Why didn't the flat bottomed cars porpoise?

[PlatinumZealot]

As the topic says, why didn't we see porpoising on the flat bottomed cars?

Welcome to both hard engineering principles and empirical information and also thoughts, ideas opinions, but I'm more interested in the hard engineering principles and empirical info.

Thanks.

[vorticism]

The flat floors produced more distributed downforce across their surface, hence the importance of coke bottling as initiated by RB 2009. Reduced pressure differential top surface vs bottom surface. An inclined plane providing less efficient downforce, yet not relying on ground proximity nor perfect flow under the car.

[Just_a_fan]

The flat floors produced more distributed downforce across their surface, hence the importance of coke bottling as initiated by RB 2009. Reduced pressure differential top surface vs bottom surface. An inclined plane providing less efficient downforce, yet not relying on ground proximity nor perfect flow under the car.

The coke bottle didn't start with Red Bull in 2009. It was already starting to be used at the end of the 1980s.

[DiogoBrand]

It didn't produce enough of a seal and enough suction to choke itself until it stalled.

Also, the step with the wooden plank was responsible for not allowing the flat floors to stall. The most likely cause of Ayrton Senna's accident in Imola was the flat floor without the step touching the floor and stalling, after which one of the safety measures was adding the step with the plank.

[vorticism]

The flat floors produced more distributed downforce across their surface, hence the importance of coke bottling as initiated by RB 2009. Reduced pressure differential top surface vs bottom surface. An inclined plane providing less efficient downforce, yet not relying on ground proximity nor perfect flow under the car.

The coke bottle didn't start with Red Bull in 2009. It was already starting to be used at the end of the 1980s.

Well if you want to be pedantic you have to mentioned the tapered engine covers of 1960s F1 cars, the boat tails of interwar grand tourers, fish that were swimming in the ocean a billion years ago.

Raked floors with maximized topside exposure was initiated by RB 2009 and all teams followed suite in the twelve seasons after.

[Vanja #66]

As the topic says, why didn't we see porpoising on the flat bottomed cars?

Welcome to both hard engineering principles and empirical information and also thoughts, ideas opinions, but I'm more interested in the hard engineering principles and empirical info.

Thanks.

Sorry if any bubbles pop, but the answer is simple - diffusers don't rely that much on very low ride height and regulated step-plane was high enough to prevent any flow blockage. Rules were made exactly to prevent this (well, not bouncing but cars straightening high speed corners due to sudden downforce loss), so obviously there was no chance of it happening. Not that there could be any, since there were no side-skirts or any other kind of restricting geometry. Teams opting for large rakes also would have prevented this from happening, even if there was no floor step.

If we want to enter more into fluid dynamics, we can also add the fact that flat floor with diffuser is much less potent than ground effect floor. Downforce from the floor was much lower than it is now, making the whole car less suscpetible to any major negative effect (downforce loss, diffuser stall, etc) coming from the floor.

In theory, there could be significant aero bouncing even with flat floor and diffuser - but this has to be a much bigger and more potent diffuser than F1 ever allowed and there must be no floor step that prevents the car from going too low. Such diffuser would generate a significant amount of vortices (of significant strength) which would burst if the ride height got too low, leading to significant downforce loss. Once the car would get high enough again, vortices would form again, leading to increase in downforce and the circle is complete.

[Just_a_fan]

The flat floors produced more distributed downforce across their surface, hence the importance of coke bottling as initiated by RB 2009. Reduced pressure differential top surface vs bottom surface. An inclined plane providing less efficient downforce, yet not relying on ground proximity nor perfect flow under the car.

The coke bottle didn't start with Red Bull in 2009. It was already starting to be used at the end of the 1980s.

Well if you want to be pedantic you have to mentioned the tapered engine covers of 1960s F1 cars, the boat tails of interwar grand tourers, fish that were swimming in the ocean a billion years ago.

