29 replies to this topic

[OO7]

I wonder if it would be possible to improve overtaking in F1 if Variable Underbody Aerodynamics were introduced.
The following illustrations show how the system would work:

The chassis' in the diagram use venturi tunnels to allow for a wide range of downforce generation, from very low levels to very high level. The F.I.A would mandate 'holes' covered with louvres ahead of each tunnel to control the flow of air into the venturi's. Some of the air that flows into the sidepods for cooling is bypassed downwards to the louvres.
Chassis A) shows the louvres in their 'Free Air' position. Because of the incredible amounts of downforce venturi tunnels can create, the louvres will be set to a position that would keep downforce to acceptable levels e.g 2010 levels.
During qualification, the range of the loading at each corner, from high speed to low speed is mapped and stored in the Standard ECU. During the race as a car approaches the turbulent air from another car ahead, the wheel load sensors sense the reduced loading and transmit that data to the the ECU, where they are summed and compared to the aero load map. The ECU then sends commands to the high frequency louvre actuators which are scheduled closed to compensate for the reduced load. The closing motion will continue until the actual wheel loadings match as close as possible the Free Air aero map for that speed. Chassis B) shows the louvres in their closed position. With this method of aero control, the amount of downforce created in wake turbulence will much more closely match the levels of downforce in free air. The result of this is that the chasing car will be able to follow much more closely, allowing much better opportunities to overtake.

Obi

[highdownforce]

It's a very elaborated solution, Obi, but I'd prefer a solution that is free to use at anytime, even knowing that this would negate the effects that you're seeking here.

[OO7]

highdownforce, on Jul 1 2010, 22:29, said:

It's a very elaborated solution, Obi, but I'd prefer a solution that is free to use at anytime, even knowing that this would negate the effects that you're seeking here.

I think the only problem with that is everyone will use maximum downforce for the bends and twisty sections and minimum downforce on the straights, so the problem will persist? The solution I proposed aims to maintain the free air downforce level regardless of whether the car is in turbulence. If the car negotiates a partcular corner on the limit of grip at 120mph in free air, this devices will allow it to continue to take the corner at the same speed, on the limit while in wake turbulence.

[highdownforce]

Yeah, the problems would persist, but I'm not really interested in solving the problem of lack of overtaking with that
This way, it would be like the movable rear wing, maybe more safe and more effective, but it only help the following car. In a way that I personally don't think it's fair.

[Supersleeper]

Great idea Obi - but doesn't it just turn out to be "fake racing"? We got to the stage a couple of years ago when drivers were using traction control - essentially software was deciding what drivers were doing - there greatest display of skill in that circumstance was pressing a button.
I'm not interested in watching software take over the sport. It castrates the role of the driver in the sport. Yes I want to see as any technological advancements in this sport as anyone else, but the role of software should be limited to "tactics" and "measures of performance", not subsidising the skill of drivers.
If Sam Michael says the sport needs more aero - then I'm entirely against it....
Great idea, though.

[Ogami musashi]

Because wake effects depend on Geometry, variable wings may or may not be useful however active floor could be a good solution because of their sensitivity to mass flow rather than flow patterns.

A solution was (is) envisionned for 2013 that is to have variable height floors. In slipstream conditions (easily recognizable because of a total pressure loss) the floor would lower to increase the mass flow in the venturi.

Of course that solution needs to be carefully shaped because of first to possibility of stalling the venturi if too low (but in fact, modern venturis design allow for progressive loss of downforce when lowering the height is not good anymore) and two teams must not use it.


Note that front wing could also be lowered under those conditions and rear wing may have its flap's AOA increased.

[Hairpin]

I think everything will be quite ok when they scrap the DD. They should try that first. Another problem is the angle of attack on the rear wings, it should be limited. I guess a standard rear wing is the only way to go in that case, but those to adjustment would most likely be sufficient. I hate the idea of any kind overtake aid. It should be possible, not easy.

The top teams want the faster cars to win all the time and it takes out a lot of excitement from the sport.

[Ogami musashi]

Hairpin, on Jul 1 2010, 23:29, said:

I think everything will be quite ok when they scrap the DD. They should try that first. Another problem is the angle of attack on the rear wings, it should be limited. I guess a standard rear wing is the only way to go in that case, but those to adjustment would most likely be sufficient. I hate the idea of any kind overtake aid. It should be possible, not easy.

