DB7 vs XJS

[extratime1983]

I remember where it was.

James May road tested a KWE XJS on Top Gear.

He commented that the XJS was supposed to be mid engined, but Jaguar changed their mind, and the buttresses remained.

[dhdove]

Dear All

pjts has got it right, to add a few details........

In the early days of the design both a convertible and a coupe design were considered, however a combination of costs and the influence of potential US legislation resulted in the coupe option going forward. Of two proposals Jaguar chose to go with that of Malcolm Sayer (over the in-house team) who had previously worked on the racing C and D-types and E-Type. Sayer had Sir William Lyons backing.
Very early on Sayer did consider mid-engined styling concepts, though interestingly his design roughs do not have buttresses.
Plaese click on pics for a.......slightly better image..........

http://www.jec-xjs-forum.org.uk/xjsbb2/ ... 5-1_tn.jpg

He was influenced by Italian sports car design of the times such as the Ferrari 206 and 246 GT Dino with their near vertical rear windows and buttresses. Sayer said
" the image sought is of a low, wide, high speed car, at least as eye-catching as those the Italians will produce"
An early experimental mock-up exercise on a 2+2 E-type had buttress like rear projections.


http://www.jec-xjs-forum.org.uk/xjsbb2/ ... 5-2_tn.jpg


Primarilly Sayer was an aerodynamicist and both he and Lyons were determined that above all the new car should be slippery. The buttresses were an integral part of this concept along with the front spoiler and undertray, allowing the car to produce a Cd figure of 0.39 compared to the E-Types 0.455. Sir William said
"We decided from the very first that aerodynamics were the prime concern."


http://www.jec-xjs-forum.org.uk/xjsbb2/ ... 5-3_tn.jpg


Further design benefits of the buttresses was their aiding of stability in crosswinds and structural integrity. Their inward curve or twist at the rear was an entirely intentional part of the design, causing aerodynamic "spillage".

http://www.jec-xjs-forum.org.uk/xjsbb2/ ... 5-4_tn.jpg

Malcom Sayer died in 1970 and never saw the XJS come to fruition. The design transferred to Doug Thorpe and the in-house team who weren't keen on the buttress design, but by then it was too late to make changes.

The rest is history.

Compiled with the following references

"The XJ Series Jaguars" - Paul Skilleter
"Jaguar XJ-S" - Brian Long
"You and Your Jaguar XJS" Nigel Thorley

NB Extratime you are right James May did say that.....but he was wrong.

On a personal note I'm always fascinated by how if a few dead leaves are lying on the car behind the rear window you can go on a long journey at high speed and they simply stay there, occasionally rolling around in a vortex. presumably held there by a low pressure area created by the buttresses.

Regards
Tony

[extratime1983]

Disappointed in James May. Clarkson is there for the entertainment, as is Hammond, but May, I classed as the respected motoring journalist who knew a bit about cars. If May said the earth was flat, I’d probably believe him! I shall stop reading his column in the Telegraph for fear of being mis-informed!

Shame on the BBC and their research team for not doing their job properly.

Going to get these books you mentioned Tony, learn a bit more about our cars.

[dhdove]

Extratime

I can certainly recommend both the Brian Long and Nigel Thorley books which contain a wealth of info. and pics. Check out e-bay, they're often both on there.
Regards
Tony