole thing but what I took away was that polyurethane does great if kept dry but is less reliable if wet...

This quote summarizes some of this information:


A moderately severe two-cycle boil test indicated polyurethane bonds varied from high to low resistance to delamination, while the resorcinol bonds were completely resistant to delamination. A very severe cyclic delamination test that qualities [sic] adhesives for structural laminated wood products for exterior exposure caused severe delamination of polyurethane bonds in lumber laminates of yellow birch and Douglas-fir.

[Venchka]

My apologies. I didn't check the date.

Wayne
In the Swamp. :D

[Popeye]

Here is an SME student analysis on different wood glue joints in trusses, includes some numerical analysis too.

ase (http://chapters.sme.org/061/Preliminary%20Report%2030Dec2004%20Release.pdf)

[Bruce Hooke]

That student analysis is cute but has little bearing on the effectiveness of polyurethane glues in a marine setting. Among other things, they used the glue in a rather odd way -- as basically a big blob that acts more like a connecting plate than a standard adhesive joint -- AND, they did not look at all at wet conditions...

[ 06-28-2005, 03:48 PM: Message edited by: Bruce Hooke ]

[wyndham]

But if I ever decide to build a boat from colored tothpicks I know which glue I'm going to use.

[Bruce Hooke]

Originally posted by wyndham:
But if I ever decide to build a boat from colored tothpicks I know which glue I'm going to use.:D :D :D

[Popeye]

Originally posted by Bruce Hooke:
That student analysis is cute but has little bearing on the effectiveness of polyurethane glues in a marine setting..composite joints of aerostructures (http://www.ilot.edu.pl/STRANG/Designs/CJoA.pdf)

[wyndham]

Does this mean that colored toothpicks and polyurethane glue is good for building ice-boats and airplanes too?

[Popeye]

http://wright.nasa.gov/ROGER/Images/02-7.jpg

[wyndham]

Sounds like a "Yes"!

[Bruce Hooke]

Popeye, I'm not sure if you are just joking around or if you are trying to make a point and if so what point. If you are trying to argue that composite joints and suchlike have serious engineering purposes I would certainly not disagree. My central point was that the performance of such joints has little bearing on how various adhesives perform in the kinds of joints commonly used in boatbuilding...

[Popeye]

I see wooden boat framing as trusses, and thus the composite glued wood joint Vs glue performance information can be extrapolated for uses in marine applications.

This is a good thread, I would like to see more posts about lab results or other experimental results showing glue performance in wood joints, but like you pointed out, the wet~dry cycle info is hard to find.

[ 06-29-2005, 10:50 AM: Message edited by: popeye ]

[Bruce Hooke]

Originally posted by popeye:
I see wooden boat framing as trusses, and thus the composite glued wood joint Vs glue performance information can be extrapolated for uses in marine applications.Yes, some wooden boat frames are trusses. No, I would very much disagree that a joint made between some dry toothpicks where the glue is a giant blob thicker than the wood structure itself has any relevance at all to a typical glue joint in a boat where the glue goes between the pieces of wood being joined rather than wrapping all around them.

Epoxy fillets bear some vague resemblance to the toothpick joints but even there I think the differences are so substantial that there is no way to draw any worthwhile conclusions. Also, fillets are generally promoted as a way to join sheet goods, not long thin members.

Also, nobody is disputing that polyurethane glues are strong if everything is kept dry, the question is what happens when the wood gets wet and the toothpick test never addressed that issue.

Yes, there may be a place in experimental boats for some sort of wild composite joints such as the ones covered in the last paper you posted, but no I don't think that has much to tell us about the adhesives and methods to use for more standard marine glue joints.

[Popeye]

I tried looking thru the ASME , ANSI and CGSB standards for a good glue strength/adhesion standard methodology, but came up nada, back to the smalser chisel test we go, or at least some first order approximations to model the problem and devise solutions.

We seem to be missing a device or a test for the applications in question, thus being able to compare glue per glue in a test matrix, as Bob suggests, there is no such information available to easily access. The student paper demonstates how to crudely measure breaking strength in a glued up truss, a starting point.

Mechanically efficient glue joints may well be 'blobs', i don't know that it isn't and neither do you, and I am being objective here, not subjective, it is erroneous to assume otherwise unless you have substantial information to the contrary. The second paper suggests to me how composite joints are another possible solution to wet/dry cycle and repairability problem.

