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Anyone on here good with carbon?
alistairolsen - 17/1/11 at 03:13 PM

I've done a bit of GRP moulding in the past but fancy a foray into carbon to try something new and hopefully make some nice lightweight parts. Ive done CSM and polyester, and some woven cloth and epoxy so Im not entirely new to it, but any advice would be greatly appreciated!

First off, if I want a similar stiffness to grp, how much can I cut back the thickness? (for wet lay, not going to have vac bag or autoclave facilities, certainly initially)

Secondly, there seems to be a huge variation in cloth prices, from 5 to 30 quid a metre for what seems to be essentially similar stuff (plain weave 2 or 300gsm...)

Where are the current cheapest places to get good quality stuff? both cloth and resin. Ive used SP systems and West epoxies in the past and got on well with both, not sure what else is out there, but while chandlers is ok for small packs, for bigger quantities it gets expensive.

Can anyone recommend any online resources for resin ratios and suchlike? I've got competition car composites but its on my "yet to read" list!

I assume that laying out the cloth to get nice cosmetic weave layout is a case of disturbing the cloth as little as possible when cutting it. How do you go about concealing joins and edges, for instance where you would cut the cloth to fit a curved surface? Ive done cloth for curves in glass but obviously gelcoat and paint cover a lot of sins!

Cheers for any advice!

fesycresy - 17/1/11 at 03:25 PM

Try this.......

flak monkey - 17/1/11 at 03:41 PM

Steve Hignett is your man, and I am sure he will be along shortly

blakep82 - 17/1/11 at 03:46 PM

steve hignett and clairetoo know a few things

coozer - 17/1/11 at 03:50 PM

Going a bit off topic there Alistair I want to 'tub' out the floor of my Jago body. Have you done anything like that?

Steve

clairetoo - 17/1/11 at 04:56 PM

A few tips here

CNHSS1 - 17/1/11 at 05:51 PM

Personally, making carbon look pretty is a lot of ballache for what essentially is paddock pose rather than performance
trying to get wet layup carbon without distorting the weave is hard work, 99% of pro stuff is domne with prepreg so it has a definite form in its pre cureed state, so much easier to keep the weave straight.

for making lightweight effective panels though, keeping the resin to a minimum is the key imho. Thats wheer prepreg wins, as its got just the right amount, no more, no less, but for the DIYer its a sod due to storage life span, temps etc and of course its not as easiliy available.

vac bagging wet layups with bleed bag layer and the 'blotting' fluffy layer, removes the vast majority of excess resin from a wet lay product, which keeps the weight down and strength up.

A lot of the hillclimb guys are very good at getting mega results from wove glass, close to carbon weights at a fraction of the cost, but of course doesnt give the 'carbon tart' look

imho its all in the technique. Generally each time i make a moulding from a mould, you get better at squeezing the weight down. CSM is resin heavy of course, but someone like East Coast fibreglass will recommend wove (carbon or glass) thats less resin hungry.

Also worth looking at the item youre making. Rolling curves, or additional fillet or rib, can make the item stiffer and allow you to drop 10-20% weight/resin cloth from the original moulding.

Gelcoat is also mega heavy for what it is. If its not a show panel, keep to a minimum or do without it.

reading McBeaths book is a must before you go any further, has excellent charts for strength to weight properties for all products inc boron, carbon kevlar E-Glass, wove and CSM.

alistairolsen - 18/1/11 at 08:24 AM

quote:
Originally posted by coozer
Going a bit off topic there Alistair I want to 'tub' out the floor of my Jago body. Have you done anything like that?

Steve


You mean like tubbing wheelarches in a conventional steel build like widening them inwards? Not done it on a Jago, but if you carefully cut the inner arch, move it inwards and wrap a polished band of thin grp into the underside you should be able to make a nice job of it. I suspect (from memory) that the chassis rails will limit you though!

quote:
Originally posted by CNHSS1
Personally, making carbon look pretty is a lot of ballache for what essentially is paddock pose rather than performance
trying to get wet layup carbon without distorting the weave is hard work, 99% of pro stuff is domne with prepreg so it has a definite form in its pre cureed state, so much easier to keep the weave straight.

for making lightweight effective panels though, keeping the resin to a minimum is the key imho. Thats wheer prepreg wins, as its got just the right amount, no more, no less, but for the DIYer its a sod due to storage life span, temps etc and of course its not as easiliy available.

vac bagging wet layups with bleed bag layer and the 'blotting' fluffy layer, removes the vast majority of excess resin from a wet lay product, which keeps the weight down and strength up.

A lot of the hillclimb guys are very good at getting mega results from wove glass, close to carbon weights at a fraction of the cost, but of course doesnt give the 'carbon tart' look

imho its all in the technique. Generally each time i make a moulding from a mould, you get better at squeezing the weight down. CSM is resin heavy of course, but someone like East Coast fibreglass will recommend wove (carbon or glass) thats less resin hungry.

