Carbon versus Fiber glass (weight)
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From: Mount Holly, NJ, USA
Carbon versus Fiber glass (weight)
I know that you can get 5.7 oz CF and 9 oz glass, but with the differences in layering and epoxies, what kind of difference is there in numbers and percentages for something like a hood? Thanks.
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From: Trapped in time, Surrounded by evil, Low on gas
Re: Carbon versus Fiber glass (SVOboy)
the biggest difference you will see is with the method of laying the fibre. dryglassing will provide the least weight increase.
in the case most production hoods the weight difference is negligible.
stan
in the case most production hoods the weight difference is negligible.
stan
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From: Minneapolis
Re: (SVOboy)
typically in a wet lay-up by hand, the amount of resin you use is about 50-60% of fiber weight, regardless of it being cf or fg. At that ratio, the cf will not be appreciably stronger than fg (a bit stiffer, but not stronger), so the only weight reduction that cf offers the home-builder is in it's fabric weight (a few ounces per yard), making it economically inefficient in thin sections like body panels. Additionally, don't even waste your money on doing cf until you have mastered layup techniques on cheap-*** fiberglass
Re: (Bjorn)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bjorn »</TD></TR><TR><TD CLASS="quote">typically in a wet lay-up by hand, the amount of resin you use is about 50-60% of fiber weight, regardless of it being cf or fg. At that ratio, the cf will not be appreciably stronger than fg (a bit stiffer, but not stronger), so the only weight reduction that cf offers the home-builder is in it's fabric weight (a few ounces per yard), making it economically inefficient in thin sections like body panels. Additionally, don't even waste your money on doing cf until you have mastered layup techniques on cheap-*** fiberglass</TD></TR></TABLE>
unless you have a vacuum bagging setup and oven. ahah then you can do pre-impregnated cf from your home also. that would help strength some and weight. but will not be as good as an autoclaved part.
unless you have a vacuum bagging setup and oven. ahah then you can do pre-impregnated cf from your home also. that would help strength some and weight. but will not be as good as an autoclaved part.
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Re: (Bjorn)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bjorn »</TD></TR><TR><TD CLASS="quote">typically in a wet lay-up by hand, the amount of resin you use is about 50-60% of fiber weight, regardless of it being cf or fg. At that ratio, the cf will not be appreciably stronger than fg (a bit stiffer, but not stronger), so the only weight reduction that cf offers the home-builder is in it's fabric weight (a few ounces per yard), making it economically inefficient in thin sections like body panels. Additionally, don't even waste your money on doing cf until you have mastered layup techniques on cheap-*** fiberglass</TD></TR></TABLE>
Yeah, and don't use Carbon fiber unless you use a vacuum bag or autoclave since you won't get a great fiber/resin ratio from wet layup only.
Yeah, and don't use Carbon fiber unless you use a vacuum bag or autoclave since you won't get a great fiber/resin ratio from wet layup only.
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Re: (gldndrgn14)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gldndrgn14 »</TD></TR><TR><TD CLASS="quote">
unless you have a vacuum bagging setup and oven. ahah then you can do pre-impregnated cf from your home also. that would help strength some and weight. but will not be as good as an autoclaved part. </TD></TR></TABLE>
even then, the strength and weight advantage doesn't really materialize, as pre-impregnating cloth is still far inferior to actual prepreg made in a factory. Pre-impregnating is still a good tip and excellent technique (and much easier w/ flexible fg). What would really be nice to have would be a warehouse that stocks prepreg and sells in small quantities to homebuilders (I guarantee anyone who starts that up will have assloads of business from car, boat, motorcycle and snowmobile guys) - the lack of tools and toxicity would be a lot less intimidating to 1st timers
unless you have a vacuum bagging setup and oven. ahah then you can do pre-impregnated cf from your home also. that would help strength some and weight. but will not be as good as an autoclaved part. </TD></TR></TABLE>
even then, the strength and weight advantage doesn't really materialize, as pre-impregnating cloth is still far inferior to actual prepreg made in a factory. Pre-impregnating is still a good tip and excellent technique (and much easier w/ flexible fg). What would really be nice to have would be a warehouse that stocks prepreg and sells in small quantities to homebuilders (I guarantee anyone who starts that up will have assloads of business from car, boat, motorcycle and snowmobile guys) - the lack of tools and toxicity would be a lot less intimidating to 1st timers
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From: Somewhere in, FL, USA
Re: (Bjorn)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bjorn »</TD></TR><TR><TD CLASS="quote"> At that ratio, the cf will not be appreciably stronger than fg (a bit stiffer, but not stronger), so the only weight reduction that cf offers the home-builder is in it's fabric weight (a few ounces per yard), </TD></TR></TABLE>
Their is some really bad info going around in this thread.
