Scafing Glue

As an interesting datapoint for Titebond III, I used it to do every scarf (hundreds) on the battens of my mold/form. These battens are 1x2's that are 50 feet long.

I have broken 2 battens through ham handed handling.

Each broke within the wood and not in the scarf or even near a scarf.

It is good stuff, but no comment on using it on boats.

 

TiteBond III is all I recommend of these products on a boat. It barely passes the type I water/boil proof test, but is subject to all the common problems with PVA's. Some of these are creep (and why it's not a structural adhesive), plastic deformation when wet, which also can cause it to lose it's grip, high clamping pressures, tight joint requirement, short open time, etc.

 

Used in a boat out on the sea !!as a structual part !
Making a mould you can use chewing gum if you want !! or even quicker a hot glue gun !!
Yes i can imagion the hammer and hitting thing !!

 

Yes, you need a good tight joint. If you had two sticks and put some TB3 between them and didn't clamp them, the joint would dissolve in water. You probably couldn't leave them out in the rain without them falling apart.

 

I've never had a Gorilla Glue joint fail on me. That includes furniture, cracked or broken stocks on high-powered rifles -- and the scarfs I made in 1x12 pine for the sides of my flat bottomed canoe a couple of years ago, which has survived some of the harshest climate conditions in the northern hemisphere. I would think that in joints that size in soft pine (which is infamous for expanding and contracting according to the weather), any shortcomings in the glue would be magnified.

It's hard to accept the notion that any 'test results' I came up with should trump my real-life experience.

 

Yeah i always used Gorrilla glue in the tube with the short cure time when i was laying solid wood floors ran it in the bottom of the groove and full length and was magic . bite up quickly and was able to lay big areas continuosly !!. just a light push up to hold it and non came out the top so was vertually no clean up at all . A sharp chisal as it was curing and it was history if it did come up . Was absolutly impossible to get apart without pulling all the tongue off the plank from end to end !. not a pretty sight !!.
But for building or anything to do with boats NO NOT NEVER!!
Household and domestic use ok !!

 

It's interesting how experiences are all over the map for this stuff. Some love it, some hate it, some don't know what to think. You would never know we were talking about the same product!

 

Cthippo,

I think the difference is what people are using it for. When woodworking, or making cabinetry or furniture I have a lot of success with gorilla glue and TBIII. But when using it on water I have had a number of joints fail, and wouldnt use it there again. The issue to me is just one of understanding the product, and it's proper application, and then not expanding its use outside of that area.

 

I ran a joinery business for more than ten years. We used three types of adhesive as standard stock: liquid polyurethane (resembles honey) tube polyurethane and PVA. Occasionally we would use epoxy.

For polyurethane:
I made it a standard practice to save off-cuts with a glue joint and later split them apart; it was a quick and easy break test that taught us a lot about what was happening and what to be careful of. We used dozens of bottles and tubes every month.

One of the reasons that experience differs with polyurethane is it behaves differently depending on whether there is foam in the joint or not. The foam has little strength and the joint will break along the foam line. If there is any space in the joint there will be foam and weakness. Where there is no foam (and a good bond) the joint is stronger than the wood.
We found hardwoods that had very clean cut surfaces (especially if burnished) did not bond well. We did not clean with solvent as the joints were not critical enough to merit it, but I believe it would make a difference on critical joints. Rough surfaces almost always bonded well as did soft woods in general.
A big factor in broken glue lines was unglued or glue starved areas especially those close to edges. Here I differ from Troy, I always used enough adhesive for a good squeeze-out along the glue line, I spread it thinly and carefully on both faces and then put a bead of adhesive down the centre of one face which gets squeezed out on both sides pushing air ahead of it. Spreading on both faces ensures the adhesive is drawn in to the cell structure uniformly (you can see the wood change colour).
Clamping pressure is important as is uniform clamping. The foam action has some power over a large area, enough to push apart flexible glued pieces between clamps. The aim should be, enough pressure to have a tight joint and not so much that all the adhesive is squeezed out.
I do not think it is necessary to dampen the surface, the water does not help the adhesion and the timber has plenty enough humidity to start the reaction. If in doubt, spread some adhesive on a scrap piece and watch it foam.
Although we never did a comparative test, my imperssion was always that the caulk tube polyurethanes were stronger and more reliable than the liquid. Certainly the foam squeezed out from the edges has more strength and flexibility.

For long term performance I grew to distrust any polyurethane in a critical situation. My first observation of this was while visiting a large conservatory we had built. The ridge was nearly seven meters long laminated out of Iroko with liquid polyurethane. We had built it with some care and yet after only a few months the glue lines were showing signs of separation. We had many minor cases of seemingly random failure.

