The idea of bending wood into arches and such, can be quite challenging if you've never done it before. There are many reasons why you might want to bend wood into various shapes, but suffice it to say, it's certainly something worth learning how to do! Whether it's an arched doorway or an S shaped guard rail, variety is the spice of life!
There are a few ways in which to accomplish this task, but perhaps the most well-known and used method is steam bending. This method incorporates a steam box and a steam source. You'll also need to prepare a mould to hold your steamed wood until it dries to keep its shape. This should be done before steaming as you'll want to transfer the wood into the mould immediately after steaming.
Your wood steaming setup can be made using primitive materials, although due caution is called for! - The steam gets very hot! The steam box can be as simple as planks of wood nailed together, although wood under an inch in thickness will let significant amounts of heat escape. The steam source can be as simple as a camping stove and kettle.
The steam box should be built to the size of your needs and should not be air-tight - for obvious reasons. Steam can build up tremendous pressure if not allowed to escape! Of course, you don't want to go over board in this and have huge gaping cracks everywhere either - just drill a small hole at the end of the box.
The idea is for the steam to soak into the wood at a maximum rate without building up the steam pressure to the point that it will go ka-boom. Simple enough no? So you've built your steam box, now you need to somehow attach your steam source to your steam box. Some may try to use a hose of some kind, but that can get tricky if you don't know what you're doing.
Remember, whatever you attach directly to your kettle will need to be able to withstand temperatures of at least 100 degrees Celsius. So in light of that, you may or may not want to go shoving on some random garden hose. I'd recommend either a metal hose of some kind, or use an open pot and bring it right up to the bottom of your steam box.
This method is perhaps the simplest. Rig up legs on one end of your steam box, and on the other, make a round opening slightly smaller than the diameter of your pot. It's important to have your setup on a stable surface with no possible disturbances. Making the whole steam box level with the pot is crucial to sealing the joint between the pot and steam box.
Now you'll also want to prop up your wood inside the steam box so the steam can get to all surfaces of the wood in as even a manner as possible. You can use wire to string it up from the top, or you can just prop it up with a couple thin pieces of wood. Wire is better in that it's thinner and will thus leave more wood surface exposed.
Well, your steam bending rig is now ready to start doing what you made it for! Simply turn on your gas stove and wait for the steam to come puffing out the vent hole. Once it does, you can begin timing. They say about an hour per inch of wood surface. Once you steam your boards, you should immediately place it into your mould for setting.
Wait for it to dry and you have your lovely steam bent boards ready to be used! But before you go skipping off happily, there are a few last tips and things to keep in mind:
Not all types of wood are suitable for steam bending. In other words, some don't respond as willingly as others do to steam.
Steam bending can leave what's called residual stresses in the wood and can sometimes lead to premature failure - in structural members - or spring-back with time.