The top teams want the faster cars to win all the time and it takes out a lot of excitement from the sport.

If you talk about the AOA of rear wing having an effect on the following car then i disagree. Race cars wings produce an upwash behind them so trailing vortices from rear wing move above the following car quite fast., Wheels trailing vortices and the coupling of diffuser and rear wing that entertain all the wake are far more damaging.

The real problem is that there's not one solution, as soon as you move away from one aerodynamic set up the wake signature is different, and this is worsened in F1 as all cars are different and of course that they change regulations every 3 years.

There're only two solutions, either the wake is lessened by the aerodynamic configuration of the car either you clean it up with counter cancel devices and or management of wake pattern.

Lessening the wake is what they have tried for years with more or less success (imho, the actual situation is by far the best since the mid 90's..and shows the level of downforce is not in question) but i doubt they will one day until they go for a really clean and radical solution (like active aeros), i think trying to clean the wake (which is what the OWG tried to make) is a better solution.

[Hairpin]

Ogami musashi, on Jul 2 2010, 01:09, said:

If you talk about the AOA of rear wing having an effect on the following car then i disagree. Race cars wings produce an upwash behind them so trailing vortices from rear wing move above the following car quite fast., Wheels trailing vortices and the coupling of diffuser and rear wing that entertain all the wake are far more damaging.

The real problem is that there's not one solution, as soon as you move away from one aerodynamic set up the wake signature is different, and this is worsened in F1 as all cars are different and of course that they change regulations every 3 years.

There're only two solutions, either the wake is lessened by the aerodynamic configuration of the car either you clean it up with counter cancel devices and or management of wake pattern.

Lessening the wake is what they have tried for years with more or less success (imho, the actual situation is by far the best since the mid 90's..and shows the level of downforce is not in question) but i doubt they will one day until they go for a really clean and radical solution (like active aeros), i think trying to clean the wake (which is what the OWG tried to make) is a better solution.

You obviously know a lot more tha me about this matter, but that will not keep me from objecting
Are you really saying that AOA is not having an effect on the turbulence? If one would allow a wider corda and allow max, say 6 degrees AOA, would it create the same amount of wake as the current wings?

[saudoso]

If you use big underbody tunnels and they provide most of the downforce there is no need for variable aeroynamics and push to pass buttons:

[Kovalonso]

A much simple solution for F1 would be using the Indy flat wing in the back for high speed ovals used some time ago - in Zanardi/Gugelmin era.

It generated a big low pressure zone that allowed the cars comming behind to take a draft and overtake.
Drivers used to prefer starting the last lap behind the leader to take the tool and win the race.

[IFRLIceman]

Kovalonso, on Jul 1 2010, 21:07, said:

A much simple solution for F1 would be using the Indy flat wing in the back for high speed ovals used some time ago - in Zanardi/Gugelmin era.

It generated a big low pressure zone that allowed the cars comming behind to take a draft and overtake.
Drivers used to prefer starting the last lap behind the leader to take the tool and win the race.

The Hanford Device caused catastrophic engine failures, but if done properly with the 'correct' mushroom-busting properties, F1 could make overtaking easier.

[Kovalonso]

IFRLIceman, on Jul 2 2010, 00:16, said:

The Hanford Device caused catastrophic engine failures, but if done properly with the 'correct' mushroom-busting properties, F1 could make overtaking easier.

Thank you!
Handford, the engineer that invented it.

Hopefully, the turbo engines will fix it.

[WhiteBlue]

Ogami musashi, on Jul 2 2010, 01:09, said:

The real problem is that there's not one solution, as soon as you move away from one aerodynamic set up the wake signature is different, and this is worsened in F1 as all cars are different and of course that they change regulations every 3 years.

There're only two solutions, either the wake is lessened by the aerodynamic configuration of the car either you clean it up with counter cancel devices and or management of wake pattern.

Lessening the wake is what they have tried for years with more or less success (imho, the actual situation is by far the best since the mid 90's..and shows the level of downforce is not in question) but i doubt they will one day until they go for a really clean and radical solution (like active aeros), i think trying to clean the wake (which is what the OWG tried to make) is a better solution.

The natural thing to do for any F1 engineer is getting the highest downforce with the least amount of drag out of a given configuration. Over the years that has led to the the well known effect of designers clawing back downforce faster than geometric restrictions can take it away. So it seems to make very little sense to fight a disadvantage of downforce for the following car by changing the configuration.

