Tech blog day four: Wet towels required

Wet towels required - Friday February 8

The first test of the Formula 1 season is over. Now teams will return the cars to the factories to be stripped, checked and rebuilt in time for the next test at Barcelona.

Over the four days most teams have been able to complete a surprising amount of mileage with relatively few red flags.

As the first test is not about developing cars, new parts are still in short supply, although Mercedes surprised us all by testing its Drag Reduction Device.

While there were few new parts to interest observers on the final day, testing does offer a chance to look into the some of the teams' more unusual practices.

Leaf blowers, height paint and wet towels

As bodywork and exhausts are forced by the aerodynamicists into ever-closer proximity, overheating bodywork and peeling paint are an undesirable side effect when the car slows in the pitlane.

Red Bull's towel solution © XPB

Teams use leaf blowers to keep airflow passing over bodywork, but McLaren and more recently Red Bull have found another way to cool it: wet towels!

As the car halts in the pitlane the pit crew greets it with towels freshly pulled from a bucket of water. These are draped over the bodywork above the exhaust to absorb the heat and protect the pristine paintwork.

McLaren uses bespoke black towels with the stylised McLaren Kiwi logo on them, whereas Red Bull appears to use simple white towels with no branding, which seems a missed opportunity for the marketing-led drinks manufacturer.

In some cases the bodywork is burning when the car is out on track, so even the airflow from a fast lap isn't enough to protect the paint.

Mercedes typically has this issue when first testing new bodywork. Avoiding burnt carbon when on track is possible by fitting heat shields, cooling ducts and using heat- reflective coatings. Both of the former solutions affect aero performance, so coatings are a good method to resolve this issue.

A singed Mercedes © XPB

Teams will send the bodywork to specialists such as Zircotech to have plasma sprayed coating applied to the critical areas. These coatings can protect carbon fibre from temperatures of up to 1400 degrees centigrade.

At the first test teams tend not to coat the bodywork with these heat reflective coatings, only subsequently adding them to areas that have been burnt at a previous test. This will end up saving weight, at the sacrifice of the first set of bodywork. We can expect to see less scorch marks when testing resumes at Barcelona.

Red Bull keeps its secrets

The team is well known for its mechanics standing around the rear wing of the car on the grid to prevent nosey photographers and TV crews looking at the details.

In testing there are far more photographers in the pitlane, but team secrecy is safeguarded as the squads do not have keep their garages open.

Thus we see the pit crew wheeling screens across the garage front as soon as the car passes in or out. Having these screens in place this keeps the cars hidden while bodywork is removed.

Red Bull brings its screens into place © XPB

However Red Bull has been going further. When the car stops in the pitlane, photographers and prying eyes are being separated from the car by roller screens being wheeled out into the pitlane to obscure the car.

Safety was the FIA's explanation for the ban on these screens over race weekends, in case an incident inside the garage needed a rapid evacuation.

But somehow this logic isn't applied to testing and teams can cover the cars and garages to preserve their privacy.

Mercedes

Having introduced the concept of double DRS, or drag reduction devices (DRDs) last year with its rear wing duct stalling the front wing, Mercedes was quick to follow Lotus with a passive system when it was clear double DRS would be banned for 2013.

Lotus was the first team to run a rear-wing stalling device since the F-duct was banned in 2010. Although new rules aimed to ban F-ducts, mechanisms were left by which the wing could still be stalled through passive means.

Hence the DRDs that appeared in practice sessions in 2012 on the Lotus and Mercedes sought to stall the rear wing on the straights for more top speed. But unlike F-ducts or double DRS, they do not need the driver or DRS moving the rear wing to work. Instead at a certain speed the flow inside the ductwork 'switches' and sends flow to the stall the rear wing.

Mercedes led the way with double DRS, now it's pushing hard on the device's successor © XPB

Mercedes had its new system on the car on Friday. It's a much tidied and more integrated system compared to the add-on nature of that tested last year.

The ductwork takes its feed from the opening behind the rollhoop. It was noticeable at the car's launch that Mercedes had removed the cooling inlet from this position on its W04 to allow for a neater DRD set-up.

This inlet feeds a specially shaped chamber inside the bodywork, known as a fluid switch. This has no moving parts and simply requires a change in airflow to alter where it directs the flow. Air exits the fluid switch down two branches, either down a large cross-section duct to exit over the beam wing, or a narrower duct that hooks up under the rear wing.

