# Thoughts on carbon fiber?



## Irishman24 (Sep 13, 2008)

I've been poking around the site for awhile now and have yet to see anything on Carbon Fiber, so what's the deal on it?


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## KiwiEV (Jul 26, 2007)

It's marvellous stuff, but at the same time It's an expensive and labour intensive product. Most people don't use it due to the cost. 
Perhaps the ground-up EV builders may use for body/framework stuff, but with good old _Fibreglass on a Metal Frame_ much cheaper it'll be a while yet.

As for standard EV conversions, I can't see them having much use for it to be honest. 
Perhaps carbon fibre motor mounts? Carbon fibre battery racks? Anyone got any suggestions for use in a typical, standard conversion?


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## Sorian (Jul 28, 2008)

replacement hood and trunk... really that is all I can think of for a standard build after a while down the road for weight reduction.


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## Irishman24 (Sep 13, 2008)

I know it's easier to make flat panels of carbon fiber so I figured if my hood was kinda flat that I could replace it with a flat panel of carbon fibre, do you guys think this would work?


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## elevatorguy (Jul 26, 2007)

I had thoughts of replacing the hood and other parts with fiberglass parts as they are available for a lot of vehicles as aftermarket replacements


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## sunworksco (Sep 8, 2008)

Lotus is prototyping a hemp/fiberglass body for the Elise model.
Hemp fabric is one of the most durable organic materials and a lot less expensive than carbon fiber.
Check out www.alulight.com for aluminum foam panels.
A 160lb. monocoqe chassis is possible.


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## bblocher (Jul 30, 2008)

I was thinking about this for an option down the road. I've found everyhing except the two rear panes for my car. However, I have no clue and can't find what the weight difference would actually be. I'd assume my panels are already pretty thin and light weight but I wonder how much could I really shave off doing hood, trunk, front fenders and doors. 10 lbs? 100 lbs? I really need to remove these items and weigh them I guess.


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## Evan (Feb 20, 2008)

I think Sorian has it right. A lot of us might want to replace more of the car with carbon fiber but most of us don't have the time or money to work with the stuff. 

If I had the chance I would make a long flat sheet to put under the car and reduce drag their. The body panels could just as easily be done in some kind of thermal plastic. Since many EV converters build battery racks in back adding a few bars from front to back to move the battery momentum from the back to front in a collision might not be a bad idea.


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## kixGas (May 2, 2008)

Also most carbon fiber applications require the use of an autoclave to cure the resin. These are incredibly expensive and add to the cost of the part. There really isn't an advantage for the average joe to make something out of carbon fiber versus fiberglass unless you are going for aesthetics.


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## Evan (Feb 20, 2008)

kixGas I wasn't suggesting it for looks but for removing the weight of heavy steel body panels and removing the drag from the less than smooth undercarriage of the car.


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## kixGas (May 2, 2008)

Evan said:


> kixGas I wasn't suggesting it for looks but for removing the weight of heavy steel body panels and removing the drag from the less than smooth undercarriage of the car.


Yes, I know- I was trying to say that Fiberglass would be just as effective as carbon fiber in a DIY application like what you describing. The only reason why one would want to use carbon fiber on a DIY project is if they liked the looks of it better than fiberglass and didn't mind a lighter wallet.


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## Technologic (Jul 20, 2008)

sunworksco said:


> Lotus is prototyping a hemp/fiberglass body for the Elise model.
> Hemp fabric is one of the most durable organic materials and a lot less expensive than carbon fiber.
> Check out www.alulight.com for aluminum foam panels.
> A 160lb. monocoqe chassis is possible.



Aluminum foam has been around for aaaaages. It's so cheap there's no excuse not to use it in sports cars.


