Boat tail on trailer vs. deflector in front: The beginnings of a clean slate project
 

Which one first?

http://i810.photobucket.com/albums/z...boxes/rig1.jpg

I'll post more detailed pictures when I get it hooked up again.

I just installed my wood bed sides/toolboxes, which allow me to tow the trailer at the proper, lower height.

http://i810.photobucket.com/albums/z.../finish021.jpg

Note that the sides of the boxes allow for an easy full wheel skirt.

I am covering the running boards with teak decking, and I am looking at a fillet fairing for that hard corner at the lower front of the toolbox/back of the cab area.

I am building new front and rear bumpers and grill. That is why I consider it a "clean slate" if you will.
The front bumper will be lower than stock and wider at the bottom to more effectively cover the front tire.

Back to the question: which to do first, a really tight articulating deflector in front of the trailer, going forward onto the truck cab roof, or a three piece folding boat tail?

I have to make the boat tail easy to fold, with a "door" I can open in front of that back window. Hinge the sides in, then lower the top down and open a door.
Advantage of the deflector: Don't have to fold it up to get parked. Don't have to worry about hitting things with it.
Advantage of the boat tail: Quicker build by far.

Start with the boat tail. The back end of the vehicle has the most aero effect.

While youre at it, faire in, or remove entirely, all the stuff on top, while you're pulling it.

Also, a boat tail will make sort of an awning for that back window, possibly reducing the cooling costs for that queen suite back there.

I have to fold that boat tail completely flat to get into many camping sites, so leaving it out is not an option. I have a design in mind that will allow that.
I am looking at the stuff on the roof to see what I can do. I might build a convex bubble fairing for the bedroom fan housing up front, and a lightweight razorback fairing to smooth things out from the front step over the AC unit.

yup, boat tail.

I suspect the back is causing more drag now. The top already has some relief at the rear compared to the loft apex. A clean bubble can't hurt but look at the rear edges. Two sides and one top. Bottom flow is limited by ground. If you could fair both that could help the wake converge instead of diverge. What's the vertical thing behind the awning leg? If it's cloned on the road side too and permanent then perhaps you could attach their.

Your custom box is very interesting! :)

That is the seam where the one piece back attaches to the sides.
I figure on installing a short stub to the one piece back cap on both the top and sides, and mounting a hinge on there. It would be an inch or two inside the edge, but I am hoping it would still be effective. From those straight stubs I would make three simple flat panels that would taper in and down. I'd put slots in the top one so the sides would be captured.
Looking at the top profile it would be nice to curve that top panel, but it gets more complicated. I have to hinge a window in it for the back window.
The folding will limit the length to around 7 feet.

What is the maximum angle I can use and still get a benefit from this partial boat tail?

Angle gets tricky. It depends how far back you want to extend relative to your width and height. Think max curvature not angle. Start with Phil's template.
http://ecomodder.com/forum/attachmen...9&d=1296941870

For height scale to ground plane reflection. For width scale to centerline symmetry. Good luck and keep us posted so we can follow progress. :)