An architect friend of mine who is assisting me in designing a roof rack for Lucinda came up with what we think is an amazingly easy and good (and relatively cheap) idea. Instead of framing out a major steel structure to which one then attaches decking material (trex, cedar, plywood), why not use structural insulated panels, as are now being used in house and commercial construction? This would make the steel framing unnecessary, and the installation almost simple.
Here's a weblink: http://www.toolbase.org/TechInventory/t ... tailID=975
The upshot is that they are panels of plywood or OSB with foam insulation in the middle. The whole sandwich is glued, and can be ordered as standard sized panels or custom. The glue and double sheets of plywood make the panels structurally sound, and they are used as roof and wall materials.
We are conceptualizing a 25-30 foot SIP, about 4" thick, and 8' wide (that's the bus width). Imagine a 25-foot panel being delivered to your site and placed on top of your bus. It would likely make direct contact with, say, a foot of the roof ridge all the way along the top length of the bus. You would space through-bolts at that one-foot spread, and put them at every structural rib of the bus.
OK, now you are done. How about THAT??!! OK, smart additions would include wedges (foam, wood, molded fiberglass, cheese, whatever) in the front and spaced every now and again to prevent it from any possible tipping (though the panel is strong enough to hold weight all the way to the edges) and to act as an air-dam at the front. Also a front air dam would be good, and some deck paint on the top (and maybe bottom for aesthetics), and some edging all the way round for clean lines and to protect the edges.
You could then install any number of railing styles, but the one we like is to through-bolt scaffold support tubes (or square-tube steel) to your window struts and then insert the scaffold (or smaller tube steel) into the sleeves when you arrive onsite. You can connect these vertical posts with a top tube (easy if scaffolding) and maybe a mid-height wire all the way around, too.
What do folks think of that?