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## Evan (Feb 20, 2008)

kixGas - That is true to a point. Long flat sheets or other things that are not curved cost less to fabricate. I am not saying you are wrong but most of the fiberglass I have seen tends to be flimsy. If you want a long flat panel to go under the car the airflow will cause it to waffle in a bad way. I see no visual improvement from carbon fiber over fiberglass lets face it you are just going to put pain over it any way. Using that metric Technologic has a point actually that might be more cost effective for the body panels. I find the ecological impact of hemp fiber dubious over carbon because the real environmental damage is made by the epoxies used to glue it all together.


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## Technologic (Jul 20, 2008)

Evan said:


> kixGas - That is true to a point. Long flat sheets or other things that are not curved cost less to fabricate. I am not saying you are wrong but most of the fiberglass I have seen tends to be flimsy. If you want a long flat panel to go under the car the airflow will cause it to waffle in a bad way. I see no visual improvement from carbon fiber over fiberglass lets face it you are just going to put pain over it any way. Using that metric Technologic has a point actually that might be more cost effective for the body panels. I find the ecological impact of hemp fiber dubious over carbon because the real environmental damage is made by the epoxies used to glue it all together.



Yea the vast majority of that environmental story is just ignorance on the part of the consumer to feel less guilt.

However, aluminum foam is an incredibly light, strong (ceramic ALO type young's modulus) and cheap for flat panels, comes in variable sizes and can be cut with a JIGSAW 

fiberglass is a good material, the issue that it's young's modulus is so low on a flat sheet you have to go fairly thick (perhaps lighter than aluminum for the same stiffness however).

Fiberglass would be great for the body (with curves), while you could use aluminum foam or better yet aluminum honeycomb for the flat single strength axis surfaces.


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## Zer0 (May 9, 2008)

Ahhh..... carbon fiber.
Others have mostly covered everything so far:
1)Fantastic material
2)but cost prohibitive.
3)and labor intensive if you decide to do yourself.

Major panels on your auto have probably already been produced by the aftermarket. Hoods and trunks are pretty common. other body panels are harder to find, but I have seen doors for some cars (huge weight reduction there)

there is also a company that will make you a custom driveshaft out of carbon fiber (RWD only). Supposedly better that metal for many reasons chief among them:
1)CF allows for some flex, which absorbs vibration and driveline shock and helps preserve other parts of the drivetrain.
2)Safety: if a CF driveshaft breaks in the middle, it will shatter and the broken ends will "broom" leaving only carbon strands spinning about. A metal shaft that failed this way would continue spinning as well, but the two halves would try to slap their way through the floorboard.
3)the obvious rotational weight savings means efficiency/power improvements.

If at all possible, buy something someone has already made, you'll waste just as much if not more time and money trying to do something that's already been done.


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## Technologic (Jul 20, 2008)

Zer0 said:


> Ahhh..... carbon fiber.
> Others have mostly covered everything so far:
> 1)Fantastic material
> 2)but cost prohibitive.
> ...


the weight reduction isn't huge... something along 200-300 lbs with hood, and most panels made out of CF...

the cost will be outrageous even prefab... in the thousands and thousands of dollars for around 2mpg more.

Go ground up and use perforated tube aluminum for the frame, full 2 piece FG body, seam it with CF.


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## Sorian (Jul 28, 2008)

Another good thing about fiberglass, is if your original body panels are in good shape (no dings), you can use it as a mold for the FG, tho I am semi-sure that goes for CF too.


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## Technologic (Jul 20, 2008)

Sorian said:


> Another good thing about fiberglass, is if your original body panels are in good shape (no dings), you can use it as a mold for the FG, tho I am semi-sure that goes for CF too.


or kevlar, or spectrum woven fibers

you can use them as molds.


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## Evan (Feb 20, 2008)

Technologic - I know 2mpg doesn't sound like much given the cost involved. I was wrong. I still would like to see someone make all the little improvements that we are always throwing around just to see what the sum would be.


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## Technologic (Jul 20, 2008)

Evan said:


> Technologic - I know 2mpg doesn't sound like much given the cost involved. I was wrong. I still would like to see someone make all the little improvements that we are always throwing around just to see what the sum would be.


