Referencing non Nokia 5110 resolution photos by Mark Sutton I’ll again revise my estimate of the MCL39-RB21 cooling outflow area fraction seen at Monaco. By eye the MCL39 cannon looks about half the size of the RB21 cannon. By pixel count, the MCL39 cannon looks to have ~60% of the area of the RB21 cannon (25k px & 44k px respectively by my measurement). Exhaust pipe diamter is effectively equal on both cars and can be ignored. Photo scale, pixel precision, and some guesswork on the exact shape of the lower side of the cannon create inaccuracy, maybe around +/- 5% here.
The louver pack was counted separately--estimated from separate photos of similar parallax since the louvers are not entirely visible when viewed from the rear coaxial to the longitudinal axis of the car. By eye, the MCL39 has about 1/2-1/3 of the louver exit area as the RB21, and by pixel (~1000 px vs. ~3300 px respectively) it is about 30%. 5-10% margin of error on these estimates.
Suspension portal exits are apparent on both cars (one per side) and seem to be of similar size, amounting to maybe 5% of total cooling outflow area. These are assumed equal for this post.
Area of MCL39 cooling outflow as % of RB21 cooling outflow area at Monaco:
Cannon including spine: 60%
Louver pack: 30%
Suspension portal: 100%
If I can scale the louver & cannon measurements to one another then that will provide the total outflow area discrepancy, but off the cuff it seems like the MCL39 had ~60% of the RB21's total cooling outflow area at Monaco.
The topic of aero correlation/estimation issues at RB earlier this season seems appropriate considering this. Beyond inherent, major packaging differences between the two cars (imo the main cause) and the use of different PUs, incorrect sizing/shaping of the RB20/RB21's ducting could help explain these major differences.
