[ijames]

I don't usually post, but I was thinking about this and had an idea how you could do an aerolid. First, cut a sheet of plywood to shape and attach it to the bed side of the metal hoop behind the cab so no air can get through. I don't know how long your bed is so I'm assuming 8' but adjust as needed. Take a flat sheet of plywood and attach with hinges to the top of the metal hoop so it can swing from below horizontal with the far end touching the bed by the back bumper, up to vertical. Make the back end something like 2' narrower than the front end to give 5-10 degrees of plan taper - the exact dimensions obviously depend on the bed and lid length and others will have to recommend the optimum target angles. Take a piece of 8" pvc pipe and rip it lengthwise into four 90 degree quadrants, and attach one quadrant across the back end of the lid. For an 8' bed and 2' high metal frame that should give about 12 degrees of downslope, which is in the range of 10-16 degrees that I've seen recommended here. Cut trapezoidal pieces of plywood to connect the front edge along the metal frame, the top edge along the lid, the bottom edge along the outside of the sides of the bed, and the back end where the pvc pipe is. Probably best to attach quarter discs to cover the ends of the pipe section to the pipe, and then have a straight edge on the side pieces. Attach the sides to the lid with hinges, add some kind of latch or bracket to attach the back edge of the side pieces to the ends of the pvc pipe, and some kind of latch or strap to hold it down in the back. Now you have an aerolid for cruising empty.

Attach two vertical pieces of say 3.5 or 4" iron pipe as tall as the metal frame, about 6-12" in from each side, flip the lid so it is standing up vertically, and drop two pieces of 3" iron pipe into the sockets and attach the lid to the pipes with some kind of loops or clamps to support it in this position, and now you have a front wall that can take a moderate wind load and can load your buildings onto the bed. Either fold the side pieces in so the pipes hold them in the folded position, or fold them out and add horizontal bars to support them so they cover more of the front of the building. Ideally, if the bed length and the height of your cargo match, the pvc pipe will give you a nice rounded edge across the top. If the lid comes out way too tall then you will either have to make a horizontal cut and add more hinges so you can fold it as you raise it, or make the lid shorter than the bed.

If you added horizontal supports to let the side flaps fold outward, you can add vertical pieces of the 8" pvc quadrants on horizontal bars that connect to those supports, and make the horizontal bars in different lengths to match 8', 10', and 12' buildings. This will give rounded vertical corners for even better aerodynamics.

After you build the wood version and test it, get one of those bulbous nose plastic bulges that they sell to go on the front of trailers, and attach it to the lid so the bottom of the bulge is as close to the cab roof as possible. This should help when you have a building on the bed, and may help or may hurt when the lid is down, it depends on how steep the side angles get and you will just have to test. Measure the bed length, the height of the metal frame at the front, and the most common building heigth and see how the angles work out, and build the simple plywood lid first for testing, then you can add the pvc edges and front bulge if you want to keep going. I don't know what to do about the openings in the bed - can you add a belly pan below the rollers and tilt mechanism? Don't worry so much about the idling time, that's where diesels excel compared to a gasoline engine.

Anyway, just one possible design you could pursue.