Quite a few updates to cover…
Over the past few weeks we have been experimenting with bending wood (pressure treated pine) using a steam box and jigs to create the curved framing members. First we tried bending whole 2x4s but the results weren't satisfactory. Lots of knots in the wood led to uneven bending, kinks, and splits. 2x4s also required a large amount of force to bend and didn't like to stay bent when unclamped from the jig.
Steam box in action.
Fast acting propane boiler starts making steam within 15 seconds.
Steamer plumbing. The red tube carries steam into the box. Clear tubing is the water feed (from 5 gal. bucket) and condensate recovery from the box. The steamer uses ~ 1 gallon of water per hour.
First attempt at bending a 2x4 was unsuccessful. The board cracked around a large knot in the center.
Closeup of the knot and cracks.
We ended up slicing the 2x4s in half on a table saw to create 1x4s which could be bent, carefully and with a lot of clamps, without steaming. This was only possible because the treated lumber still had a high moisture content which makes it more flexible. It was much easier to work with these if they were steamed and bent close to the radius that was needed, especially for the smaller radii.
Resawn 2x4s ready for steaming.Out of the steamer and into the jig.
After bending.
On Sunday, after some trial and error, Russ, Mike and I were able to get about half of the berm rim joists installed on the structures. We laminated four resawn 1x4s to make a 4x4 beam. Polyurethane construction adhesive was applied between each layer to add strength and seal the joints from water to prevent rot and freeze thaw cycling. The layers were clamped to close glue joints, as much as possible, and screwed together with 3” deck screws at 1 foot intervals. The 1x4s were staggered along the length of the span to keep the end joints from overlapping (like bricks in a wall). This creates one very strong continuous beam.
Starting to take shape.
Russ prepping a board with polyurethane glue. I still have this stuff on my hands two days later...
Laminated 1x4s make up the rim joist for the elevated berm.
Have to leave a gap for the existing trail at the moment.
Berm bridge progress.
After finishing the rim joists, the next step is getting the mid berm joists bent and installed. These will sit on the angled braces between the outer posts and the cross-members and support the middle of the berm planks. These will be constructed in a similar fashion to the rim joists but will be more challenging because they require a complex curvature (curved in two directions). We will be working on this for the next few weeks until the decking arrives.
The rough cut oak decking is currently being sawn at the mill and is on schedule for delivery at the end of March.
Many more photos here.
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