Slow in, Fast Out is a myth

Rob, these guys repeatably hit a braking point within a couple of meters from 180MPH or more and you're telling me they miss apexes by a foot!

 

Not true, there is a turn at Thunderhill, turn 8, where the clipping point is well past the geometric apex, and believe me, you do want to clip it. You might want to call it a late apex but that just reinforces my point about apexes being dynamic.

 

This is my point, what they're aiming for might be different from what you're aiming for or what you think they should be aiming for because of the different car characteristics and what preceded and followed the turn or sometimes because of a following or leading car.

 

I think he's saying they don't hit the same spot every lap, they're off by a couple of feet each time. I've seen it as well, but I think with the tires as much of a moving target as they seem to be and the lack of testing, it's to be expected to a degree. I've seen some truly good qualifying laps where the drivers don't appear to be off an inch, but it must be when they have that golden lap with the tires spot on that they can do it. Schumacher in Monaco and Vettel in Montreal stick out in my mind.

 

Some can do it lap after lap (from http://www.ferrarichat.com/forum/showpost.php?p=141499414&postcount=486):

Pete
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Exactly, and that's why the article is wrong.

Imagine the 3 simplest, constant radius lines through a uniform corner. These lines follow the inner radius, the middle radius and the outer radius. The innermost line has the slowest entry speed (tighter radius) but is the shortest line. The outermost line has the fastest entry speed, but is the longest line.

What "slow in" refers to is not to actually be slow, it's that you enter slower than the fastest possible entry speed. Even when the time in the corner is the same for 2 different lines, the better line is the one with a faster exit speed (just considering a standalone corner). For a uniform corner, that line MUST be the one with the slower entry speed, since the faster exit speed is a result of being able to get to power sooner -- relative to the fast entry line.

Now we take that to the extreme and we have the line with the fastest exit speed, and the slowest entry speed relative to all other lines that spend the same time in the corner. In other words: slow in, fast out.

This line also happens to be the safest line, since by definition you have the most room from apex to exit. By definition, because to have the fastest exit speed you have to be able to add as much power as possible as soon as possible, and that can only occur if the radius opens quickly -- which gives you the most room for error.

 

Your terminology is very nonstandard. The "apex" is well understood to be the part of the turn where you come closest to the inside edge of the road. It is different for every car and every tire. Nobody means the geometric apex when we just use the word apex by itself. Unless of course they just happen to coincide.

 

You're right, I suck at explaining things, never have been very good at expressing myself. Sorry

 

It depends if it's a compound corner or not.

Unfortunately I can't remember which circuit this is... I recall one track where it looked like 3 small right turns, but the way the cars took it was to hit the apexes of 1 and 3 and drift out 5 feet from the apex of 2 - the effect was that they were taking all three corners as one smooth and very large corner that kept the cars more stable for continuous power, rather than trying to keep in tight at the second apex in that series and unsettling the balance. So, I'd say it's rare but not impossible that the fastest line is to miss the apex.

Can anyone remember the track? I'm really struggling here. I don't think it's a current one on the calendar.

All the best,
Andrew.

 

I thought the apex of a turn was the point where the car had the greatest amount of steering lock turned into the corner - which COULD be the point closest to the curb or edge of the track (and usually is) - but not necessarily.

 

At Winfield they taught the apex is where you stop slowing and turning in, and start accelerating and drifting out.... it can move but there is an ideal apex for every car.

As for the F-1 guys, and from the pics shown - Monaco, its critical to hit your apex lap after lap... there no room for error. at Montreal only place that its critical is the chicane at the entrance to pit straight...

In F-1 and to some extent modern ALMS Prototype racing its about rotation vs. "clipping an apex". if you look at the f-1 cars they rotate around a lot of the sharper bends, and simply slam on the brakes & down shift as late as possible and get back on the power ASAP, that is where the time is made up ... not in traditional 1970's racing style.

Nick Mason was talking about modern F-1 cars, and how difficult they are to drive becuase you have to adopt a completely different driving style that seems very un natural compared to the cars that he routinely drives. even his 78 F-1 312T3 is more about traditional lines and slip angles, todays cars demand the following sequence:

full throttle, down shift, brake, rotate, full throttle up shift... try that in your track car ... and you'll be off.

That being said most F-1 drivers today learn the craft on go karts, so that is the style they use.... a fast shifter kart is full on all the time, and you rotate "thru" the corners. The apex is not really relevant in F-1 UNLESS you are at a tight track like Monaco.

At Spa this weekend... there are several turns that you need to be spot on apex wise... Eau rouge, and the run up from malmady... back to start finish... the hair pin is not so important as its so slow...

But for Rob, keep focused on apex and exit speed... that is the "fast" way around.

 

Great thread.

 

I use much of the same language you're using and understand you completely. Fundamental corner theory.

I'm actually concerned for those who don't understand you.

I would appreciate it, though, if you expanded on what you mean by "dynamic". I think I know, just not certain.

 

Figure one describes a corner's geometric apex.

Figure two describes a corner's typical clipping point.

Does this make sense?
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Yes, that's right. In fact the apex may not be the closest to the inside. Turn 2 at laguna, for example. I guess I oversimplified.

 

Having raced bikes and go carts with some success, I think that the following is true: there are three kinds of corners: 1. Those that lead to a straight, 2. Those that are an exit from a straight, and 3. Those that lead to another corner. There are variances to those three, such as their cornering speed, i.e., fast medium or slow. That said, you need to analyze the corner to see whether you wish a high exit speed, high entrance speed, or highest cornering speed. I used to diagram a track to see what the optimum should be, then walk it to set the apexes. Riding would determine the specific braking and turn in points with traction determining when to start with the throttle. We used to spin the rear tire to force oversteer on some corners (we'd call it backing in), but not much whelspin off the corner bucause it slowed the acceleration.

Might not work for everyone, but it did work for me.

Art

 

I never think of slow in fast out or fast in fast out. My friend, another SCCA racer, does not use these terms either.

He coined the phrase, "you need to driver angrier everywhere.."

There is a fine line between "driving angrier everywhere" and driving in anger and making mistakes lossing time. I don't know where that line is but i do know that I can always find a half second if someone pisses me off.