That's what I was told by the people at PF's wind tunnel, but I haven't got any lift coefficients available.
I for one am deleighted that the thread has generated this much interest. It seems that we have two seperate but related issues going on. 1) What is that spoiler for? 2) How well was the 3X8 designed when it came to slipping through the air? I think that we have answered the first question partially. The spoiler does not in all likely hood generate any downforce to the car. But, it may be that it does do something to help lower temperatures of the engine compartment. By looking at airflow around the moving car we might be able to answer the above leftover question and determine how efficiently the car goes through the air. So now the question seems to be how to best go about that. Wind tunnel vs software simulation? I have tried to summarize this discussion so it stays on track. I suggest that we attempt both. Since I have no access to a full size wind tunnel I am going to make a scale version with my smoke machine and any wind generating thing I can get my hands on and I am already bidding on the model on Ebay. I am open to any help in calculating scaled down wind factors and such or suggestions on building this thing. Yes, the winter months are hard when you can't drive your car and that is why I am doing this for those that think I have lost all sanity.
Reynolds number... you need to up the wind speed to get something intelligent - if you want to test a model, use minimum a 1/5 scale; 1/4 or 3/8 is better. A rolling road and wheels help too
Yea then my nephew can sit in it afterward. Are you kidding? I am talking about a small plastic model that you glue together. Wouldn't that show dead areas behind the spoiler or whatever?
I think the gap between the car roof and the spoiler (shown clearly in the photo I attached above) are critical. That needs to be modelled accurately. It will be creating complex vortices that will then hit the air passing over the spoiler.
So it seems that in calculating a Reynolds number for comparison we need an equivalent diameter or measure which seems arbitrary depending on what type of object you are measuring. By convention diameter is used for a sphere, length or width for an airplane. It also appears that for my small scale model water (see below) instead of air will show the smaller eddies better in the flow particularly around the "gap" before the spoiler. So, by convention what eq. diameter or measure would we use for the Ferrari? "Alternatively, tests could be conducted in a water tank instead of in air (provided the compressibility effects of air are not significant). As the kinematic viscosity of water is around 13 times less than that of air at 15 °C, in this case the scale model would need to be about one thirteenth the size in all dimensions to maintain the same Reynolds number, assuming the full-scale flow velocity was used"
Body length. Also, generally, gaps smaller than about 1/2" act almost as "closed", there is very little to no airflow going through. It would be interesting to measure minimal gap distance, and if someone could tape a wool tuff and go drive to see if there is actually air going through, that would help understanding what is going on.
You think that the gap is less than 1/2" ? http://www.ferrarichat.com/forum/showpost.php?p=141194048&postcount=84
My understanding is that at around 120 to 130 mph the front end starts to get light and float. I suspect it may be more prevalent on the US spec front clip with the upward angle of the air dam versus the euro version that is flat on the bottom.
Yet to be determined. I think the model is open top. So I will of course now have to test it both ways. Thanks!
Bummer, lost the bid on the Ferrari model. Back to looking. If anyone comes up with one please give me a shout. Thanks. I did come across this but too much: http://www.ebay.com/itm/FERRARI-308-GTB-RED-ELITE-EDITION-1-18-DIECAST-MODEL-/400193828687?pt=Diecast_Vehicles&hash=item5d2d69374f and http://stores.ebay.com/WHOLESALE-DIECAST-MODELS/Ferrari-Diecast-Cars-/_i.html?_nkw=308&submit=Search&LH_TitleDesc=1&_fsub=3&_sid=208321451
You could add a simple vertical air dam below and behind the existing front spoiler with an end point at the lowest ground clearance dimension, so in horizontal front view, the lowest thing you see is the horizontal edge of that air dam. That usually takes care of front-end lift quite effectively on road cars. I do not think that the roof spoiler would have any noticeable effect on front end lift.
Likely. Anyone wants to tape some wool tuffs and shoot some iPhotos from another car while driving? I'd also tape some on the engine cover, trunk and rear spoiler to see what is going on there.
You would have to drive both versions, with and without spoiler, to see if there is more buffeting inside the car with the top off.
What that roof spoiler does in terms of side view geometry is 3 things: - it reduces the roofs taper - t increases the taper of the rear of the car - it shifts the end of the roof backwards (red vs. green lines) That has en effect on drag and lift - which one, I don't know, and it is likely to affect the flow through the engine bay. Was this added with the introduction of the GTS? > raising the roof geometry to reduce buffeting with an open top? Less wind noise with a closed targa top? If something gets added to car (cost, weight, complication), there should be some positive, measurable effect (on sales?) Or maybe it is just a sun shade for the rear screen? Image Unavailable, Please Login
