Drip Rail Removal and Flush Mount Window question(s)

[wheels777]

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?

[kiwi belly tank]

Yes.
 Is it legal in your class?
  Sid.

[wheels777]

Yes.
 Is it legal in your class?
  Sid.

I am not specifically building it for a class.  Will enter whatever class I can.  The value of the modification will determine if the work is done.   Visual aerodynamics (mental gymnastics) are deceptive...just because I think it looks like it can help does not mean it will.   Hence, the request for a relative Cd improvement number.  I would hate to invest significant hours to see a .00001 Cd change and a .11sf frontal reduction.

The drip rail looks ugly front and rear.  The lack of a recess for the window look ugliest in front and possibly negatively influential at the rear.  But all modern vehicles have that/those area(s) cleaned up.

[jacksoni]

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 if you want (don't have to). At the outset if this is a new car/proposition for you and considering your concern that the modification may not give you much, I'd suggest not going to the trouble, build your car to whatever class you want otherwise, run it and see what you get. If you then want to step up the program to the normally faster classes, go for it. Some of what you want to do can be simulated in a wind tunnel (tape, cardboard etc). (where do you live? The A2 in North Carolina can answer these questions within an hour or two. )In addition to someone here having first hand knowledge,  some searching around you might find some information that answers your questions directly.

Oops, see you are in York, Pa. The trip to NC is not too bad if you really are serious about this. I have done it from here (Annapolis, MD)

Additionally if you are thinking ECTA and running /RS or /SS, no body cares what you do to the body, in essence.

[wheels777]

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 if you want (don't have to). At the outset if this is a new car/proposition for you and considering your concern that the modification may not give you much, I'd suggest not going to the trouble, build your car to whatever class you want otherwise, run it and see what you get. If you then want to step up the program to the normally faster classes, go for it. Some of what you want to do can be simulated in a wind tunnel (tape, cardboard etc). (where do you live? The A2 in North Carolina can answer these questions within an hour or two. )In addition to someone here having first hand knowledge,  some searching around you might find some information that answers your questions directly.

Oops, see you are in York, Pa. The trip to NC is not too bad if you really are serious about this. I have done it from here (Annapolis, MD)

Additionally if you are thinking ECTA and running /RS or /SS, no body cares what you do to the body, in essence.

I search the forum long enough to decide to post the question.  I was just hoping someone had some relative numbers for these mods. 

[kiwi belly tank]

The advantage would be relevant to your body design only & not a given number across the board. You could run it with them on to come up with a base line & then wack them off. I believe the fastest pro Z car is Burton Brown, Victory Motor Sports.
The first production car I owned with drip rail delete was an 85 Starion & that was way ahead of the mob for aero in it's day.
  Sid. 

[GH]

I removed the drip rails on my Studebaker, but did some other things at the same time, so I don't know if that helped any or not. Sure looked better.

[SteveM]

"What Class" is not just a trivial question.  How the rest of the car is built depends heavily on the rules for the class, and the existing record in that class.

Unless you are happy running in Time Only, it really needs to be built to satisfy the rules and existing record of whatever class you choose.  A lot of people, (myself included) have had "false starts" with vehicles, having invested time and money, only to realize later that whatever they are building won't work within the structure of the rulebook.

My 2 cents -

Steve.

[wheels777]

Please excuse the dust being blown off this thread...

I was hoping to run Competition Coupe.  I did cut the rails off and flush mounted the windows.  The car was used for drag racing and now the LSR itch is burning again.  When I read the rules it looks like I need the drip rails.  When I look at pictures, it looks like folks have removed them. 

[Stainless1]

Are you confusing drip rails and roof rails?  drip rails are to remain in production but can be filled or removed in modified I think.... Roof rails (4.X) are required for vehicles over 200 mph... they are an anti-lift device when the car is not going the direction intended... 
 

[Milwaukee Midget]

Depending if it's actually a 240Z and on which engine you're using, it should be eligible to run GT, MS or MGT.

When the 260Z came out, it was available optionally as a 4 seater, so that would, by default, regardless of whether or not your car came with the jump seats, put you in a coupe class. See rule 5.E.3, pp2.

But if it's a verifiable 240Z, they never made one with jump seats, which opens up the GT and sports classes.

MGT let's you remove the drip rails - a process I'm working on this afternoon on the Midget.

[wheels777]

It is a 1974 260Z.  The front has been lengthened 16inches in front of the firewall.  The side windows are flush mount we d and the drip rails are removed.

[KATIE]

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

[RaceEngineer]

If it is a 240Z, with extended wheelbase and cowl, it would be legal in the Modified Sport and could have flush mounted side window and removed drip rails.  Modified Sports are two seaters only.

Since its a 260Z it would be legal in Comp. Coupe (because it's a "four seat car", not legal in Modified Sport) and could have lengthen cowl (12" max), flush mounted side windows and removed drip rails. 

4X. Roof rails shall be installed on any Coupe, Sedan or Truck when the existing class record exceeds 200 mph.

Don   

[RaceEngineer]

Sorry for the error.  The 12" is a minimum in Comp Coupe not a Maximum.