What sort of costs are involved in going carbon over glass! Im looking at doing a bonnet for the pulsar and tossing up doing it in carbon for the looks and weight saving.
But cost. how much more pricey is the carbon sheeting over equivalent strength glass! I havn't got any experience fibreglassing so dont wanna go play with carbon if its going to cost too much if I balls it up!
mgmad,
Nov 3, 8:44pm
Last time I looked, carbon was about 10x the price of glass, and the difference in weight between equivalent glass and carbon fabrics is not that much, so a for a non-structural component like a bonnet I'd just go glass - but get a good woven fabric and not a random mat.
gammelvind,
Nov 3, 8:53pm
You can buy carbonfibre looking material, 3M make it looks just like the real thing, much easier than making a new bonnet, and your mates will never know.
morrisman1,
Nov 3, 9:02pm
can I double the extra power by painting matt black on top of the fake carbon fibre! That would be fully sik az aye
Ive found some pricing on a nz store, $75 per sqm of 200g cloth, 1m wide. Compared to glass cloth which was $6 for the same. Id need about twice the amount when using glass from what I read.
With a lightweight glass bonnet for race, pinned at each corner and running reinforcement ribs around the edges, how many layers of 200g glass cloth should I use! for the main area! Ill put more around the securing points of course.
Also what sort of weight would you normally use of chopped mat for the mould!
kaymay88,
Nov 3, 9:15pm
based on this post, you will not be doing a carbon bonnet . . .
morrisman1,
Nov 3, 9:20pm
crawl back into your hole, gotta learn somehow and if everyone says "dunno how to do it so Im not going to" then we would still be banging rocks together for amusement.
Seeing as you think Im not capable of it, tell me exactly what makes carbon fibre so difficult to work with as opposed tofibreglass.
mgmad,
Nov 3, 10:34pm
I'd use continuous filament mat for a mould if you can find it, otherwise just whatever choppo you can find.
As for the bonnet design, you won't need much, probably 4 layers of 200 gsm woven glass. Personally I'd be looking at doing a sandwich panel with a thin (~5-10mm) foam core - in which case you may only need 2 layers of glass per skin. However, a lot depends on you manufacturing method - I presume you will be doing hand layup!
incar.,
Nov 3, 11:12pm
weights in the resin, so depending on how much resin you use will determing the weight, going light will also make it flex, there is a place in auckland that supplies retailers which you can buy carbon for about $60 a meter x 1.5m there is different grades of fibre to consider as well.
mgmad,
Nov 4, 2:17am
You're 100% right that there are many different grades of glass fibre around, and many many different fabrics to use - unidirectional, woven (plain, twill, harness weaves), stitched, different orientations and different areal weights.
However flex is determined by what resin you use - most are brittle, but there are some which are quite flexible - expensive though.
As for weights - glass fibre is ~2580 kg/m^3, carbon ~1770 and epoxy resins ~2250. So, assuming the same part volume (and hence thickness), a higher fibre volume fraction for carbon fibre will lead to a lighter part, but the inverse is true for glass. However, this is only applicable when the thickness is controlled - for hand layup and vacuum bag infusion it is not. In these situations you can reduce the weight of the component by reducing the amount of resin in the part (by using a roller in hand layup). This leads to a higher fibre volume fraction, and hence generally better specific properties - however the result is a lower part thickness. This is usually not a problem but does lead to lower bending stiffness which is why sandwich structures are the way to go.
bill-robinson,
Nov 4, 5:32am
the last time I did anything like this was with fibreglass doors for a capri. the glass doorwas 0.5pound lighter than the trimmed out steel door and a lot of work needed to fit same. Much cost not much gain but I built race cars for a living then. CF is lighter but requies more effort so it becomes a cost/peformance gain/BS factor.
wrong2,
Nov 4, 5:41am
the fact that you need a specialist pressure cooker to cure your CF item !
mgmad,
Nov 4, 6:32am
No different than curing a glass component. It's not the fibre that needs curing properly, it's the resin/
mgmad,
Nov 4, 6:32am
Why does carbon require more effort! More cost yes, more effort no.
