Steam bending EU oak ( problems)

[Davon]

I've been trying my hand at steam bending using EU oak.

The test piece I used was 70mm wide x 19mm thick x 400mm length

I placed it in the steamer for 1hr and then tried to bend it around an mdf form I have made, but it wouldn't bend enough, tried another piece for 1 1/2hrs still would not bend enough and this time I got this

I used the following method to steam the wood

But outside of course. Would I be way off the mark by thinking that kiln dried wood takes longer to steam, and that the longer you leave it in, the more chance there is of getting problems.

Davon

 

[Anonymous]

400mm :shock: Good luck ! Try steaming a 2m length bend that around your former and then cut the waste off . Should only need half an hour , maye one hour in the steamer you have made . I use the same method of steaming myself .
What steaming does is soften the fibres in the timber . If you look at it another way , would you be snap the same bit of timber 2m long if you put it between two blocks and jumped on it . The same bit 400mm long between the same two blocks and you have no chance .

 

[Davon]

400mm :shock: Good luck ! Try steaming a 2m length bend that around your former and then cut the waste off . Should only need half an hour , maye one hour in the steamer you have made . I use the same method of steaming myself .
What steaming does is soften the fibres in the timber . If you look at it another way , would you be snap the same bit of timber 2m long if you put it between two blocks and jumped on it . The same bit 400mm long between the same two blocks and you have no chance .

I understand what your saying jfc, but to use 2mtrs of hardwood to get a piece 400mm seems a bit much when you need twelve off.
Maybe I'll forget the bending bit on lengths of this size and cut out of thicker stock

Thanks
Davon

 

[Anonymous]

You may get two out of the same bit if you made your steaming jig to take it . Its all a bit of trial and error but you have the steamer spot on as far as i can see . Whats it for by the way ?

 

[johnf]

!9 mm is to thick to bend such a short length try two bit of 8.5 mm and glue them together after bending

 

[Davon]

Dining room chairs...

I'll have to think about it .....no rush

Davon

 

[Davon]

!9 mm is to thick to bend such a short length try two bit of 8.5 mm and glue them together after bending

That's not a bad idea John

Thanks

 

[laird]

+1 for Johnf's view.

 

[Anonymous]

Chairs ? I thought you where going for the bow of a boat with that size !
You will probably be able to do all four legs in one length if you make a former and use longer timber . 2m may well do all four if its just chair legs .

 

[Jeff Gorman]

Bending something usually compresses the material on the inside of a bend and the outside in tension.

The effect of steaming is to heat the wood so that its fibres become compressible, ie the inside of the bend will readily compress yet the heat will have had little effect on the bend's outside, so as the photo shows, the stretched fibres part.

In the case of a fairly shallow curve (chair back?) possibly a clamping a concave-curved pad over the vulnerable area will do the trick, though it will complicate things when we need to work quickly.

I wonder whether the wood got hot enough, and whether some insulation on the steam chest, or even making a wooden one, would help?

Jeff, being dogmatic.

 

[Davon]

Thanks for the replies guys, I'm wondering now about the amount of steam escaping,( thus, as Jeff says, not getting hot enough) I had built in a vent half way down the pipe intending to put an end cap on the opposite end from the steam pipe, but decided to block the open end with rags ( so effectively I now have two vents ) maybe it would be better to block off the built in vent?

Davon

 

[Argus]

.


Oak generally is unforgiving when it comes to intentional distortion and doesn’t want to steam bend, especially if it’s been dried – as a rule of thumb 25% mc is about the lowest limit for unpressurised bending. This is far too wet for most furniture making.
Trying to re-introduced moisture in the from of steam to timber that is already seasoned is usually unsuccessful


If the timber is sawn from a billet with random growth direction it will have short cut grain at intervals due to the saw blade going in a straight line and the growth grain being wavy -hence the breakages and splits. I think that this describes most European Oak types and random grain features is one of its main attractions for makers. Typically steam bent components tend to come from Beech and Ash.

Ideally timber intended for steaming needs to be

A) Wet – i.e. just felled

B) Riven straight lengths, not sawn

When it’s bent it needs to be over bent slightly in the former to compensate for spring-back and left under tension until it is dry enough to use, released then allowed to settle to its own final shape.

You will see from this that steam bending chair components using natural processes is probably an annual batched exercise. Though even with riven Oak there is a high failure rate - it's a feature of the timber, I'm afraid.

There is an excellent section on the rudiments of steam bending (Ash in his case) in John Brown’s little book on Welsh Stick chair making. I think he sums it up as “cut it down today, steam it tomorrow – use it in about 6 months”.

As an alternative I have laminated sawn Oak, glued and bent it for chair sections with some success – but it can be messy in the gluing operation.

Good luck


.

 

[Davon]

Many thanks Argus

Davon

 

[navypaul]

!9 mm is to thick to bend such a short length try two bit of 8.5 mm and glue them together after bending

not entirely true
i bent 4 x9 mm silky oak strips (kiln dried) 60mm wide and 450 long around a 50mm radius. i soaked them in a bucket for a week then steamed them left them for quite a while to dry.
paul

 

[marcros]

!9 mm is to thick to bend such a short length try two bit of 8.5 mm and glue them together after bending

not entirely true
i bent 4 x9 mm silky oak strips (kiln dried) 60mm wide and 450 long around a 50mm radius. i soaked them in a bucket for a week then steamed them left them for quite a while to dry.
paul

but !9mm is a typo. the OP said 19mm, so your example is exactly what was being suggested above, give or take half a mm.

 

[navypaul]

!9 mm is to thick to bend such a short length try two bit of 8.5 mm and glue them together after bending

not entirely true
i bent 4 x9 mm silky oak strips (kiln dried) 60mm wide and 450 long around a 50mm radius. i soaked them in a bucket for a week then steamed them left them for quite a while to dry.
paul

but !9mm is a typo. the OP said 19mm, so your example is exactly what was being suggested above, give or take half a mm.

that makes more sense i dont have a load of experience in the area and managed it with few setbacks

19mil hmmm? think i have enough scrap some useful data could be gained from it