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The retractable spoiler on the coupé has a number of horizontal grooves on the underside. Any idea what for? I know nothing about aerodynamics and very much doubt it but could those grooves have any aerodynamic effect and affect the high speed downforce that the spoiler provides?
Just came to think of this as I'm planning to put a sticker there which obviously would cover a large part of the grooves.
I'm sure that the grooves provide resistance to flexing and sagging. Covering up the grooves won't hurt anything (although your sticker may not last as long).
Others can tell me I'm wrong. I don't know THAT much about aerodynamics either, but I DID stay at a Holiday Inn once.
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Good point, that actually sounds like a very good explanation.
Yeah we'll see how the sticker lasts. It's nothing new really since loads of F-Type owners have put stickers there. Most of them seem to be union jack stickers and I'm not a fan of that so I'm trying out a custom made leaper sticker.
The SPOILER itself, creates downforce (And a bunch of drag!) from the air going over it. The ribs and other contours under the spoiler panel are for rigidity and support. Decals, or whatever you are covering with will not have any adverse effect.
Cheers Therock88 - I think you're absolutely right - up to a point. The rear spoiler certainly creates drag, but a wing (inverted) produces downforce. The purpose of a spoiler is to 'spoil' the airflow over the rear which can create considerable lift at higher speeds, (I recall reading of 120 lbs of lift on the F-Type.) Anyone know for sure?
I did a quick SEARCH because I remembered something that Ian Callum mentioned when he discussed the design of the F. (About fitting the deployable spoilers as a compromise between style and stability)
Haven't looked at all these links, but this might help.
Cheers Therock88 - I think you're absolutely right - up to a point. The rear spoiler certainly creates drag, but a wing (inverted) produces downforce. The purpose of a spoiler is to 'spoil' the airflow over the rear which can create considerable lift at higher speeds, (I recall reading of 120 lbs of lift on the F-Type.) Anyone know for sure?
Not sure why you want to create lift at the rear of a car? That would reduce traction and make it very unstable at speed. I have Bi-Plane spoiler setup on my 911 Turbo and it also creates 273 Nm of DOWNFORCE...No lift. They work on the same concept of aircraft wings, only sort of in reverse. And downforce is less about pushing down and more about lower pressure underneath, pulling. The content below is directly from the operation section of the F-Type repair manual. Want to make sure correct information is provided here.
DC
From F-Type Repair Manual
OVERVIEW The Deployable spoiler provides an increased aerodynamic down force at the rear of the vehicle to maintain vehicle
stability at high speed.
The Deployable spoiler is electrically operated and controlled by the CHCM. The basic system consists of a spoiler
mechanism, which operates the Deployable spoiler blade. The action is a single stage deployment or retraction. The
actuator is powered by the AJB (Auxiliary Junction Box), and controlled by the CHCM.
The spoiler automatically deploys when the vehicle speed exceeds the 'Auto deployable speed' and retracts when the
speed falls below the 'Auto retraction speed'. The driver can manually operate the Deployable spoiler with the
Deployable spoiler switch, which is located in the floor console adjacent to the TCS (Transmission Control Switch).
AUTOMATIC OPERATION
In Automatic operation mode, the spoiler automatically deploys when the vehicle speed exceeds the 'Auto deployable
speed' and retracts when the speed falls below the 'Auto retraction speed'. The deployable and retraction speed
thresholds depends the vehicle body style. In the deployed position, the spoiler provides an increased aerodynamic
down force at the rear of the vehicle which enhances vehicle stability at high speeds.
Speed thresholds for automatic operation
BODY STYLE AUTO DEPLOYABLE SPEED AUTO RETRACTION SPEED
Convertible 96 km/h (60 mph) 64 km/h (40 mph)
Coupe 112 km/h (70 mph) 80 km/h (50 mph)
Didn't intend to imply that you want to produce lift at the rear; it's caused by low pressure air accelerating at the rear of the vehicle. The Porsche wording is confusing. The primary purpose of a spoiler is to prevent low pressure air causing lift. As a by-product, higher pressure air = more downforce. Some earlier BMW's were fitted with a spoiler and a wing.
A spoiler can reduce drag, reduce lift, and increase high-speed stability. It can also increase drag and provide no benefit other than style. Implementation is key. Use of "reduce lift" and "create downforce" is often interchanged in these discussions. The net result is the important part. The pedantic (or which I've been accused) can split hairs over that. A true wing creates downforce at the expense of drag, and needs to be high enough to be in clean air to be effective.
For a concise summary of spoliers, see the section here on "Passenger vehicles."
Grooves under spoiler and aerodynamics?
