GT3 Gurney lip
03-24-2007, 03:08 PM
#16
Burning Brakes
If they were losing speed on the backstraight the lip was probablly a bit too high, but not bad. Each car is different and the optimal lip height is one of experimentation and will even change from day to day on the same car.
03-25-2007, 12:16 AM
#17
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Ray
It is the way it was set by the factory for the Supercup race cars as delivered. they cannot (by regulations) alter the aerodynamics.
http://forums.rennlist.com/upload/spoilercfaddon.jpg
I agree with you however that it depends on how it is setup...less drag or more downforce.
It is the way it was set by the factory for the Supercup race cars as delivered. they cannot (by regulations) alter the aerodynamics.
http://forums.rennlist.com/upload/spoilercfaddon.jpg
I agree with you however that it depends on how it is setup...less drag or more downforce.
03-25-2007, 12:18 AM
#18
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Ray
It is the way it was set by the factory for the Supercup race cars as delivered. they cannot (by regulations) alter the aerodynamics.This is one of the cars.
I agree with you however that it depends on how it is setup...less drag or more downforce.
It is the way it was set by the factory for the Supercup race cars as delivered. they cannot (by regulations) alter the aerodynamics.This is one of the cars.
I agree with you however that it depends on how it is setup...less drag or more downforce.
03-25-2007, 02:00 AM
#19
Burning Brakes
Jean,
That may very well be the case. I'm not an expert on Cupcar regulations but Porsche has more than likely provided a generic compromise height to cover most cases on a particular design car. F1 guys are the only ones I can recall seeing making changes to the height during races. One height for qualifying and one for race day.
Although I was at Farnbacher-Lowes and noticed they had a strip just taped to the wing of their Sebring car, totally not stock. So who knows?
If the strip is exactly the right height there will be no additional overall drag, which is the beauty of it.
That may very well be the case. I'm not an expert on Cupcar regulations but Porsche has more than likely provided a generic compromise height to cover most cases on a particular design car. F1 guys are the only ones I can recall seeing making changes to the height during races. One height for qualifying and one for race day.
Although I was at Farnbacher-Lowes and noticed they had a strip just taped to the wing of their Sebring car, totally not stock. So who knows?
If the strip is exactly the right height there will be no additional overall drag, which is the beauty of it.
05-22-2007, 02:06 AM
#20
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Ray,
Did you end up installing a gurney flap? I noticed this weekend that lowering the ride height (with a 5mm increase in rake) reduced my rear wings effectiveness (964RSA with 3.8RS wing). Raising the element would obviously correct this but I'm not willing to try that until I can go back to the original spoiler for driving around town. So I would like to try a flap which will probably require that I fabricate something. In researching this I came across the following: "Numerical Investigation of an Airfoil with a Gurney Flap," "On the Theoretical Background of a Gurney Flap" and "Navier-Stokes Analysis of Lift-Enhancing Tabs on Multi-Element Airfoils."
Did you end up installing a gurney flap? I noticed this weekend that lowering the ride height (with a 5mm increase in rake) reduced my rear wings effectiveness (964RSA with 3.8RS wing). Raising the element would obviously correct this but I'm not willing to try that until I can go back to the original spoiler for driving around town. So I would like to try a flap which will probably require that I fabricate something. In researching this I came across the following: "Numerical Investigation of an Airfoil with a Gurney Flap," "On the Theoretical Background of a Gurney Flap" and "Navier-Stokes Analysis of Lift-Enhancing Tabs on Multi-Element Airfoils."
Last edited by JasonAndreas; 05-22-2007 at 05:02 AM.
05-22-2007, 08:46 AM
#21
Burning Brakes
Jason,
Still waiting for delivery of the CF lip, you know how kids are, nothing gets done in a hurry. If you're looking to try out this setup, you could always have a fab shop bend up a light aluminum one and tape it in place to see how it might work on your car. This would be relatively inexpensive solution. And you could have a couple of different heights and angles made up at the same time. Once you found the best setup/design, you could have a CF one made to match. One last comment, if you are limited to the stock 5mm by regulations, you can effectivly reduce the height by changing the angle and tipping it back and, not sure, but believe tipping it forward will give an increase in effective height, to some degree.
