Peter and I pulled out the large curved timber which is truly the piece de resistance of this frame. It is a 15' long piece of American elm (Ulmus americana) which I acquired in the Summer of 2008 from East City Park in Moscow. Specifically it came from an area just to the North of the stage in the park, from a tree dying of Dutch Elm Disease. This timber was a large, curved limb of the tree that was left behind by the arborist.
This curved timber is 15' long and about 11" tall and 9" thick. I milled it to a 9" thickness on the Woodmizer bandsaw mill.
I painted the end grain to slow down checking due to uneven drying. The pith (center) of the tree is nearly centered.
Our plan is to reduce the timber to a 10" height throughout, removing the rounded top and bottoms. Peter had the great idea of creating a large template curve by using a thin piece of wood attached to the timbers by screws and clamps at the extreme opposite ends and at the center. We used a 1/4" thick piece of Western Larch that I had intended to use from trim in my cabin. It easily bent into a fair curve. Using an electric Stihl chainsaw and using the larch template as a guide, we cut a series of kerfs on the top surface of the beam.
Using chisels and mallets, we knocked out the remaining wood between the kerf cuts. This is exactly how I make tenons, but this is on a far larger scale.
We smoothed out the surface using a chainsaw and a wide handheld electric beam planer. We got the top relatively squared and smoothed out.
Next, we flipped the timber over and repeated the same process to remove the rounded portion of the beam on the bottom.
This picture really shows off the natural curve in this beam:
We used the wide beam planer to clean things up and smooth the bottom surface.
We are both very happy with how this beam turned out. It is now nearly symmetrical, and we got a near-perfect 10" height on the beam. We need to do a little more milling on this beam to reduce its thickness down to 8", and we'll either drag this timber back out to the Woodmizer mill, or we will use an Alaskan chainsaw mill in my shop.