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  #1 (permalink)  
Old 03-10-2012, 10:56 AM
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Default Why not a carbon fiber body?

It would seem a carbon fiber body would be a perfect fit for a Cobra, but from searching, it seems like a rare thing? Why?
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  #2 (permalink)  
Old 03-10-2012, 12:13 PM
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Fiberglass is cheaper and with business its all about the bottom line profit, plus with these cars being so light as it is fiberglass works fine, easy to repair and alot of shops do it, there are some carbon shells but the costs really is'nt that justifiable when glass is so much cheaper.
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Old 03-10-2012, 02:44 PM
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The Cobra body shape doesn't lend itself to exotic materials. There are too many compound curves. In order to fully take advantage of graphite's stiffness, you really need matched dies or vacuum-bagging, neither of which is practical with a one-piece (wrap-around) body. Graphite's great on easier shapes where you can use a low resin-to-reinforcement ratio, but more complex shapes are very difficult. Not to mention, figure roughly $40/lb for materials when properly laid up with epoxy.

The bottom line is you don't gain much except for the status.
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Old 03-10-2012, 03:00 PM
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Actually carbon fiber works better than fiberglass when it comes to the curves and fender wheel wells etc. My car is carbon fiber and the lips on the fenders are rolled just like aluminum and very difficult to tell the difference. Hard to do that with fiberglass...The only thing about carbon fiber is under high fluorescent lights you can see the carbon fiber imprint like expensive race cars, but I actually like that.
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Old 03-10-2012, 05:45 PM
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G-Pete has a carbon fiber body also. I expect they will become more common as time goes on. The ones I've seen are amazing.
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Old 03-11-2012, 07:17 AM
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I don't really know much about the process of making a carbon fiber body or working with it. Could a CF body be made in a mold used for fiberglass?
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Old 03-11-2012, 07:33 AM
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Quote:
Originally Posted by LMH View Post
I don't really know much about the process of making a carbon fiber body or working with it. Could a CF body be made in a mold used for fiberglass?
Larry
Yes, it does not matter which mold you use.

CF is expensive and the technique to do it right is complicated (compare to fiberglass).
The result are strong thin lightweight bodies. Whenever you drill holes or cut CF you need to wear a class III respirator these dust particles a pretty toxic.

If you like the looks of CF you can sand the surface and just apply clear coat.

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Old 03-11-2012, 08:18 AM
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cost.....benefit
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  #9 (permalink)  
Old 03-11-2012, 01:20 PM
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G-Pete the carbon fiber body on your car looks sweet. I probably missed it, but looking at your build pages I didn't see where you got your 289 FIA body? Make it yourself, had some dude make it, or bought it from a company?

Seems like the big thing is light weight. As always a lot of different numbers get tossed out. G-Pete did you weigh your 289 FIA body?

As a comparison, I saw an article from what appeared to be the man who runs ERA, and he put up a number of 300# for his body. That would seem a good touchstone for the potential weight savings.
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Old 03-11-2012, 06:41 PM
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I think I remember hearing Gary and Pete say their bodies are less than 50 lbs.
If so, that's a significant weight savings.
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Old 03-11-2012, 09:13 PM
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I have one of Roger Bollick's (Exact Cobras) Carbon fiber bodies and it is a thing of beauty. And the weight is well below 50 lbs. and very stiff.

Bob
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Old 03-12-2012, 01:34 AM
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Default Weight

I was told that the weight savings from 'glass to Carbon Fibre is not that drastic in a wet lay-up, unless you use an autoclave - which is impractical for a complete body.

The CSX4000 main piece weighs 30kg in fibreglass. Add boot lid, spare tire insert, doors, hood, main tub (where you sit) with aluminium firewall and tunnel and you are at 70 to 75kg.

The tubular door/boot/hood frames are excluded. Give or take 5kg to be added to the 95kg of the chassis.

Total: 170kg for body and chassis.
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Old 03-12-2012, 09:17 AM
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The body, trunk, doors and hood all together 39 pounds.

The body was made by Brian Bumgarner of Missouri (816-309-1930) - in the picture below you see his car. He will just clear coat the car to show the CF finish. We plan to have the cars done by end of May...

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Old 03-12-2012, 10:30 AM
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My (former) Shelby Cobra CSX4005LA was a carbon fiber car. I think 6 were made (maybe 7) by HST. Two of the LA cars were CF.
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Old 03-12-2012, 02:22 PM
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the Exact body weighs 46 lbs.
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Old 03-12-2012, 04:28 PM
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Double Ugly,

Do you still have your Exact?
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Old 03-12-2012, 05:29 PM
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Wow - 39lb or 46lb vs. estimates of 70kg (154lb) or 300lb, that seems like a huge wt savings.

Not sure if all the body pieces included in each wt estimate are apples to apples, but it seems different in a major way.

How do you join the (I think you guys call it) 'birdcage' to the body? Is the body reinforced double thickness cf there or other places?
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Old 03-12-2012, 07:11 PM
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I can tell you first hand from my cycling background that carbon fiber is super strong, light, and very good at absorbing vibrations, particularly if laid with nanotubes and particularly in the direction they are laid to resist forces.

The negatives include cost & repair, and while they are strong in the intended direction of design, they can be quite fragile if impacted on the "wrong" direction, and then once they break, your best turfing it, b/c no repair will replace its strength & integrity. That said probably not a deal breaker on a cobra as its just the "skin" & for aesthetics.

On a chassis, a carbon skinned cobra body would look really cool (IMO). Not classic or authentic but cool none the less.

If you're keen on carbon, why stop there... I'm thinking titanium!
I wonder if the Kirkham boys would consider that in their skunk-works, the panel beating would be a b!tch, but wouldn't it look sensational, be scratch resistant, rust proof & can be made in an alloy form to prevent oxidizing or pitting!
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Old 03-23-2012, 08:21 PM
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I build 289 fia bodys Pete has one, carbon is the way to go if your wanting a car that is better than the original in performance. Weight is everything ,look at a F1 car, but it starts with the frame .the only reason the original has a bird cage is to hold the flimsy alum body. Fiberglass cars run it because glass has no stiffness, with carbon we don't need the substructure. We build any structure out of carbon and keep the steel out. I've spent 2 years in the development of a new frame design with the help of Larson Race cars.You might have heard of him for having the fastest street car in America. If you are wanting to go all carbon give me a call, Bryan- 816 309 1930 . I have all the tooling done now for everything on the car that you might want carbon including new coyote engines .The cool thing about carbon is that you can simulate the alum car details like hood and doors that match the original. In the end it takes analizing the frame and body to achieve the ultimate light weight car. it doesnt cost anymore to go first class.
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Old 03-23-2012, 08:26 PM
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my car is all clear carbon
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