Still waiting for delivery of the CF lip, you know how kids are, nothing gets done in a hurry. If you're looking to try out this setup, you could always have a fab shop bend up a light aluminum one and tape it in place to see how it might work on your car. This would be relatively inexpensive solution. And you could have a couple of different heights and angles made up at the same time. Once you found the best setup/design, you could have a CF one made to match. One last comment, if you are limited to the stock 5mm by regulations, you can effectivly reduce the height by changing the angle and tipping it back and, not sure, but believe tipping it forward will give an increase in effective height, to some degree.
05-23-2007, 02:45 AM
#22
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Gurneys or 'wickers' are always 90deg or normal to the trailing edge of a wing element - and do in fact add aero drag. Buuuut, they are often used to add confidence to the driver, which makes for better lap time.
Of course L/D is dependant on many many factors, weather included. Aluminum L shaped material can be purchased at your local Home Depot or Lowes. These can be successfully taped onto the wing element with aluminum tape or helicopter tape.
If you want to get creative in minimizing the aero drag penalty, a saw toothed profile typically reduces the above mentioned drag penalty by ~7% for a given D/F increase.
Of course L/D is dependant on many many factors, weather included. Aluminum L shaped material can be purchased at your local Home Depot or Lowes. These can be successfully taped onto the wing element with aluminum tape or helicopter tape.
If you want to get creative in minimizing the aero drag penalty, a saw toothed profile typically reduces the above mentioned drag penalty by ~7% for a given D/F increase.
05-23-2007, 04:59 AM
#23
Burning Brakes
Chris
If implemented correctly, in theory, Gurney strips do not add net drag. The intrensic turbulance under the lower trailing edge of the wing sans the strip actually causes some drag. If you install a strip just tall enough to illiminate this lower disturbance, no higher, the increase in drag due to the strip is about equal to the reduced drag from the lower wing so it is a net wash as to drag re:no NET increase. The optimum height is very specific to condition variables, as you mention. The Porsche 5mm height is probablly simply a best case compromise. Thinking is, it's better to err on the high side and gain the aero and a bit more down force and sacrifice the speed than to be on the short side and loose some the aero downforce. It's when you exceed the minimum height to gain more down force, same as tipping the entire wing up, you will see an increase in drag. These are two seperate issues. The cup cars are using the Gurney for two reasons, one to clean up the wing aero and for additional down force. It's the additional down force that accounts for the slower speeds.
The Gurney's are "always" 90 deg mostly because it easier to use 90 deg angle and just change the height than it is to change the included angle. Similar affects can be attained by both methods. Any configuration that will disturb the air flow at the trailing edge will work to some degree, no pun intended. If you look at the GT3 RS wing, the last 1/2" is tipped up about 3 deg (not 90) to remedy some of the lower wing aero. I've seen Gurneys that are shaped like small triangular ramps which work in the same way. There's a myriad of inventave solutions to this issue, it's whatever works best for you. Although in my opinion, simple is always best.
Great comments guys.
If implemented correctly, in theory, Gurney strips do not add net drag. The intrensic turbulance under the lower trailing edge of the wing sans the strip actually causes some drag. If you install a strip just tall enough to illiminate this lower disturbance, no higher, the increase in drag due to the strip is about equal to the reduced drag from the lower wing so it is a net wash as to drag re:no NET increase. The optimum height is very specific to condition variables, as you mention. The Porsche 5mm height is probablly simply a best case compromise. Thinking is, it's better to err on the high side and gain the aero and a bit more down force and sacrifice the speed than to be on the short side and loose some the aero downforce. It's when you exceed the minimum height to gain more down force, same as tipping the entire wing up, you will see an increase in drag. These are two seperate issues. The cup cars are using the Gurney for two reasons, one to clean up the wing aero and for additional down force. It's the additional down force that accounts for the slower speeds.
The Gurney's are "always" 90 deg mostly because it easier to use 90 deg angle and just change the height than it is to change the included angle. Similar affects can be attained by both methods. Any configuration that will disturb the air flow at the trailing edge will work to some degree, no pun intended. If you look at the GT3 RS wing, the last 1/2" is tipped up about 3 deg (not 90) to remedy some of the lower wing aero. I've seen Gurneys that are shaped like small triangular ramps which work in the same way. There's a myriad of inventave solutions to this issue, it's whatever works best for you. Although in my opinion, simple is always best.
Great comments guys.
