Thread: Getting wood bent

have a close look it may not be bent.
it may in fact be cut to shape on a band saw
that may be an option any way.

Arron

The easiest way that I know to bend wood is to laminate it. Begin by slicing the timber (that will make up the 21 mm section) for the chair back into several strips on a bandsaw (make sure the grain continues to run the length of the timber). Then glue these on top of each other, one at a time, placing the first layer on a MDF form (copy) of the bend you wish to recreate. When the glue dries then timber will largely hold its shape. There will be a little bend-back, so allow for this.

Regards from Perth

Derek

Derek,
I am dubious about your method of making glued laminations by gluing them "one at a time". The usual way of making them is to glue all the laminations simultaneously clamping them to a form, as recommended in an excellent article on Lamination bending in the current Fine Woodworking (#164).

Another important point about glued laminations is that it is essential to use a glue that will not creep under stress. Thus ordinary PVA glue is unsuitable. I have found urea formaldehyde glue to be best for the purpose, but you can use a slow-setting epoxy.

I use urea formaldehyde for the laminations of the rockers and backslats of my rocking chair, see http://www.st.net.au/~dundas

Rocker

Rocker

You're right. Bad choice of words on my part - not "one at a time" but should be "one on top of another".

Also agree that the choice of glue is important. I usually go with epoxy resin since it has a little more flexibility in it than other forms.

Regards from Perth

Derek

Can someone elaborate as to the reason why you must laminate all the layers at the same time?

I can see the obvious time saving but also the mad rush to get it all together if it is a longish part.

I laminated the hand rail for a 14 step spiral stair in one single piece from 15 strips Oregon 6mm thick and I glued it one at the time for a very good reason, the length would not give me enough time to do it all at once. I tried to do two at the time and managed to do it by gluing sections at the time and clamping and gluing another section, but it was more trouble than it was worth. So I finished doing one at the time. I used F clamps 4 inches apart.

As for glue, I used Sellies tradesman choice. It has a short open time but allows the clamp to be released after 1/2 hour. The glue line after 3 years is only visible with magnifying glass.

PS
As for bend back, on a 3.5 meter spiral handrail and 3 other curved one I built, the "bend back" was exactly zero on all of them by laminating one at the time.
And creep . . . . what creep?

Marc,
I think it is a case of horses for courses. You can get away with using PVA glue for bent laminations if you are using softwood and a faily gentle curve, as in the case of your spiral staircase rail. However hardwoods and tight curves are a different matter. I have read horror stories of people who have spent a couple of hundred hours making a Maloof-style rocker and glued the rocker laminations with PVA, only to have the rockers delaminate after a few weeks.

Rocker

A few months ago there was an excellent article in one of the WW magazines about steam bending.
The article made it sound very easy (don't articles do that!)

Give me a couple of weeks to go home and fish out the magazine. I can't remember whether the magazine was FWW or AWW, but I'll re-post here when I find it.

I know someone in Gympie who bends wood commerically. He is a wheel wright and I supply him with silverash on occasions that he uses to make the half rim of wheels for old wheels of carriages. Give me an email and I will look up his telephone number and pass it on. I know that he occasionally does other jobs.

Arron,
As Soundman said, it is doubtful whether you need to bend the wood for your chair back. The back-splat of a chair is not put under any great strain, and it should be quite feasible to bandsaw the curved profile from thick stock. I have done this for a Chippendale-style chair I made, and it worked out quite satisfactory.

Rocker

thanks for the replies guys. Looking at the back again, I still cant tell whether it is bent or simply bandsawn from an extremely twisted piece of wood. In any case, I dont have a bandsaw so it looks like my best option is to learn to steam bend.

Arron

I agree that sawing such a shallow bow from solid stock is the most practical way to go. Without a bandsaw there are several alternatives.
Get a local joinery to cut it for you
or
Make a Bow-Saw and cut it from a solid block
or
Cut the back stock block into say 1.5" x 1.5" strips then cut the strips to shape with a jigsaw and edge glue them back to the correct depth.

In addition to the three options that echidna suggested for removing the waste from the concave side of the curved back-splat, you could use a router to remove the bulk of the waste by routing a series of dadoes across the back-splat about 5 mm apart; then removing the intervening waste with a chisel. The convex side can be shaped easily enough with a plane. I have used a similar router method to remove the bulk of the waste when making a contoured solid-wood chair seat.

I remember my first Kitchen stool I ever made had a backrest and I really wanted it to be concave but had no clue as to how to achieve this.

So I built a jig, from 3mm plywood with the curve I wanted and a slot in the centre mounted on a little frame and on a flat back. So I clamped the contraption on the wood for the back, and cut successive grooves until the back had a nice convex curve.

On a side thought. I remember as a kid I use to play in a boat builder's workshop. He use to bend the timber for the sides of the boat, (whatever it's name is) not by steaming but by boiling it in a long metallic container full of water and with plenty of fire under it. He used hardwood for this and the size if I remember correctly was something like 1.5" x 3.5" and bent on the smaller side. He did the same with the ribs but I think he used cedar for that, yet not the cedar we know here, a much harder one using the same procedure. Not sure if he added anything to the water. May be some parsley . . .

So perhaps to achieve a backrest for a chair, you have nothing to loose. Cut your timber and give it a good boil in a pot, and clamp it on a mould. It may just work. At worst, you have thrown away a $5 peace of timber.