I have a ground up EV project in the works currently (hence my not checking the forum as much as I was 3-4 weeks ago), using aluminum tubes with hollow fiberglass reinforcements down the middle, the tubes are currently on hold till I finish the welding jig.

it will be a tantum 2 seater with a CdA roughly 2-3 times less than the Aptera. Not getting anyone's hopes up on the build till I have something tangible to document and post.

In the meantime continue the CF discussion


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## Evan (Feb 20, 2008)

Technologic - Just curious David85 and I were talking in an earlier thread about composites and lighter car design. What kind of modeling did you do if any prior to construction. I know for diy cars the rules are different but did you do a fem/fea simulation of the car in a crash or anything like that?


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## Technologic (Jul 20, 2008)

Evan said:


> Technologic - Just curious David85 and I were talking in an earlier thread about composites and lighter car design. What kind of modeling did you do if any prior to construction. I know for diy cars the rules are different but did you do a fem/fea simulation of the car in a crash or anything like that?


I don't have the tools (or knowledge tbh) to do that kind of simulation. I do however have a strong physics background (picked it up on my own during college). I intend to employ the dual materials method for maximum energy absorption. Placing a plasticly deforming material (aluminum) on the same axis as a shatter deformation material (fiberglass or carbon fiber) provides a strong yet super light crash material. I'm not sure yet how far I'll go on the frame in the next 2 weeks but I'll update you with specifics what seems to work out best. Also this way the frame will be able to absorb quite a bit of damage without permanently deforming (the fiberglass will act like a spring for the aluminum, at least until the fiberglass itself cracks and breaks permanently)

just general "engineering" will tell you quite a bit about how the car will peform in a crash, my guess currently is vastly better than the steel subframes as the car will be totally enclosed with the frame.


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## wakinyantanka (Apr 8, 2008)

Technologic said:


> I don't have the tools (or knowledge tbh) to do that kind of simulation. I do however have a strong physics background (picked it up on my own during college). I intend to employ the dual materials method for maximum energy absorption. Placing a plasticly deforming material (aluminum) on the same axis as a shatter deformation material (fiberglass or carbon fiber) provides a strong yet super light crash material. I'm not sure yet how far I'll go on the frame in the next 2 weeks but I'll update you with specifics what seems to work out best. Also this way the frame will be able to absorb quite a bit of damage without permanently deforming (the fiberglass will act like a spring for the aluminum, at least until the fiberglass itself cracks and breaks permanently)
> 
> just general "engineering" will tell you quite a bit about how the car will peform in a crash, my guess currently is vastly better than the steel subframes as the car will be totally enclosed with the frame.


This is very true.
I am also doing a ground up build using an all composite matrix with a foam core and aluminum sub-components for the suspension and drivetrain. Mine is a sports car, 2 doors, 4 seats, dimensions based on the Lambo Murcielago. Working on the body right now, very labor intensive!!!
I don't know if you've done any research on s-2 fiberglass, but it's what I'm using through out the entire structure. S-2 can be produced with "slip" joints in effect creating crush zones with in the composite matrix. It's also very inexpensive and is very close to strength ratios of carbon fiber, with out the risk of shattering under catastrophic failure. The US Navy uses it to missile proof the decks of battleships.
This is a great thread just stumbled onto it.


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## Technologic (Jul 20, 2008)

wakinyantanka said:


> This is very true.
> I am also doing a ground up build using an all composite matrix with a foam core and aluminum sub-components for the suspension and drivetrain. Mine is a sports car, 2 doors, 4 seats, dimensions based on the Lambo Murcielago. Working on the body right now, very labor intensive!!!
> I don't know if you've done any research on s-2 fiberglass, but it's what I'm using through out the entire structure. S-2 can be produced with "slip" joints in effect creating crush zones with in the composite matrix. It's also very inexpensive and is very close to strength ratios of carbon fiber, with out the risk of shattering under catastrophic failure. The US Navy uses it to missile proof the decks of battleships.
> This is a great thread just stumbled onto it.