[ 06-29-2005, 12:23 PM: Message edited by: popeye ]

[Bruce Hooke]

It may be that blobs of glue are a mechanically efficient joint, however my practical experience tells me that such a glue joint would be hard to scale up to boatbuilding sizes. Even with epoxy, which is the most likely candidate for such a joint, there are serious problems with trying to cure a lump of epoxy 1" thick without it overheating. Furthermore, I do not think I am being subjective when I say that such a joint is clearly different enough from standard glue joints that trying to apply test results from one to the other is more than a bit of a stretch. At best the toothpick tests might be a guide to developing some hypotheses that could then be tested in tests that would be more relevant to marine situations. However, that is once again an attempt to develop new gluing methodologies, whereas what I thought we were discussing was the efficacy of polyurethane glues as they are currently commonly used in marine settings.

The fact that you can't find standards for joint testing that would apply to our situation does not mean that it is not possible to set some reasonable parameters around what such a test should look like.

[Popeye]

Originally posted by Bruce Hooke:
At best the toothpick tests might be a guide to developing some hypotheses that could then be tested in tests that would be more relevant to marine situations. Yes, develop a test.


Originally posted by Bruce Hooke:
The fact that you can't find standards for joint testing that would apply to our situation does not mean that it is not possible to set some reasonable parameters around what such a test should look like.Yes, develop a test.

Now that we have a standard test, we are ready to proceed in an orderly fashion with a great big bottle of polyurethane glue in hand.

Phase II would be, how do we improve upon such joints...

[ 06-29-2005, 02:21 PM: Message edited by: popeye ]

[wyndham]

I would argue that there is a test although calling it standard would be a stretch. The test is the test if time. There are any number of wooden boats that are composite hulls, strip planked, cold moulded. The ones that have survived are the ones that were built with eopoxy or resorcinol. I don't know of any other marine adhesive that has been used for this type of condtruction. I beleive Gypsey Moth was three layers of mahogany laid up with resorcinol. She's still here. There are some beautiful edge glued hulls around, inch and half, two inch mahogany resorcinol glued.Lots of cold moulded veneer and epoxy hulls still alive as well. If PL and titebond and Gorillas glue were meant to be used in the marine environment they would be marketed as such. The fact that the makers of gorilla glue won't return a phone call about being used on boats speaks volumes. Do yourself a favor and stick with what works and is proven.

[Bruce Hooke]

While Wyndham is certainly correct (in my opinion) that the safe way to go is to stick with the tried and true, if advances are to be made somebody has to step out and try some new things. I would, however, add the caveats that anyone doing that stepping out should:

A. Know that they are trying something experimental and understand the risks.

B. Take a step by step approach to testing the idea rather than leaping at the deep end.

C. The best experiments are constructed on the basis of a solid understanding of what has gone before so the best approach is to first learn well what has worked in the past before trying to come up with new ways of doing things.

Finally, I would add the I personally prefer to experiment, if I experiment at all, in areas other than adhesives so don't look to me to lead the charge on trying out new ideas with Gorilla Glue... :D

[Popeye]

Sometimes small steps work also, somewhere along the line someone recognized, for example, how moisture in the wood affects glue adhesion and possibly another 'experimenter' may have found how 'keying' gluing surfaces helped improve the joint.

It does not have to be a radical departure from the tried and true to make improvements. The test of time will eventually show which glues and techniques work best for each application in various environments for various woods, having a good test method that everyone agrees with, speeds the process along and removes the guess work.

[wyndham]

I agree with Popeye when he states that radical change doesn't have to be a big step but rather can be small steps. I think if you mapped the evolution of wooden boats you would find that it is a series of baby steps interspersed with some huge giant steps. Frum a floating log to a dugout canoe is a baby step. From a dugout to a plank on frame boat is giant step. From wood frames to iron frames is a giant step. From mechanically fastened to glued is a giant step. In between each of these giant steps are a series of small steps, not radical but more like refinements. Plywood and waterproof glues are to my mind the last big steps. Are there more to come? Who knows. What we are seeing now are the refinements. Glued lapstrake comes to mind.
It seems from reading the posts in this string and the other glue string that people are seeking the next step in glued construction. The tried and true are being challenged, not by the industry, if there is one, but by the little guys who are looking for a better way.
I am all in favor of a better mousetrap but it's going to take me a long time and a lot of convincing that there is one coming any time soon. Until some manufacturer is willing to stand up and say, this product is designed to be used in the marine environmnet and has been specifically tested as such, I am unwilling to be the guinea pig that finds himself in a boat that is coming unglued. Use PL premium, use 5200, use whatever you think is going to work, but do so with caution and the knowledge that you are going out on a limb that might just come unglued.

