Read time: 11.2 minutes
‘When it shines like gold, you'll remember me.’
The closing lyrics to The Killers’ soaring, and aptly named, song ‘Bling’ have no doubt echoed in the ears of countless fans of the Las Vegas rockers, but just what exactly is it on the MCL35 that ‘shines like gold’ and why is it there?
In the teaser shots taken during the build of our 2020 Formula 1 challenger, the eagle-eyed among you may have spotted flashes of this precious metal and, put simply, it’s all to do with heat shielding.
As McLaren Design Engineer Sukhi Bhogal explains, “there’s a lot of heat generated by the engine and exhaust gas temperatures upwards of 1,000°C. The surrounding components have to be shielded to protect them from this heat. Hence the reason for having heatshields.”
But that’s where the simplicity ends. Delve a little deeper and you’ll find there are a myriad of different materials and techniques to thermally manage the MCL35. We’re talking high-performance paints from our technical partner AkzoNobel, space-age foam from NASA, and heat-resistant composites.
So while the exterior of the MCL35 still remains under wraps, let us take you under its skin to give you a rundown of how we’re going to keep things cool this season:
1. It’s all about the flow
“Think of the heatshield itself as a carbon fibre barrier that protects vital components from high temperatures expelled from the power unit and exhaust,” explains Bhogal.
“We have to shrink wrap these shields as close as we can to the engine and exhaust because the aerodynamicists are looking to keep the bodywork as tight as possible.
“The design team and aerodynamicists will develop a shape, sculpted around the power unit and its exhausts using CFD to optimise the airflow underneath the bodywork. Optimising this flow is vital to ensure we keep the car cooled to extract every ounce of performance from the engine, while delivering the aerodynamic performance with having such tight bodywork.
“If we are not able to expel the hot air from the radiators efficiently enough through to the back of the car, the car can overheat which in turn loses us performance.”
2. It’s not rocket science (actually, it kind of is)
“When it comes to the heatshield, we don’t put any gold foil on it,” explains Principal Composites Engineer Steve Foster. “But you will be able to find gold foil on the MCL35 chassis. It’s used to reflect infrared rays.
“Anyone that’s seen a satellite or a space shuttle up close will have spotted gold foil somewhere, but where NASA might use 50 layers, we use just one.
“Often, we’ll cure the gold onto the carbon fibre. Take the carbon fibre brake drum of the MCL35, for example. If we just let the heat spit out radially from the brake disc onto the wheel rim in an uncontrolled way, the wheel rim would melt and there would be a massive risk of failure. Not only that, but it would severely hinder our ability to manage tyre temperatures.
“Although gold foil is very good at controlling infrared heat coming from the brake discs, it’s not great at stopping conduction of heat. And one of the ways in which we prevent conduction is to use silica-based aerogels.”
3. Solid smoke
No, it’s not McLaren’s take on Solid Snake, the cult hero from hit video game series Metal Gear. ‘Solid smoke’ is the codename, okay nickname – but let’s say ‘codename’ because it sounds so much cooler – for the silica-based aerogel material we use to stop conduction of heat.
Possessing the lowest bulk density of any known solid (3%), this very fine foam substance is made up of over 95% air – providing about twice the resistance to heat per unit thickness compared to the next-best materials. It was developed by NASA for space shuttle programmes, but things get even cooler than codenames and space travel when you consider that you might be able to find this substance in your own home because it’s now frequently used for loft insulation.
“Its low density means there are very few paths for the heat to conduct through, and any heat that does find its way through has to negotiate a very complex path before it gets to the other side,” explains Foster.
“You’ll find that some parts of the brake ducting on the MCL35 have a sandwich construction, consisting of a layer of gold foil, silica-based aerogel and carbon fibre.”
But what about when all that glitters on the MCL35 isn’t gold? What if most of all that glitters is actually silver? Before you turn on your Xbox to change your gamertag from ‘FieryChilli55’ or ‘MilkLover4’ to ‘Solid_Smoke’, here’s how a paint originally designed for the marine and energy sectors is being used on one of the fastest and most technologically-advanced cars on the planet.
4. Silver lining
When you think about paint on a Formula 1 car, you probably conjure beautiful images of iconic liveries in your mind. In fact, we’d wager you’re thinking about swathes of papaya right now. But did you know that much of the MCL35 will receive a lick of paint underneath its svelte, carbon fibre skin?
If you were to flip over many of its sculpted body panels, you wouldn’t find exposed carbon fibre. Instead, you would be greeted by flashes of silver from AkzoNobel’s Intertherm® 50 paint.
“We heavily rely on AkzoNobel’s Intertherm® 50 as our general heat-resistant, reflective coating,” reveals Foster.
“We also apply it to the internal surfaces of the heatshield – so the unmoulded face gets a layer of Intertherm® 50 as another protective barrier from the heat,” adds Bhogal.
But just what makes this paint so special? As you might expect, it’s extremely resistant to heat. And when we say heat, we’re talking temperatures of up to 540°C.
AkzoNobel Product Manager George Sykes reveals more: “Intertherm® 50 is an aluminium pigmented, thin-film silicone coating, and its silver shade comes from the aluminium. It reflects heat due to the way in which the aluminium pigment aligns with the surface of the coating.
“Aluminium has very low emissivity, so reflects a large amount of the infrared heat rays that hit it. This reflective property is why you see marathon runners wrapped in foil. The heat they give out is captured inside the blanket, which allows them to regulate their temperature as their body heat drops.”
Still not convinced? Here’s something for you to try at home. Hold a sheet of aluminium foil close to your face, and you will eventually feel the warmth of the infrared rays from your face bouncing back at you. You can thank us for helping you to top up your tan later.
5. Thinner than a human hair
A single coat of AkzoNobel’s Intertherm® 50 is 25-microns thick. Or should that be ‘thin’? Now we’ll admit, you’ve probably got no idea just how thick 25 microns is, but to put it into context, the width of a human hair is an ‘enormous’ 75 microns.
Why is this so important? The thinner the paint, the less it weighs, and keeping weight down is critical to performance. Naturally, Sykes is keen to emphasise that this is far from the kind of paint you would use to coat that feature wall in your living room!
6. Step up to the plate
While Intertherm® 50 will reflect heat, it won’t insulate against it. Therefore, when we require a coating that will inhibit the transmission of heat, it’s time for a ceramic coating to step up to the plate (no pun intended).
“To apply a ceramic coating to carbon fibre, first we apply a copper bonding coat to the composite and then the ceramic coat,” explains Foster.
“It provides a thermal barrier that protects the carbon fibre from delamination – fracturing into layers – and prevents resin from melting. Highly resistant to vibration and flexing, ceramic coatings are ideal for the MCL35 brake hubs.”
7. Cut and blow dry
“Thermal management isn’t just about stopping heat, it’s also about dissipating any hot spots,” elaborates Foster.
“For example, you tend to get pinch points where a very hot part of the exhaust is close to another component. To counter this, we can use very conductive materials to direct heat away. If we don’t do this, the car could switch off because the electrical components are often temperature regulated.
“Make no mistake, it’s a massive design effort. There’s so much performance to be gained from managing the flow structure through the car and protecting the MCL35 from the heat.”
Make sure to keep an eye on TEAMStream and the McLaren App for more updates on the MCL35.
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