 
Agreed, however I don't really have the inclination in my build to employ a ridging crumble zone (though that would make 80-100mph collisons with a wall survivable if done correctly).

The car I intend to build will weigh between 500-700 lbs all inclusive (me in the car) I hope that's light enough to avoid needing large aborptions outside of the tube frame/fiberglass binding itself.

gl on your project I hope to see threads about it as you progress


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## wakinyantanka (Apr 8, 2008)

Technologic said:


> Agreed, however I don't really have the inclination in my build to employ a ridging crumble zone (though that would make 80-100mph collisons with a wall survivable if done correctly).
> 
> The car I intend to build will weigh between 500-700 lbs all inclusive (me in the car) I hope that's light enough to avoid needing large aborptions outside of the tube frame/fiberglass binding itself.
> 
> gl on your project I hope to see threads about it as you progress


Cool..
My car is clocking in at 1800lbs all inclusive. With 240kw of power to the wheels I'm hoping it will be a beast at the track as well. I'm actually designing mine to divert any impact around the passenger compartment. Another advantage of composite construction.
Good luck on yours as well, I'll definitely be keeping folks up to date with pics as soon as the body is finished. Hope you do the same, I will follow with interest.


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## abudabit (Sep 18, 2008)

Carbon fiber isn't all it's cracked up to be. It snaps.

You can buy a weave which combines S-Glass / Basalt with Kevlar / Spectra / other Aramids.


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## Technologic (Jul 20, 2008)

abudabit said:


> Carbon fiber isn't all it's cracked up to be. It snaps.
> 
> You can buy a weave which combines S-Glass / Basalt with Kevlar / Spectra / other Aramids.


that's like saying diamond or aluminum oxide isn't all it's "cracked up to be" even though it's 4 times less mass per CC than steel and 600% stiffer... just cause they "crack" under non-uniform pressure 

ceramic shattering has massive energy absorption properties compared to simple plastic deformation of metals


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## electric85 (Apr 10, 2008)

i'm in the process of converting a pontiace fiero and love that there are so many kits for the car to modify the body and look of the car. but i had hoped that there would of been a carbon fiber body kit for it. there are lots of other fiberglass kits, and replacement pannels...but no carbon fiber that i could tell. now i know fiberglass is lightweight... but carbon fiber is crazy light! has anyone ever felt how lightweight it is? i used to be into competetive mountain biking. when i was buying a new bike one season i looked into a bike that was carbon fiber and the weight difference was huge! between aluminum and CF there had to be at least 10 pounds difference! thats just a small bike frame!


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## Evan (Feb 20, 2008)

Technologic - I think you are right about carbon fiber. I am also not a mechanical engineer or physicist. I have seen in electronics the semiconductor was invented and in the beginning most people scoffed at them because they didn't have the power to easily be connected to the old tube based stuff. Eventually it was realized that tubes should just be phased out almost completely. (contrary to popular belief there are some very useful places for tubes) Eventually the world will learn how to rework the mechanics of vehicles around composites. It isn't that people have written off composites the way so many other new things have been it is just that we have not yet worked out all the ways to take advantage of what we consider to be limitations.

As for doing a computer model of it. Hey I can't do that ether, welcome to the club! I have been trying to learn it but my mindset is not mechanical enough. There is a fare amount of open source software out there for it however, learning that stuff is hard. If you have ever used an electronics simulation system like spice you know that changing the time step can change the answerer in some situations. New spice engines can use recursive algorithms to solve this problem by stepping more near points of intersection and such things. For things like diodes that switch sharply this can be problematic but not unsolvable. However, for mechanical modeling they haven't got that yet. Doing things like changing the number of points in a mesh or the mesh type can radically change the results or at least that is what I am told. 

