Veloce Raptor

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Veloce Raptor

Indeed.






Professional Racing and Driving Coach

Veloce Raptor

CORRECTED






Professional Racing and Driving Coach

SundayDriver

OMG - What a train wreck. I am away for some hours and MK goes on, yet another, posting marathon. Well, saying the wrong thing over and over does not make it less wrong.

With all the BS flying here, I really don't know where to start. I will say a couple of things and then MK can reply with dozens of posts denying how things work, in the real world.

I never said that MK would lose 10% of his wings effectiveness with tape. I repeated what I was told by some very knowledgeable people. I made a huge mistake and I apologize - I assumed that MK could understand that I was making the point that small changes can have very unexpected consequences in aero. I clearly over-estimated MK's abilities in communications. MK, you can twist what I said any way you want but those lies do not become true because you post them over and over and over and over and...

There is a lot of misunderstanding in this thread about splitters and diffusers. Splitters rely in part on the high pressure at the front of a car but also upon smooth flow under the car. THAT is why some cars (including the one in my avatar) have front diffusers. I find it hilarious, and typical, that MK is now lecturing about what a front diffuser is supposed to do and how it works on his car, when a few pages ago he said the didn't think there was such a thing as a front diffuser.

Finally, a couple of misconceptions - moving more air over the top does not create downforce - quite the opposite in most cases. Cars create lift from the top surface and many devices are there to counteract this lift. Stagnation is NOT the most significant part of aero, though it is significant with the front splitter. Almost everything else is about laminar vs. turbulent flow.

Now if someone else wants to start a thread about aero topics, I would be happy to participate until MK starts to take over 50% of the total posts (which might give us a day). I certainly don't know everything - only MK can make that claim. But I do have a fair amount of experience - the car in my avatar weighed ~1,000 lbs with fuel and driver and made in excess of 1,400 lbs of downforce at ~130mph. It included the sensors and data to measure downforce (F/R) and calculate center of pressure. So I am in possession of a few facts about aero.

But with all that, I readily admit I do not know the specifics of 928 aero and "Frankly Scarlett...".

multi21

^^^ but you didn't answer if those pieces on your car were made in your basement. You also didn't mention if you've tested them by yourself on the street. What do you have to say about that?

Circuit Motorsports

Come on Pete. Everyone knows that D and C Sports Racers use super speciall carbon fiber dust sprinkled on their car to create obscene downforce.

mark kibort

Ok, one last post. Yes Sundaydriver, it is a train wreck. I got some good out of it, but spent 90% of the time explaining where i got my information
Now, you say that you didnt say that you lose 10% of the downforce with a piece of tape. Sundaydriver said:[B]"This causes separation and turbulence earlier and that little, thin tape can cost 10% of the total downforce on a wing. That helps point out how little most of us really know about aero[/B]. "
Then you say that website with drawings is 75% wrong.
Now, Bryan says that the diffusers are not used for brake cooling and that Im wrong. Heck, I never said I knew where the difusers went, it just looked like they were routed to the brake area, geezzzz. cant we have a discussion? And this has been the confusion all alone. someone says something they dont mean or mean to say in the way they did. Thats fine. Im guilty of that as well

What started out as a discussion, turned out to be a bash fest on anyone disagreeing with the original concepts, or disagreeing with the disagreeing. Man, this is a tough place.

As I have always said, this kind of discussion is better in front of a white board or on a napkin in a bar. never seen a bar fight break out over racing, but it always seems to happen here on the list.

I posted to get a discussion going that could help me in designing my prototype splitter. this is a racing forum but it really is an ego forum. I would love to continue, but dont have time for the BS. So, ill keep it private among racer buddies that want to help or discuss. I thought what I found was interesting. Most racers would love to have pressure data at points all over their cars. I found a $100 solution that does it and does it very well. what we do with the information, is apply it to what is known in the motorsports aero world. we tie it to the how the car behaves and try and make changes. As crude as some of the things ive done are, they are effective, sometimes not in the rigth direction, but Ive learned to either drive around the problem or fix it. Constantly learning, its part of the fun, but driving is most of it. Its the reason I pinged the list. Thought we could discuss with some maturity. Not possible, again.