I believe that it may be possible to use active aero as proposed by the OP or with other means to compensate for the disadvantage of the following car by giving the defender a more restrictive set of parameters in which the active aero can adapt. But as already pointed out this would be a highly artificial thing making the cars sophisticated aerodynamic missiles with big electronic brain and dumb pilots. Technology would rule and not driving skill because it would not be the same for all. Drivers would always blame the aero control program for their successes or failures to pass or defend. So from a sporting point of view I believe that any solution relying on artificially giving the defender a handicap to help the attacker is going in the wrong direction. If we use active aero - and I'm not against that - all sides of the battle should have the same weapons.

As Ogami says we may have a pretty good configuration presently. I don't know. I have to trust his word there. But it isn't really practical with the wide front wing that the drivers cannot see due to the high nose that everybody runs and the extremely reclined driver position. So I would fix that by mandating that drivers must have a less reclined position and must be able to see the front wing. The front wing rules should also mandate less width by perhaps lowering the wing position to take advantage of ground effect. It would limit the damages we see in passes today.

It would leave us with the problem of finding a suitable mechanism that restricts aerodynamic forces (downforce and drag) in a sensible basic configuration. After all you cannot loose downforce that you do not have in the first place. Two tons of DF at the end of the straight that we seem to be running today appears quite excessive compared to what was agreed some years ago between the OWG and the FiA (1.25 metric tons). A good way of limiting the aero forces IMO would be giving the cars a restricted fuel budget as it is already planned for 2013. Designers would automatically go for minimum drag as they do now but they would also have to stay within a given energy budget for the aero forces. The power of the engine and the energy of the fuel basically goes into accelerating the mass of the car and sustaining the aero forces. With a limited fuel budget those constructors with the most efficient power train and the most efficient aero would have an advantage while the restricted energy budget would automatically keep the aero forces on a desired level. Research would have to be done which downforce level is appropriate to restrict the defenders advantage to a sensible level and still provide enough DF to generate the desired performance.

Edited by WhiteBlue, 02 July 2010 - 04:27.

[cheapracer]

Step one is to remove all diffuser strakes now, as in now before the next GP.

This will immediately help to clean up the wake while not changing downforce so greatly teams have to rush for new designs.

Strakes are the small verticle plates you see inside diffusers, their job is to create turbulence for extra DF that in the end also disturbs the following car

[Ogami musashi]

Hairpin, on Jul 2 2010, 00:50, said:

You obviously know a lot more tha me about this matter, but that will not keep me from objecting
Are you really saying that AOA is not having an effect on the turbulence? If one would allow a wider corda and allow max, say 6 degrees AOA, would it create the same amount of wake as the current wings?

No i say that because race cars wings are downforcing, they create an upwash downstream; Thus the trailing vortex (the turbulence) of the wings move upward and get out of the way/decay fast enough especially since they are now positionned at the max height.

In fact that very upwash is used to clean the turbulences for the diffuser since 2009 and that's why it is crucial in the current regs to have narrow wings (so that the upwash movement "captures" the turbulences from diffuser and put them above the following car).


If you look at a wing only, then yes, AOA is a major contributor to turbulence since it increases the Cl but you have to look at the flow pattern in its globality.

see for example, trailing vortices in planes are dangerous at certains aspects but in some condition (of close formation flying) they are beneficial. All depends on the signature of it.

[Ogami musashi]

cheapracer, on Jul 2 2010, 05:59, said:

Step one is to remove all diffuser strakes now, as in now before the next GP.

This will immediately help to clean up the wake while not changing downforce so greatly teams have to rush for new designs.

Strakes are the small verticle plates you see inside diffusers, their job is to create turbulence for extra DF that in the end also disturbs the following car

Definitely.

[OO7]

Supersleeper, on Jul 1 2010, 22:51, said:

Great idea Obi - but doesn't it just turn out to be "fake racing"? We got to the stage a couple of years ago when drivers were using traction control - essentially software was deciding what drivers were doing - there greatest display of skill in that circumstance was pressing a button.
I'm not interested in watching software take over the sport. It castrates the role of the driver in the sport. Yes I want to see as any technological advancements in this sport as anyone else, but the role of software should be limited to "tactics" and "measures of performance", not subsidising the skill of drivers.
If Sam Michael says the sport needs more aero - then I'm entirely against it....
Great idea, though.

