I've been wondering about what a CF roof would do to lower the CG on the car. The weight savings wouldn't be anything like a CF hood, but it should be relatively simple and cheap to produce. Anyone already done this or considered it?

 

This is what is being done on the Asia Experience SLK55.

I am sure that it makes one heckuva difference: first there is the substantial weight difference between a CF roof structure and the high-strength steel structure's build; and then there is the fact that the roof is at the highest point of the vehicle, making the COG effect extreme in my understanding....

 

I wasn't sure exactly how much the current roof weighed. I didn't know that the whole thing was high-strength steel!

 

The special edition SLK55 has not only a CF roof, but the C-pillar is carbon as well. On top of that, it saves more weight by removing the entire retractable roof mechanism from the trunk.

On a C-class, you'll only be able to replace the top of the roof, not the greenhouse arches, since they are attached to the rear quarter panels as well.

 

Btw, I wonder how a carbon fiber hood would behave in a frontal crash. Would it crumple like a metal hood, or would it stay rigid and maybe slice into the passenger compartment? I really don't know. Anyone seen crash test video of the SLR?

 

The frame - which is the heaviest part of the roof - is all high-strength steel.

The CF roofs stay intact and do not deform or shatter, period. How they react with the other members of the roof, or car, I don't know - but the only time I have ever seen a CF structure actually shear was in that one Enzo crash where the car came in two at the middle(!) -- that one still amazes me.

Every single other wrecked car with major CF structures that I have ever seen (and I have looked at quite a few because many of my cars are built with CF) has all of the major CF structures completely intact (obviously except for the actual collision-point which always has an area of damage), and seemingly unaffected by the collision forces. This is especially true with the roofs -- I have NEVER seen a deformed or damaged CF roof....

 

yeah, that's what I was referring to- the top panel.

ClayJ- I wonder if replacing the wrong part with CF could affect the crash-worthiness negatively by transferring the impact force to components that would normally be spared the impact by the original part crumpling to absorb energy.

 

Seriously - I wouldn't screw with it!

I am not one to do crazy stuff - well, not 'crazy', but 'radical' is probably a better terminology - to my cars.... My passenger cars are passenger cars, my track cars are track cars -- and I tend to buy both with the modifications, or in the trim, in which I want them for their intended use....

Do think about it. Keep gathering more information.

I do think that your car was safety-engineered with the roof structure that it has as an integral part of both passenger-cell, and overall, structural safety and integrity involved....

 

I second ClayJ's admonition. I mean, when you buy a MB, you buy a lot of safety engineering. Replacing major structural components of the car for minimal performance or purely aesthetic reasons seems like a real bad idea. You just don't want your daily driver to have some weakened structural aspect, or create some kind of flying debris in a crash that cuts you in half.

 

I wasn't aware that the body panel itsself was so structurally integral. If it's so strong then why does it have a few hail dents

I was also under the impression that CF would be STRONGER. Although, not getting cut in half is my reason for not going with a CF hood

 

it's a unibody car all of the parts are integral in a crash esp. the roof the safety cage under gives it most of it's strength and crumple zones but the exterior sheet metal plays a large part in this also.

 

CF will be stronger IF and only IF it is the REAL CF and not what most people see on the market today.

The M3 CSL and the M6 has the CF roof which cost 3-4 grand to produce. They are made in the same process that McLaren, Porsche, and Ferrari produce the SLR, Enzo, and Carrera GT's chassis which consist of many layers of CF baked in high temp high pressure for strength. It's not just something with 2-3 layers of CF in rasin like most CF products today.

for example you can get a Vorsteiner M3 CSL front bumper in CF or so they say which cost $1200 or more a bumper. OR you can get a REAL M3 CSL CF bumper which made from the process mentioned above that cost $3500.

today's car the sheet metals play little to no part in crashes. They are usually very thin aluminium. i.e. the R230 SL front fender weight so little you can pick up the entire panel with just one pinky finger. Crash safety pretty much comes from the design of the chassi underneath.