The weight savings from CF comes in the fact that you can use much less layers than glass. This means that you can use much less epoxy/resin in your layup where most of the weight is found.
Their is a significant weight difference between a glass body panel and a Cf panel. A well constructed CF hood made with only Cf could be made to weigh 7 pounds vs the normal 15 pounds for CF/glass combo.
When I fabricated body panels It would sometimes take me 10-12 layers of glass to match 1 layer of CF in strength and rigidity.
Where are you getting your info from if you don't mind me asking?
Their is some really bad info going around in this thread.
The weight savings from CF comes in the fact that you can use much less layers than glass. This means that you can use much less epoxy/resin in your layup where most of the weight is found.
Their is a significant weight difference between a glass body panel and a Cf panel. A well constructed CF hood made with only Cf could be made to weigh 7 pounds vs the normal 15 pounds for CF/glass combo.
When I fabricated body panels It would sometimes take me 10-12 layers of glass to match 1 layer of CF in strength and rigidity.
Where are you getting your info from if you don't mind me asking?
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From: Calgary, AB, Canada
Re: (dasher)
I have only a bit of experience with CF, but so far it is much easier to work with than fibreglass (which I have spent countless hours with). The main thing I dislike about glass is the resin and MEKP metering. 
But back on topic, I agree with dasher above concerning the number of layers to get a reasonable amount of strength. CF is much lighter IMO as a finished product than fibreglass and generally does not require a lot of bracing if any to resist warpage.
But back on topic, I agree with dasher above concerning the number of layers to get a reasonable amount of strength. CF is much lighter IMO as a finished product than fibreglass and generally does not require a lot of bracing if any to resist warpage.
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I havn't started looking into fiberglass or carbonfiber a whole lot yet, but i've been curious as to how you guys select which weight fabric and how many layers would be needed for each application?
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Re: (WhiteSol)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by WhiteSol »</TD></TR><TR><TD CLASS="quote"> The main thing I dislike about glass is the resin and MEKP metering.
</TD></TR></TABLE>
If metering the MEKP is bothersome you can use epoxy with your glass lay-ups. It is slightly more expensive than either a vynyl ester resin or polyester resin though.
</TD></TR></TABLE>
If metering the MEKP is bothersome you can use epoxy with your glass lay-ups. It is slightly more expensive than either a vynyl ester resin or polyester resin though.
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Re: (dasher)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dasher »</TD></TR><TR><TD CLASS="quote">
Their is some really bad info going around in this thread.
The weight savings from CF comes in the fact that you can use much less layers than glass. This means that you can use much less epoxy/resin in your layup where most of the weight is found.
</TD></TR></TABLE>
true, if the cf develops to it's max potential (about 2-3x the UTS of e-glass?), you can use fewer plies which means less resin sandwiched between plies
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dasher »</TD></TR><TR><TD CLASS="quote">
When I fabricated body panels It would sometimes take me 10-12 layers of glass to match 1 layer of CF in strength and rigidity. </TD></TR></TABLE>
not to call you a liar, but I doubt 1 ply of cf has the strength of 10 plies of fg of similar weave and resin matrix - stiffness, perhaps, but not strength (understandable as rigidity is more important in a hood than max strength). You can probably get 40kpsi uts for e-glass with relative ease, are you saying that cf can make 400kpsi uts?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dasher »</TD></TR><TR><TD CLASS="quote">
Where are you getting your info from if you don't mind me asking? </TD></TR></TABLE>
a couple of books, like Composite Basics by Marshall (should be considered mandatory reading) and a couple dozen lab hours of EAA workshops doing foamcore setups and jointwork
lastly, comparing a 7# cf hood (which would be top notch race quality) vs. a 15# cf skinned, fg skeletonned (probably chopped mat) bling hood with a 2# gel coat is not an accurate representation of cf's advantages over equivalent weaves of fg. Not to mention that the 7# hood would likely be of a much lighter and far stiffer foam or honeycomb core construction
my original point was that the full benefits of cf are very difficult to be achieved by a home-builder, and that fg can be a FAR more economical solution for the average joe
Their is some really bad info going around in this thread.