 

Nick, I know you have a lot more experience than I do -- and that I'm starting to sound like a broken record. I'll leave the subject alone after this.

But the unreliability you've experienced with Gorilla Glue may be at least partly due to the fact that you were ignoring some very specific directions. I'm not particularly anal; there are few things in writing I pay attention to as though they're gospel. One is the recommended powder loads in reloading manuals, and another is glue manufacturers' instructions.

I think I understand your rationale for applying an even layer, then adding a stripe down the middle and squeezing it out. It has some logic to it, especially if you can control your clamping pressure by starting in the middle and working the extra glue toward the edges. It's akin to putting a thin layer of grout under tile,making sure the edges have plenty, then slapping more into the middle and troweling it out to the edges. It's a way to make sure there are no thin spots. But I think it's an invitation to winding up with an uneven layer of glue, and uneven clamping pressure.

 

...Your experiences are as valid for you as mine for me
I was just trying to put a handle on why people have such different views about polyurethanes. ("Gorilla glue" isn't sold here, I'm assuming it is a liquid polyurethane)
I am not a chemist but I have read quite a few times that humidity is only required in polyurethanes to kick off the reaction and that normal timber has sufficient to do this. If any one can say otherwise I'm happy to learn.

I think for anyone making things, joint failure is interesting. I have always taken the opportunity to break apart joints when possible. It is surprising how much of a joint can be dry. I don't think this is neccessarly due to uneven spreading, sometimes it can be caused by movement of the pieces as they go together. Spreading on both faces etc did improve our joints.

Lastly..
The break tests once showed up a faulty batch of adhesive, I called the supplier who then did some tests of his own and confirmed that his new stock was faulty. He got on to the "maker" who explained to him that they didn't actually make the stuff but imported it from India and they had just changed supplier...same bottle, different product. I think a lot of products are sold by marketing businesses who may have little expertise beyond marketing....not saying that's the case for Gorilla, I don't know.

 

GG and other poly glues do not need additional moisture except under extraordinary circumstances. To make sure, I just breath on it before I join the parts together. That's quite sufficient. Since it is a catalytic reaction and nothing is moving* only minute amounts of catalyst are required.

Additional moisture is useful when working with Titebond III which sets off too fast for some jointing operations. Slightly moisturizing the wood before applying the glue - or diluting the glue about 10% - will extend the working time without any detectable loss of joint strength. I have confirmed this with the manufacturer.

* unlike a vehicle exhaust catalytic converter . . .

 

I hit one side with a spray bottle of water and apply GG to the other, unless that's not feasible for some reason. It definitely goes off faster with the water addition.

I've also found that not all polyurethanes are the same. I tried the Titebond poly and the joint strength was nowhere near what GG produced in identical circumstances. and besides that, the Titebond is black. It dries to an off white-ish color, but black is just wrong.

 

That's downright depressing and a little scary, but not surprising,

I've never eaten enough KFC chicken to notice any difference, but I've had people bitterly complain that the company must have substituted cheaper ingredients for Colonel Sanders' hallowed 'eleven secret herbs and spices,' because the chicken doesn't taste the same.

 

Of all the joints and seams I've disassembled over the years, glue failures, without significant exception, could be traced back to prep and improper application, not the adhesive or glue itself. I have my reasons for dislike of the polyurethanes, which for discussion's sake fall into two basic categories, moisture vapor or accelerated moisture vapor cure.

Both rely on moisture vapor, but accelerated versions typically use cyanoacetate in varying degrees, to expedite the cure. Both can be promoted to cure quicker with additional moisture vapor (not water, but vapor, a substantial difference). Accelerated cures tend to make the end result more brittle, of course depending on acceleration conditions. The cyanoacetate modified polyurethanes do a great job of sealing the cut wood tubules and mechanically "keying" to the fibers (as a result), but if accelerated too much (how much is this) the interface at the bond line, just past the end of the wood fibers tends to fail in shear, just as the adhesive exits the cut cellular tubules. If you look at these failures (really closely), you'll see the broad glue pool, above the faying surface is intact and the keyed portion of the adhesive is also intact, but a clean shear at the connection between the two areas. This usually means you slice the joint perpendicularly and pull out a microscope. For those of you that don't have one laying around the shop, trust me, you don't want to get carried away "pushing" polyurethanes. I think polyurethanes are great, unless you try to remove most of it's elongation with formulation at which point other adhesives are better candidates for bonding.