At lower speeds the airflow passes harmlessly out of the larger duct, then at higher speeds the flow inside the fluid switch changes and sends it to the narrower duct.

This duct then blows through small slits in its sides across the rear wing's surface. Having a crossflow blowing under the wing breaks up the airflow and stalls the rear wing. This reduces downforce and critically reduces drag for more top speed.

The difficulty in these systems is having the fluid switch operate at a certain speed. It needs to work at about 155mph, which is above the speed for most corners, so the loss in rear downforce doesn't unbalance the car.

But following another car or experiencing different wind directions can alter the switching effect, so it might not switch at all or even worse switch at a lower speed, robbing the car of downforce in a turn.

Also causing developmental issues are the obstruction the duct adds to the rear wing and the drag of the ductwork itself. It's possible that at lower speeds the flow out of the stalling duct might even rob the car of a little downforce.

Resolving all these issues will be decisive in making this systems top speed gain worthwhile. It is expected that Lotus and a few other teams will follow this development path in 2013.

Time for new parts - Thursday February 7

As day three of testing concludes, the teams are still diligently working through their run sheets, racking up the laps and gathering data. Most spent today completing long distance work and race simulations.

They like to keep their cars set up at baseline specification but we have seen the first of the new parts being fitted to the cars. Most significantly, the new Mercedes front wing.

Mercedes

Mercedes has created a new front wing, with each side formed of five separate elements. This was a critical design feature lacking on the launch car and will form the basis of the W04's aerodynamic set-up.

Front wing design has increasingly become focussed on complex shapes. This is aimed both at creating downforce and sending the wake around the outside of the front tyre. To achieve this and not send disturbed airflow over the centre of the car, teams make the outboard sections of the wing work hardest.

Mercedes ran a new front wing © XPB

Front wings used to be made up of two elements. Today, there can up to six, and that's not to mention the cascade winglets above the main front wing, which can introduce a further two elements.

The harder you work the wing, the more airflow is likely to separate from its surface. To combat this, slots are added to prevent it stalling. These slots are not only on the wing's horizontal surface, but the wing also curves down at its tips and the slots help to direct the air around the front tyre.

Each side of the wing is formed with five short chord elements. Unusually, these five elements each span from the inboard end of the wing all the way out to the footplate.

Normally, the most slots are on the hardest-worked outboard end of the wing. This suggests Mercedes is working the entire wing quite aggressively. This should, in theory, rob the aero surfaces along the centre of the car of good airflow. But it seems Mercedes is able to split this airflow by using the shape of the wing where it intersects with the neutral, regulated, centre section.

At this joint, the wing is reduced to a single profile. The shape induces a vortex that helps split the airflows and drives a stronger flow over the centre of the car.

Aside from the adventurous five-element wing, the cascades and endplates are fairly typical of previous Mercedes designs and, indeed, of most other teams on the grid. This new wing brings Mercedes onto a par with its rivals in front wing design.

Caterham exhaust vane

As testing is not subject to full FIA regulations, teams can run parts that would not be allowed on a race weekend. So far, Caterham has been running a vane inside its exhaust channel that has been a point of contention for some other teams.

Is Caterham's exhaust vane legal? © XPB

But as with most technical issues, the issue is clouded by the rules written in a vague manner and the unpublished FIA technical directives that clarify these matters. The exhaust rules brought in last year preventing exhausts overtly blowing the diffuser included a series of demands that the exhaust's exit path must not be covered with bodywork.

But the wording was specific to bodywork over an imaginary cone exiting along the same exist as the exhaust tailpipe. As we have seen with the Coanda exhausts, the exhaust plume does not exit along this axis, but bends downwards. So it does seem that legal bodywork could be added to divert the exhaust plume without contravening the wording of the rules.

Caterham's vane in the exhaust channel appears to sit below this imaginary cone, so according to the published rules, it is allowed. However, a technical directive issued for last season said that exhaust gasses must not be re-ingested or re-directed. This clarification was aimed at banning Red Bull's proposed exhaust system, which blew into the brake duct fins in order to redirect the exhaust plume under the diffuser.

In Caterham's case, the vane clearly redirects the exhaust plume and therefore appears to be in contravention of the technical directive. It's likely this part will need to be discussed with the FIA Technical Delegate before its run in Melbourne.

Lotus

Lotus seeks aero efficiency with a new inlet © XPB

Most teams launched with aerodynamically efficient front brake ducts that did away with the scoop feeding the brakes by moving the inlet between the tyre and brake duct vane. Last year, Ferrari also adopted this idea on its rear brake ducts.