WhiteBlue, on Jul 2 2010, 05:23, said:

I believe that it may be possible to use active aero as proposed by the OP or with other means to compensate for the disadvantage of the following car by giving the defender a more restrictive set of parameters in which the active aero can adapt. But as already pointed out this would be a highly artificial thing making the cars sophisticated aerodynamic missiles with big electronic brain and dumb pilots. Technology would rule and not driving skill because it would not be the same for all. Drivers would always blame the aero control program for their successes or failures to pass or defend. So from a sporting point of view I believe that any solution relying on artificially giving the defender a handicap to help the attacker is going in the wrong direction. If we use active aero - and I'm not against that - all sides of the battle should have the same weapons.

I can see there has been a misunderstanding in what the system I have proposed does.

It isn't a driver aid in the traditional sense and doesn't provide an advantage to the driver behind over the driver infront (as the variable rear wing proposed by the FOTA will do). The purpose of the Variable Underbody Aero System (VUAS) is to allow the chasing car to have the same level of downforce that it would in free air as when in wake turbulence, here is an example:
Imagine two identical cars, A and B, both running the VUAS. The F.I.A will have already manadated the standard free air position of the VUAS e.g 80% open for all teams. Now this doesn't mean all teams will produce the exact same level of underbody downforce, just as reducing the width of the rear wing didn't mean all rear wings were suddenly equal. Running with the system 80% open is simply a way of limiting the maximum downforce levels created. With the system set to 80% open, top teams may be able to generate 4000lbs of D/F at 200mph, while a lesser team with the same 80% opening may only manage 3500lbs of D/F, so there is still technical design scope for the engineers.

Now going back to cars A and B. Imagine they are racing around a course which has 6 corners, T1-T6 with the VUAS inactive. The following figures are an example of the downforce created from the underbody with the VUAS set to 80% open (in clean air) but inactive:
T1 is taken at 40mph, underbody downforce in clean air = 160 lbs
T2 is taken at 130mph, underbody downforce in clean air = 1690 lbs
T3 is taken at 75mph, underbody downforce in clean air = 562.5 lbs
T4 is taken at 90mph, underbody downforce in clean air = 810 lbs
T5 is taken at 110mph, underbody downforce in clean air = 1210 lbs
T6 is taken at 150mph, underbody downforce in clean air = 2250 lbs

Now lets assume Car A leads Car B into the final corner T6. Both cars are equal but Driver B is faster than Driver A and has closed in on the straight between T5 and T6. Driver A who is in clean air drives through T6 at 150 mph (the underbody of his car produced 2250 lbs of downforce to allow him to do that). Driver B who was close behind attempts to negotiate T6 at 150mph (the normal clean air speed of the bend), but because he is in the wake turbulence of Car A, his car loses downforce e.g 427.5 lbs, so Driver B can only take T6 at 135mph and has to back off.
With the VUAS installed on both cars and active, Car A will race around the course in exactly the same way as it had previously, taking the bends at the same speeds listed. As Car B approaches T6 closely behind Car A, the wheel load sensors would have been transmitting data to the Standard ECU, which would compare the current wheel loads with that of a clean air map. Because Car B is in the turbulent wake of Car A, the wheel load sensors will record less than standard loads and send that data to the ECU. The ECU will compare the data with the aero map and calculate an error. A signal is then sent to the VUAS to begin closing the louvres, until the wheel load values match as closely as possible the values from the internal map at the current speed. So in doing this Car B will be able to negotiate T6 at 150mph i.e it will produce 2250 lbs of downforce while in the turbulent wake of Car A.
Now as you can see the VUAS didn't give Driver B an advantage (that is not its purpose), it simply nullified the effect of the wake turbulence. The only advantage Driver B would receive, is the increase in acceleration/topspeed from being in the slipstream of Car A.

As you can see the VUAS is not a driver aid, in the traditional sense anyway and doesn't make for 'artifical racing'. As for drivers blaming the system for not being able to pass, I don't think so. Firstly with the cars as they are at the moment, how often do we hear drivers saying, 'I was much quicker but I couldn't get close enough through Turn X. I had to back off because I was losing so much downforce and had heaps of understeer.'. If the new system allows drivers to get closer, I don't see how they can complain. The active rear wing next year (despite being an 'artifical' means to improve the racing), will enable drivers to get much closer to the car ahead, I can't see why they would complain about the rear wing not allowing them to pass.