Raked floors with maximized topside exposure was initiated by RB 2009 and all teams followed suite in the twelve seasons after.

So you didn't mean the coke bottle then. Thanks for confirming.

[vorticism]

The coke bottle didn't start with Red Bull in 2009. It was already starting to be used at the end of the 1980s.

Well if you want to be pedantic you have to mentioned the tapered engine covers of 1960s F1 cars, the boat tails of interwar grand tourers, fish that were swimming in the ocean a billion years ago.

Raked floors with maximized topside exposure was initiated by RB 2009 and all teams followed suite in the twelve seasons after.

So you didn't mean the coke bottle then. Thanks for confirming.

Deciphering others' intents isn't your strong suite. Coke bottle refers to a body shape tapering from wide to narrow. Used outside of F1 extensively. I think it's a reference to a Pepsi can but etymologies can be confusing, as you illustrate.

As it relates to the thread, RB 2009 onward were in part trying to maximize the exposure of the floor past the widest point of the sidepods where the radiators were (coke bottle taper/waisting), because of the new importance of flat floor dynamics in the revised '09 regs. OP asked why those cars didn't skip and jump, it's partly due to the nature of using a simple inclined plane as an aero device and the RB5 onward typified the optimization of that.

[jjn9128]

They did, or could, up until the step plane was introduced in 1995. After then because of the increased ground clearance the stall behaviour was much more benign.

[Just_a_fan]

Well if you want to be pedantic you have to mentioned the tapered engine covers of 1960s F1 cars, the boat tails of interwar grand tourers, fish that were swimming in the ocean a billion years ago.

Raked floors with maximized topside exposure was initiated by RB 2009 and all teams followed suite in the twelve seasons after.

So you didn't mean the coke bottle then. Thanks for confirming.

Deciphering others' intents isn't your strong suite. Coke bottle refers to a body shape tapering from wide to narrow. Used outside of F1 extensively. I think it's a reference to a Pepsi can but etymologies can be confusing, as you illustrate.

As it relates to the thread, RB 2009 onward were in part trying to maximize the exposure of the floor past the widest point of the sidepods where the radiators were (coke bottle taper/waisting), because of the new importance of flat floor dynamics in the revised '09 regs. OP asked why those cars didn't skip and jump, it's partly due to the nature of using a simple inclined plane as an aero device and the RB5 onward typified the optimization of that.

Ignoring your personal attack, the "Coke Bottle" refers to the shape that is wide then narrows. Like a, wow amazing, Coke Bottle.

The Coke Bottle shape was actually used in aircraft back when F1 cars were simple tubes.

But you knew that, didn't you? No, obviously not.

Never mind.

[vorticism]

It's great when their hubris increases as the sarcasm flies over their head, like a sinuous can of krating daeng.

[Rodak]

The Coke Bottle shape was actually used in aircraft back when F1 cars were simple tubes.

Ignoring the putdown included with this comment, aircraft coke bottle shapes have nothing to do with downforce (or upforce), they are there to reduce shock wave drag effects in trans-sonic flight between Mach 0.75 and 1.2; this is known as the 'area rule' in aircraft design. F1 cars don't go quite that fast......

[peewon]

Wouldn't the inerters have also damped out the heaving wing effect?

[DiogoBrand]

Wouldn't the inerters have also damped out the heaving wing effect?

I think it would make the cars porpoise in slow motion, but not avoid it.

[Stu]

They did, or could, up until the step plane was introduced in 1995. After then because of the increased ground clearance the stall behaviour was much more benign.

I was going to say this, it was the reason why Lotus started looking at active ride and why the (Re)active Williams project gained traction (pun intended ). Part of the reason the 1994 season (peaking at Imola) was such a mess, the teams had their toys taken away.

We have also seen a certain amount of ‘porpoising behaviour’ from cars recently at CoTA, for instance, which may have been induced by the bumps - Mercedes in particular were very affected by it. I also wonder if it was also the cause of their issues over a number of years at Singapore…