I'm planning a solar kiln. I need advice on support for the rear of the kiln above where the doors will go. I want a clear door opening of about 16'4".
First, my assumptions. I want to be able to dry up to 16' long, or have two 8' stacks next to each other (end to end). I want to be able to dry slabs up to 60" wide. I'll have about 4' of internal height at the shallow side of the kiln. Most of my stacks will be 4' wide. If maxed out, (with one stack, 16' long, 4' wide and 4' high, 4/4 lumber, with 1" spacers, with 4X4's at the bottom of the stack as bunks, it will hold roughly 1500bf. I'll be drying mostly hardwoods, and I'm not in a hurry.
I'm considering a footprint of 17'4" x 6'8". The front (framing height, exterior) will be approx 4'7" and the rear will be 9'. This creates about a 35° slope of the roof. My latitude here is 30.22°N.
For the area above the doors, I'm considering a rectangular (floor type) truss as pictured. My goal is to not have any sagging of the framing down on the doors. I would gusset the meeting points of the truss members with 1/2" ply both sides.
What do you think? Is a truss overkill? My "get 'er done" dad suggested just using a couple 2X8's, 17'1 long with 1/2 ply between them, with vertical supports up to the upper framing members. Any other advice or suggestions?
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