Seasonal Testing of Aerodynamic Cap
 

I get my best numbers here in Arkansas from about the first of April till about mid November. When air temperatures drop below 40 degrees, so does my fuel efficiency. Below freezing, it is terrible.

Since all vehicles are subjected to the same conditions, with or without aerodynamic enhancements, those with superior aerodynamics will still get better fuel efficiency than a vehicle with out any aerodynamic modifications. In cold weather, this percentage will be lower.

Aerodynamic add on devices like boattails and aerocaps do produce a larger reduction in aerodynamic drag because of their greater surface areas over that of a front air damn, wheels skirts and other smaller aerodynamic add ons. All of these devices will see a drop in effectiveness in cold air.

The thing to always try to design into any product is functionality and utility. With the areocap I constructed, this was a driving force in the design of the article. My plans were then, as they still are now, to get the product to market. There have been some excellent aerocaps built by others on this site which are done very well along with boattails and other devices which show remarkable reductions in aerodynamic drag. However, in the real world, you have be able to get into your truck bed or be able to park your car in a parking garage and also adhere to 5 mph bumper regs , third brake light and other DOT specs.

My product is intended to replace the old square camper shell, which has poorer aerodynamics than a baseline truck with nothing over the bed. A truck running a squared off camper shell in very cold weather will get worse gas mileage than a truck running an aerocap in the same conditions, the percentage of difference between the two will be less. In warmer air, it is a different case all together.

Bondo

Cap
 

Science is behind you! And the utility aspect is certainly not lost on anyone living with a one-off prototype designed for aero,and no other consideration.
Some days,my creations cause me great *+%$#@+?X*&^%$#@!. And you can quote me on that!:eek:

Ever thought of replacing the moveable part of the lid with a roll-up tambor tonneau - something like a ReTrax tonneau?

You would gain ease of conversion for max utility. Simply roll up the "tonneau" part and drive the four-wheeler or yard tractor into the bed. When you don't need to accommodate the bulky freight (99% of the time) you roll the "tonneau" down and enjoy the increased MPG.

Of course, there is no free lunch. Using a ReTrax would be uber-flexible and very sturdy but you'd lose the center window altogether.

You could make it like a convertible top "glass".