Thread: Bending timber

Use a piece of rain gutter down spout as your steaming chamber.
Tie that to a chair leg and use an electric kettle as the steam generator at the bottom.
Stuff a sock in the top end as an adjustable vent.

Got a chicken roaster pan in the kitchen?
Boiling water and a stone or brisk piece to hold the wood underwater.

The heat uses the steam as a transfer agent to soften the plastic-like biochemicals in the wood.
Your wood is small, I'll guess 30 minutes and you would be finished.
Allow the wood to cool in service (clamped in a jig.) That should be the end of it.

My Dad steam bent a lot of oak boat keels. We tied the pipe to a step ladder.
The first ones got pulled out and bent as test for time.

Originally Posted by Robson Valley

Use a piece of rain gutter down spout as your steaming chamber.
Tie that to a chair leg and use an electric kettle as the steam generator at the bottom.
Stuff a sock in the top end as an adjustable vent.

Got a chicken roaster pan in the kitchen?
Boiling water and a stone or brisk piece to hold the wood underwater.

The heat uses the steam as a transfer agent to soften the plastic-like biochemicals in the wood.
Your wood is small, I'll guess 30 minutes and you would be finished.
Allow the wood to cool in service (clamped in a jig.) That should be the end of it.

My Dad steam bent a lot of oak boat keels. We tied the pipe to a step ladder.
The first ones got pulled out and bent as test for time.

Awesome, Thank you. I'd never thought about the pipe and the kettle, best I buy a Kmart $9.95 jobbie and set it up in the shed.

As for setting in the jig, should i over bend or just to the right curvature?

It might be an idea to use a piece of Al rectangular tube or corian as a back up piece for the Blackwood being glued to.
Anything will do so long as it isn’t able to be glued onto it and is strong enough to resist bending.
That should keep everything ok until the glue dries.
H.

Overbending? How much is too much? I can't give you any numbers at all. I think that some couldn't hurt.
The softened hot oak keel went straight on the boat and in went the brass screws.
I don't remember much else. I wasn't very old and my job was to keep the kettle from boiling dry.

Originally Posted by Fumbler

Advice please. I am trying to bend 15mm wide circa 3-4mm thick Tassie Blackwood, In short I am attaching them to a thin 110mm long x 10mm thick blackwood. And although the strip is only 3mm thick, is quite stiff to bend. I only want to take the stress out of the curve for gluing. If you look at the pic, the piece (in black) is actually quite thin itself so i need to take the stress of the strip to avoid it transferring the stresses through and distorting the piece its glued to.

I have submerged the strip in tap hot water for a few minutes, and it flexed a lot more easily and is now clamped to a jig to put the curve in so hopefully it holds the shape somewhat.

Does anyone have any recommendations ie, length of time to be submerged, should I over bend the strip whilst drying so that when it comes out of the jig, the curve will relax close to what I need? I also don't have a steam bender.

I think you are asking quite a lot here.

bending the 3 mm thick Blackwood should be pretty straight forward -- as you have found heat works quite well.

However, what you are gluing the strip to is itself very thin -- at 10 mm perhaps too thin to maintain the shape you want the Blackwood strip to take up.
Can your design be modified to either
beef up the thickness of the backing piece, or
thin the Blackwood strip where it attaches to the backer?

Guitar makers bend up the sides using a heated Al former.
I can’t remember but I don’t think they even wet the sides first.
A mate of mine does this with Blackwood but he has a bending former with an electric element in it.
You might be able to rig up something with a gass burner and Al tube with one end blocked off.
You do this by eye so you can bend to exactly fit your other piece.
H.

Guitar makers do use water, depending on the type of timber being bent they may soak first or just spritz with a spray bottle. Temps of 140c up to 180c are used.
By the looks of the diagram you are trying to bend with the grain, with guitars they bend across the grain which I would think would hold shape better than the way you are doing it. Guitar sides are also only 2mm thick which helps with the bending process as you are not fighting with the timber as much.
How has the Blackwood been sawn? Quarter sawn would be best as it should take less effort to bend and not want to spring back to its original flat form. I think the kettle and pipe method would best suit your requirements.

I think guitar sides are typically around 2 mm thick.

Thank you to all the tips. After a hot water bath for 20min and clamping in a jig with a shorter radius to allow flex back closer the curve desired the clamping was easy and a success. Although they are only 12hrs into a 24ht glue up. I'll post pics of finished product when out and sanded.

IMG_4531.jpg

Great news. It worked fine and you got it done.
Fresh wood with it's higher water content should bend like rubber and then cool to set in a new shape.

Here in the Pacific Northwest, great kerf-bent boxes are used for storage, cooking (and coffins) by Haida First Nation and others.
The wood is always split and the kerfs are hand carved and always tangential to the cylinder of the log to allow for less stress in steam-bending.

Going back to my childhood when kit boats were popular, the parts of the boat that were needed to be bent were wrapped in newspaper. Then the newspaper wrapped timber was left in the basement and watered twice daily. After a week or two, the strips of timber had the consistency of cooked spaghetti.

Well, done and cut to length. For the application of these, please see the WIP in the box making threads.