Originally Posted by Abitibi
Building the base as you did, does it end up being lighter and/or stronger than using plywood? (it sure looks better!)
I experimented with leftover cherry I had laying arround (which is what I ended up using) and the same construction with 18mm Baltic Birch (11 ply). The BB was significantly less stiff, I imagine partially due to the glue layers being in shear loading when you sit on the panel. Plywood strips glued up on edge in a panel may have worked better.
To be fair, the BB plywood strips would have been skinned top and bottom with 1/8" plywood to yield a 1" thick panel, which I did not try, since I didn't want to waste good wood after deciding on the cherry. This skinning would have resulted in a much stiffer panel I'm sure (you would need to GLUE the skins on covering the entire top and bottom of the panel to maximize stiffness), since the stiffness of a beam increases with either the square (2nd power)-can't remember off the top of my head-have to look it up) or the cube (3rd power) of the height/thickness. That's one reason that I went with 1" thick panels that are more air than wood; to maximize stiffness and minimize weight.
The other design considerations here are:
Taller/thicker panels mean less height for cushions if storing the setup with the PH down. There is a possibility of storing the panels on the PH rails with the cushions facing down, but that requires even narrower cushions to clear the PH rails. I'm planning on having the cushions attached to the panels.
Since I'm using AL channel for part of the support I cannot have the wood panels inside the upholstery (like the SMB bed); I need to have 3/4" of panel width beyond the cushions to properly engage with the channel. If the design was not cantilevered in bed mode and didn't require sliding out, then one could use aluminum angle instead of channel and full width cushions and stick the wood inside the upholstery if desired. If I was 6" shorter I would have considered this.
Alternatively, if I could live with the support box on the passenger side sticking forward into the barn door opening about a foot, the design could be all AL angle (no channel required), and full width cushions.