In another thread “Frontal Protection in a '40” the discussion moved around to aerodynamics. With a tip of the hat to Ron who recently suggested we avoid mixing the topic of threads, I though I would ask for additional comments about GT40 aerodynamics here.
In that other thread I think Lynn makes a good observation about practical vs. theoretical aerodynamic GT40 issues. Likewise another thread named “Rear Spoiler” (imagine that) also reveals that despite its functionality, everyone thinks a rear spoiler is a very cool styling detail (and it is relatively easy to fabricate). Now heaven knows it is very difficult to actually measure performance differences even in highly controlled environments but I cannot tell if we really know enough to make any data based decisions. The data Lynn referenced was:
Lift/Drag for the MK II
100 lbs. @ 150 mph, with 525 lbs. of drag
144 lbs. @ 180 mph, with 756 lbs. of drag
177 lbs. @ 200 mph, with 933 lbs. of drag
That data is also quoted elsewhere (for example: Products - Aerodynamic Devices) but I have not been able to find more detailed information. Does anyone know the configuration of the car being tested. Were the measurements for the MKII as raced in 1966 with a 2” rear spoiler, no front winglets, and 3” of ground clearance? How are the lift numbers for the car divided front to rear?
DRAG
Most of our cars are MKI configuration with no spoiler, no snorkels, and only 1 air scoop per side. I would guess that the extra drag created by the MKII snorkels and scoops would be very significant. It seems like they are in the optimal position to create drag. And, because the frontal area of the scoops and snorkels is about equal to that of the exposed lip on the spoiler, one could argue that the drag created is greater than or equal to that of the spoiler itself. If drag on a MKII at 200 mph is 933 lbs, what might be the drag on a MKI at the same speed with no spoiler, no snorkels, and no extra scoops?
LIFT
Presumably the intent of the rear spoiler is to maintain the front to rear weight distribution of the car as the speed increases. Up to a point as speed increases does the air pressure on the front of the car press down as lower pressure at the rear creates lift? Is it generally believed that the spoiler cancels lift on the rear of the car so front to rear proportion stays constant?
In that other thread I think Lynn makes a good observation about practical vs. theoretical aerodynamic GT40 issues. Likewise another thread named “Rear Spoiler” (imagine that) also reveals that despite its functionality, everyone thinks a rear spoiler is a very cool styling detail (and it is relatively easy to fabricate). Now heaven knows it is very difficult to actually measure performance differences even in highly controlled environments but I cannot tell if we really know enough to make any data based decisions. The data Lynn referenced was:
Lift/Drag for the MK II
100 lbs. @ 150 mph, with 525 lbs. of drag
144 lbs. @ 180 mph, with 756 lbs. of drag
177 lbs. @ 200 mph, with 933 lbs. of drag
That data is also quoted elsewhere (for example: Products - Aerodynamic Devices) but I have not been able to find more detailed information. Does anyone know the configuration of the car being tested. Were the measurements for the MKII as raced in 1966 with a 2” rear spoiler, no front winglets, and 3” of ground clearance? How are the lift numbers for the car divided front to rear?
DRAG
Most of our cars are MKI configuration with no spoiler, no snorkels, and only 1 air scoop per side. I would guess that the extra drag created by the MKII snorkels and scoops would be very significant. It seems like they are in the optimal position to create drag. And, because the frontal area of the scoops and snorkels is about equal to that of the exposed lip on the spoiler, one could argue that the drag created is greater than or equal to that of the spoiler itself. If drag on a MKII at 200 mph is 933 lbs, what might be the drag on a MKI at the same speed with no spoiler, no snorkels, and no extra scoops?
LIFT
Presumably the intent of the rear spoiler is to maintain the front to rear weight distribution of the car as the speed increases. Up to a point as speed increases does the air pressure on the front of the car press down as lower pressure at the rear creates lift? Is it generally believed that the spoiler cancels lift on the rear of the car so front to rear proportion stays constant?