PZT Construction v1Late in the evening I finally completed a structure light enough to be dragged about the yard and strong enough to hold up the POD dome. I went for a light weight ribbed design with a thin (5mm) plywood as the top surface. The ribs are 1"x1.5" pine stock screwed in from the top with 2 to 3 countersunk screws. Unfortunately the thin pine members split easily, and the top plywood veneer was very hard forcing me to predrill the holes and use a countersink bit. Very time consuming for 25 screws. The pressure treated 2"x4" that spans the trusses is screwed to the top surface all the way along. The span connects to the trusses with 1"x6" deck boards reinforcing the joint from below. This type of attachment makes joining the two tippy trusses a piece of cake, since the deck board can be fixed to the truss first (the table top is not in place at that point), and the span laid on the deck board for fitting an fixing.
Fitted under the dome lip I realized that I may have not left enough clearance with the table top. As the dome is rotated around the leading corner can be as much as a 1/2" lower than the rest of the surface, knocking the table out of the way instead of climbing onto the surface. Once the table is loaded with some mass the dome swings easily thru, the additional friction being only a small fraction with respect to the force required to move rotate the dome. I had arranged the bays such that the door was to the NW and a bay on the North wall in which I planned to put the computer. The table pictured below spans over the NE bay, the image on the left is looking SSW, the one on the right is looking WNW. As I started work on the second table, I noticed the clearance of the spanning 2x4 was very tight to the top of the door when open. In fact I could not lower the table top to accommodate the required leading dome corner clearance and miss that door unless I started shaving the spanning member in the direction the most important to its strength!
In any case the large surface area, making it susceptible to wind gusts, and the real PITA of drilling all those holes for the ribs made me think, there must be a better way...