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Iconic 60s Replica Hand-built Using Composites

  • Thursday, 17th October 2019
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  • Reading time: about 5 minutes

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For classic car enthusiasts of the 1960s British AC Cobra two-seater racing roadster, very deep pockets are needed to afford an original sports car. Back in 2001, world champion auto racers, Tony Martin and Reg Dodd founded Backdraft Racing to offer enthusiasts worldwide an affordable replica or custom built sports car based on the iconic AC Cars racing roadster. 

Backdraft Racing combines 60s styling with modern suspension, braking and powertrains, producing cars for both road and race track driving experiences. Based in the US and South Africa, Backdraft Racing works closely with manufacturing partner TR-Tec, located in Durban, South Africa. Since 2002, TR-Tec has been hand-building niche automobiles and ‘turnkey-minus’ rolling chassis for Backdraft Racing, which are produced with fibreglass bodies made using proven Scott Bader tooling, laminating and structural adhesive products. Backdraft Racing completes the production of the roadsters in its state-of-the-art facility in Florida, installing the engine, transmission, drive shaft, differentials and final drive. 

Fibreglass Body & Tooling 

While the original AC Cars have an aluminium body, all Backdraft Roadsters are manufactured with a lightweight, strong, highly durable, fibreglass body. The main body section is moulded in one piece on a rotating jig, with separate tooling for the doors, hood, truck and various interior parts. To ensure a high quality build, the attention to detail by TR-Tec is meticulous throughout the construction. For all of the fibreglass components on Backdraft Racing models, TR-Tec specifies pre-accelerated unsaturated polyester (UP) matched Crystic resin and gelcoat systems, which are manufactured locally in South Africa by Scott Bader Pty in Hammarsdale. The glass fibre laminate system for the entire main body is a spray applied combination of black pigmented Crystic LS 97PA, a high quality isophthalic spray gelcoat, with three layers of 450gsm chopped strand matting with Crystic 491PAT isophthalic back up resin, which is thixotropic and so can be sprayed or brushed. For certain areas a core mat reinforcing layer is added, with extra glass reinforcement in the wheel arches. 

The individual fibreglass body parts, such as the doors, hood and trunk, are all moulded by hand lay-up, double skinned for a smooth finish and added rigidity, with steel inserts in the hinge and lock areas for added durability and strength. Once again, Crystic 491PAT is the laminating resin, which is brush applied behind a black Crystic LS88PA gelcoat. The door surrounds, hood and luggage compartment surrounds and other strategic points are reinforced by applying a chopped fibre compound and an extra layer of glass mat. The cockpit floor, transmission tunnel, fire wall, front inner wheel wells and the luggage compartment are all laminated into the main body moulding in a jig to ensure accuracy, rigidity and strength. The engine bay and front inner bumpers are also finished in black Crystic LS88PA gelcoat for a smooth appearance, durability and ease of cleaning and maintenance. 

The use of high performance isophthalic grade gelcoats for all body parts provides the bodywork with a long lasting water and UV weathering resistant barrier behind the paint system as well as helping to minimise any fibre print through; the gelcoat layer is sanded back and then primed ready for painting.    

The fibreglass tooling used by TR-Tec for the Backdraft RT3 and RT3B roadster body parts are produced using Scott Bader’s Crystic Primecoat and Crystic Glosscoat for the plugs and the Crestamould matched tooling system. The moulds are produced using Crestamould 15PA(B) vinyl ester brush tooling gelcoat with one layer of Crestamould 125PA ortho UP tooling resin immediately behind the gelcoat, then a minimum of eight layers of Crestamould RTR 4010PA rapid UP tooling resin, which has easier handling properties, a lower viscosity, improved shrinkage control and also uses a standard MEKP catalyst. 

Lightweight FRP Adhesive   

To minimise weight, avoid surface defects and increase productivity, for the interior components, such as the door surrounds and luggage compartment sections, TR-Tec uses Scott Bader’s MEKP cured Crestomer 1152PA structural adhesive to bond in and join parts together in preference to using mechanical fixings. 

The range of Crestomers are proven structural adhesives, originally developed for providing structural joint bonds in demanding fibreglass deck and hull marine applications. The 1152PA grade is suitable for gap-filling joints up to 25mm and offers a good level of shop floor leeway during assembly, having a working time of up to 50 minutes (at 2% w/v catalyst, 25°C). Published Scott Bader technical data for cured Crestomer 1152PA gives typical physical property values (to BS EN ISO 527-2:1196 test method) of 100% elongation at break and a maximum tensile strength of 26 MPa; the limiting strength factor is the fibreglass laminate substrate which breaks first, not the Crestomer adhesive joint, which provides a very tough, high impact strength bond. 

Technical Support Service

TR-Tec has been supplied by Scott Bader for many years and values not only the quality of the products supplied, which is critical for making luxury sports cars, but also the pre and post sales technical support and advice they have had over the years. Tony Martin, Production Director for TR-Tec and Backdraft Racing SA explains, “Backdraft Racing uses Scott Bader South Africa because they provide us with comprehensive technical support and are ready to assist with any challenges faced by the production team. They go the extra mile to ensure that all our technical requirements are met. For me and my TR-Tec team, this level of service along with their extensive range of extremely good, consistently reliable products, is the perfect combination for our business needs.”


Image provided by Scott Bader


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