Glue for Split-top Roubo slabs

[Brad Swanson]

I'm gearing-up to laminate the ash slabs for my spilt-top Roubo. Is their a standard glue used for this process? One of the extend products from Titebond? I'd prefer the glue lines to be as invisible as possible.

Cheers,
Brad

[Jim Ritter]

I used epoxy in my ash bench build. But as a boatbuilder I always have epoxy in the shop. The glue lines are only noticeable where the grain diverges.
Jim

[Andrew Pitonyak]

It would not have occurred to me to use anything other than the Titbond that I have in my shop. Well, I usually use III and I might prefer something with a longer open time.... So now my curiosity is peaked.

[Malcolm Schweizer]

+1 for epoxy from another boatbuilder. If you want invisible glue lines, it's the way to go. With epoxy the down side is it's very slippery stuff, and requires a very robust clamp setup. Use clamping cauls to keep the boards from shifting. Wrap the cauls with clear packing tape to keep the epoxy from sticking to them. Roll the epoxy on both faces with one of those 2" foam rollers just enough to wet the surface. With epoxy you don't want a lot floating on the surface- just enough to wet the grain. Clamp the heck out of it, and unlike yellow glue don't worry about glue starvation from too much pressure. Epoxy is harder to compress than water based glues- kind of like comparing hydraulic fluid to water. If you did everything right, the only squeeze-out should be a thin bead along the glue line. Let it fully cure and plane it off just like wood. Glue line? What glue line? ;-)

Note: Use a quality two-part epoxy like West System, Raka, or Silvertip. Mix in small batches. If not used to working with epoxy, I suggest gluing up two boards at a time rather than the whole layup at once.

[Christopher Charles]

I used titebond ii and it came out fine. I glued up in stages-only 2 surfaces at a time (four faces), which helped reduce stress. Best,
Chris

[Phil Mueller]

I used Titebond III and I don't think it's coming apart in my lifetime. I initially just glued two boards, then one at a time every two hours or so. Took longer, but much less stress.

Just make sure you get the grain running in the same direction to avoid tear out when you plane it flat. I thought I had read the grain correctly, but didn't in a few boards. Next time I would run a plane down each to confirm before glue up.

[Robert Engel]

Standard TB II here. Any normal wood glue will work epoxy not necessary.

I recommend splining them which increases strength plus provides worry free alignment.

[Malcolm Schweizer]

Note: I recommended epoxy because the OP wants invisible glue lines and that's the best way to get invisible glue lines, but Titebond would certainly be fine for gluing up the top.

[Phil Mueller]

Malcolm, thank you for restating that...didn't sink in the first time through. I'm curious; what makes expoxy give a more invisible glue line? I always thought it was just a matter of good prep to the two surfaces and proper clamping....

[Robert Engel]

Phil you are correct. If the edges are jointed well enough, you can't see a glue line with PVA glues.

However, if you need some gap filling then epoxy is a better way to go.

[Brad Swanson]

Thanks everyone for the recommendations. I will be using a Domino for registration purposes, so slippery surfaces with epoxy wouldn't be a problem.

[Robert Hazelwood]

Nothing wrong with epoxy, but I had good luck with TB3 and a helper (fiance) gluing up 8 laminations at a time. We poured a bunch of glue into a paint tray and used a couple of foam rollers to apply the glue, working from opposite sides. I used a couple of big cauls to maintain vertical alignment and straighten out some of the bowed pieces (I did minimal prep on the laminations, concentrating only on the face to face joints). I attached the bottom jaws of the cauls to the old workbench to keep them still, and to help prevent a twisted glue up- I think this worked out well in my case. We applied the glue with the lams sitting on the lower caul jaw, which saved a bit of time since we only had to thread on the top jaw after getting the glue on. A couple of extra cauls would have been a good idea in my case, but if your laminations are straighter then mine it shouldn't be necessary.

I used 1 clamp per foot, top and bottom, so 18 total. This was adequate to bring the (8) 1-1/2" thick lams together. The clamps were carefully pre-positioned to speed up the process. You get about 10 minutes to work with TB III, a few extra if its below 60 degrees F.

I did a blog post on this step if you're interested: https://roberthazelwoodwoodworking.w...ating-the-top/

Hope this helps.

[Pat Barry]

Titebond 2 should be fine. Any woodworking glue should be fine. I wouldn't go with epoxy unless you have it on hand and need to use it up. Epoxies stink, are difficult to cleanup, are a mess to ratio and mix. I personally wouldn't want the headaches (figuratively and literally) that epoxy can produce.

[Dave Anderson NH]

I used Titebond Extend when I built my latest bench. The extra open time was most appreciated and took out a lot of the potential stress of gluing something almost 8 feet long.

[Malcolm Schweizer]

Malcolm, thank you for restating that...didn't sink in the first time through. I'm curious; what makes expoxy give a more invisible glue line? I always thought it was just a matter of good prep to the two surfaces and proper clamping....

Good day, Phil,

The main reason is that you can clamp an epoxy joint with a lot more pressure than a PVA glue joint. Epoxy requires very little glue in the joint itself to form a bond. If you clamped a PVA joint with as much pressure as an epoxy joint, it would starve the joint. Epoxy also soaks into the wood better and is mostly colorless whereas PVA glues are yellow to brown. The image is of two mahogany pieces glued up and my finger is pointing to the glue joint. Wood is unvarnished in this image. Once varnished, the joint will be completely invisible.

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