As for the deletion of the double diffusers in 2011 improving the racing, I'm alittle skeptical that it will make much difference, with regards to the cars being able to follow each other more closely. Early in 2009, only three teams (6 cars) had double diffusers, but how much close racing did we see between the none DD cars, if we discount KERS?

Obi

Edited by Obi Offiah, 02 July 2010 - 11:26.

[primer]

Improving overtaking or increasing overtaking? Seems like there is no difference between the two terms for most people.

If people like overtaking so much, please watch NASCAR. Why turn F1 into open wheeled NASCAR.....

Edited by primer, 02 July 2010 - 11:14.

[OO7]

primer, on Jul 2 2010, 12:08, said:

Improving overtaking or increasing overtaking? Seems like there is no difference between the two terms for most people.

If people like overtaking so much, please watch NASCAR. Why turn F1 into open wheeled NASCAR.....

True, why have overtaking at all?

One of the main reasons we have seen alot off overtaking this year is due the the F-Duct systems. This why the FOTA have proposed a variable rear wing for next year. What I think many would like to see is duelling between the top teams. Ignoring special features such as a much more powerful engine or F-Duct system, when is the last time we saw overtaking between two top cars, where one didn't enjoy some sort of technical advantage over the other? It doesn't really happen. If a car is a quarter of a second quicker than the car ahead (and remember on race day it is usually very close between the top teams) then you can forget about the car behing getting past.

[OO7]

Another point I'd like to address is that of 'fake/artifical' racing. The moves by the FOTA to have the F.I.A include variable rear wings, that can only be used by the chasing car is said to make for 'fake/artifical' racing. Well we can argue that the current regulations, with F1 car aerodynamics they way they are, makes for 'fake/artifical' racing. When a car infront is two seconds a lap slower than the car being and cannot be overtaken simply because of the turbulence the car is producing i.e not down to the drivers defensive driving skills or placing the car on the limit of its capabilities, isn't this a form of 'fake/artifical' racing. You could argue that the variable rear wing rule creates 'fake/artifical' attacking racing and the current aero issues create 'fake/artifical' defensive racing.
I think perhaps the fact that these aero issues have continued for such a prolonged period of time, they have become ingrained into the minds of some as something which is normal and exceptable. Considering the lenght of time it has continued on for in F1, it is perhaps normal, but compared of other forms of motorsports it is not and in my point of view shouldn't be exceptable.

[Ogami musashi]

In both the considered active floor by FIA and Obi Offiah idea, the concept is simply to retain downforce while being in the wake; I don't see anything artificial here.

And please remember that prior to downforce, cars in the wake had not only lower drag, but lower lift too which means better grip.

Edited by Ogami musashi, 02 July 2010 - 13:22.

[OO7]

Ogami musashi, on Jul 2 2010, 14:21, said:

In both the considered active floor by FIA and Obi Offiah idea, the concept is simply to retain downforce while being in the wake; I don't see anything artificial here.

And please remember that prior to downforce, cars in the wake had not only lower drag, but lower lift too which means better grip.

Exactly

Thats the thing Ogami, as you mentioned prior to the advent of downforce, the persuing car when close enough had the advantage, however this wasn't viewed as being artifical, the same goes for Formula Ford racing, which isn't considered artifical..

[WhiteBlue]

Whatever you do with the SECU in terms of programming, drivers (and fans) will always complain that it is going to distort their effort unless it is 100% same for all in both attack and defense.

Edited by WhiteBlue, 02 July 2010 - 13:42.

[OO7]

WhiteBlue, on Jul 2 2010, 14:41, said:

Whatever you do with the SECU in terms of programming, drivers (and fans) will always complain that it is going to distort their effort unless it is 100% same for all.

Well it will be 100% the same for all.

[Ogami musashi]

WhiteBlue, on Jul 2 2010, 13:41, said:

Whatever you do with the SECU in terms of programming, drivers (and fans) will always complain that it is going to distort their effort unless it is 100% same for all in both attack and defense.

That's not an argument and certainly not one justifying the non use of those solutions. The secu already limits and control many things depending on the certain situations, and nobody complains and even if they did, reality of engineering is there with DATA.

Edited by Ogami musashi, 02 July 2010 - 14:06.

