McLaren: European GP wing movement

UPDATE: While I am still awaiting a response from McLaren, I have had a direct reply from Charlie Whiting, FIA Formula One Race Director, to my questions. He responds “The slight anomaly you refer to has been investigated and we have told the team improvements need to be made”. I also asked if this area is subject to any specific deflection tests or construction of the wing\pylon interface “there is no stated permissible deflection of the parts you’re referring to, we do of course have a blanket restriction on any bodywork moving but, in some cases, we define limits given that no bodywork can be designed infinitely rigid”. So it seems any movement there should not be evident at the British GP.

McLaren sported a new front wing at the European GP last. Although the endplates, main plane and cascades were all new, it was the way the wing mounted to the nosecones pylons that has caught attention. From the onboard Tv footage the wing can be seen to apparently and progressively separate from its mounting. However this movement is caused, it is likely to spark questions on flexible aerodynamics, although its clear the McLaren was passed as legal by the FIA scrutineers checks.

http://www.twitvid.com/NLDQ1 Video via Ian Doreto

As McLaren place their camera pods on the front wing pylons (the two vertical plates bonded to the nose cone) and also slightly behind them, the onboard footage presents a clear view of the side of the pylon and the wing below it.

Typically the construction of this area is relatively simple. The wings central section has a metal plate bonded to it, through which run threaded studs. These studs pass up inside corresponding holes in the pylons and are then fastened down with nuts. This makes the assembly rigid, with no freedom of movement. Teams fit a spacer shim into the gap, to ensure the wing sits at the correct static ride height when fitted to the car. Almost every team follows this basic design.

However from the onboard footage, it appears that the McLaren wing is hinging on the pylons allowing the wing to rotate backwards slightly. What can be seen is a gap incrementally opening up at speed towards the rear of the interface between wing and pylon (pictured above). Then as the car slows, the gap closes back up to nothing. I have seen two onboard shots of both the cars in the race and both appear to behave in a similar way (pictured below).

This would have the effect of flattening the front wings angle of attack at speed, decreasing downforce. Depending on the way the diffuser sheds downforce at speed, this would have the effect of inducing understeer, probably for the purpose of making the car more balanced and stable for the driver at high speed. The practice of flattening front wings has been seen before, historically it’s not been unusual to see a front wing flap flatten out at speed, as the compliant flap is subject to aero load.
By achieving a better aero balance at speed, this achieves a different effect to the Red Bull, which appears to droop the front wing into an anhedral shape at speed, this creates more downforce rather than shedding it. So Red Bull are seeking more performance, rather than managing the cars balance.

McLarens wing behaving in this way could be explained in several ways, perhaps as the result of a manufacturing fault, I will ask the team if they had any such problems with the new front wing in Valencia.

I have heard previously from several ex-designers and technical directors, that even in recent seasons teams have had springs in designed into this area. Designed in such a way, that a gap opens up by creating some compliance in the wing\pylon interface. Normally by having a sprung mount, the spring being preloaded to meet any FIA test, but above the FIA load the spring is able to move the wing in a controlled manner. This is of course a far easier way to control the wing than compliance designed into the carbon fibre lay up. The rules do not specifically state that such compliant mechanisms are banned, although a similar wording has been created for the T-Tray splitter mounting. Following the precedent of the Red Bull front wing, which also appears to move at speed, it seems that any movement of the wing is allowed as long as the wing passes the FIA deflection tests. Which is in turn contradicting the FIA demand for bodywork to be rigid and having no degree of freedom in relation to the body/chassis unit.

3.15 Aerodynamic influence :
With the exception of the driver adjustable bodywork described in Article 3.18 (in addition to minimal parts solely associated with its actuation) and the ducts described in Article 11.4, any specific part of the car influencing its aerodynamic performance :
– must comply with the rules relating to bodywork ;
– must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom) ;
– must remain immobile in relation to the sprung part of the car.