More than one way to behead a cat.
Following the carmaker’s remarkable return from near-death only three years previously, America’s movers and shakers were once again buying Jaguars in number. “The word has got out on the cocktail circuit that the Jaguar is the car to have”, as Jaguar Inc Press Officer, Mike Cook told journalists in 1983. But the lack of an open-topped XJ-S model would soon become a genuine impediment to sales growth. From this point onwards, US requests for a convertible would become increasingly strident.
The Jaguar board realised that the expediently engineered XJ-S Cabriolet could only buy them a certain amount of time, but meanwhile something needed to be done to mollify potential US customers, for whom nothing but a full convertible would suffice and who would otherwise simply turn towards the three-pointed star.
Having obtained factory approval, Jaguar Inc began to look towards domestically based options, commissioning Cincinnati-based coachbuilder, Hess & Eisenhardt to engineer a full-convertible XJ-S; an agreement being formalised between the two companies in January 1986. Hess & Eisenhardt were well versed in this nature of custom work, having carried out similar factory-approved conversions for Cadillac and Buick, meaning they had both the skills and the facilities to carry out such high-quality work.
Much like the UK-based Lynx conversion, the H & E XJ-S retained as much of the standard car as possible, the main alterations being to the superstructure to compensate for the removal of the roof and sail fairings. Additional strengthening was added to A-posts, door sills (rocker panels in US parlance) and the rear seat-pan. The fuel tank was also redesigned, to provide space for a specifically designed hood mechanism.
The H & E car was a semi-official product, so customers placed an order at their Jaguar dealer, chose their colour and specification and the completed XJ-S coupé would upon landfall be shipped straight to Cincinnati for H & E to carry out the four-week conversion. Hence, the standard Jaguar warranty would apply, while Hess & Eisenhardt would provide additional cover for their own work. Demand for the model was strong – so much so, that Hess & Eisenhardt apparently had to put aside all other work for a time.
In mid-1985, the factory XJ-S Convertible programme was initiated at Browns Lane, with a tight three-year deadline. A tough gig, particularly given the size of the project team – only 12 people in total. Part of the reason for this shortfall was that Jaguar’s engineers were at a crucial stage of XJ40 development, with that vitally important saloon only a year from series production. Hence, the appointment of acclaimed specialists in the field of low-volume engineering and open-topped development, Karmann of Germany.
This was no simple roof-off conversion à la XJ58, the convertible being a completely re-engineered vehicle. Areas such as the transmission tunnel and front and rear bulkheads were re-enforced and retooled, the floorpan double-skinned, while the body sills and A-pillars contained steel tubing for additional strengthening.
Like the cabriolet model, the XJ-S convertible was a strict two-seater, with the space behind the seats being devoted to providing additional luggage space and a recess for the fabric roof, to ensure an elegant line. The Karmann-engineered roof mechanism was powered, apart from the two release catches at the header rail, the rear quarter windows being lowered simultaneously upon the activation of a single button. A great deal of proving effort was expended to ensure reliability and secure weatherproofing.
The result was a car which weighed only 100 kg more than the Coupé, had 15% less torsional rigidity, and at 0.39, was only marginally less aerodynamic, although any diminution in straight line stability owing to the loss of the rear sail fairings was undocumented.
Jaguar’s styling team under Geoff Lawson were responsible for the car’s well-considered aesthetics. Because it was largely a first-principles project, Jaguar’s stylists were able to make the convertible a notably sleeker, cleaner looking car than any of the aftermarket efforts, or indeed its own somewhat rudimentary open-topped forebear. Central to this was the new, more steeply raked screen and A-pillar which also allowed for a lower roofline and a very tidy hood arrangement. Furthermore, the removal of the front quarter panes, gave the DLO a less cluttered appearance, so even with the roof erected, visual harmony reigned.
The press was as one in lavishing praise on both car and carmaker, the launch location of the French Cote d’Azur perhaps aiding matters to some extent. For it was in locations such as these (not to mention the likes of Beverley Hills or Miami) that the XJ-S convertible was intended for, not the dank, leaden skies of the West Midlands. Here, the UK’s journalists crowed, was the XJ-S perfected. It needed to be, since it was the most expensive Jaguar ever (only the Daimler Limousine was pricier), but for most, including those hard to please US customers, the wait was deemed worthwhile, the price worth paying.
Illustrating just how pent-up demand for the convertible was, US sales leapt immediately upon the model’s American introduction, taking 57% of US-market XJ-S sales in 1989 (itself up on previous years), and with XJ-S sales reaching an all-time peak the following year, with the open-topped car taking the lion’s share.
Not that it was faultless, however. Driving a UK press car across East Sussex B-roads, respected freelance journalist, Roger Bell noted the car’s lack of rigidity on rough roads, comparing it unfavourably to that of the earlier XJSC model. He also criticised the car’s suspension settings as being too soft, perhaps an intentional move on Jaguar’s part to mitigate the car’s inferior integrity on poor surfaces. For most however, this was to prove an acceptable payoff. With cocktail kitty, Jaguar, it would appear, had nailed it.
 A downside of the H & E conversion was that the fabric roof looked rather homespun when erected, with a tiny rear screen. There were also some reported issues with petrol fumes from the repositioned tanks. According to historian, Graham Robson, Jaguar did not see the Hess & Eisenhardt conversion until after their own convertible design was complete.
 From 1986 to 1988, US customers could choose from the XJ-S V12 Coupé, the V12 Cabriolet or the Hess & Eisenhardt Convertible from their friendly Jaguar dealer.
 In all, around 2000 H & E convertibles were made from 1986 to 1988.
 The factory convertible programme (XJ77) was headed by Ken Giles. Giles recounted that the Jaguar Chairman demanded a “world class” product, briefing that it had to be ready for a Geneva 1988 debut.
 Aiding matters considerably, the project team were augmented by the commissioning of the Structural Dynamics Research Corporation, who carried out dynamic finite element modelling (DFEM). Tooling for the new panels was also designed by Karmann. Additionally, the German specialist was commissioned to produce the fully engineered prototypes and to engineer the roof mechanism.
 Writing for Car, LJK. Setright described the XJ-S Convertible “almost impossible to better.”
 Sir John Egan later suggested that, given the level of demand for the Convertible, they perhaps under-priced it.
 Jaguar Inc PR officer, Mike Cook: “The new convertible was a major success. It didn’t kill the Coupé – there were still people wanting an XJ-S with a roof – but it started outselling it almost at once.” (Source – Graham Robson)
 Jim Randle, speaking to this author in 2016, declared that XJ58 performed considerably better from a resonant frequency perspective than the later full convertible XJ77 model.
Sources: See Part One