The problem there is with your assumption that that is a 'draggy plate' - it's not - there's a massive amount of outwash in that area by then, and the plate is pretty much in line with the flow there, F1 cars are turning the flow laterally by about 70 degree's in that area already.
I don't disagree that more development around there would be beneficial - we've seen a massive arms race around the bargeboard area, and I personally was expecting more updates around there and the leading edges of the sidepods already, but that doesn't mean that portion is particularly draggy.
The problem there is with your assumption that that is a 'draggy plate' - it's not - there's a massive amount of outwash in that area by then, and the plate is pretty much in line with the flow there, F1 cars are turning the flow laterally by about 70 degree's in that area already.
I don't disagree that more development around there would be beneficial - we've seen a massive arms race around the bargeboard area, and I personally was expecting more updates around there and the leading edges of the sidepods already, but that doesn't mean that portion is particularly draggy.
I understand that the plate is supposed to guide the airflow that's following the contour of the bargeboards. However the flow in that area also has another vector interacting with it. That plate creates flow stagnation under certain yaw conditions, the result is transient instability under initial turn in, and the problem exacerbates itself in aero dependent slow corners. The good thing is that the rest of the McLaren package is very good, and now that they have the new nose, they'll be able to fully exploit that area.
I find it a little more than coincidental that all the teams with the lowest trap speeds for their respective power units have that plate in exactly that area. I think there's a heap of time to be found streamlining that area.
That area of barge boards seems to be very important. Interestingly, it was Ferrari's 2017 development direction that most teams chose to include in 2018 car concepts, with two (though Ferrari now have 3) pieces of airfoil-shaped vortex generators. Even though they don't look like conventional VGs, they seem to be doing the same thing as their outboard floor cousins (Ferrari literally had the same shape early in 2017, that piece that was seen to be flapping and needed to be reinforced).
They make a pressure difference on top and bottom side (being airfoil shaped) and since some of the air near the trailing edge has a lateral velocity component (i.e. it's going along the trailing edge) it causes a spin. The series of small flaps at the very tip of barge boards induce the initial vortex, while this second one induces another. Since most teams chose to remove a piece of bodywork between them, I have a feeling they want to separate these two vortices.
Mercedes, it should be said, mentioned that this area (those 2 new pieces they added for 2018, the ones we are talking about of course) is very important for overall floor sealing, especially for their higher rake this year. Since all 3 top cars now have the same shape in that area, it makes perfect sense. Also, the floor is obviously sealed even there, not only on its sides. Which is amazing for diffuser performance.
In any case, those little flaps should form a wing, and like I mentioned in the previous page that area has a few different flow vectors interacting with it. The trick is to turn the horizontal bargeboard into a gurney flap that compliments the other wing elements in front of it.
With this new knowledge it instantly becomes apparent how bad the Williams aero is.
That area of barge boards seems to be very important. Interestingly, it was Ferrari's 2017 development direction that most teams chose to include in 2018 car concepts, with two (though Ferrari now have 3) pieces of airfoil-shaped vortex generators. Even though they don't look like conventional VGs, they seem to be doing the same thing as their outboard floor cousins (Ferrari literally had the same shape early in 2017, that piece that was seen to be flapping and needed to be reinforced).
They make a pressure difference on top and bottom side (being airfoil shaped) and since some of the air near the trailing edge has a lateral velocity component (i.e. it's going along the trailing edge) it causes a spin. The series of small flaps at the very tip of barge boards induce the initial vortex, while this second one induces another. Since most teams chose to remove a piece of bodywork between them, I have a feeling they want to separate these two vortices.
Mercedes, it should be said, mentioned that this area (those 2 new pieces they added for 2018, the ones we are talking about of course) is very important for overall floor sealing, especially for their higher rake this year. Since all 3 top cars now have the same shape in that area, it makes perfect sense. Also, the floor is obviously sealed even there, not only on its sides. Which is amazing for diffuser performance.
Right on the money. This is why this car was so fast. They knew and they've focused on this area over the winter.
Raked cars especially benefit from this as it's in line with the floor, it's the most ground effect wing on the car. Also, riddle me this, what are the deflection limits on that part of the floor? The possibilities are endless, but first step would be for McLaren to ditch that vertical plate, and add more chicken wing, and rely on vortex generators upstream to guide airflow instead of that plate.
It seems counter intuitive but it makes sense if you run it in CFD I promise you. Creating an upwash right after the bargeboard creates a lot of downforce.
Why?
If you treat the bargeboard as a wing, it will create an upwash much like the current cars rear end does. This upwash will send some air over the floor leading edge. Increasing the air mass traveling under the sidepod and over the floor to the back of the car. Why is this important? Because air is full of itself, if you deny air at the leading edge of the floor especially when you've tried to open the leading edge of the floor to the full capacity of the regulations and added all sorts of vortex generators to coax air in there. The air will do everything in it's power to follow the path of least resistance and will pull air in from the first place it can, right where the rear tire meets with the floor. There is a little path between the vortecies travelling at the wheel and the shear forces from the tire. A space right between the boundary layer. The air that's being denied at the front of the car will enter through there splitting the stagnation zone by the rear tire(the path of least resistance), and essentially seal the rear diffuser.
Note I never say completely deny airflow under the leading edge of the floor, I say increase the air mass over the floor.
Downvote away brothers.
The over generalisations and over simplifications recently in this thread are astounding and yes the hundreds of aerodynamicists working in F1 across various teams are idiots who don't have as good CFD eyes as those on this forum.
Narcissism and arrogance are both a hell of a thing.
Just to point out a fact that you are way oversimplifying things and that you can't just modify things willy nilly as you think.
To illustrate this point, McLaren stated that they had to wait for the new nose to run the new barge boards in front of and turning vanes around the sidepods. This is because the flow structures were wrong with the old nose to work with the new parts. That's how careful teams have to be with changes.
The Haas for good measure.
