[Saad]

Hey all

Recently I’ve started making a Windsor chair and got stuck at steam bending.
So I’m bending ash but it’ll break while bending. Some details: I used straight grain, soaked overnight, steamed for over an hour, piece was 1x1 inch, used snug fit compression strap, lumber was air dried. Two variables I’m not sure about - didn’t have thermometer for steam but burner was pretty high and water was constantly dripping from box, lumber may have gone past ideal moisture content when bought but soaking and steaming would’ve offset that some. Any tips or ideas?

Thanks!!

 

[Rebelwork]

Do you have a steam box?

 

[Brian T.]

There are three components to wood.
1. Cellulose fiber in the cell walls.
2. Lignin as a supporting "adhesive."
3. Pectic substances. Gummy carbohydrates which soften and go plastic when heated.

The purpose of the steam is to act as a heat transfer agent to get the pectic substances heated up.
% moisture content has very little to do with it.
However, it takes time for dry wood to come up to the equivalent temperature of steam heat and stay there long enough to soften the pectins.

I suspect you didn't heat the wood for long enough. A chair leg might need 2+ hours, you can't damage it that way.

Which direction are you trying the bend the wood? Radial or tangential? I haven't done this for so long it's hard to remember which cracks and which doesn't (oak boat keel strips). For kerf bent steamed wooden boxes, it's always in the radial direction to avoid breaking.

 

[BigJim]

I never had any luck bending wood that thick, you may need to thin it down and laminate it. I would suggest 3/8 inch thick and give that a try. I have had good luck with thinner wood bending with heat.

 

[Brian T.]

Grandpa was a builder of big wooden boats. The shed was 3 car garages dragged together in a row.
We used a length of down spout rainwater run-off house pipe. The upper end was tied to a step ladder.
Had a rag stuffed in the top end for a steam valve.
There was an electric kettle at the bottom end on the cement floor.
My job as a little boy was to shut up and keep the kettle from boiling dry. Took all day.
Then grandma would come out with oven mitts to help hold the keel while it was being attached to the boat.

I'm learning how to carve and bend the kerf joints used by First Nations here in the Pacific Northwest.
The boxes are waterproof with one corned sewn with spruce root. I have diagrams for 11 different kinds of corner joints.
I can carve an under cut joint corner (6") in about 30 minutes. It takes an hour of boiling water to bend the 1/8" thick wood part.

 

[DrRobert]

Sounds like it needs longer time to steam.

In chairmaking I think one of the keys is using riven wood slats where all the grain is completely parallel.

Are you familiar with Curtis Buchanan?

 

[Kudzu]

Brian gave you good advice and I can't add anything other than it is harder than it looks. Grain is VERY important!! I was trying to bend white oak ribs for my boat and the sharp bend would split every time on me. I can barely find white oak, perfect grain was out of the question.

So I gave it and laminated mine. I had no other choice though.