First off, apologies for not having read all 155 pages. I did some searches within the thread around the keel and didn't see anything about this, so I was curious what's going on here in this picture?
I've heard reports that RB and Ferrari (and more?) are using some kind of sprung keel / T-tray / splitter. This is obviously a critical area of the car. Previously when cars needed more ballast, the keel was the place to put it to get the right weight distribution and put it as low as possible. Since 2001(?) we've seen teams (notably Ferrari) running sprung T-trays. This was done such that rake could be increased without raising rear ride height. Normally the splitter would bottom out before the front wing would drop as much as designed. Stepney revealed specific numbers about the deflection of the splitter and the subsequent drop at the front wing (at 100mph, the deflection allowed 7-8mm lower T-tray which resulted in 19-20mm lower front wing).
From the same information revealed by the Spygate investigation, it appears (at least then) that the ideal F1 car produces max downforce at 125mph or below and then shed drag above that speed. This would generally explain all of the attempts we have seen at stalling the rear wing or stalling the diffuser. An item that was never (AFAIK) fully explained was the use of a "buckling stay" in this area, essentially a non-linear spring, a spring with a distinct inflection point. This would in theory be tuned to the speed at which the transition to drag-shed should occur. Talk about the Merc last year near the end of the season mentioned a stalling rear diffuser as part of their package.
Clearly this was a very important area of the car and based on what I have seen in design variations in 2022, it would seem to be even more critical. Lots of components have been relocated to this area on many teams, suggesting a return to using this area for 'ballast' (not that the cars need much/any ballast now).
What do you make of this hinged access panel in the keel on the Merc? From what I can tell, this panel would be in the vertical position when the car is ready. Certainly access to components in the keel is important, esp. if teams have relocated things like various electronics there. However this seems to be something more. There is a large arm on a hinge in the rear portion of the panel and another smaller hinge just forward of the center of the panel. I'm rather baffled at what's going on here; thoughts?
[Another thought after looking at the RBR keel with the spring setup, is this the actual keel and the large arm is some sort of lever/spring? I have trouble w/ that bc the RBR keel is much much thicker, missing something?]
(credit: Giorgio Piola and Sutton Images)