[Gary E]

Until some manufacturer is willing to stand up and say, this product is designed to be used in the marine environmnet and has been specifically tested as such I think you are correct about that and would add that the search for new sealants and glues for WOOD BOATS is probably slim to none. What company will spend mega $$ to research a product for such a limited and obsolete market? Developing for the current market of Fiberglas / Composite and space age materials is where the future is, not old fashoned wood.

[Popeye]

Originally posted by Gary E:
What company will spend mega $$ to research a product for such a limited and obsolete market? Developing for the current market of Fiberglas / Composite and space age materials is where the future is, not old fashoned wood.It is a simple matter to reach across industries for wood boat construction applications, epoxy was first developed for use in aircraft.

[wyndham]

I'm not entirely sure that the product has to be developed specifically for the wooden boat niche market, I agree that the niche is too small, but there may be some spillover from a similiar niche in the overall amrine retail marketplace.
My understanding is that 5200 was sepcifically designed as a sealant/adhesive for the hull to deck joints common in just about every mass produced fiberglass boat. A number of glass boat manufacturers use it as a marketing tool and tout their hull to deck joint as being sealed/glued with 3M 5200.
As long as there is wood on boats, trim, rubrails, coaming, someone will want to glue it to something. I would guess thats where the next marine glue comes from rather than from the commercial construction or wood products and woodworking industries.

[Venchka]

I think it is interesting to note that a year or two ago the folks who make PL Premium and other adhesives had an emtpy page to watch for Marine Products. That page is gone now. Makes you say, "Hmmmmmmmmmm."

On the other hand, if dig around this Forum you'll find that Norm used Titebond II between the strips on Prairie Islander. He also used oak dowels between the strips and covered the hull inside and out with fiberglass cloth set in epoxy. Makes you say, "Hmmmmmmmmmm."

What does it all mean? Don't ask me. I don't know.

Wayne
In the Swamp. :D

Wayne
In the Swamp.

[ 06-30-2005, 01:55 PM: Message edited by: Venchka ]

[RonW]

Wayne when you say the people from pl premium had a open page to wooden boat glue and didn't jump on it, so you say hmmmm....
Well that is no surprise to me. They sell it to the construction industry at the rate of tons per day, and if it is used in the marine industry it would be lucky to be used at the rate of ounces per day..So which market would you go after if you where the ceo of the company. This is also the reason for the difference between marine labeled products and non marine labeled products.

A couple of years ago I talked to pl about using pl premium for boat construction and they said no problem, it is 100% waterproof, go for it.
My 2 year old boat is glued with it and there is no problems, very happy with the product.

If you look at the test chart listed in the original post, you will see that polyurethanes where tested against resorcinol, and in soft woods and dry joints it actually superceeds resorcinol in sheer strength, very close in hardwoods and dry joints, not as good as resorcinol in water sturated joints but only by a little bit.Don't forget to use a few fasteners.

I have repeatedly tested liquid varieties against the tube variety and every time the tube variety wins hands down.And I would like to use the liquid variety but it foams too much and does not have the strength of the tube varieties of polyurethane.

Remember these tests are 7 years old and I am sure that the poly's have improved since.
They are 3 types, basically the liquid in a bottle that you have to dampen the wood, then the tube glues that are ready to use, such as pl premium and then last and least is gorilla. I put gorilla glue in it's own class, because as far as I am concerned it is the biggest advertising scam of the 20th century and other then being used for chair legs is a joke to say the least.Gorilla glue turns into a useless foam and is not waterproof, the reason that they will not return e-mails concerning using it in boat construction.And they are located in cincy and I have driven by they place many times, and would not use there product for anything.

Bottom line on pl premium, it is readily available, $3 a tube, easy to use, will rip wood apart and almost the equal to resorcinol and does superceeds resorcinol in some areas, 100% waterproof, can be used to glue almost anything, has flexibilty to the joint which is important in wood joints under certain conditions,and has a very long life span.BUT It can not be used to make fillets like epoxy can, and I think would make a excellent glue for cold molding. A very good product but lots of people are not going to know till they get a tube and play with it. Do not put it on too thick, it is not designed to be real thick like epoxy.

I have talked to the technical people at pl or actually osi sealants a couple of times and they have always been stright forward and answered questions with out stuttering. I have found all they products to work excellently, just as adertised. I also talked to the techs at 3m about 5200 and found a lot of stuttering and not straight forward answers, particularly when you ask about the life span of there product.