Aided by the KERS effect on braking, the rear brakes do not need the same level of cooling as the fronts, so the scoop is normally much smaller.

The rear brake duct area is also exploited with fins and aerofoils designed to create downforce directly at the rear wheel. Having the brake cooling scoop obstructing these fins robs them of performance.

Lotus has now done away the protruding scoop on the rear brakes and fitted an inlet next to the tyre. Looking at the Lotus brake ducts, these fins are now in clear airflow, which will bring some useful aero efficiency.

Sauber

The Sauber has a chin under the nose © XPB

In common with several other teams, Sauber has now fitted a small chin under the nose of its car.

These have been fitted to cars since Williams launched its 2009 car with a far larger bulge.

The bulge improves the flow over the neutral centre section of the front wing and also redirects the airflow over the turning vanes.

It seems that this approach will be almost standard across the grid in 2013.

Secrets and sensors - Wednesday February 6

McLaren

On day one of the test McLaren suffered a high pressure fuel pump failure.

The pump was an updated version of the part that failed on Jenson Button's car at the Italian Grand Prix. It is actually a Mercedes part; it sits inside the fuel tank and is driven from a shaft on the front of the engine.

As the pump provides the engine with fuel pressurised to 100bar, it's a precision component, but it's rare for them to break.

McLaren's work schedule has included aero data gathering runs. The car has been fitted an array of pressure sensors arranged under the floor in front of the rear tyre.

McLaren featured new front brake ducts © XPB

As these sensor arrays are wide and feature dozens of tiny tube-like devices, they are commonly termed aero-rakes. Each of these tubes is linked with thin plastic pipes back to a controller inside the car, where the pressure is measured. The data gathered is built into a map of the pressure changes across the rake's width. These results should correlate to data gathered in CFD or the windtunnel.

As well as the new turning vanes, McLaren appeared today with new front brake ducts. These are of the scoop-less design where the cooling air enters the brake drum through an inlet between the tyre and the protruding vane of the duct. This set-up means the airflow off the front wing is less obstructed by the brake duct.

Mercedes

Having rectified yesterday's problems with the electrical loom, Mercedes was further hampered by a brake issue in the morning.

On his first day in the car Lewis Hamilton had a brake failure that sent him off the track and into the barrier. It transpired that there was a problem with the brakeline connected to the right rear brake caliper, meaning Hamilton had no rear brakes when he pressed the pedal.

More glitches for Mercedes © XPB

As with road cars, Formula 1 cars have brake systems split between the front and rear wheels, so Hamilton still had some braking effect from the front brakes to control the car.

Of course the resulting crash also damaged the front wing and the suspension, so running was again suspended for the day.

Sauber

No obvious updates were apparent on the Sauber, but suspicion is always aroused when a team runs bare carbon fibre parts. This is usually done by teams either because the parts are new and have not had time to be painted, or the dark carbon fibre surface is good for hiding detail.

Is Sauber hiding something clever at the rear? © XPB

So it's interesting that Sauber has an unpainted section under the middle of its rear wing. I can see no obvious explanation for this, as the unpainted section features no special slots or add-ons.

When looking closely at the back of the C32, two small sensors attached to the wing endplates are visible. These are infra-red temperature sensors pointed at the tyre sidewalls. With the new Pirelli construction and the new cars' exhaust possibly blowing onto the tyres, teams often monitor sidewall temperatures in this way. No team would want the tyres being overheated by the exhausts this year as Pirelli's compounds are getting softer.

Ferrari

Ferrari was another team running an aero rake today, in its case a square rig of sensors mounted in front of the sidepod. This will be mapping the airflow off the front tyre and over the sidepods.

Ferrari was looking at the airflow over its sidepods and trying out exhaust ideas © XPB

For the afternoon session Ferrari announced it was trying different exhausts for the F138, although no obvious differences were visible on the car.

Force India

While other teams were running aero rakes, Force India had a more complex set-up.

An articulated arm mounted the rake to the side of the car behind the front tyre. The arm can move up and down along the strait, allowing the array of sensors to map airflow over a larger area. This way the engineers will be able to gather a greater understanding the airflow for cross-checking against simulation data.

Williams was yet another team fitting an array of sensors © XPB

Williams

Like Force India, Williams also ran an articulated arm with an aero rake. These large add-on sensor arrays tend to be run in the mornings of tests as it takes some time to fit and tidy away the pipework and cabling that links the sensors to the car's telemetry system.

