Drip Rail Removal and Flush Mount Window question(s)

[jacksoni]

jacksoni wrote; "The way I read the rules, drip rail removal puts you in /Alt and mounting windows flush with outside, if they were not there in the stock configuration, puts you in /CC. You would normally run Classic" , etc, etc
  And the way I read it is that "CLASSIC" is a combo of "Modified" and "Production", , , so if you're ?/CBFALT , you should be able to follow the Altered guidelines regarding drip rail removal. You should be allowed to wack em off. But that's where the controversy starts . I wish that the rule book had a more defined direction towards "CLASSIC" and "DRIPRAILS"
  KATIE

Couple of things. the car is lengthened 16" in front of the cowl already. The (my opinion) ONLY class you can run in is Comp Coupe. Second. Classic is a category, not a class. Classic is pre 1981 and has some engine (ignition and efi limitations.) It has nothing to do with the classes per se. It FOLLOWS the rules for modified (GC, ALT, CC,) and production. In addition, the window rules are a bit different than what I said in 2016. All non laminated glass (windshield is the only one generally laminated these days as far as i know) must be lexan or covered with safety film. Over 200 all non laminated MUST be lexan equivalent. There are no specific comments about mounting the lexan other than bracing to avoid blow out. To me this means moving out to more flush is OK but with the caveat that  anything is open to inspector interpretation. Other than the requirement for lexan which is a safety issue and addressed at tech inspection before running, if someone is going to object about where the window is mounted it will be in impound where class legality is checked. As a comp couple you can do pretty much anything you want basically as long as the firewall back is not changed (and specifically is stated that window opening may be covered with flush flat plates. )

[jacksoni]

Is there a relative Cd improvement value for the removal of the drip rails on my 1974 Datsun Z?  Similarly, a relative Cd improvement for flush mounting the side windows?  Is it worth the effort?

To answer this original question I took a car to the A2 wind tunnel last fall. The  door windows stock were set in a fair amount. A couple pieces of cardboard cut to shape to fill the space to essentially flush was worth 10 counts Cd. This is well above run to run variation. In reading about other people's experience with drip rails in a street driven car someone posted a change in wind noise that was significant with removal of the rails. Don't know  what that may mean actual drag wise but would surmise a benefit. Kind of like a noisy vs quiet intake port.  If you look at a lot of modern cars, they don't have  drip rails but do have a crease in the roof line that extends down to a step between the rear window and the body work. I'm pretty sure is there for a reason.