For the illustration of this technique I will use the runners for a toboggan as the project. The first thing to consider is the design and shape of the curl of the front of the toboggan. Once that is determined you will need to build a form in relation to the shape you will want for the front of the toboggan. I won’t get into the details of building a form but will include a picture that will be descriptive enough to help you. Be sure to include enough clamping points to help secure the steamed wood to the form.
For this project we will use a hardwood for the runners. Soft woods can also be steamed and bent but a hardwood is much stronger and will take the abuse that tobogganing will demand. I have found the wood of choice is ash, although I have had success with cherry. I have also found that with the basic equipment that I use to make steam the thickest piece of wood to try bending is ¼ inch thick. Anything thicker and you may get splintering. If your project requires a thicker bent piece of wood then you may want to consider laminating several pieces.
The heat and moisture from the steam is what softens the wood fibers. Once you start bending the flexible runner you need to bend slowly but continuously to get the piece bent and clamped around the form. You have approximately 45 to 60 seconds to complete this. This almost assuredly requires two people…one for handling and forming the wood runner and the other to do the clamping.
Now I’ll discuss the equipment needed to build a simple steamer. The old style electric kettle is, for all practical purposes, as simple a steam supply as you can get. The new style kettle has an automatic shut-off and will shut-off as soon as the water boils and you will not get a constant supply of steam to do the project. You need a constant source of steam, so find the electric kettle that doesn’t shut-off automatically or a means of supplying yourself with a constant heat supply. Remember, you need to make certain you don’t run your kettle out of water. Make sure it has an adequate reservoir.
Another good source of steam is an old style vaporizer. The new ones don’t seem to put out an adequate supply of steam.
Okay, you have a source of steam in place. Now you need to contain the steam in a small enough area to steam the wood. For my projects a 4” piece of plastic PVC pipe has worked just fine. You need only to steam the area of wood a bit longer in length than what your bend is, so the pipe needs to be a few inches longer than the area to be bent. A good rule of thumb is to steam wood for I hour for each inch of thickness. So, for a ¼ in thick runner 15 minutes should be enough. If you find you need more time add a few extra minutes of steaming time.
Depending on the length of your project it might be necessary to put a 90 deg. elbow on the end of your pvc steam box and have your steam box horizontal rather than vertical.
Before starting have everything in place. Clamps, rags and items such as sturdy gloves should all be in place and ready for action. It’s also a good practice to make a practice run and go over what your helpers’ responsibilities are.
Now you are ready to go…fill the kettle with water, slip the end of your pipe or elbow over the end of the steam supply and pack rags around the spout so the steam is directed outwards and up the pipe. When the water starts boiling slip the wood in the steam box and plug around the other end with more rags. Steam the wood for roughly 15 minutes or until the wood is bendable. Once the runners are bendable remove them from the steam box and position them to your mold. First clamp at the end and start bending around your form. The other person should clamp as the bending is proceeding. You don’t want to rush this bending process. You do need to allow the clamper time to secure the clamps at each clamping spot. Do not over tighten the clamps as that will cause damage to the wood.
Once you have completed the bending process leave the strip clamped in place at least overnight, two days won’t hurt. Remove the runner from the form and tie a cord around the end and back around the end of the curve to help retain the curve some. Now you proceed to the other runners or whatever it calls for with the project that you are building.
To view a picture of the bending form and the toboggan go to image gallery and click my file name. The form I built was specifically for the toboggan but I have other forms for other projects.