It boasts all-carbon panels draped over
a space-frame, weighs under 700kg, packs Honda VTEC power, Wilwood brakes,
adjustable suspension and is a proven front-runner in the upper echelons of
targa racing. The Skelta is a creation like no other in Australia and is
arguably the most sophisticated low-volume production vehicle in the land.
We take an in-depth look at what makes
this machine tick...
Why
Build It?
The
Skelta road/race screamer is the creation of Ray Vandersee. Ray, a
Toowoomba-based business man, former Queensland rally champion and successful
Targa Tasmania campaigner, had the urge to build his own registerable tarmac
race vehicle after reaching the limits of what he could achieve in a Clubman kit
car (see
Podium Pouncer
. Even
with its very strong power-to-weight ratio, the Clubman lacked the outright
speed of competition prep’d Porsche GT3s, was uncomfortable to drive fast for
prolonged periods, had limited suspension sophistication and poor aerodynamics -
which contributed to some pretty unfavourable handling and braking
characteristics at high speed... A huge rear wing and some other aero
refinements helped the situation but were quickly outlawed by the governing body
of Targa Tasmania.
So
the goal was to build a vehicle with similar principles to the Clubman – very
light weight and the ability to ‘get away’ with a near-standard engine – but
using advanced materials, modern suspension and a full aero package. The vehicle
was also to have a removable roof panel and much improved comfort compared to
the Clubman.
Oh
and, despite the inordinate amount of time and money invested in design and
assembly, it also had to be built for consumers at a semi-affordable price. The
challenge was on!
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Frame and Body
So where do you start when building a
vehicle from scratch?
Ray kicked off by laying some sheets of
plywood on the floor and placing on top the engine, gearbox, diff, seats and
other vital components. (Note that, from the early stages, Ray decided to go
with a Honda S2000 engine due to its combination of power, flexibility,
reliability, weight and cost.)
With the components laid out, Ray began mapping
where the suspension and steering would fit and determining the wheelbase and
track. The next step was designing a frame to tie it all together while
maintaining a low aerodynamic profile and maximum rigidity – but without
excessive weight.
A 1:5 scale balsa wood frame was then constructed
and when everything looked like it would fit together nicely, a prototype frame
was built using a combination of square and round chrome moly tube. Chrome moly
was chosen for its relative light weight and availability. As seen in this
photo, production versions are assembled using a full-length jig and are TIG
welded. Ray set a very high goal of achieving a chassis rigidity of 10,000lb/ft
per degree – enough to accommodate a high output V8 engine with significantly
more power than the Honda S2000 four-pot.
Ray says the prototype frame fell
j-u-s-t short of his goal but it’s likely all subsequent production versions are
slightly stiffer – the prototype lost some rigidity because of some
imperfections in the junctions where the round tubes met. Production models use
laser cut square tubes which give a neater and stronger result. The frame also
integrates a CAMS approved roll-over bar and extensive drilling to reduce
weight.
The front cross-member is particularly intricate.
Ray considered casting a magnesium cross-member but has settled on a chrome moly
plate which is bent to form a high-strength box section – it looks heavy but in
fact it’s relatively lightweight. The cross-member mounts the steering rack,
front coil-overs and associated rocker arms.
The suspension pick-up points are located near the
corners of the frame to ensure maximum suspension rigidity and efficiency and
Ray added extra bracing to create a stiff engine bay and passenger compartment –
areas that are typically quite weak in a vehicle of this sort. The passenger
area also achieves extra strength from a carbon fibre and aluminium structure
that forms a tunnel for the tailshaft and exhaust.
The Skelta’s body is an exercise in
carbon fibre lightweight extravagance.
A small scale body mould was scanned, upsized and
the prototype body was built in fibreglass. All subsequent models are carbon
fibre with panel thicknesses varying from 1.5 - 2mm. Even the all-important A
pillars to support the windscreen are made from multi-layer carbon fibre. The
only exceptions are the honeycomb side panels - which are coated in carbon
fibre...
After the lessens learnt in the Clubman, Ray was
keen to develop a vehicle with a full-blown aero package. A high level of
downforce and aero efficiency have been achieved with a combination of a front
splitter leading to a flat floor (including engine tray) and a gigantic rear
diffuser. The top and side panels are also adorned with integrated air intakes
and exits, NACA ducts on top of the rear guards, vortex generators and, of
course, there’s that huge adjustable rear wing. Taillights are from a Mazda 6
and Hella projector style headlights and indicators help achieve Le-Mans style
front guards. Ray says the upswept nose draws from F1 styling.
Interestingly, Ray invested many hours performing
on-road measurement of aerodynamic pressures and airflow patterns (using a
manometer and wool tufts respectively). This photo shows the nose of the
prototype Skelta being tested to observe airflow patterns into the radiator
intakes (mounted in the bonnet), splitter and around the guards. Subsequent
manometer testing showed there’s up to 3.25 inches of water aero pressure in the
lower nosecone and around 1.2 inches of water pressure beneath the undertray (at 120 km/h).
Driveline
When it comes to long distance targa events, the
importance of maintaining near-stock mechanicals cannot be overstated. It’s much
better to have a lightweight, aero-efficient body with a modest power output
compared a heavy, bluff machine that needs lots of power - and therefore tends
to suffer reliability issues.
The Honda F20C S2000 engine was the ideal choice
for providing plenty of power, linear torque, lightweight and reliability – at a
modest price. In standard form, the F20C punches out 176kW at a heady 8300 rpm.
However, by the time it’s fitted with custom 4>1 extractors (required for
packaging reasons), a 2½ into 3 inch exhaust and custom airbox, you’re looking
at a little bit extra. Ray’s targa prep’d car has recently produced 186hp
(139kW) at the wheels. Before fitment into a Skelta, each engine is
comprehensively checked and, if necessary, a rebuild is performed. The engine is
fitted on low compliance mounts and runs the standard Honda engine management
and electrical systems. There are two aluminium radiators in the nose which are
fed cooling air by a pair of large bonnet intakes.
Fuel for the VTEC is stored in a custom aluminium
tank with a capacity of around 40 litres and an ADR-approved filler system. Ray
says the engine consumes around 30 litres per 100km at full noise but is very
economical overall – the 40-litre tank is perfectly adequate for most racing
events.
The ex-Honda S2000 engine is installed together
with its associated six-speed manual gearbox and LSD rear-end. The tailshaft
needs to be shortened slightly. Road-going Skeltas typically retain the standard
S2000 solid axles while Race versions can be equipped with lightweight hollow
shafts. These are recommended where you’re chasing every last bit of
performance.
Stick around for the second part of this series
– we’ll examine the Skelta’s suspension, steering, brakes, cabin and price. And
we also drive it!
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