guttertalk

[JHertzman@domain.elided]

Brian Shorey speculates on an aerodynamic rationale for rain-gutters:

"i'd be curious to know what the drag coefficient is for the alfetta vs the
gtv6.  i'd imagine that the gutter, in addition to keeping rain from
dripping over the roof line and down the sides, might also serve to keep air
channeled front to rear while the car is in motion.

"any 'rain' gutter that was added behind the doors, it would seem to me,
would have less to do with keeping rain from dripping on the passengers than
it would to do with aerodynamics.  the 17" that john mentions might not be
for rain at all.

"anybody know for sure?"

Don't know NUFFIN for sure, but the gutters on older cars constitute an 
easily spot-welded flange joining a top pressing to a side pressing and/or 
other structural stampings, with seam-sealer slathered in as a next step. 
Whether this is the primary reason or a fortuitous secondary use for a 
primarily aerodynamic device would be hard for me to prove, but it did serve 
this assembly purpose on many profoundly unaerodynamic cars from the twenties 
to the early seventies, and is conspicuously absent from the Milano, 164, 
ES30, 155,145, 146, 156, new GTV etcetera on which the spot-welded joint is 
evidently under the extruded black strip usually seen between the smooth 
door-top and the gutterless roof.  

There are photos of wind-tunnel tuft-studies of the Alfetta (p.34 in Fabrizio 
Ferrari's book, for one) which I don't think support Brian's "channeling" 
hypothesis. My guess is that the initial absence of the last seventeen inches 
of gutter was a question of late sixties aesthetics (the Alfetta project 
dating to 1968) and the addition of the last bit with the GTV-6 was equally 
an aesthetic choice (see the alternate restyling studies on p.38-39 op.cit.) 

I'm not sure how much aerodynamics affected most of Alfa's styling decisions. 
It is well known that the Giulia Super was aerodynamically cleaner than the 
GT Veloce, and I would be surprised if the Alfetta coupe was really 
aerodynamically cleaner than the Sport Sedan. The volume-produced sedans were 
generally carefully studied, and the lower-production sporting models were 
styled for eye-appeal. The raised fender edges of the GT Veloce were 
certainly less aerodynamic than the smooth transition of the hood and fenders 
of a Berlina. The diagonal gash on the side of the current GTV coupe is not 
there to correct the aerodynamic shortcomings of the 164. It is there to turn 
heads. Fashion.

John H.
Raleigh, N.C.

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