If you want to play with some fun stuff check out www.caelinux.com
It is GNU licensed but uses Opencascade for a back end geometry engine. Sadly Opencascade is only free as in beer not as in speech as they say. Hopefully in time they will change to something else.


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## TexasCotton (Sep 18, 2008)

Currently carbon fiber only has "Tesla EV" using technology and this smart guy pushing the idea http://http://en.wikipedia.org/wiki/Amory_Lovins


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## abudabit (Sep 18, 2008)

I just don't think carbon fiber is as safe as some of the lower performance composites because you can't tell when carbon fiber is going to break. I met someone whose carbon fiber handle bars on his bike randomly snapped. I know that can happen with anything, but it seems carbon fiber is especially 'surprising' when it weakens. I don't know, maybe it's paranoia but it seems like carbon fiber parts unexpectedly breaking is kind of common. Aramids or hybrid weaves seem so much more trust worthy which is important when going fast speeds every day, as we do in our vehicles.

Plus with the low costs of aramids and glass and basalt compared to carbon fiber, I don't know it seems a little over hyped.


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## Evan (Feb 20, 2008)

abudabit - To be fair that is a rare problem from situations where regular vibration has stressed the frame to the point where micro fractures have happened. This can happen even to steal though I suspect it is a rare occurrence there. They use acoustics to check for these kinds of faults.


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## Technologic (Jul 20, 2008)

Evan said:


> abudabit - To be fair that is a rare problem from situations where regular vibration has stressed the frame to the point where micro fractures have happened. This can happen even to steal though I suspect it is a rare occurrence there. They use acoustics to check for these kinds of faults.


actually carbon fiber fairs better than steel with regular vibration, it's the uneven pressures that fracture it... (over long periods as well).


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## Evan (Feb 20, 2008)

Sorry I got that wrong. I have more reading than I though. 
Thanks for setting me right.


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## Technologic (Jul 20, 2008)

Evan said:


> Sorry I got that wrong. I have more reading than I though.
> Thanks for setting me right.


carbon fiber rods are now being used in the concrete of bridges instead of steel rebar... it performs a lot better and doesn't add weight (actually reduces it quite a bit).


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## enganear (Jun 16, 2008)

Some points I did not see mentioned.



It is conductive
It will burn
Conventional mounting methods (holes and fasteners) created stress concentrations that negate nay strength advantage you may have had.
Cutting and drilling it generates toxic dust.
I won't be using any soon.
-enganear


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## Evan (Feb 20, 2008)

enganear - 

1. being conductive is not a problem. You shouldn't have any power connected to the frame any way. Steel has the same problem.
2. The flame retardants in most car dashboards are very toxic and cause health problems for firefighters. Not burning is not always better it is all about how it is done.
3. If you are doing carbon fiber then yes you have to change the way you design. But if it leads to a better end result who cares about changing.
4. Well I would hope you would minimize the amount of cutting and drilling involved. Fiberglass has this problem too. Obviously drilling is inevitable but you should make it too size in molds.


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## enganear (Jun 16, 2008)

1. being conductive is not a problem. You shouldn't have any power connected to the frame any way. Steel has the same problem.
-It can be a BIG problem if someone makes a battery of the stuff thinking it is just like really strong fiberglass....that application was mentioned, I thought everyone should know.

2. The flame retardants in most car dashboards are very toxic and cause health problems for firefighters. Not burning is not always better it is all about how it is done.
-Those flame retardants are not conductive...Steel is conductive but won't burn.

3. If you are doing carbon fiber then yes you have to change the way you design. But if it leads to a better end result who cares about changing.
-The stuff is so expensive, no one in this community is going to use much if any of it. This whole thread is really moot. 1/8" CF is about $150 per square foot. What app could you possibly have to justify a material that costs that much. BTW, there is a LOT of fake CF out there for less money...