I do what do with what I got, and thankful that I can. yes, Im a racing addict, what can I say.

mk

Bryan Watts

Forget, CSR/DSR's...I've seen SRF's drive upside down! Noted, it wasn't due to downforce, but rather due to launching off of another SRF and skidding down the track on the roll bar.

quickxotica

Is that a promise?

Bryan Watts

Come on Mark. In other words, you made a statement about something you knew nothing about. There was no misunderstanding. I did not reorganize what you said or stretch your statement. You made a definitive statement that said diffusers were used for cooling. I said they weren't. You didn't say maybe they are used for cooling or they could be used for cooling...you attempted to make something up on the spot to explain away the diffusers that you had previously said did not even exist. Turns out that you didn't have any idea what you were talking about.

Frankly, I'm wondering whether you realized that a well designed splitter actually extends back behind the nose of the car until people started posting pictures of them since all of your focus on this thread has been around it pushing air above the car.

Still wondering why you won't post that picture to show your downforce measuring device for your rear wing.

SundayDriver

Here is a question...

How much downforce does the combination of an upside down SRF make with a Formula Atlantic driving underneath it? Paging der Perfessor - can you help us out with that question?

DaveM993

Not to give MK more reasons to post and I agree with everything you said...with one small exception. You may be confusing the effect of overall lift on a car as a whole vs. localized forces across the car from front to back.

Cars do create lift because they are shaped like crude airfoils and sending more air over a car does increase this NET affect, BUT, and its a biggee, the effect is not the same locally if you look at particular points from front to back. The affect of moving more air up over the car creates a localized increase in downforce ONLY on the front of the car. The additional lift starts to occur once the airstream moves over the highest point on the car and is "sucked" downward on the back portion of the car (a crude description - yes).

An airfoil's natural tendency is to "nose-down" in straight level flight for this reason, which is why aircraft need elevators on the back of the airplane to counteract this tendency (ie rotate nose down) and maintain level flight. The exact some dynamic is happening on the car, there is an increased downforce on the front AND increased lift on the rear...which of course needs to be counteracted by various devices (rear spoilers, vortex generators, etc. etc.).

mark kibort

Yes, many of us made statements that we have little or high knowlege of. I certainly was not familar with the use of front defusers, other than venting air into the engine compartment and/or out the hood . i certainly said this, but not in those words. Plus, what i ment by brake cooling in thier use was also for downforce as i did mention several times that the air was vented out the sides via the wheels or behind the fenders. thats what I was thinking, maybe it didnt come out that way. I dont want or have time to look back through this mess any more.

my contraption was made from a valve spring , a guide and some pointers with a chart. All video taped with the speeds correlated. I came back and placed weight on the wing to equal the pointer movement. I got up to 200llbs on the wing for speeds of 100mph. I rougly extrapolated that that would be near 275lbs at 120mph. the lower speeds were most interesting and the values did go up with the square of speed. I cant find the video, but I know its somewhere.

Thats it. I had to at least post one last time for a real question.

mk

quickxotica

OK… my last post was mean. Sorry...Couldn't resist.

But I'm glad to see you removed those self-incriminating YT videos. That lessens your immediate risk of legal problems (unless YouTube employees are under some obligation to report videos of illegal activity, or unless a LEO happened to have seen those videos before you took them down).

I hope you realize how lucky you are that that big splitter you were testing at 130mph on the highway didn’t fly off and go through the windshield of a minivan or school bus full of kids, causing it to crash. If that had happened you’d have been looking at some serious time in the California prison system…. Which is, to hugely understate the matter, a lot less forgiving that this place.

But above I see you are alluding to some other test you did at 100mph with some other contraption attached to the rear wing of you car! Honestly, did it occur to you what a valve-spring travelling at 100mph would do if it flew off and hit the windshield of an on-coming car full of kids? Why do you value your personal freedom/assets and the safety of others so little? This is not the behavior of a rational personality.

jgrant

If you're interested in reading an incredibly interesting story about wings, ride heights, and "proper" highway testing, go check out Jack Olsen's post on the subject.

He's a guy that's trying to learn the stuff himself, the RIGHT way.

Damn inspirational, and full of tons of good information.


http://forums.pelicanparts.com/showthread.php?t=305438