Also worth looking at the item youre making. Rolling curves, or additional fillet or rib, can make the item stiffer and allow you to drop 10-20% weight/resin cloth from the original moulding.

Gelcoat is also mega heavy for what it is. If its not a show panel, keep to a minimum or do without it.

reading McBeaths book is a must before you go any further, has excellent charts for strength to weight properties for all products inc boron, carbon kevlar E-Glass, wove and CSM.

Cheers ladies and gents!

Ive watched all of carbon mods videos 

Can anyone offer any advice on layup? Claire, what do you use for your trumpets? What would you use for say a nose cone or bonnet?

Where do you all get your materials?

Im interested in all the wee tricks like using spray adhesive to hold the fibres in place and so on, the small things you wouldn’t immediately think about!

I agree on the paddock pose factor, but while not imperative it would be nice to be able to do a decent job cosmetically too. Im less interested in ultimate performance (would go prepreg for that) and more the process, for experience (give anything a go)

Yeah, prepred IS the answer, but not in a home garage sadly!

Vac bagging is something Id like to try ultimately, but probably not for a first try! It requires a bit of further investment in both materials and clean space.

How do they do it? I know the density difference isn’t enormous, but surely there is an advantage? Or do you mean that while huge in percentage terms (say 0.5kg in a 3kg nose) it’s still only 0.5kg heavier and £200 cheaper…..

Yeah, CSM has it’s purpose but that purpose is not finished panels moulds, sub boxes and cheap consumer grp is about it.

How do you mean rolling curves? You mean modifying the shape to include double plane curves for stiffness?

Yeah, I detest gel tbh and have laid up panels without before. From what I read about carbon, generally a thin coat of basic epoxy is all that’s needed?

It’s the next one in the pile!

Cheers

CNHSS1 - 18/1/11 at 10:22 AM

Can anyone offer any advice on layup? Claire, what do you use for your trumpets? What would you use for say a nose cone or bonnet?

Where do you all get your materials?

Im interested in all the wee tricks like using spray adhesive to hold the fibres in place and so on, the small things you wouldn’t immediately think about!

I agree on the paddock pose factor, but while not imperative it would be nice to be able to do a decent job cosmetically too. Im less interested in ultimate performance (would go prepreg for that) and more the process, for experience (give anything a go)

Yeah, prepred IS the answer, but not in a home garage sadly!

Vac bagging is something Id like to try ultimately, but probably not for a first try! It requires a bit of further investment in both materials and clean space.

How do they do it? I know the density difference isn’t enormous, but surely there is an advantage? Or do you mean that while huge in percentage terms (say 0.5kg in a 3kg nose) it’s still only 0.5kg heavier and £200 cheaper…..

Yeah, CSM has it’s purpose but that purpose is not finished panels moulds, sub boxes and cheap consumer grp is about it.

How do you mean rolling curves? You mean modifying the shape to include double plane curves for stiffness?

Yeah, I detest gel tbh and have laid up panels without before. From what I read about carbon, generally a thin coat of basic epoxy is all that’s needed?

It’s the next one in the pile!

Cheers



i use East Coast Fibreglass mostly, great service and really useful advice and carraige on quantities are pretty good. Always try and place a large order, rather than little ones regularly, coz the carriers screw you!

You can with practice get a pretty good cosmetic finish with a bit of practice and forethought (cut patterns of shapes in paper and tape together to ensure you have max coverage with min material, before you start cutting cloth)

apply resin with a fluffy roller (buy from grp supplier, often resin attacks the glue on 'normal' paint rollers and they fall apart in the resin!). Cover evenly and sparingly.
Wet out the cloth on a resin board swiftly (hardborad shiny side up) and try not to make the cloth sodden or the weave sags and its like platting fog!
drop into place and add all the other sections. If no gel used, use ally roller paddles for at least twice as long as you think you need to, to get all the air bubbles out. Weaves are worse for trapping air, csm is easy to get the bubbles out of, weaves progressively harder.
for strongest lightest components, lay up in one go, adding bits after cure will always be weaker.

being accurate with cloth cutting, minimum resin to cloth (difficult to get right without oin holes if carbon to be left unpainted) and practice. Vac bagging helps a lot, but as you say is an investment in time and additional cost.

basically no large flat areas. design in a curve slightly convex, or fit a rib underneath to support.
i use foam coremat a lot. Bulks out panel thickness, adds strength but with vey little additional weight providing you dont go mad with resin! its like a sponge and will absorb lots, but basically doesnt need it. Just a surface damp with resin (wetted out cloth), give the core the briefest run over with a resin damp roller and then apply. i dont usually add any more resin to the top surface, just drop a wetted cloth over the top to compelte the sandwich. Give a quick roller on top but not too much or you push all the resin from the top layer cloth into the cora and compromise the strength of the upper layer of cloth.

alistairolsen - 18/1/11 at 02:44 PM

quote:
Originally posted by CNHSS1

i use East Coast Fibreglass mostly, great service and really useful advice and carraige on quantities are pretty good. Always try and place a large order, rather than little ones regularly, coz the carriers screw you!