[OO7]

Ogami you seem to know more that most (me included, not that aaai know much ) about the effects of certain designs on aero and I agree that the most elegant solution would be to remove some of these complex aero devices that create turbulence and vortices around the cars. I think it may be alittle like the F-Duct systems we see, where (using fluidics) a small volume of airflow can have a huge impact on aero. With F1 cars in their current guise, it seems as if these intricate devices (turning vanes etc) are switched off just like with the F-Duct devices, when in turbulent flow which drastically alters downforce. If the regulations were rewritten to as to simplify and eliminate much of these aero devices, wouldn't this severely limit the scope and challenge offered to the aerodynamicists? If so this could be beneficial in perhaps reducing costs and maybe shifting more focus towards the mechanical, vehicle dynamics portion of development and perhaps relaxing and opening the regs in that area?

Edited by Obi Offiah, 02 July 2010 - 15:04.

[Ogami musashi]

Obi Offiah, on Jul 2 2010, 15:03, said:

Ogami you seem to know more that most (me included, not that aaai know much ) about the effects of certain designs on aero and I agree that the most elegant solution would be to remove some of these complex aero devices that create turbulence and vortices around the cars. I think it may be alittle like the F-Duct systems we see, where (using fluidics) a small volume of airflow can have a huge impact on aero. With F1 cars in their current guise, it seems as if these intricate devices (turning vanes etc) are switched off just like with the F-Duct devices, when in turbulent flow which drastically alters downforce. If the regulations were rewritten to as to simplify and eliminate much of these aero devices, wouldn't this severely limit the scope and challenge offered to the aerodynamicists? If so this could be beneficial in perhaps reducing costs and maybe shifting more focus towards the mechanical, vehicle dynamics portion of development and perhaps relaxing and opening the regs in that area?

The vortex generators are imho overrated. They use to be a lot of VG in cascade (the max being 2008) but those were small scale vortex generators; The diffuser and wheels as well as front wing vortices are far more damaging imho.

As i said, the solutions are either to lessen the wake or control it so that the effects are not felt by the following car. Trying to lessen the wake may work, but it will always be constrained by the fact F1 is a technological competition , that specs part are not thinkable for the moment and that you need to rethink the rules every 3 years for safety reasons.

If you control the wake by making the following car less sensitive and directing the wake away from it then it will be okay whatever the teams chose as solution.


Now as for the mechanical side, i don't know, i'm under the impression the mechanical side of an actual F1 car is not so constrained in regard to aeros; The thing is nothing beats aeros in term of lap time; That's not for fun everybody embraced them, they are by far the best lap time improvement/Cost ratio.

And in any way, there's no way mechanical grip can make up for 2,7 tons of downforce on a car simply because downforce's grip is multiplied by tyre's grip so there'll always be more advantage running lot's of downforce plus grippy tyres than grippy tyres alone.


I really think this year is really good, i mean, you've seen on the dry, top grip cars running very close to each other and overtaking each other, less slower cars blocking the other (at least not for aerodynamics reasons) and the whole impression i've got is that we are down into the 0,2-0,4 second of advantage to be able to overtake which is quite satisfactory.

honestly, with this year configuration+active floor on wake it could have been superb.

We'll see next year.

[OO7]

Ogami musashi, on Jul 2 2010, 17:03, said:

I really think this year is really good, i mean, you've seen on the dry, top grip cars running very close to each other and overtaking each other, less slower cars blocking the other (at least not for aerodynamics reasons) and the whole impression i've got is that we are down into the 0,2-0,4 second of advantage to be able to overtake which is quite satisfactory.

honestly, with this year configuration+active floor on wake it could have been superb.

We'll see next year.

Yes this year has been really good, but the ability to follow closely has been track dependant. Remember in Malaysia where Hamilton was 1.5 - 2 seconds per lap quicker that Sutil and still couldn't pass despite the use of his F-Duct system?

[Ogami musashi]

Obi Offiah, on Jul 2 2010, 17:21, said:

Yes this year has been really good, but the ability to follow closely has been track dependant. Remember in Malaysia where Hamilton was 1.5 - 2 seconds per lap quicker that Sutil and still couldn't pass despite the use of his F-Duct system?

You have to be very cautious of those gaps; Being 2 seconds faster than someone 500 meters away is one thing, but as you close on him, there's a point where you are forced to slow down or you'll hit him. And then depending on how you follow him you will be able to overtake..or not.

However, high downforce trim tracks may be a bit more damaging yes because the rear wing may be at a higher camber thus being very sensitive to flow perturbations.