Steaming yew

[JW_Halverson]

I have a yew stave, 1.5 inches by 1.5 inches by 74" long. It has 3 inches of decurve at the worst part, one limb having a long, gradual decurve, and the other limb having most of the decurve in the last 15 inches.

I am thinking of building a steam box and steaming the whole thing all at once and pressing it into a form to bring the whole thing straight in one go. To create the jig, I am thinking of creating a jig that allows for "springback" by taking the wood 10% past straight. If I take the wood down to front profile and taper thickness close to where I will start shaping/tillering, it should not need to steam for an excessive length of time.

I have traced the side view profile on a long sheet of paper and have measured every 3 inches and then drawn the new shape with the extra 10% figured in at every 3 inch interval.

Does this make sense? Kick holes in my theory, point out flaws if you can see them.

[Pat B]

John, I prefer to do one limb at a time, clamped at the handle and out the limb.

[bownarra]

Same as Pat here. One limb at a time. I would just heat treat it
Also do not rough in the tapers. Make it the same width and thickness along the length.
You could probably achieve the same thing by gving it a good heat treat. Make sure it is dry, dry, dry if you go this route tho!

[Del the cat]

I'd go with whatever is most manageable and convenient*. Bear in mind it often take more than one steaming to get it right. I'm in favour of rough it down in thisckness but leaving plenty of width. The less thicknes, the quicker it gets up to temoerature and the less stress wehn bending.
* E.g The available size of steam chest, form, number of clamps, potential speed of clamping phase of moon etc.
Del

[superdav95]

I agree with del and bownarra here.  One step at a time.  You’ll lose a lot of heat quickly out of the steam box or bag before getting to your clamping jig set up.  You’ll be hard pressed for time to get it all done in one go in my opinion.  I’ve never tried it like this in one go like you say with steam myself but can just imagine the rush to get it all done.  With the heat treating smaller sections like what’s been already said you’ll have the time and can be more precise and still perform your slight over corrections as you want by measured degrees.  I’ve used a similar method told to me by bowed and it has helped me a ton with twisty and badly bent wood.  Just a word of caution. Yew only likes to be heated up one  time in the same spot for corrections. I’ve gotten away with a second treatment correction but watch your heat and just work your way out from the handle.  Also I’ve had luck with minor corrections at the handle with trying to align the string in the middle of handle too with clamping bow sideways.  I’ve seen whelyn do this and I’ve since done it this way with good luck.  Best of luck.  Lots of good suggestions here.   

Cheers 

[JW_Halverson]

The jig I have in mind is more like a press, having a back and belly side that clamp the whole stave into the desired shape. The idea is to use two 2x4's so that I can use three clamps, one on each end and one in the middle. They should have plenty of rigidity to handle clamping the entire length.

[BowEd]

Gary Davis used to do what your attempting with osage blanks.

[superdav95]

The jig I have in mind is more like a press, having a back and belly side that clamp the whole stave into the desired shape. The idea is to use two 2x4's so that I can use three clamps, one on each end and one in the middle. They should have plenty of rigidity to handle clamping the entire length.

If you attempt this id be interested in a few pics of your set up for this.  Best of luck. 

[bownarra]

Remember that time is of the essence with steam. What would be the advantage of trying to do it all at once?

[JW_Halverson]

Remember that time is of the essence with steam. What would be the advantage of trying to do it all at once?

I was watching a video of a 2 1/2 by 12 inch oak plank 18 ft long pulled out of a steam box and trunneled onto the ribs of a wooden sailing vessel. The plank was bent along all three axes IN ONE GO. I want to adjust in the x and y axis in one go, rather than try to fart with doing it in bits and pieces along the way.

[bownarra]

No you misunderstand I mean what is the point of trying to do both limbs at once...Of course you would correct everything on the one limb at the same time. It doesn't work trying to do it is left/right, then up/down.
I've steamed and corrected many staves. I would suggest that there is no advantage to trying to do a whole stave at once. You will have more time and control doing one limb at a time.

[mmattockx]

I am thinking of building a steam box and steaming the whole thing all at once and pressing it into a form to bring the whole thing straight in one go.

A member of the local woodworking group I belong to forms laminations for furniture legs by steaming them inside a long plastic bag instead of a box. This lets him keep the steam flowing the whole time he is clamping the pieces into his form, then shut it off after the clamps are tight. PM me if you want more details on his method and the equipment he uses.

I agree with bownarra that it will take too long from pulling it out of the box to being clamped for this to work well. My experience with test bends and forming lams for recurves and the like says you have less than a minute out of the steam before the piece has cooled off substantially and stops bending easily. Bigger, heavier pieces retain the heat better but not that well. I expect what will happen is you find that it takes a lot of force to clamp it into the form and then it just pops back to near its original shape when pulled off the form.


Mark

[gutpile]

I have steamed a whole bow in a PVC pipe about 6 inch.. I run some bolts through pipe to keep stave suspended during process. cap one end use a tee in middle and plug end bow goes in with rubber and a strap.. tee part runs to metal gas can over propane turkey fryer.. fill can with water.. works like a charm.. just got to work fast once you pull the stave.. gut