Stretch a piece of canvas over the opening.  Air can't get in and whip
around to make noise and drag then.
TEMiller
----- Original Message -----
From: "Martin Jagersand" <jag@CS.UALBERTA.CA>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, March 30, 2004 10:45 PM
Subject: Re: On the Issue of Drag Coefficient Numbers for the Vanagon

> > the later Vanagon with front spoiler lip,the values are: 0.44 and 3.08
m2;
>
> > for the Westfalia, the numbers are 0.52 and 3.17 m2;
>
> To mee it looks like the reason for the worse number for the Westy
> is the front luggage rack. Anyone thought about making a cover
> for it that would allow for a smooth transition from the front
> to the roof? Even better, anyone knows how to actually calculate
> a shape that would avoid cavitation and extra drag?
>
> Subjectively it feels like my '82 westy "hits an air wall" at about
> 120km/h. Wind noise goes from quiet at 90 km/h to moderate at 100-110
> to deafening at 120km/h and over. Can't even hear the engine, which
> itself isn't exactly quiet with fully open turbo wastegate and
> 2.5" Dynomax performance exhaust.
>
> The relative Cd ratio .44/.52 = .85 suggests that a 15% reduction
> in drag should be achievable if somehow it is possible to restore
> good airflow around the westy luggage rack.
>
> Anyone has a solution?
>
> /Martin ('82 Westy 1.9TD and '94 Westy 2.5l)
>