Discussion
Harris_I said:
Can you tell us more, Steve?
Yes please do Steve. Actually a few people have told me not to but I went ahead and brought one anyway..... But haven't done any research to be honest. Main motivation was I couldn't fathon why anyone would spec a sunroof on a GT3 and that set me on my way to changing it out. My logic was less weight up top especially in eliminating the sunroof. But for sure I understand the importance of the roof, hence why cabriolets need so much structural support which adds the weight. But I thought the skin itself is just a thinish layer anyway and it is the cross beams that gives the structural support?I am not a chassis engineer or a carbon fibre specialist but i have a little knowledge of both. The roof on a GT car is generlly a fully stressed a element of a monocoque structure transferring loads constantly around the rest of the chassis. The stiifer the suspension, the greater the loads transferred. My guess is that the bonding element of a carbon roof must be at least as effective as the steel counterpart if the chassis is to retain it's strength and rigidity. Also in my experience, whilst carbon fibre is very strong, it is not as effective as steel in absorbing multi impacts and is prone to shatter on secondary impacts.
My personal view - for what its worth - is that unless a car has been specifically designed to incorportate a carbon roof, I would not consider fitting one. On a risk/reward basis, it isnt worth it.
Thats a personal view. I've seen some horrible accidents in cup cars but the chassis are extremely strong and it's very rare that ive seen a chassis deform to an extent that the driver was injured by the chassis itself. I'm not sure that would be the case if the roof's were made of carbon - especially if the accident involved multi roll/multi impact event. Without a roof holding the structure together, the shell would collapse like an egg.
Obviously, it's your call. You could be fine with a carbon roof, but if i were you, i'd fit a steel, non sunroof replacement and leave it at that.
My personal view - for what its worth - is that unless a car has been specifically designed to incorportate a carbon roof, I would not consider fitting one. On a risk/reward basis, it isnt worth it.
Thats a personal view. I've seen some horrible accidents in cup cars but the chassis are extremely strong and it's very rare that ive seen a chassis deform to an extent that the driver was injured by the chassis itself. I'm not sure that would be the case if the roof's were made of carbon - especially if the accident involved multi roll/multi impact event. Without a roof holding the structure together, the shell would collapse like an egg.
Obviously, it's your call. You could be fine with a carbon roof, but if i were you, i'd fit a steel, non sunroof replacement and leave it at that.
I'd be surprised if it's not transferring some loads. I think that the default lightweight roof material for Porsche is magnesium currenlty. Carbon would be a cheaper option but they wont take it. Impact absorbtion could be a bigger factor but they are happy to use carbon on other unstressed areas of factory racing 911's. My guess is that the roof panel does transfer some load.
I have been thinking about it some more. The roof skin is extremely thin and borderline flimsy, plus I think it is largely bonded with adhesive into place along with some corner rivets (?) so surely if it were flexing under stress the adhesive would break away or if not the thin skin would crease over time? Also, I wonder if the installation of the rollcage (and the other strut braces) would mitigate any marginal loss in rigidity anyway as these will greatly increase the overall rigidity of the chassis structure vs a stock non roll cage car? Lastly, if carbon weren't appropriate how then do some manufacturers make entire chassis out of it?
Edited by M32GER on Tuesday 21st November 19:17
https://www.youtube.com/watch?v=0n8MhZhw_sQ
I'm not sure a carbon roof would have kept it's integrity through this. If it comes off or splits open, you have a big problem. I know that kelvin was glad that it was metal. If im racing a Gt car, I prefer a fully metal shell. Carbon is good for the first impact then it tends to explode. it's risk V reward. The honest answer is, until you prang, you wont know.
I'm not sure a carbon roof would have kept it's integrity through this. If it comes off or splits open, you have a big problem. I know that kelvin was glad that it was metal. If im racing a Gt car, I prefer a fully metal shell. Carbon is good for the first impact then it tends to explode. it's risk V reward. The honest answer is, until you prang, you wont know.
Edited by Steve Rance on Tuesday 21st November 19:45
Steve Rance said:
https://www.youtube.com/watch?v=0n8MhZhw_sQ
I'm not sure a carbon roof would have kept it's integrity through this. If it comes off or splits open, you have a big problem. I know that kelvin was glad that it was metal. If im racing a Gt car, I prefer a fully metal shell. Carbon is good for the first impact then it tends to explode. it's risk V reward. The honest answer is, until you prang, you wont know.
Yes certainly wouldn't want to have been in that. I guess mine is not intended to be an all out GT car, just a road car that does a few track days a year but it is good advice and food for thought, thank you Steve.I'm not sure a carbon roof would have kept it's integrity through this. If it comes off or splits open, you have a big problem. I know that kelvin was glad that it was metal. If im racing a Gt car, I prefer a fully metal shell. Carbon is good for the first impact then it tends to explode. it's risk V reward. The honest answer is, until you prang, you wont know.
Edited by Steve Rance on Tuesday 21st November 19:45
M32GER said:
Hi Harris, I plan to keep the stock doors, these are just the internal door cards. There is a cage going in but only a half cage
Ah I see.I love this project. I had ARM in Dubai do a 996 project for me several years ago. The carbon panels were from GT-Racing in the US. Probably not as high quality as Manthey - I can hear the wind whistling around the gap at the leading edge of the door! But it still makes me smile every time I sit in it.
Look forward to seeing the finished product.
Ah fantastic do you have any pics?
The Manthey ones do look lovely quality but will probably also have some kind of noise trade off but since I am removing all the sound proofing anyway throughout the car I doubt will make any difference, loud and proud : )) I ordered a lightweight carpet set from Cargraphic just to add back a token nod of factory look but given it is about as thin as a few sheets of paper I doubt will do anything to dull the road noise, just how I want it! I love hearing all that clattering underneath, the sm flywheel chatter and the stones clipping the underside....
The Manthey ones do look lovely quality but will probably also have some kind of noise trade off but since I am removing all the sound proofing anyway throughout the car I doubt will make any difference, loud and proud : )) I ordered a lightweight carpet set from Cargraphic just to add back a token nod of factory look but given it is about as thin as a few sheets of paper I doubt will do anything to dull the road noise, just how I want it! I love hearing all that clattering underneath, the sm flywheel chatter and the stones clipping the underside....
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