4. Well I would hope you would minimize the amount of cutting and drilling involved. Fiberglass has this problem too. Obviously drilling is inevitable but you should make it too size in molds.
-I guess from your comments, you have never worked with the stuff. I have used it in combat robots and it is a PITA. As long as you cover up completely with no exposed skin, goggles, and a respirator you are safe. LOL

You can find the MSDS for Hexcel brand CF at http://www.robotmarketplace.com/products/images/CF_material_safety.pdf

-enganear


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## Technologic (Jul 20, 2008)

enganear said:


> 3. If you are doing carbon fiber then yes you have to change the way you design. But if it leads to a better end result who cares about changing.
> -The stuff is so expensive, no one in this community is going to use much if any of it. This whole thread is really moot. 1/8" CF is about $150 per square foot. What app could you possibly have to justify a material that costs that much. BTW, there is a LOT of fake CF out there for less money...


Akulon injected fiberglass reinforced plastic 

2.7g/cc with a YM of 600GPA... but the damn thing has the dampening properties of a rubber!


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## sunworksco (Sep 8, 2008)

Take a look at this website : www.fiberforge.com


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## Evan (Feb 20, 2008)

enaganear - Who would make a battery using carbonfiber? You shouldn't have power on the frame of an EV. This is a basic safety issue. Just think about the ground fault situation where a person plugs in the thing to charge it and ends up becoming the alternate grounding path. Not to mention the EMI problems from having noise from the PWM on the frame. There are other situations too. No power of any kind on the frame. Steel being conductive is not a good thing unless you are going for a Faraday Cage, which is only useful against lightening a very very rare problem. Look at the EV-1 that car's body was aluminum with plastic panels mostly. I know of only 1 that burned and that was due to bad manufacturing. All power electronics should be shielded by metal if only to reduce EMI.

You and I might be limited in budget from building a whole car out of it but a few panels is not out of the question. No one here has an autoclave to process it properly in their home but having parts prefabbed from it should be possible. You have the same health and safety handling troubles from CF which you seem to like. The only real differences between the two are performance, cost and conductivity. The conductivity I see as being moot. As for performance vs cost well that is up to the people who are thinking about starting these projects not you or me. You are taking this much more personally than it was meant at least on my part.


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## enganear (Jun 16, 2008)

Evan said:


> enaganear - Who would make a battery using carbonfiber?


Sorry, I meant battery "box". CF would be a bad choice for a battery box, even if one could afford it.
-enganear


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## Evan (Feb 20, 2008)

enganear - Sorry I tend to misinterpret things all the time. The mistake was likely more mine than yours.


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## sunworksco (Sep 8, 2008)

You can build a battery box with www.alulight.com aluminum foam panels.There is a Livermore,Ca. carbon fiber supplier that will hydraulically press a mat of differing types of fiberglass materials to the aluminum foam panels making them indestructable and non-conductive.


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## Evan (Feb 20, 2008)

sunworksco - that is very interesting. especially if you wanted to make the battery box part of the frame. However I would just as soon have the box separate from the frame on insulated stand offs. So just strait aluminum would do.


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## Wirecutter (Jul 26, 2007)

I have done a little research on making a unibody type thing out of CF. My conclusion was that, for a whole lot less money, you can make something respectably strong and light using good old fiberglass. After all, the technology for building boat hulls and car body panels is pretty mature. I wouldn't tout the strength of car body parts, but boat hulls are pretty tough, especially for their weight.

IMHO, *Carbon Fiber* suffers from the same hype as *Billet* in the auto parts aftermarket. The big difference is that *Carbon Fiber* is an actual material, with many many different grades. *Billet*, when referred to as the base material for some car- or motorcycle-bolt on, might just as well be called "bullsh*t". But anyway, when you look at a non-structural part made from *Carbon Fiber*, as with *Billet*, you're talking more about a surface finish and look. (i.e. Real carbon fiber doesn't necessarily look like that sleek black and grey checkerboard pattern.)

-Mark


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