Читать книгу Wood & Steam - Charlie Whinney - Страница 12

The grain is the most important factor in the science of successful steam bending, especially for a maker without access to industrial bending tools. As you will discover, wood is not a consistent material – there will be weaker and stronger parts of every plank. The strongest part is where the grain is straightest and runs parallel with the edge of the board, and the weakest is where there is most “run-out” (when the grain runs least parallel to the edge of the board because that part of the tree was not straight or there were branches there). For most woodworkers these subtle changes do not matter and give wood its character, but for us it is vital information. The hot wood will offer least resistance where there is most run-out, and we must notice and act to support and clamp the wood during the bending process to prevent the weakest parts of the plank developing kinks, which can then develop into cracks. We can also plan ahead to employ the straightest grain over the tightest part of the bend.

You may also want to use a steel compression strap if the bend is too tight to achieve safely, for example any bend tighter than 1:10 thickness to radius ratio, or if there is any doubt about the quality of the wood. Results of about 1:5 thickness to radius ratio is the limit I normally recommend; however, with very straight-grained ash, oak, elm, or yew, results of 1:2 thickness to radius ratio, or even tighter, are possible with the right setup.

Working with wood in this way is an art as well as a science, and I find the process addictively interesting. In my workshop if wood breaks this is rarely a bad thing, as amid the drama there is always an opportunity to learn something, and it is the continual learning process as well as the opportunity to make wonderful things that keeps me hooked.