The New ADESS-03 Wing
3.1 Modeling the New Wing
The CAD software used for this thesis was Dassault Syst `emes CATIA V5 since it is the CAD software package used at ADESS.
Before the design of the new wing started there was a special consideration to take into account: a new car was being developed at that exact same time and this car was based on the ADESS-03 LMP3.
The main difference regarding the wing is that instead of two pillars, the Pininfarina H2 Speed 2018 only has one central pillar, as shown in Figure 3.1, so the attachment points for the wings of both cars must be made in a way that both can be manufactured from the same mould.
Figure 3.1: Pininfarina H2 Speed 2018 at the 2018 Geneva Motor Show. On the figure is visible the central attachment of the wing to the central pillar, hidden inside the fin. Retrieved from [52].
The first thing decided was to keep the rear wing profile so to not upset the dynamic balance of the car. This profile is a standard National Advisory Committee for Aeronautics (NACA) profile capable of
generating 400 kg of downforce at a speed of 280 km/h [53].
After defining the profile, the next thing was the rib design. One certainty was that the rib would need to follow the whole width of the wing to prevent weak zones damage on the structural integrity of the new part. The need to be able to hold the wing a single or double pillar was also taken into account.
The middle section of the new rib has three indentations, shown in Figure 3.2, so the mould can be manufactured just one time and the same rib can be used for the wing of both the ADESS-03 and the H2 Speed with no need for further changes.
Figure 3.2: New rib and lower skin design. Visible on the figure are the three indentations that allow for both a single pillar or two pillars.
Speaking of indentations, two different configurations, illustrated in Figure 3.3, are planned for the top skin: one with two supports for the ADESS-03 and one with one for the H2 Speed. The cavities for the two support methods were designed to have the exact same size so the final top skin could be changed by swapping the location of an add-on on the mould for the part.
Figure 3.3: On the left side, wing configuration for the LMP3 prototype with two indentations for both rear pillars. On the right side, wing configuration for the Pininfarina H2 Speed 2018 with one indentation for a single pillar.
Before finishing the design of the wing, three types of inserts, shown in Figure 3.4, were developed to be bonded inside the whole wing assembly. These inserts have standard thicknesses that are readily available from regular aluminium suppliers so that they can be waterjet cut from the original aluminium plate with no need of further machining. The first type is a profile like aluminium insert to close each end of the wing and allow the endplates to be attached. The second and third one are a bigger and smaller variation of the same insert, these ones are intended to go between the rib and the lower skin and their goal is to screw an M6 screw on each to hold the wing supports to the wing itself.
While defining the dimensions for each element one important thing to take into account is bonding
Figure 3.4: On the left, aluminium inserts that fit between the rib and the lower skin and on the right, inserts to close the wing profile and allow the attachment of the endplates.
areas and bonding gaps. A bonding area on both the top and lower skin, displayed in Figure 3.5, was designed protruding from the wing leading edge to allow a perfect bond between both halves of the profile. Areas like the one mentioned previously were also left on the rib to ensure a correct adhesion to the lower skin.
Figure 3.5: Side profile of the wing before bonding the closing aluminium inserts. Here it is possible to see the aluminium inserts between the rib and the lower skin and in detail, the bonding areas for both the top and lower skin.
About bonding gaps, the theoretical gap suggested is 0.1 mm [54] for the best mechanical properties but, to account with manufacturing defects, at ADESS the usual gap left for bonding is 0.5 mm. This gap needs to be taken into account when dimensioning each part of a bonded assembly. For the moment, the dimensions chosen were those that allowed a proper bonding when the layup in use is the standard layup for the parts of the ADESS-03. After the optimization process is over and when the final theoretical thickness is obtainable, this dimensions should be updated to take into account the new thickness of each composite part and allow for correct bonding straight out of the mould with no need for corrections that would imply sanding down composite parts to allow a correct fit.
Finally, the last parts designed were the support inserts that attach the wing to the pillars, shown in Figure 3.6 and Figure 3.7. These inserts are machined from a solid block of aluminium and they need to take into account the adjustability of the wing. In order to extract the best times out of each circuit, the aerodynamic load must be adapted to fit both high speed circuits and low speed circuits.
High speed circuits require lower amounts of downforce to be able to achieve a higher top speed on straights while low speed circuits require higher amounts of downforce to help with cornering and braking distances.
The wing on the ADESS-03 LMP3 has seven positions ranging from 10o to 4owith the zero being
Figure 3.6: New wing ready to be attached to the endplates and the pillars.
Figure 3.7: Detail of assembly – the M6 bolts hold the support insert against the body of the wing and screw directly to the aluminium inserts below the rib.
6oregarding the profile neutral line [53]. The wing adjustment is obtained by choosing the correct slot combination between the holes on the pillar and the holes on the wing insert, shown in Figure 3.8. The details for each configuration can be found on the technical data of the ADESS-03 LMP3 Prototype.
Figure 3.8: On this illustration retrieved from the Aero guide for the ADESS-03 prototype it is possible to see all he possible wing adjustments and the correct slots. Retrieved from [53].
As mentioned before, the aerodynamic setup of the car will not change so, in order to keep the design as simple as possible the holes from the original insert assembly where projected to the new attachment inserts. This way, the pillars can stay the same and each team that orders the new replacement wing can simply rely on the old technical documentation to choose the downforce settings for each circuit.