Laminating question

[Hornbeam]

I am making a display cabinet which has sides which are slightly curved and scalloped. I am making these from a series of laminated sections 40mm wide which I will then run the length through the spindle moulder to create the scallops. & of these are then glued together to make each side.
I only have enough walnut for teh external laminations so was going to use some oak for the internal lamination. Could I use birch ply laminates instead instead as this would make it easier or would I have problems with cross grain movement. The external walnut laminates are 5mm on one side and 10mm on the other but 2/3rds of this has been scalloped away

Ian

 

[Mr T]

Over 40mm I don't think cross grain movement will be an issue.

Did we talk about this at the Harrogate show?!

Chris

 

[Hornbeam]

Did we talk about this at the Harrogate show?!

Hi Chris. Yes we did.
I am not worried about each 40mm laminate. It is when I glue the laminates next to each other then with 7 of them the total width is 280mm.
Am I just being lazy and should get on with cutting another 28 oak laminates. ( did the walnut ones this afternoon)

Ian

 

[custard]

I am making a display cabinet which has sides which are slightly curved and scalloped. I am making these from a series of laminated sections 40mm wide which I will then run the length through the spindle moulder to create the scallops. & of these are then glued together to make each side.
I only have enough walnut for teh external laminations so was going to use some oak for the internal lamination. Could I use birch ply laminates instead instead as this would make it easier or would I have problems with cross grain movement. The external walnut laminates are 5mm on one side and 10mm on the other but 2/3rds of this has been scalloped away

Ian

That's an interesting question.

I think I understand what you're planning, if so you shouldn't really use birch ply instead of Oak as the substrate. As Chris says, 40mm wide might well let you off the hook, but it's not generally considered best practise. There's some debate about what is the thickest veneer you can lay on a ply or MDF substrate, but almost everyone agrees that anything over 1.5mm thick is too risky because as the veneer tries to move it's held fast by the substrate at the glue line, but can still move on the show surface, which leads to micro fissures opening up on the show face. Substitute your Walnut show laminations for veneer and it's exactly the same principle. If the cabinet is actually made up from a series of 40mm strips glued together (as I suspect it is) then ply is even more tricky, but with Oak underneath (which for all practical purposes will move in step with the Walnut), you can pretty much do whatever you want in terms of shaping the Walnut and having it at any thickness.

It's quite common to laminate a show layer onto a different timber. A lot of table legs are done that way for example, because you'll often be in the situation where you can source some beautiful 30mm thick boards for the top, but there's no 75mm thick boards for the legs. In those circumstances you'll usually take some 5 or 6mm saw cut veneers from your 30mm boards and glue them onto an Oak core for the legs. Most workshops where I've worked call that "cladding" in order to distinguish it from veneering or laminating.

Good luck!

 

[Hornbeam]

Thanks Custard. My gut feeling was to go with the oak laminates, Its just a lot more time consuming. Monday evenings job sorted. Will post photos as project progresses

Ian

 

[custard]

Look forward to the photos, it sounds like a very worthwhile project.

One thing you might want to think about is the glue-up. Curved or coopered projects like this often succeed or fail at the glue up stage, because getting the cramps to apply pressure in the right places and at the right angles often requires a fair bit of planning and ingenuity. This is the sort of thing you often end up with.

Even with a fairly shallow curve you might need to make a male former, slather it with wax or parcel tape, and glue up on that.

 

[Mr T]

I was hoping you were going to comment on this Custard. I must admit it was a bit outside my area of expertise, I would have said that the movement over 40mm would not have been a problem and would not have caused issues at the joint between the staves, but I am sure your expertise is greater than mine Custard.

As I understand it the curve will be along the staves the glue up will be a flat clamp viewed along the line of the clamps.

Looking forward to some pictures Ian.

Chris

 

[Hornbeam]

Chris you are right with the glue up and that there is no angle between each stave.
Pics will take a few weeks as I have a whole load of extra laminates to cut and plane and need to make the laminating former.
Thankfully all the walnut external laminates have survived teh thicknesser.
So far so good
Ian

 

[Hornbeam]

Thanks for the advice from Chris and Custard. Used Oak laminate cores.
Parcel tape on the former works really well.
Glue up or laminates edge to edge was tricky but used biscuits for alignment.
I am now enjoying curved joinery.
Note to self for next time that putting ciurves in can more than double the work require
Thanks
ian

 

[custard]

Note to self for next time that putting ciurves in can more than double the work require

I understand from furniture makers who trained at Parnham that they used to have a training section on costing your work, the advice given was that furniture curved in one plane adds approximately x3 to the build time, and furniture curved in two planes adds x10! No one believes that until you do it, then you quickly discover it's about right.

Incidentally, another intriguing rule of thumb for build times, and one which I've certainly found to be true, is that just adding arms to a chair can double the build time.

It's no wonder it's so difficult to make any money from furniture making, even the tiniest deviations from strict rectilineararity means you get punished with build inefficiencies that beggar belief.