wrong2,
Nov 4, 6:35am
you might be totally correct for basic items
but its probablly a different story for more complex structures
proper CF autoclavs are multiple hundreds of thousand dollar items
mgmad,
Nov 4, 7:41am
Autoclave prepregs are a different story, and still only dependent on the resin - the fact remains that the resin is independent of the fibre. The fibre doesn't cure!
kaymay88,
Nov 4, 8:38am
sigh, settle down sunshine, dont get shitty.
its alot more exoensive for the materials, alot more work, and if you want it to look right, you are going to need to use a more difficult process. There are plenty of youtube videos explaining whats necessary, if you look those up you will save me an awful lot of typing.
neville48,
Nov 4, 7:37pm
He's right matey, you probably are most capable of sorting it all out but by the time you do, unless you have guidance on hand it will have cost you mega-bux. It will cost you lots just for a pair of scissors capable of cutting your carbon fibre matt believe me. Buy a steel bonnet and 3M it with carbon fibre vinyl or whatever they call it or go ahead and make a mould for the bonnet [$400 at least for materials] then a carbon fibre bonnet, properly finished and chassised up with either pin supports or hinge fixings, then possibly have to get it certified because some drongo at the VTNZ wont warrent it, the dollars just keep leaving your pocket.but when you have acheived the skills of good fibre-glassing and mould making it is an excellent skill to have when working with and/or building modified vehicles, good luck.
spottie,
Nov 4, 8:04pm
Don't need special scissors to cut Carbon the special diamond coated ones are for Kevlar. If you only want the look of carbon you can get dyed glass fabrics that look exactly the same but cost a whole lot less than the real thing. Be aware that you will have to use a UV stabilised clear gelcoat if using a mould or a clear automotive paint over your resin if just glassing over your part. The comment on using continuous fibre mat for your mould will only work if infusing or using a compression type system with resin injection as CFM is not suitable for hand layup as it is not easily mouldable when wet unlike chopped strand mat which is easily mouldable when wet out. Also if you want the strength of carbon you will have to use either vinylester or epoxy resin, polyester doesn't have the strength in its makeup to match the carbons potential.
morrisman1,
Nov 4, 9:32pm
thanks guys. I have priced up materials and it seems like its going to cost around $300 all up including making the mould. I hope I have accounted for everything. I also want to make a front air dam & splitter too, but that will be once I have gotten familiar with fibreglass as its not a nice flat panel!
This car isnt on the road so it doesn't need to meet cert requirements or anything like that, as long as it holds its shape with the minimum possible weight.
bill-robinson,
Nov 5, 10:39am
weigh both when finished and post please, and keep anote of your time so we can see if it was worth it.
bill-robinson,
Nov 5, 10:43am
PSremember the fire risk as well
noswalg,
Nov 5, 10:48am
Not always about the money, there is also the the satisfaction of achieving something yourself, you cannot put a dollar value on knowledgeand as morrisman said earlier you gotta start somewhere, I say good on him for giving it a go. I've tried a few things myself that probably cost me twice as much, took twice as long and looked half as good but I still got satisfaction out of completing the job
bill-robinson,
Nov 5, 1:05pm
where did I mention money! i wondered if the performance increase due to a decrease in weight was worth the time and effort. no cost just performance gains.
doug207,
Nov 8, 12:09am
I pay $50m2 or so, depending on the dollar for carbon If you're doing it the cheap way, just buy a few m2 of a finer weave (easy to work with) and lay it on top of a glass fibre bonnet Or the reeeeeaaaaaaal cheap way is to buy woven black glass fibre cloth. some poeple tell me it looks the same (it does when you close your eyes)
There are countless weights and weaves with carbon, do your research composites nz may help (I think that was their name)
raymond00001,
Nov 8, 11:47am
If your doing it for the looks.Don't. You won't get 'the look' from a home job as it will be riddled with air bubbles, thats why most fibreglass stuff like boats etc has gelcoat. To get the wow factor look from carbon fibre it has to be the expensive prepreg stuff dont in an autoclave. While it looks easy, preparing a proper mould and laying a up a finished product is a specialised job even with fibreglass.
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