Chassis stiffness

[NickS]

Does anyone know how the torsional stiffness of the monocoque of a modern sports racer or GT compares with that of a contemporary F1 car?
Are there significant differences in strucural characteristics (strength, stiffness, weight) purely as a result of different shape and size?
If the tub is bigger X-section-ally, can it be made stiffer for the same weight? Or will there be a weight penalty in order to stop it becoming too flexible?

Thanks in advance.

[GT1]

I can't give any details because of the lack of knowledge, but here are a few tidbits, mainly about F1 though.

When McLaren first used carborn in 1981, it was built in a couple of pieces as shaped peices were around yet. Thats one reasonf or the rather cigeratte package looking front nose section. AdC wrought off a few chassis every week it seemed, but it was Watson's shunt at Monza that got the attention of everyone.

John Bernhard later said that at least someone from anythign flew, swam, or rode contacted them about this "carbon fiber" that had been built in the USA by Hercules, a special R&D firm I think.

When McLaren started taking off some of the excess carbon buildup on the tub, they lost some structrual rigidity but lost a lot of weight.

One of the reasons for Ferrari's dominance this year has been their intergration of things like supsension componets into the tub and/or engine (or is it the gearbox?) I have a mag that tells all about it, I try and dig it up for you.

When the rules changed in 1998 and we got smaller track cars, some designers saw this as a chance to help stiffin teh sides even more and intergrate better because there was less mass to worry about and worry aobut it reacting in a negative or positive way.

On problem with the Jaguar R3 was torrisonal stiffness, or lack of. Their monoques had flexing issues and the aero wouldn't work right because the car flexed so badly. Niki Lauda, later fired (suprise) said something about "When I said I wanted a flexable car, I didn't mean the chassis!".

Thats not what your looking for, but maybe it helped a little.

[911GT3RS]

Chassis Flex is one of the big reasons the Caddillac LMP never won..Jaguar could have won, if they had one more year.

[GT1]

Well that was the R3 and the R5 was the last one. Jaguar and Cadillac were too politically motivated to ever win anything.

[Patrick B]

The only number that i can remember is the torrsional stiffness of the Multimatic DP @ 53,000 Ft-lb per degree. Maybe Mulsanne Mike has some numbers...