Conversely, removing them is a little quicker because as the larger mechanical parts of the system are removed, the cabling can be taped out of the way on the car for the rest of the day's session.

Tuesday February 5 - The day one jobs list

Ten teams ran their 2013 cars at Jerez on the opening day, with Williams using its '12 machine.

With the regulations allowing just one chassis to be used and limits on tyres and engine usage, simply pounding around to gather data isn't possible. That means that each run is pre-planned, with specific aims of what is to be gained from the run.

It's impressive that these cars appear on the first day of testing, most having never previously turned a wheel. The chassis may have been tested on a rig and the engine on a dyno, but when the whole car is assembled, the car's first run in front of the world's press is often the first mileage under its own power.

During the first runs, team will often use old aerodynamic parts as photographers frequently shoot the first runs and then become less interested. That means teams are able to guard precious new designs by holding back new parts. Plus, there is also the danger of wrecking prototype parts with an early off.

The early test days are a unique period in the development of the cars. Some tasks that are carried out on these first runs will not be completed again.

Lewis Hamilton watches on as Mark Webber assesses the Red Bull © XPB

The first run is the installation lap, after which the cars return to the garage to be partially stripped down for inspection. Here, the team is looking for leaks, burning bodywork chaffing wiring or anything to suggest that there is a problem with the car.

Once the car is reassembled, it's usual to complete a three-to-five lap run. At this point, the car is fully rigged-up with additional sensors to log temperatures, pressures and vibrations. Teams will also run pressure sensitive stickers and apply paint to any surface where it is suspected that heat might be an issue.

One odd procedure is for the car to sit in the pitlane with its engine running for up to a minute on returning from a run. This is to ensure that no bodywork is burning when the car is stationary. It's a good test to replicate the condition of the car when it is sat on the grid.

During the first runs, the driver has the chance to get comfortable in the cockpit. Padding will be adjusted to improve the seating position and other adjustments can be made. It's rare for the driver to make alternations after the first test.

It's rare that drivers are required to go out and set blindingly fast times. Instead, some runs will demand that a set speed is used on the straight to gather aero data. Alternatively, runs might be completed with or without KERS or the DRS being activated.

One run often completed late on the first day is the fuel tank pick-up test, where the car will run out of fuel on purpose to see what fuel remains in the tank in order to plan fuel loads for qualifying and the races.

Only once the initial runs are complete does the team start to experiment with set-ups and new aero parts. Up until this point, lap times are irrelevant and only when the team complete s longer runs on heavier fuel will we start to get a feel of race pace. Occasionally, a team might run on low fuel or underweight, but although this type of showboating has been done in the past, it serves little purpose.

Paul di Resta brings the Force India into the pits © XPB

As the teams start to learn the car and the set-up variables, later tests will include full race simulations and other scenarios. New development parts will be fitted throughout testing but often the real Australian Grand Prix specifications will not emerge until the last day of testing.

Once this is completed, the cars will be returned to the factory, stripped and packed up. They won't turn a wheel again until the first free practice session in Australia.

McLaren

McLaren was coy about a lot of aero details on its launch car, but the testing-spec car is running with the simpler front wing introduced at the United States Grand Prix last year. Also, new turning vanes have been added under the front suspension. These are the common curved design, but feature three blades to better direct the airflow around the sidepods.

Lotus

The new E21 bears a striking similarity to the 2012 E20 and the renders released at the launch show the Jerez testing spec. So the car is running with the stepped nose and the pointed nose design that wears the same 'chin' used towards the end of last year.

Importantly, the car is running with the triple roll hoop inlets, with the outer pair used to feed the so-called double DRS device. As the ducting for the device is not yet being tested, Lotus covered the unused inlets.

Rosberg had a short day © XPB

Mercedes

As if to underline the importance of testing, Nico Rosberg had his car stop out on track with electrical problems.

Mercedes found a fault in the electrical loom. This is tightly packaged in and out of channels and holes in the chassis, so it's not normal to have spares or practical to repair the loom in situ.

Williams

Observers were confused when Williams ran its car with a modesty fairing even though the new FW35 is not to be unveiled until the next test at Barcelona.

Despite the confusing front end, it was the 2012 FW34 in action as planned, but with some aero updates, including the fairing over the stepped nose.

It's widely known that Williams will have a modesty panel on its new car, so having this fitted will provide some consistency in the data gathered from these first tests in the old car.