Hello Fred
I built a 3m dome a few years ago, can I tell you some of my experience/s?
I think there are photos of the process here but if not I can put up a link.
I made mine from aluminum T section for the ribs and .6 and .4mm ally sheet for the covering.
I cut the covering segments and crimped and rolled the edges so they would sit flat on the ribs. Initially, I did the segment in one piece but then went to a join about half way up. I used a " non setting " mastic between the vertical joints and have no problems with leaks - at all.
If I was to build another one -I'm not! I would change the design from a rolled rib to a series of straight cuts, maybe 250mm or 300mm long, that would allow for the sheeting to be trapezoid shaped and because the rib was flat under the sheeting, the sheeting could be folded. Mine needed to be crimped to stop the covering from creasing. Overall it would be a much simpler way of building a dome.
Just be careful about the covering, I have seen lots of ply and or fiberglass covered domes and the all have one thing in common - they eventually ( or sooner ) leak. Silicone isn't your friend, good planning and building practices are.
I would look into the cost of gal sheet and aluminium sheet, the gal may be a little cheaper but you can cut he ally easily by hand or by circular saw.
Hare and Forbes have folder / guillotines that are fairly cheap as well that would handle both materials.
As for control, I'm using Levesdome
http://www.dppobservatory.net/DomeAu...b9b3b01fecee62 to control the dome, through ASCOM, it works well.
If you have any questions or want to talk to someone who has done what you are doing PM me.
Ed