Wednesday, August 25, 2010

Wood Bending Experiment 3

So in case you haven't caught on yet, this month is wood bending month - which to at our place, is sort of like the equivalent of SHARK WEEK on the Discovery Channel.

Here is a test piece made from a set of mis-bends to suss out the joining methods/issues.
So far so good!!!

- Heather.

Monday, August 16, 2010

Wood Bending Experiment 2

A few days ago we bent some more wood for the dining table. Last time the compression strap was not substantial enough so it was beefed up with one band of 2 inch wide 16 gauge steel instead of two thin 20 gauge straps. This stopped the tension cracks from forming on the outside of the bend which is what happened last time. Added to the steel were some large maple handles to replace the laminated plywood.

The New Compression Strap

Two pieces of wood were steamed and then bent over the form, one ash, and one white oak.

Bent White Oak and Ash

Compression Side of the Bend

Tension Side of the Bend

The two other forms are now complete and all the blanks are cut. The next step is to bend all the necessary profiles and assemble. We will have more process shots of building the rest of the table soon!

And now for something completely different, Jim Bryson playing among the butterflies and the Weakerthans at the Wolfe Island Music Festival.


Friday, August 6, 2010

Wood Bending Experiment 1

Last weekend we experimented with bending some wood for the dining table that we are building. We have wanted to try bending wood for a long time, and however nerdy this may sound; it was very exciting. The legs of the table we are building have three different bent profiles, with the center profile the one that we are trying to make first.

We built a form allowing for over-bending (to account for spring back), a drying form to hold the wood in position as it dries overnight, and a small steam box. The box was made to only steam the center of the wood slats as that is the only part that is bent and we wanted to keep the ends as straight as possible.

The Steam-Box Setup

The steam box sat directly on top of the kettle which worked quite well except for when we had to refill the kettle with water. A simpler solution will have to be found for this to stop the box from losing heat when the kettle is taken out. The box is "sealed" with damp cloths to help keep the steam in.

The Bend-Form

The bending form is kept close to the steam box so the wood does not cool off before it can be bent into place. The setup used a male form with a compression strap to stop the wood from failing in tension as it is bent.

Freshly Bent Wood

This piece of wood has just been bent. The wood is clamped onto the form at the bottom and then bent up around the first corner. The second clamp is then put on to ensure the straight bit between the two corners. The wood is then bent around the second corner and the final clamp is put on. This process needs to be done in around one minute or the wood will have cooled off too much to make it around the second bend. It takes quite a lot of force to make the wood bend to this degree, making it feel like the wood is going to snap at any moment.

Tension Failure!

The compression strap we used did not cover the whole piece of wood, allowing a small crack where it wasn't supported. We think that the bend would have been successful using the a better strap and are currently in the process of making this addition.

Cooling Down

The wood cools in the form for 20-30 minutes. This allows the bonds in the wood to re-form resulting in bent wood that is almost as strong as the original straight piece despite the deformation.

The Drying Form

The bent wood then sits on a drying form for a day or two to fully cure. The drying form is closer to the intended shape of the wood as the spring back after this stage will be less.

The Result

After reading many books and articles on steam bending, the main thing to take away is that there are no clear cut rules for the process, and that trial and error are the best ways to get familiar with it.

With what we have learned we are already building a new form and compression strap for the next round. There was much less spring back than we expected, and our compression strap needs to be more robust. We have also given the form a larger radius in the corners so that the wood has an easier time bending without failure.


Sunday, August 1, 2010

Jennifer's Dining Table

We are currently working on a dining table commission. The table was to incorporate a round glass top with wooden legs. We have been wanting to experiment with steam bending wood for a while now, so we designed legs that utilize three separate bent profiles.

The profiles of each leg are designed so that the solid wood visually splits and reforms further down the leg. Laminating the three bent profiles together will help to strengthen each leg while adding the dimensional stability that steam bending lacks.

The three legs are then joined in the middle with knockdown hardware.

The wood we chose is white oak because it is one of the best woods for bending. The profiles have very tight curves that would not be possible with other woods. Our first attempt at steam bending happened today, and we will get some pictures of that up soon. All we know so far is that there is a steep learning curve...