md11plt

Chris,

First thing I thought when I saw that first PIC was that I'd trade you flying lessons for driving lessons in that car. Then I saw the second PIC and realized you don't need flying lessons. Although it looks like your runway alignment could use a little work! Nice flare though!

Steve Weiner-Rennsport Systems

I saw a 6-7 mph bump on my old '74 RSR (with AIR bodywork and modified RSR tail) during my IMSA days with factory 935 A-pillar fairings. Same results on the 993 cars,....

While I couldn't afford wind tunnel time, we DID do a lot of tuft-testing and filmed the car while on the road at varing speeds. The airflow was not as turbulent and appeared to be more laminar down the side windows of the car. Airflow going to the tail was also less disturbed but we had no way to measure downforce aside from driver seat-of-pants inputs.

Being self-sponsored, we didn't have the big bucks so we improvised a lot.

ca993twin

Steve,

Here's my old IMSA car at Riverside. I used white duct tape on the a-pillers to act as a poor man's fairing. This was about 25 years ago. Maybe I saw you out there?

So, bottom line, you feel that shaving the gutters improved your aerodynamics at high speed?

chris walrod

While I am not a proper aerodynamicist, I do have some experience with ground effect cars. I would venture to guess blocking the frontal area of the rain gutters could easily yield 5 mph (speed squared law) straight line, losing the top of the rain gutters may decrease directional stability. Whether it could be felt with a car so soft with respect to pitch and roll remains to be seen. Gotta tap into the extensive experience in the folks like Mr. Weiner and go from there

Here is an image of some rather simple flo-vis (flow visualization) techniques we sometimes do with full scale cars to better understand what exactly airflow is doing. Its just a little dye mixed with gearbox oil

Edit: Notice the funky airflow around the 1" hole on the roll hoop above the Toyota decal. More evidence that holes or features like these need to be taped-up to minimize drag. It all adds up!!

LA964RS

From a safety point of view. YOu'll notice when Ruf shaves the gutters he puts in a full cage or his IRC. All the strength in the ruf...I mean roof is I understand is in the welded lip. I considered doing mine, but don't want to run a full cage...so I'll probably just do the a-pillar farings. Plus here in LA, you got to get up at like 4:30 am if you're going to do a +200mph run. Great way to start the day.

chris walrod

Orrrrrr, one can do some theoretical analysis in CFD --
Notice the orange-red colors as high drag areas or hotspots --

Ima2nr

IMHO- it looks WAY better with the gutters removed... (yes, my car still HAS the gutters)

Steve, your not in it for the speed, your in it to look good... plus, those rain gutteres must weigh at least 2 lbs (per side)!

Steve Weiner-Rennsport Systems

Nice ride, sir......

I never raced at Riverside but plenty of other tracks on the circuit. We were at Portland, Sears (oops, Infineon), Laguna, Road America, Brainerd, Mid-Ohio and Daytona, of course,..

We didn't shave the gutters on our car; I simply installed a set of 935 rubber A-pillar fairings per some advice from some factory engineers. For drag reduction, it worked. I cannot say for certain that I felt a major change in stability since we used the superior AIR front & rear RSR fenders and ran a vertically-extended RSR tail that was better than factory RSR bodywork.......

Chris and others raise a point about the possible role that the gutters might play in high-speed stability but I have no data about that. We did race a 935 for some time (after the RSR) that didn't have any gutters and it was stable as a rock. I think that was due to the completely different aerodynamics of that car and less about whether it had gutters or not.

Like Chris, I'm certainly no aerodynamicist but having owned and flown several aircraft over the past 35+ years, it seems like the gutters are not positioned suchly nor tall enough to make a big difference, at least to compared to other things. Without hard windtunnel data, thats only an semi-educated guess.

JasonAndreas

If you have a stereolithography machine I have a laser scanned, cleaned up and triangulated 993TT.

leonsamonas

I have no gutters and the only downside i can think of is rain pouring in the window when i need a smoke.....

chris walrod

Sadly, we JUST turned-in our SLA machine. There are better(and less costly) alternatives out there for rapid protoyping.

fc-racer

Some aero analysis on the 993 Turbo including a tuft test: http://autospeed.drive.com.au/cms/A_1065/article.html

ca993twin

That is a GREAT article on the 993TT aero issues. Thanks for shairng that. The Ruf areo mirrors, shaved a-piller and flush rear glass look like some easy fixes... but the big problem is with the entire rear of the car.

clubsport1

Having looked over a couple of genuine RUF CTR (yellowbird) based on the 911 bodyshell of the late '80s, they had all the guttering removed. There must be something in it, have you asked RUF directly?

Jussi

How about installing Rain cutter spoiler set instead of cutting it?

FVD :
http://shop.fvd.de/shop/?VID=123823&...Body=&CarYear=

or RUF