The weight savings from CF comes in the fact that you can use much less layers than glass. This means that you can use much less epoxy/resin in your layup where most of the weight is found.
</TD></TR></TABLE>
true, if the cf develops to it's max potential (about 2-3x the UTS of e-glass?), you can use fewer plies which means less resin sandwiched between plies
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dasher »</TD></TR><TR><TD CLASS="quote">
When I fabricated body panels It would sometimes take me 10-12 layers of glass to match 1 layer of CF in strength and rigidity. </TD></TR></TABLE>
not to call you a liar, but I doubt 1 ply of cf has the strength of 10 plies of fg of similar weave and resin matrix - stiffness, perhaps, but not strength (understandable as rigidity is more important in a hood than max strength). You can probably get 40kpsi uts for e-glass with relative ease, are you saying that cf can make 400kpsi uts?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dasher »</TD></TR><TR><TD CLASS="quote">
Where are you getting your info from if you don't mind me asking? </TD></TR></TABLE>
a couple of books, like Composite Basics by Marshall (should be considered mandatory reading) and a couple dozen lab hours of EAA workshops doing foamcore setups and jointwork
lastly, comparing a 7# cf hood (which would be top notch race quality) vs. a 15# cf skinned, fg skeletonned (probably chopped mat) bling hood with a 2# gel coat is not an accurate representation of cf's advantages over equivalent weaves of fg. Not to mention that the 7# hood would likely be of a much lighter and far stiffer foam or honeycomb core construction
my original point was that the full benefits of cf are very difficult to be achieved by a home-builder, and that fg can be a FAR more economical solution for the average joe
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From: Somewhere in, FL, USA
Re: (Bjorn)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bjorn »</TD></TR><TR><TD CLASS="quote">
my original point was that the full benefits of cf are very difficult to be achieved by a home-builder, and that fg can be a FAR more economical solution for the average joe</TD></TR></TABLE>
Glass would be cheaper, especially with the prices of CF these days, but I still hold the opinion one should stick with Cf when building replacement body panels.
I agree with your opinion that one should practice with glass first.
I also think that one should stick with Glass when fabricating molded kick panels and sub-boxes.
IMHO it would be a complete waste of time fabricating a part made specifically for weight savings with the intention of using glass for the home builder.
Most home builders wont have a Pneumatic Chopper Gun or a gel coat spray gun which is where Glass really provides the ease of fabricating over CF. Instead they will spend a lot of time soaking a thick mat or multiple layers of glass cloth with really smelly polyester resin or the slightly better vinyl ester resin instead of epoxy.
The difference in cost when you factor in the huge difference in the amount of resin you would have to use vs epoxy with the Cf wet layup and the shear amount of glass needed vs CF to achieve the same strength and rigidity further dilutes the value of glass.
Some components wouldn't even be worth fabricating with glass because the weight difference is non existent like front quarter panels.
An amateur will not be able to fully take advantage of CF properties doing a wet layup vs vacuum bagging/RTM/autoclave/ect.. BUT the benefits are apparent enough , especially when ones original purpose is to "add lightness" to begin with.
my original point was that the full benefits of cf are very difficult to be achieved by a home-builder, and that fg can be a FAR more economical solution for the average joe</TD></TR></TABLE>
Glass would be cheaper, especially with the prices of CF these days, but I still hold the opinion one should stick with Cf when building replacement body panels.
I agree with your opinion that one should practice with glass first.
I also think that one should stick with Glass when fabricating molded kick panels and sub-boxes.
IMHO it would be a complete waste of time fabricating a part made specifically for weight savings with the intention of using glass for the home builder.
Most home builders wont have a Pneumatic Chopper Gun or a gel coat spray gun which is where Glass really provides the ease of fabricating over CF. Instead they will spend a lot of time soaking a thick mat or multiple layers of glass cloth with really smelly polyester resin or the slightly better vinyl ester resin instead of epoxy.
The difference in cost when you factor in the huge difference in the amount of resin you would have to use vs epoxy with the Cf wet layup and the shear amount of glass needed vs CF to achieve the same strength and rigidity further dilutes the value of glass.
Some components wouldn't even be worth fabricating with glass because the weight difference is non existent like front quarter panels.
An amateur will not be able to fully take advantage of CF properties doing a wet layup vs vacuum bagging/RTM/autoclave/ect.. BUT the benefits are apparent enough , especially when ones original purpose is to "add lightness" to begin with.
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