Sunday, 6 January 2013

Steam Bending Yew

There are plenty of questions when trying to work out how to straighten a lateral bend.
Obviously it's easier to bend a slimmer section (e.g the tips), but is it better to do two small bends or one big one? Is it better to try and get it ramrod straight or just line up the tips and centre?
There is often no one 'right' answer, so I tend to adopt a piecemeal approach. Hope for maybe one bend but with a view to where the second will be. The stave is remarkably symmetrical. The pencil in the first pic marks the area where the first bend will be, note, it's not a sharp bend at a single point. A good length is heated and pressure applied at the tip of the bow to let the wood bend as it wants, rather than trying to force it.
You'll see from the pics how I jig it up dry first which also helps to show where the bends need to be.
The work bench is tilted to allow the condensed steam to run out, and extra insulation is wrapped around to help keep the heat in.
After about 45minutes of steaming I could feel some give in the wood so I bent it over and put in a coach bolt with an offcut of garden hose round it to hold the limb tip in place (last pic). It was then left steaming until it had done about 70minutes total. I'll leave it jigged up for a couple of days, then see if it needs any more.
It might be lined up about right, but there may be some spring back and the tips might want some straightening. I'm hoping that this will be the main bend.

A 5L plastic container with a couple of holes cut in it keeps the steam in the right place, the steam from a wallpaper steamer goes into a hole in the cap of the 5L container.
Any gaps and holes are plugged with plastic packing foam offcuts and extra insulation draped everywhere. (No point wishing I'd got it hotter after an hour of steaming).
The water was dripping over the old duvet I was using as insulation so I moved it around and put a bowl to catch the drips.
You can see in the last pic the tip has come a good way across. Better to bend it a little to much as it may spring back a bit, and if it doesn't a little heat will relax it back a tad.

I've taken off the plastic container and had a look at the bend, it looks pretty good with just a bit of spring back. I've put the coach bolt back in place to let it dry out clamped in position.

No comments:

Post a Comment