Thread: Bending Jarrah

Smidsy,

Several people have described making rocking chairs - myself, Wongo, and others. See for example this thread: http://www.woodworkforums.ubeaut.com...ad.php?t=35118 .

The method of constructing the rockers is, as you suggest, to glue laminations about 6 mm thick together with epoxy in a former lined with polypropylene tape.

Rocker

Rocker,

I have built a version of the Dundas rocking chair from your CD plans but I used 4X3mm laminated jarrah strips glued together with Titebond PVA glue to make the back slats. I made the former desribed in the plans to attain the shape. The slats have begun to crack at the lower bend after only a short period of use. Do you think that it was the thickness of the laminates or the glue that most likely caused these failures? If you think it was the glue can you tell me the epoxy you use / recommend for this task? Please let me say that I made these changes to try to simplify things using my existing equipment and what I already had laying around and am in no way suggesting it is a design fault as I could not recommend the Dundas rocker more highly and I am wrapped with the way the rocker came out. When I took it to the upholsterer to have the seat made he liked it so much he offered to sell them for me. This is a credit to the design moreso than my workmanship. Just, unlike me, novice builders should follow the plans as now I have to figure out a fix.

Regards, Paul.

Paul,

I am at a loss to explain what caused the cracking in your back slats; maybe, if the grain is curly, back-slat laminations only 3 mm thick would be prone to cracking. Anyway, I think that using PVA to glue bent laminations is asking for trouble, as I emphasize in my instructions, owing to its tendency to creep. I believe that Techniglue epoxy, obtainable from Carbatec, is ideal for bent laminations. I am also concerned that, if you glued the rocker laminations with PVA, that the rockers might start to de-laminate.

I think the best fix for the back-slat problem would be to cut away the existing back slats and make new ones glued with epoxy; and make a curved 'shoe' about 12 mm thick with mortices routed in it, which could be glued to the top of the lower back rail, with the back slats sitting in the mortices. It would be tricky to shape the 'shoe' so that it didn't look obviously botched, but it probably would not be too noticable.

Another possibility, if only one or two back slats are affected by cracking, might be to cut away the damaged back slat(s) and then cut a slot the same width as the mortice in the top of the lower back rail, so that a new back slat could be slid into position, and then patch the slot.

Alternatively, it might be possible to make new back slats and bend them enough so that they could be fitted into the existing mortices. I have not experimented to discover whether this would be feasible. But it would probably be worth a try as Plan A.

I should point out that in the course of building about 10 chairs with bent laminated back slats, I have never had any problem with cracking in back slats made as described in my rocker instructions.

Rocker

Rocker,

I built my version of the rocker based on your plans, not exactly to them. I made the rockers based on a different design that is shorter and thicker and they were cut from solid 250mmX50mm pieces of jarrah.
I was thinking along the same lines regarding trying to bend the new ones into place as the originals are fitted into the mortices without glue. I'll cut & remove them AFTER I successfully make new ones AS described in your rocker instructions.
Thanks for the quick reply and I'll let you know how I get on.

Regards,
Paul.