[Bruce Hooke]

Originally posted by RonW:
...has flexibilty to the joint which is important in wood joints under certain conditions,and has a very long life span.Do you know if this flexibility leads to any issues with joint creep? Creep is clearly a critical issue in some situations.

I've never used PL Premium...is a well made joint glued with PL Premium as hard to see as, say, a well made joint glued with epoxy?

[RonW]

Joint creep is wood movement by either dry wood taking up moisture and exspanding, or excessive drying of wood, the larger the wood pieces are the more the creep.The more the creep the more pressure being applied to the glue line, and here is where some glues fail and thus you have a crack.
A well made pl joint will still be able to be seen, it is not clear like epoxy.
Here is a place if you want a clear glue line on trim or so forth you would find epoxy hard to beat.
But for hard core construction of a boat, I think pl is hard to beat provided you are not talking a stitch and tape boat with fillets.

[Venchka]

RonW,

Clarification RE: PL Marine Products.

On the products page where you would click various icons to go to different products, one of the icons said "Marine Products". So, I clicked that icon. I was taken to an empty page that said something to the effect of "watch this space for exciting new marine products." Not there anymore.

I have also read on some boat building group somewhere that one of the Concrete adhesives (sorry-forget which one) from OSI is even better on wood in boats. Any history of using that product in a boat?

Wayne
In the Swamp. :D

[Bob Smalser]

As 5200 fails the water-soak test rather dramatically, pulling off in long ropes of goo, I strongly suspect PL Premium will too.

We'll see.

[Bruce Hooke]

Originally posted by RonW:
Joint creep is wood movement by either dry wood taking up moisture and exspanding, or excessive drying of wood, the larger the wood pieces are the more the creep.The more the creep the more pressure being applied to the glue line, and here is where some glues fail and thus you have a crack.As I understand it, joint creep can also occur when the joint is simply under a constant "sliding" load. One obvious example of this is a bent lamination... at the least it seems like a flexible joint would likely lead to more springback in such a situation...

[RonW]

Wayne- I haven't been on the pl website for a while, so you are telling me something new, appearantly pl or osi was or is going to list some of their products for marine. They had no problem in talking straight to me on the phone.

Haven't tried the concrete stuff, but have played with the window and door sealant that is polyurethane, mike or oyster mentioned this stuff way back. I am very impressed with it, it is a lot like 3m5200 and the thicker you get a joint the more flex it has and is amazing at how much it will stretch. And it is paintable unlike 3m5200 which has paint adhesion problem. They advertise it as a 50 year life span and that is as a caulking around a door or window which also gets all the weather as well as sun.
On my next boat I am going to use it as a bedding compound under the outside rails and bottom runners.They do say on the tube under -limitations- not to be used under water, but I believe what they are referring to is a situation like inside a swimming pool or aquarium, and not a trailer boat, but one might want to check with them before using it a sailboat below the waterline that will live in the water.

Speaking of limitations, on the side of the pl premium the only limitation they list is not to be used below 40 degrees.

I have been very impressed and satisfied with products from osi, and have found them to perform as advertised and the advertising to be straight forward with out a lot of bull.

As for lifespan I first used a pl product 32 years ago, and that was pl 400 a subfloor adhesive that is polyurethane. No problems.
There is a lot of urethane products used in high end commercial construction.

Add.- Wayne, remember the post I put up on mdo update, where I talked to olympic concerning signal mdo and highway hdo, well doing the conversation, I discussed the panels on a framed boat with pl glue and fasteners. The olympic people said that would be great and they had high praise for pl as well.

[ 06-30-2005, 04:47 PM: Message edited by: RonW ]

[Bruce Hooke]

As I think about this I'm realizing that flexibility in a glue joint and joint creep are pretty close to being the same terms for different things (with the caveat that creep may act slower). So, on a joint where some flexibility is good joint creep is probably pretty much a given and on a joint where creep would be bad a flexible adhesive is probably the wrong choice.

[RonW]

Bob says----
As 5200 fails the water-soak test rather dramatically, pulling off in long ropes of goo, I strongly suspect PL Premium will too.

We'll see. ----

Bob for the last couple of years, you have constantly knocked pl premium, but I believe you just bought your first tube of it and just now started experimenting. I think you will be surprised at the results. Reread the link to the above as to the tests results with saturated wood, and you will find that it's holding power is only slightly less then that of resorcinol.
Now if it came off in big long ropes of goo I think the us forestry people would have found that to be a serious problem and would have reported it.
Give it a fair shot before criticising it.