mark kibort

Hmmm. i think i understand the question. you have most of your weight in the rear and you want the car to be more balanced in a corner? I suppose there might be some high speed corner where the balance of the car , aero dynamically was biased to the rear and you would want to lessen the down force in the rear. this happens all the time in the fast courses by lessening the angle of attack of the wing (AoA). sometimes balance of the aero wins out over sheer downforce numbers. in fact, its car and track dependent. the advantage any race car and driver has is the perfect balance of downforce, balance and drag with the HP available.

so, yes, you could turn the wing upside down in the rear (or right side up as ACE mentioned ) and get lift in the rear.. cant think of too many situations where this would be something you would want to do.. maybe drifting at 130mph around willow springs comes to mind.

mark kibort

What he is asking, is that are there conditions where aero changes of the rear wing can be helped by introducing lift vs downforce, and this is a common techique used by everyone trying to achieve balance of downforce. for many years, before people used wind tunnels, they used your view of "more" being "good".. this is not the case. balance is sometimes worth more.
taking wing out, is lessing downforce and that is a common practice. now, since most wings make downforce (a lot sometimes) with 0 angle of attack and there are some cars that have a lot more lift up front, reducing rear downforce is something that sometimes needs to be reluctantly done in the pursuit of balance. sure, its a hypothetical qustion by Slacker, but the real answer is that sometimes yes, lift is reduced in the rear of the car. adding lift, is not common , but im sure there are situations where that is possible

Yes, there is a sweet spot for drag vs downforce as we have discussed on the board before. most are in the 7-10:1 range. this means if 10:1, at some moderate wing angle (AoA), if you have 300lbs of downforce, you would have about 30lbs of drag at that speed. (put in perspective, that 30lbs of drag, at 120mph, with a 4:1 total gear ratio, would be about 8lb-ft of toruqe at the engine.) the bad part of that downforce is that it is there whether you need it or not. .. so the balance of downforce required for some turns, vs the drag down the straights, is a challenge in race car set up.

interesting that there are some techniques of materials that flex enough under aero forces, that change the shape enough to provide downforce when needed and flaten out , with those forces to reduce drag. those forces to distort are not free, so i wonder the drag effects to have such effects on the wing structure. do you have values of drag vs lift at different speed ranges for such a wing?
interesting.

ace37

Mark, here's a recent high level case - Toyota's LMP in 2014. This one is different as the wing chord stiffness itself isn't the driver, the end plates twist the wing.

http://www.mulsannescorner.com/newsjan15.html
http://www.mulsannescorner.com/newsjuly14.html
http://www.mulsannescorner.com/RCELeMans2014.html
Racecar engineering also did a short bit on it in August 2014.

Sorry, I don't know of any with hard numerical data available. It's not too hard to analytically estimate 2D airfoil chord stiffness though - to go dirt simple and intuitive you could consider a thin flat plate airfoil at 20 degrees. High aero pressure would bend it (especially near the trailing edge) to bleed off the angle of attack. If it needs to bend more just use a thinner piece of sheet metal. It can work pretty efficiently.

Slakker

Can't wait to see how it turns out! I'm not sure that a turbo can qualify but you should at least check into the 944cup series. The guy that runs it has been awesome to deal with on a few transactions and it sounds like a total hoot!

And as for uplift, yes, that was exactly the kind of theoretical informative but practically useless discussion I was hoping for. Thanks for taking the time to chime in guys.

GPA951s

[QUOTE=Slakker;13901147]Can't wait to see how it turns out! I'm not sure that a turbo can qualify but you should at least check into the 944cup series. The guy that runs it has been awesome to deal with on a few transactions and it sounds like a total hoot!

Plan is start out in PCA Stock F Get some seat time, Then move to the SP3 class..

fleadh

I don't think there's any allowances in any GT rule book that'd let you run a wing upside down, but I know at tracks like Daytona it's relatively common to configure/adjust the wing (if allowed by the rules) in such a way as to create lift on the rear of the car instead of downforce (it's really not very fun to drive for an endurance race, but do you want to win or have fun?).

-mike

linzman

Why not just come straight to SP3? In F, you'll be classed with other letter cars, and will be the slower car in class. In SP3, you'll be with SP1-3 , usually SBOX, and occasionally D or E cars, usually a split start ( on east coast. anyway) so you'll be at the front end speed wise. I bought my car as an E car, and switched to SP3 after the first year. Should have started there, as it was just more competitive for my 968. Those E class 911s were tough to keep up with.

GPA951s

I have a Friend in the Club who races in "F" (Have to because of it being a turbo-s). I wanna go door to door with him here (Watkins is home track)... Then make the move to SP3..I think Ill backdate my car and put the smaller turbo on for SP3, 200 Extra pounds is not worth 30hp to me.. As it stands right now the only class I could run in Right away would be GT3 With the Setup I have on the engine stand...So I will Get my Racing License This summer and Do DE's with a REALLY fun car. I Really cant wait though! It looks like an absolute blast...

linzman

Hope to see you at the glen then. Stop by, we should have at least 4 SP3 cars