You can with practice get a pretty good cosmetic finish with a bit of practice and forethought (cut patterns of shapes in paper and tape together to ensure you have max coverage with min material, before you start cutting cloth)

apply resin with a fluffy roller (buy from grp supplier, often resin attacks the glue on 'normal' paint rollers and they fall apart in the resin!). Cover evenly and sparingly.
Wet out the cloth on a resin board swiftly (hardborad shiny side up) and try not to make the cloth sodden or the weave sags and its like platting fog!
drop into place and add all the other sections. If no gel used, use ally roller paddles for at least twice as long as you think you need to, to get all the air bubbles out. Weaves are worse for trapping air, csm is easy to get the bubbles out of, weaves progressively harder.
for strongest lightest components, lay up in one go, adding bits after cure will always be weaker.

being accurate with cloth cutting, minimum resin to cloth (difficult to get right without oin holes if carbon to be left unpainted) and practice. Vac bagging helps a lot, but as you say is an investment in time and additional cost.

basically no large flat areas. design in a curve slightly convex, or fit a rib underneath to support.
i use foam coremat a lot. Bulks out panel thickness, adds strength but with vey little additional weight providing you dont go mad with resin! its like a sponge and will absorb lots, but basically doesnt need it. Just a surface damp with resin (wetted out cloth), give the core the briefest run over with a resin damp roller and then apply. i dont usually add any more resin to the top surface, just drop a wetted cloth over the top to compelte the sandwich. Give a quick roller on top but not too much or you push all the resin from the top layer cloth into the cora and compromise the strength of the upper layer of cloth.


Ive done paper templates for glass cloth before, any advice on how to lose the edges? easyish on something with defined corners but say a nosecone, how do you avoid seeing the joins prominently?

Interesting to hear you wet it out before application, id have thought that would make life more difficult but I guess it becomes a little like prepreg if its done right.

Do you calculate resin weight for an ideal resin/fibre ratio and add a little, or weigh out more than you need and try to use as little as possible? in other words how close to ideal can you get?

only flattish area I will have is the bonnet and its hard to reinforce due to lack of clearance. What layup would you use for a bonnet in carbon? resin, let it go tacky, 2 layers of 200gsm weave, 5mm coremat and another layer of 200gsm in the right ballpark?

Cheers for all the advice!

CNHSS1 - 18/1/11 at 03:56 PM

theres no pretty way to hide the edges imho, at least i havent found the way! TWR Volvo touring cars used to paint black gelcoat 'lines' in a pattern on the mould, and then hide the joins and overlaps under the black gel lines. Looked pretty good, sort of making a design feature of a problem as it were. Probably easier to paint them on the outside of the finished moulding and then high gloss laquer over the top to give a nicer tart finish

as for wet out, its pretty quick, run over the cloth with the damp roller on a damp board (not resin loaded) and throw into the mould. Dont leave it to wet out properly or it is like platting fog, no mechanical form at all. If you put it in dry, you run the risk of too many air bubbles or end up putting more resin on the surface before the dry cloth goes down. Just my experience, im sure theres a better way. Carbon cloth and all weaves to a certain extent, dont wet out as well as CSM, and often epoxies are more reluctant to wet out than polyester resins. Its such a fine line between lightweight and pretty, and i doubt you will get the balance right every time (i never have lol)

No i dont calculate it, sort of wing it. You get to know how a cloth wets out, and how certain resins flow. Again im sure Simon McBeaths book will have better guidlines.

In my opinion, theres no better way than having a go on a smaller moulding. Time yourself start to finish too, gives you a timeline to work with. I usually mix approx litre to 2 litres of resin at a time, and pour into a large painting tray. larger surface area slows exothermic reaction and slows 'gel' time. Only gives you a few extra minutes, but all worth it!

is it a bonnet for a locost? if so the actual 'flat' centre section is pretty narrow.
Your estimates of cloth should give you a stiff enough bonnet. if i was a betting man, i would guess you could go 300gsm/3mm coremat/200gsm and that would be OK, but you will only know by trying it.
my grp mentor is a mate that builds & races yachts for fun, and one of his fave sayings is 'appropriate technology', meaning if it needs weave use weave, if it doesnt, use CSM etc. He tends to use tows to strengthen areas in tension, or a different twill weave juts in the small areas, rather than the whole panel. Generally ive slapped together a first mould panel and ruin it on the car, seen where it flexes, star crazes or if its too heavy, and then made the 2nd panel using that knowledge as the one to use, keeping the mk1 as a spare when the scenery gets *ahem* too close....
using DIY methods, i cant see a way to get the construction parameters perfect without a sacrificial Mk1 panel.