Such is the pace of development, Lotus had made at least two changes from the specification I described in my last analysis of the Lotus E20.
The teams have further modified the front wing with a revised cascade winglet and the sidepod fronts have reverted to an old shape without the peaked visor below the sidepod inlet.
The revised front wing detailed previously has now gained a different cascade element. Rather than the narrower free standing winglet, the cascade is now wider and joins to the vane on the endplate. The winglet has a distinct twist to its profile, having far more angle of attack at its outboard edge to send a stronger tip vortex to direct airflow around the front tyre.
Where as the wing was new, the sidepod goes back to the design first tested, where the sidepod inlet now has only an upper peak. Where as the upper peak also houses a short Side Impact Protection spar, the peak that used to side lower down at the of the sidepod of the sidepod inlet appears to be a purely aerodynamic addition, as it did not house a SIP. Potentially the lower peak was to reduce the effect of airflow spilling back out of the duct at high speed. Lotus made great efforts with the E20’s internal aerodynamics, with the streamlined heat shielding beneath the outer bodywork improving flow of the sidepods to create less drag. Perhaps there was more spillage than expected with the early and this has subsequently been resolved.
As mentioned in the previous analysis, the sidepod fronts exploit a small vortex generator (VG) on the top edge of the sidepod; this is also aided by another VG under the wing mirror.
This may seem stupid, but can I ask a question? Maybe the answer is blindingly obvious, and I just don’t see it, but don’t cars like lotus have a disadvantage against cars like Mercedes and mclaren? If it’s black in colour, won’t that create a lot of unnecessary heat absorption from the sunlight? Shouldn’t everyone be painting at least their engine covers a brilliant chrome?
Interesting question! And conversely, is there a weight penalty for the fancy chrome paint jobs?
The folk-tale goes that the tradition of silver as Mercedes’ racing colour originated from running bare-metal bodywork to save the weight of paint.
when you travel average 120mph or more, i don’t think the little heat will contribute much on any kind heat issues.
American Airways make a lot that their bare metal aluminium planes save a huge amount of weight as a consequence. Would be interesting to know what percentage of weight is the paint on an F1 car given it has to be 640kg. I suppose it probably is classed as ballast!
The folk-tale is a fact. The cars were overweight and something had to be done.
2000 Jaguar (green) and 2006 Mclaren (silver) are 2 teams I can recall having to find lighter paint solutions for that very reason of excessive weight penalty.
The real question is whether it’s hotter under the engine cover than ambient (which it undoubtedly is); if it is hotter then you should paint the cover flat black for best emissivity and hence heat loss.
That doesn’t sound right… the ambient temperature (i.e., the air temperature) is surely only important to convection, and we’re talking about radiation. Wouldn’t the temperature of the incident radiant energy be the important thing? In the case of radiation from the sun that’s of the order of thousands of Kelvin. Which would be why a dark coloured object (for example an asphalt road) can get much hotter than the ambient air temperature when exposed to the sun.
But, Iceman, it is right although perhaps counter-intuitive. If we are talking about radiation heat loss and not convective loss, the best emitter is a black body. A black body is also the best absorber, so ambient temperature determines which direction the heat loss goes; under the engine cover temperatures are much greater than ambient. The silver McLaren would be the poorest emitter and retain the most heat.
The emissivity of a material (usually written ε or e) is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. A true black body would have an ε = 1 while any real object would have ε < 1. Emissivity is a dimensionless quantity.
In general, the duller and blacker a material is, the closer its emissivity is to 1. The more reflective a material is, the lower its emissivity. Highly polished silver has an emissivity of about 0.02
I still don’t understand how the ambient temperature of the air comes into it, when we’re talking about radiation. As your excerpt from Wikipedia indicates, the amount of energy radiated depends only on the temperature and emissivity of the body – not on the temperature of the surrounding medium.
And for radiant heat flow in the opposite direction, surely the amount of i/r emitted by air molecules is going to be miniscule compared to the amount of energy falling on the car from direct solar radiation.
Almost all heat exchange with the air is going to be by conduction/convection, and that’s not going to be affected by the emissivity of the paint.
Maybe you should paint the back of the car chrome and the front black. Let radiation pressure drive you forward.
Not bad at all! Very feasible!
The color has nothing to do with how much heat the paint absorbs.
MW – you mean because the reflectivity of the paint in the infrared is not necessarily related to the reflectivity in the visible? That may be true, especially in the highly-specified world of F1. But visible wavelengths still account for almost half of the energy in sunlight.