Glue Up Sanity Check?

[Mike Cutler]

Hey folks, I'm back in the shop, of course I waited until winter to get back in there, and I am building a fairly large Table/ Center Island Cooktop.

A little background;
The table is an adaption of a Limbert #153 Library Table that will be made of Padauk and Cocobolo. The top is Padauk, 1 1/2" thick, and will measure 36" x 67". It will have a 36"x21" gas cooktop built into it, and be used as a casual dining area.

My plans are to edge glue the padauk top, and use epoxy as the adhesive. So I guess the question is; Will and edge glueup alone be sufficient with a top of this size/weight, or should I do a tongue and groove joint, or integrate some form of a mechanical fastener for strength along the glue lines? (There will be two glue lines.)

It's supposed to be 8 degrees tomorrow, so I have a little time to contemplate this.

[Joe Chritz]

Edge grain to edge grain glue joints are as strong as any. The wood will fail before a properly glued joint will and other stuff (biscuits, splines, etc) will add to help with alignment but not much in strength.

Why epoxy? Regular PVA glue is plenty strong. I don't think (someone correct me if I am wrong) that Padauck is one of the woods that has resins that can interfere with glue. Cocobolo is, and a wipe down with solvent just before the glue is a good idea. Acetone is best but any thinner works.

I would be concerned about the heat from the cooktop. Does the sides or underside get warm at all during use?

Joe

[Leo Graywacz]

1 1/2" is plenty thick to just run with a glue joint. A couple of biscuits or dowels to help with alignment might make your life easier. Make sure the Epoxy will be compatible with the temps you are going to be gluing this up with. Usually epoxy will glue in almost any temps, just a lot slower to cure in cooler/colder temps.

[Peter Quinn]

I haven't used padauk but i am at the tail end of a large teak project and tests we did at the onset and over the last several years indicated that titebond III worked better than either PL glue or epoxy (west systems) and was much easier to work with to boot. I glued up 28 panels ranging from 9X36 to 30X50 each a 2-5 board glue up. Clamping pressure was kept over night in all cases, no initial failures and none several months later. Other teak projects completed years earlier were also processed with titebond III, no failures reported.

I didn't even any glue line creep. All panels were stickered for minimum three days before processing to allow the glue to fully cross link, failure to do so I'm told is the primary reason for glue line creep with type II and III PVA adhesives. Unless necessary for alignment I would skip the glue joint or T&G, a long grain glue up is typically sufficient for strength. Of course I was using a wide belt to flush panels, so if you will be flushing them by hand a very careful alignment may be in order.

[Steve Rozmiarek]

Why epoxy? Regular PVA glue is plenty strong. I don't think (someone correct me if I am wrong) that Padauck is one of the woods that has resins that can interfere with glue. Cocobolo is, and a wipe down with solvent just before the glue is a good idea. Acetone is best but any thinner works.



Joe

Anyone else remember something in Fine Woodworking about the need to wipe with acetone? If I remember correctly, they found no difference in joint strength by doing so, and determined that pva, Titebond 2 or 3 was best. Maybe my memory is failing though.

[Mike Cutler]

Joe

I prefer epoxy simply for it's open time, and in this case any water that may end up spilled after it's finished. The Cocobolo gets a wipe down with acetone prior to glueing,and a tropical epoxy, by the company that make Rot Doctor, will be used. Nothing at all wrong with PVA glues, A waterproof PVA with an extended open time is definitely an option.
The cooktop is propane,and the burners(flames) are going to be ~ 1 1/2" above the surface, which is ceramic. The rest of the cooktop is a sealed assembly, and there won't be any material above or below the cooktop in contact with it to trap heat. Everything "should" work out OK. I hope.

Leo

I'll do the actual glueup in the basement after milling everything in the garage. I have quite a bit of System Three epoxies on hand. I think their lowest temp hardner may not be sufficient for the low temps we're expecting for the next week or so. I just may use a PVA glue on this one, I'm still on the fence.

I'll be using some 1/2" thick loose tenons for alignment along the edges. They'll probably go 2"+ deep into each side, and be 3" wide. The trestle under the top should provide enough support, but man that top is going to be heavy.

Peter

Finish work will be by hand. Planes, sandpaper and scrapers and such.
Consesnus seems to favor a PVA glue, ie. Titebond. You guys having me rethinking my use of epoxy for the top.

Steve

Not sure about the FWW info, not disputing it though, I've always read that the oils need to be removed prior to glueing. Hopefull it's just a case of "gilding the lily", and there is no actual negative consequence.

[Brian Hinther]

The reason I would consider using epoxy (or something other than Titebond) is Bob Smalser's thread "Are your glue joints repairable?" http://www.sawmillcreek.org/showthre...ble#post195012
Among other things, he makes the point that Titebond is the least repairable glue you can use. Of course that's not a problem, unless there's a problem.