Banned: The ingenious twin-chassis Lotus F1 car

The Lotus 88 was Colin Chapman's ingenious attempt to continue Team Lotus' reputation as an avant-garde pioneer in Formula 1, but his twin-chassis solution was banned before it could race

Following its successful adoption of the very first fully-stressed monocoque - the Lotus 25 - with the Lotus 72 that defined the wedge shape all F1 cars would subsequently follow with radiators housed in sidepods, and the first car to properly incorporate ground effect - the Lotus 78 - Chapman's team endured winless seasons in 1979 and 1980.

The '88 was the result of his efforts to return Lotus to the top and circumvent the banning of sliding aerodynamic skirts ahead of the 1981 season, but was immediately protested by its competition and never turned a wheel in racing trim.

The ground effect rush

Ground effect is a catch-all term used to describe the aerodynamic principle applied to the cars designed during the late '70s, as teams rushed to copy the principle that carried Lotus to a dominant drivers and constructors world championship double in 1978 with Mario Andretti.

The designs, also known as 'wing cars', included large Venturi tunnels housed under the sidepods that extended to the back of the car.

To take maximum advantage of these tunnels, Lotus pioneered a skirt solution using plastic panels that were hung from the edge of the sidepod and touched the track's surface.

This closed off the tunnels, improving flow through them and reducing airflow egress, resulting in much more downforce.

Ever-more complex skirts arrived as teams developed the solution and re-engineered their cars to find more performance. The below illustration of the Lotus 79 - Chapman's all-conquering development of the 78 - shows the effort made by the team to create as narrow a body as possible in order to have wider and longer Venturi tunnels.

This was continued further with the Lotus 80, although the car proved a disappointment and was abandoned in favour of continuing with the more predictable '79 after only three races in 1979.

However, by the end of the decade, with speeds climbing at a faster rate than safety improvements, the governing body stepped in to minimise the impact of ground effect by banning skirts and mandating a consistent 60mm ground clearance.

Chapman, unable to let go of the knowledge his team had gained, therefore set about finding ways to make up for the loss of downforce.

The 88 takes shape

Lotus had already worked on a car that utilised the twin-chassis concept - the Lotus 86. However, with skirts then a viable option, it was never pressed into service as it wasn't as effective as its single chassis counterpart.

But the landscape had changed for 1981, so Chapman pressed on with the twin-chassis concept, this time using a mock carbon monocoque much like John Barnard's McLaren MP4/1.

Short on time and the affiliation that McLaren had with composite specialist Hercules Aerospace, Lotus was forced to build its own version in-house.

Although likely better than its aluminium counterpart, the monocoque used entirely different techniques to Barnard's in its construction, favouring a Nomex honeycomb centre over the aluminium honeycomb used by McLaren.

A wet lay up procedure that wasn't cured in an autoclave reduced the overall strength further still.

The idea of the twin-chassis concept was to have two sprung bodies, the inner body responsible for the mechanical forces exerted on the car and the outer taking care of the aerodynamic forces.

The outer body would be sucked down to the track at speed and the force would be exerted onto the inner chassis.

To prevent the use of such designs, the regulators cited the rulebook that: "aerodynamic parts must remain immobile in relation to the sprung part of the car".

The specific wording has been tailored to suit the prevailing regulations over the years, but can still be found in article 1.4 of the technical regulations today.

Chapman was outraged by the decision and made several attempts to race the '88, but, with staunch opposition at every turn, was eventually forced to abandon the design.

Lotus returned to using the '81 it had used in 1980 for the first four rounds of 1981 before reverting to the 87 - a more conservative iteration of the 88 - for the rest of the year.

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