Fubeca....thanks for the snaps of the interior, it really makes your construction technique quite clear. I posted yesterday here on your thread singing the praises of your work...then, I kept blabbing and someone rightfully moved my overblown post into it's own thread. So again Fubeca...Excellent Excellent work,
your Aero Cap is far and away the best "Value" DIY cap on this planet right now.
I know I have not been at this aeromodding game long....(<24hrs) but I have spent some good energy thinking about this. I also have a keen intuition for what makes sense in the engineering world and at 47, have a good deal of life experience. It would seem that your rounded corners are better in the sense that flow tends to become separated at sharp corners. If a sharp corner is always parallel in the slip stream it won't matter much. But what are the odds we have guessed that right and have the corner right there??
And this would only be good for a calm wind day, any kind of cross wind will upset the balance, and turbulence will get created.
By having rounded corners, it delays the formation of this separation which causes turbulence and minimizes the separation if it does happen.
Fubeca, if I could make a suggestion on your design, as I see it, it would be to lower the trailing edge of your cap down so you don't have an additional 4 inches or so of vertical surface, You also could have included a 3 to 4 inch radius into this trailing edge instead of making it a sharp edge. I think a radius edge on the very back would help in reducing the size of the "Behind the Tailgate" vortex a bit more. Sorry to criticize, I just thought I'd put this out there for anyone else who may want to consider other ways of improving on the already amazing job you have done.