The Mazda MX-5 Roadster Coupe | Part Five

The retractable hard top was developed by Mazda with Webasto Japan and consists of three moving sections and the rear deck cover, which is also a moving element.

A total of four electric roof motors - two on each side of the vehicle - facilitate the metamorphosis of the car from coupe to open-top roadster and back again. Before opening or closing the hard top, the windows (if in the up position) are automatically lowered by approximately 100 mm to make sure there is enough room for the roof to fold back unimpeded.

In its efforts to keep additional weight for the hard top version as low as possible, Mazda used two different kinds of materials, sheet moulding compound (SMC) for the outer panels and glass fibre-reinforced polypropylene (GFPP) for the inner panels of the retractable roof.

SMC material is a fibre/plastic composite material with high rigidity and heat resistance and, to the joy of the designers, is easily formable into shapes that would never be possible with steel or aluminium. And SMC’s smooth surface structure gives an excellent paint finish, which contributes to high levels of build quality and craftsmanship. GFPP combines the virtues of low weight and high strength. This material allowed the inner panels to have a dimpled surface, which looks so good it doesn’t need to be painted. For these reasons, Mazda engineers could do without a moulded roof liner – the combination of SMC and GFPP makes the MX-5 Roadster Coupe’s hard top just 20 mm thick as a result.

The Power Retractable Hard Top Weighs just 18 kg more than the Soft Top

These materials also ensure that the hard top structure is light and compact. The roof itself (not including rear deck cover) weighs only 18 kg more than the soft top of the Mazda MX-5. And not only that, owners of the MX-5 Roadster Coupe can also transport a case of 12, 1.5-litre bottles upright in the boot, even with the top down.

Wind management has also been perfected with the new MX-5 Roadster Coupe. Naturally, Mazda roadster fans have the most fun with their car when a warm summer breeze blows through their hair. This would not be the case with cabin turbulence blowing on their neck in the process. To avoid this with the MX-5 Roadster Coupe, whose rear deck is nearly 40 mm taller at its front edge, designers added an air guide made of polypropylene to the standard aero board behind the seats. This air guide runs the entire width of the aero board and forces air flowing forward from the back of the vehicle upwards.

Designers improved drive comfort even further by lowering cabin noise levels on the motorway. At a speed of 120 km/h with the top up, the measured noise level was reduced by 8 dB for the MX-5 Roadster Coupe.

continues... | Part Six
Published 6 September 2006 Melanie Carter

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