Quote:
Originally Posted by JohnForde
I agree tail lights solve a great deal. To get at the wiring requires removing the cuff. I am working on getting info how to do that. I will have a pro do it and it will be expensive.
KEY QUESTION: Am I safe in assuming the stock "cuff" of 19 deg for 11" is designed to hold smooth flow? (diagram 1)
Extending the exact 19 deg angle for 10" more over lexan seems reasonable to me.
I can then experiment with door angle. I would love it to adhere at the same 18-19 deg. At the maximum legal distance of 48" behind the step bumper that would leave an 'aperture' of about 40", cutting aero drag in half from the 84" stock width.
If I cannot get flow to adhere one option would be to add tail lights, put the hinge an inch or two further to the side and build a rounded shallower cuff. That is a big project I am hoping to not have to do. (diagram 2)
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A constant 19 degree angle is unlikely to keep the flow attached. GM did not design that rear trim for optimal aerodynamics.
You won't know until you test but if you are using straight panels I would shoot for 15 degrees. I would do some research on Class 8 trailer tails and see what angles they are using. No reason to reinvent the wheel.
As Aerohead said - it is a trade-off between build complexity, practically, and aerodynamic performance.