chances of steam bending white oak?

[jaythornley]

I'm going to have a go at steaming some American white oak for a run of cabinets with a curved end unit. The pieces I'm going to try and bend are 40mm x 19mm but quite long lengths so I want to keep mistakes to a minimum! I know ideally I should be using wet oak, not kiln dried, and riven rather than sawn timber. However I can't get hold of either of these!

What would you say my chances are? The kind of bend I'm looking at is a quarter circle with a 300mm radius.

Any nuggets of wisdom before I get stuck in? I gather it is better to compress the internal face of the timber rather than stretch the external side too much. But not quite sure how to do this in practice.

Jay

 

[Random Orbital Bob]

Ive seen footage of people using 4" plumbing pipe with one permanent end (steam proof) and one openable end fitted with hole for a steam pipe to pass through. The length can be as long as you need ie as long as the desired stock. Wack it in...shut the door and leave to steam for a good time (probably half an hour or more) then clamp the oak to a former you've pre-made out of a sheet of MDF or similar. The radius of the former should be slightly (say 5 degrees) more than you want to allow for some spring back. Probably leave the oak in the clamps overnight and then use straight away on the job.

No idea if AWO has the necessary pliability to work. I know Ash would but my guess is that if the radius isn't too tight oak would work.

 

[custard]

Along with ash, oak is just about the easiest timber to steam bend. That's the good news. The bad news is that all the American Oak I've seen has been kilned to fairly low moisture content, generally well below 10%, which will reduce your chances considerably. Can't you find some air dried European oak?

 

[SteveF]

might be worth a visit to a sawmill

i know my local mill has oak sawn and stacked outside...bit rotten on outside but solid a few mm in

 

[rdesign]

why not laminate rip down to 4 mm thickness and then no need to steam, or source air dried stock.

Regards Richard

 

[jaythornley]

thanks guys.

I found a local-ish saw mill that does green oak. They say on their website that green oak will shrink and crack as it dries. That may not matter so much if you're building a barn, but a bit worried about shrinking and cracking on a 40mm x 19mm batten!

The place i was going to get the oak from also does ash. But it is kiln dried. Would this still be better or much the same?

 

[xy mosian]

Hi, I recently thought about bending wood for a recent Windsor chair, changed my mind in the end. However in the course of steam bending research I came across this :- http://robroy.dyndns.info/baidarka/bending.html . The piece seems to be written by someone with a good deal of experience.
HTH
xy

 

[Random Orbital Bob]

thanks guys.

I found a local-ish saw mill that does green oak. They say on their website that green oak will shrink and crack as it dries. That may not matter so much if you're building a barn, but a bit worried about shrinking and cracking on a 40mm x 19mm batten!

The place i was going to get the oak from also does ash. But it is kiln dried. Would this still be better or much the same?

I'm not sure on this one. Ash is a classic traditional material in coach building and of course is still used in some of the older Morgan Motor Car models. It's very bendable whilst retaining it's strength. Oak on the other hand is widely used in boat building, apart from it's strength and ability to bend it is of course very water resistant. So maybe both would do?? I agree though that risking green oak in a finished piece is asking for trouble. I turn green oak bowls every now and then and the warpage is extreme....and the cracking. So you're just engineering in a future customer complaint if you take that route in my view.

 

[Sgian Dubh]

What would you say my chances are? The kind of bend I'm looking at is a quarter circle with a 300mm radius. Jay

Your chances of success are poor to very poor with that small a radius in American white oak of that thickness. You're a new poster here so I don't know what experience you have, but I've been making furniture for a while now, and I'm also pretty familiar with what does and doesn't work in steam bending. American oak purchased here in the UK is all kiln dried to a target MC of 7% ±2% prior to export, and even with likely moisture regain since then to about 10 or 12% the elasticity of the fibres are forever somewhat compromised after drying to that low an MC.

The best compromise material for steam bending is air dried wood at about 20% MC or so. This way some of the shrinkage will have occurred which will go some way to mitigating potential drying faults, but the wood retains much of its elasticity. In your circumstances I'd seek out another material to American white oak and use something native or European that's been air dried. Classic woods for steam bending are European oak or ash, and beech. There are other timbers that bend well, but those are almost certainly the easiest with which to work. Slainte.

 

[Chris Knight]

If you don't need to mould the resulting pieces, I suggest you consider cold laminating the curves. It's easy enough to achieve tight radii that way - depending how thick you make your laminations. I have used veneers and construction veneers for tight l curves and using these saves a lot of work cutting laminations.

 

[Andrewf]

Have never steamed wood for windsor chair backs but have helped putting steamed ribs in boats. The grain orientation on the piece being bent is important. It needs to be parallel to the former its being bent round.
Speed is important, out of steamer and bent quickly. If it starts to cool you are buggered.
Also no matter how good you are or quick you are there will be wastage, so have plenty of spares cut and ready.
A friend steams various pieces of wood in some polythene tube , a bit like a continuous plastic bag that he got from somewhere that comes on a roll. He steams it in the plastic tube with the ends sealed and then whacks that on the former without removing from the bag. Think he insulates the bag with some old blankets while steaming to keep the heat in.