[Shepherd777]

Originally Posted by some_other_dave

I think I might be seeing something that says the truncation of the trailer is accounting for an 80-90 count increase in drag. Possibly that means 0.08-0.09 higher Cd? soD, I think that may be a viable assumption.

So if you tapered the trailer, you might see less of a spike there. We would absolutely see less of a spike there. The dilemma is trailers are made to haul a certain amount of freight. And most trailers cube-out before they gross out. In other words, all of that cubic capacity is used in a high percentage of loads. There are many more loads of cereal and toilet paper, than say anvils. So here in the good ol' US of A, we cannot taper the rear of the trailer like they have experimented with in Europe. Our shippers would never allow that. All high-cube loads are based upon and created using so much cubic feet of capacity.

BTW, the front of the template can almost be ignored. Don't worry about where it puts your windshield. It's the rear of the vehicle that contributes the most to Cd, as you're seeing with that big jump at the tail of the vehicle. We were concerned with the template on the front end only to the extent of where it placed the windshield in relation to the drivers eyes. It was way too far forward and we really couldn't relocate the driver and passenger locations at all. I absolutely agree with you that the rear of the vehicle is most important. Think how much the Cd would have spiked there without that 48" boat-tail there.

That's an interesting graph, BTW. I wonder how it gets made, and how reliable it is? Very cool if it is reliable! It absolutely real and reliable. We used ANYSYS CFD software. There are 70,000,000 data points (yes, 70 million) in that model and it took over 800 hours of parallel-processing CPU time to do that graph.

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