Do convertibles benefit from even more raked (laidback) windshields?

[Big time]

I heard that for hardtops there's a limit on windshield rake angle that yields no further drag reduction.
Somthing around 30 degrees from the horizontal if I'm not mistaken.

Do convertibles benefit from even more inclined windshields than their hardtop counterparts?
Something like 20 degrees from horizontal?
Of course you'll need a pretty transparent and non reflective glass, and a really really long and dark dashboard for such angles.
http://deepblue.lib.umich.edu/bitstr...pdf?sequence=1

[kach22i]

You may wish to visit the Wind Tunnel Images thread to get a feel for it.

On the technical side, I'll wait for someone with more knowledge to chime in.

[Frank Lee]

I'd posit that if the more laid-back windshield results in the windshield header being lower and further back over that open cockpit than otherwise, that it would help aero.

I sat in a Shelby convertible of some sort once at the Detroit Auto Show; I don't recall how laid back the windshield was but I do vividly recall noticing how close that windshield header was to my face. That was a very discomforting feeling- just imagine if I was a left-foot braker!

[aerohead]

Originally Posted by Big time

I heard that for hardtops there's a limit on windshield rake angle that yields no further drag reduction.
Somthing around 30 degrees from the horizontal if I'm not mistaken.

Do convertibles benefit from even more inclined windshields than their hardtop counterparts?
Something like 20 degrees from horizontal?
Of course you'll need a pretty transparent and non reflective glass, and a really really long and dark dashboard for such angles.
http://deepblue.lib.umich.edu/bitstr...pdf?sequence=1

If they did,the automaker may be restrained from doing it due to optical effects stemming from the steep inclination.There is a point where outward vision is aggravated by internal reflections of the dashboard on the windshields underside.
Also,the non-triangulated A-pillars would have to be more massive to deal with Federal vehicle rollover standards in the event that you went turtle.

[freebeard]

http://http://www.hotrod.com/techart...ics/index.html

The biggie: windshield rake: According to Eaker, "Here's a myth I can bust. Once the windshield is past 45 degrees of rake-and many stock cars average like 60 degrees-you will not see an improvement from laying it down at an even steeper angle." We proved this on the Camaro, building a hugely sloped "windshield" out of foam core. It did nothing.

The optical nature of glass is that reflection and refraction are complements. As one falls the other rises. Refraction is dominant normal to the surface, as the angle goes acute reflection overwhelms refraction. The dashboard may be covered with black velvet and there's still less light coming in from the outside.

Compound curved glass causes eye strain.