PDA

View Full Version : Glue for Split-top Roubo slabs



Brad Swanson
11-27-2016, 9:03 PM
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
11-27-2016, 9:20 PM
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
11-27-2016, 9:42 PM
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
11-27-2016, 11:32 PM
+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
11-28-2016, 1:28 AM
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
11-28-2016, 7:20 AM
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
11-28-2016, 7:59 AM
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
11-28-2016, 8:39 AM
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
11-28-2016, 9:00 AM
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
11-28-2016, 9:28 AM
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
11-28-2016, 9:56 AM
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
11-28-2016, 10:41 AM
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.wordpress.com/2016/03/06/roubo-build-4-laminating-the-top/

Hope this helps.

Pat Barry
11-28-2016, 11:07 AM
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
11-28-2016, 12:23 PM
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
11-28-2016, 1:31 PM
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.

348459

Prashun Patel
11-28-2016, 1:57 PM
TBII or III here. III will give you a little more open time. The problem with 2part epoxy is that you have to keep remixing, and on a large bench, the clean up can be messy. With TB, the clean up is soap and water. TB is plenty strong here.

On light woods, TB2 can sometimes dry to an orange/yellow that will telegraph through the seam. TB3 dries dark brown and less noticeable, IMHO.

The biggest bang for the buck for a seamless look is to joint very well, and clamp your boards one at a time with cauls, so you can get perfect pressure throughout the entire length.

Thomas L. Miller
11-28-2016, 4:03 PM
Brad,
I used Titebond Extend on my ash Roubo. No problems, no open joints and easy to clean up as Prashun said. I ordered a gallon of the stuff as recommended by Benchcraft and had about 1/2 left over. I was really liberal with the glue. I did use an awful lot of clamps and like Prashun only laminated one board at a time using cauls. The joints are invisible.
Regards,
Tom

Phil Mueller
11-29-2016, 7:55 AM
Thank you Malcolm for the explanation. Also, glad to see you're back in the shop and making progress on the bench. Look forward to the rest of that build (as I'm sure you are as well!).

Skip Helms
12-01-2016, 8:21 AM
I just made one with TB II this summer. I used 5/4+ red oak and glued-up 4 boards at a time so I could flatten one side on a 6" jointer. Two of the boards had already been routed for square dog holes. Then I glued them all together as close as I could. It hasn't fallen apart yet. sh

Randy Karst
12-01-2016, 10:57 PM
Malcolm,
Thanks for clarifying; I had been under the impression of it the reverse i.e. that it was easy to starve an epoxy joint with too much clamping pressure - not sure where I even heard that.

Jim Ritter
12-02-2016, 10:06 AM
I agree with Randy you can have too much pressure and starve an epoxy joint. I feel it does depend on the wood species too.
Jim

Malcolm Schweizer
12-02-2016, 12:46 PM
Well gosh, seems Google University agrees, but I clamp the heck out of epoxy joints and have never had a failure. My belief is that the epoxy infiltrates the wood and when it hardens it makes the two pieces as one. This is not so for less porous woods like rosewood.

I saturate the faces to be glued (both faces- very important) and let it soak in, then clamp it. I have had to separate screw ups before and the wood splits out before the epoxy fails.

Chris Fournier
12-02-2016, 7:46 PM
In my experience it is far easier to starve an epoxy joint than a PVA joint. If you don't want to see a glue line then you simply have to make a good joint and any glue but resorcinol will get you there. There is no need to suffer with epoxy for your build PVA will outlast all of us and be invisible if done properly.

Personally I would use plastic resin glue in place of epoxy every time. Less expensive, long open time, easier clean up, no creep, water based if you use the powdered form. Epoxy will always be the glue of last resort in my shop. I have used plenty of epoxy...

Joel Thomas Runyan
12-02-2016, 8:19 PM
If you're worried about an invisible glue joint, you need to worry about your joint, not your glue.

Jason Lester
12-03-2016, 10:33 AM
I used TB3 on mine a couple of years ago.

Chris Hachet
12-06-2016, 8:48 AM
Thanks everyone for the recommendations. I will be using a Domino for registration purposes, so slippery surfaces with epoxy wouldn't be a problem.

Domino seems like an excellent idea, will probably be my next corded tool.