carbon fibre question...
Discussion
neal1980 said:
How much lighter is carbon fibre over fibreglass on a bodyshell??
Is it still very very expensive?
Thanks
Neal
totally depends on lay-up technique, materials (not all carbons are equal) and matrix used, but on a like by like basis of strength it varies between "not a lot" and "substantially" Is it still very very expensive?
Thanks
Neal
Cost varies almost as much as weight, but it will be substantially more expensive than glass - as an example I've just been quoted £23 per sq/m for ~300gsm low temp pre-preg standard modulus 2 x 2 twill weave carbon (with fair discount if I buy 100m roll) whereas the last lot of 300 gsm woven glass I got cost more like £3 per sq/m
Davi said:
totally depends on lay-up technique, materials (not all carbons are equal) and matrix used, but on a like by like basis of strength it varies between "not a lot" and "substantially"
...tending toward the 'not a lot' end of the scale when it is used for bodywork. There's practical minimum in terms of lay-up thickness with any composite, just for general robustness, and the non-structural elements of bodywork on kit cars can't realistically be made much thinner in carbon than they can in glassfibre.I own the only Westfield FW400 built with full carbon fibre bodywork (as well as carbon fibre monocoque chassis, which they all had). The body mouldings are wet lay-up rather than pre-preg, but even so... you certainly don't go 'wow'! when you lift them off for the first time, either in terms of weight or stiffness.
For a structural monocoque/bodyshell, though - where stiffness is a major factor - it's a different matter.
not done the "take it to somewhere" route before personally, look for places in the yellow pages. If you have a boat builders close to you they are always a good bet.
Just to expand on Sam_68's comments a bit - it would be a good idea to have a look at what you have already (don't know TVR's methods). If they have used a heavy and overly thick hand lay-up technique using chopped strand mat and polyester resin, and you were to have those recreated with woven glass using VIP layup, that in itself could effectively halve the weight - going to carbon maybe end up with a bodypart weighing in at 1/3rd the original, BUT if your original part is a thin VIP layup of woven glass already then your savings are going to be minimal.
Of course if you are going for lightweight you may feel you can sacrifice some of the robustness of the panels if they are non-structural - I've seen a carbon bonnet made of just 2 layers of 200 gsm pre-preg carbon, which you could throw like a Frisbee with one hand it was so light.
Just to expand on Sam_68's comments a bit - it would be a good idea to have a look at what you have already (don't know TVR's methods). If they have used a heavy and overly thick hand lay-up technique using chopped strand mat and polyester resin, and you were to have those recreated with woven glass using VIP layup, that in itself could effectively halve the weight - going to carbon maybe end up with a bodypart weighing in at 1/3rd the original, BUT if your original part is a thin VIP layup of woven glass already then your savings are going to be minimal.
Of course if you are going for lightweight you may feel you can sacrifice some of the robustness of the panels if they are non-structural - I've seen a carbon bonnet made of just 2 layers of 200 gsm pre-preg carbon, which you could throw like a Frisbee with one hand it was so light.
TVR's are a pretty heavy wet lay-up in chopped strand mat/polyester grp for the most part (there is some very localised reinforcement in carbon around the screen, I think). My Griffith was really very good quality for a GRP bodyshell, but was similarly hefty.
It wouldn't be difficult to save a lot of weight by simply getting a new lightweight shell moulded using a thinner lay-up in GRP, but you'll run into a number of issues:
1) access to the moulds, now that TVR has gone belly-up
2) quality; the main reason TVR's lay-up is so heavy is to give decent finish, that doesn;t have ripples and doesn't craze the first time you roll it over a kerb.
3) stiffness; the TVR backbone chassis isn't brilliant and almost cerainly relies on the hefty shell for additional stiffness.
You could certainly overcome (3) by using carbon fibre, but the cost of having it done to a high quality would be extraordinary. If it's performance you're after, you'd be better pushing the TVR into the nearest canal and buying a second-hand Murcielago. It would work out cheaper...
Rumour has it that the main reason Westfield didn't build more than the first batch of my FW400 was that when they approached the tub manufacturers to renew the contract after the first batch of 10 or 12 (figures vary), they claimed the first batch had cost them far more than anticipated and upped the price to the point where the car - a simple 'Seven' type, remember - would have cost well into Porsche 911 territory.
It wouldn't be difficult to save a lot of weight by simply getting a new lightweight shell moulded using a thinner lay-up in GRP, but you'll run into a number of issues:
1) access to the moulds, now that TVR has gone belly-up
2) quality; the main reason TVR's lay-up is so heavy is to give decent finish, that doesn;t have ripples and doesn't craze the first time you roll it over a kerb.
3) stiffness; the TVR backbone chassis isn't brilliant and almost cerainly relies on the hefty shell for additional stiffness.
You could certainly overcome (3) by using carbon fibre, but the cost of having it done to a high quality would be extraordinary. If it's performance you're after, you'd be better pushing the TVR into the nearest canal and buying a second-hand Murcielago. It would work out cheaper...
Rumour has it that the main reason Westfield didn't build more than the first batch of my FW400 was that when they approached the tub manufacturers to renew the contract after the first batch of 10 or 12 (figures vary), they claimed the first batch had cost them far more than anticipated and upped the price to the point where the car - a simple 'Seven' type, remember - would have cost well into Porsche 911 territory.
Sam_68 said:
Rumour has it that the main reason Westfield didn't build more than the first batch of my FW400 was that when they approached the tub manufacturers to renew the contract after the first batch of 10 or 12 (figures vary), they claimed the first batch had cost them far more than anticipated and upped the price to the point where the car - a simple 'Seven' type, remember - would have cost well into Porsche 911 territory.
I hear this frequently, and it confuses me no end. Although I've not done any serious structural work in CF yet, I've made numerous parts out of it and although yes there is a cost implication in the materials, in the actual working process there is very little difference and the parts I've made from CF have not worked out anywhere near as expensive as one would expect from the stories.If the TVR is a wet lay CSM then IMO moving to woven glass and epoxy VIP would yield massive weight savings without any stiffness penalty - just getting a fibre ratio nearer 70% than typical wet lay CSM of 30%, epoxy having 3 times the specific tensile strength of polyester plus the additional strength of the woven glass. Add in some well thought out core material...
and then wonder why you've spent so much effort on a TVR
Still - if the TVR layups are that bad I'd have thought it quite easy to save ~100kg just by having any hinged panels made in a light carbon copy?
Edited by Davi on Thursday 20th December 18:54
Davi said:
Sam_68 said:
Rumour has it that the main reason Westfield didn't build more than the first batch of my FW400 was that when they approached the tub manufacturers to renew the contract after the first batch of 10 or 12 (figures vary), they claimed the first batch had cost them far more than anticipated and upped the price to the point where the car - a simple 'Seven' type, remember - would have cost well into Porsche 911 territory.
I hear this frequently, and it confuses me no end. Although I've not done any serious structural work in CF yet, I've made numerous parts out of it and although yes there is a cost implication in the materials, in the actual working process there is very little difference and the parts I've made from CF have not worked out anywhere near as expensive as one would expect from the stories.The chassis on my Westfield was one of the prototype batch, effectively made up of individual flat panels with a honeycomb core, rather as you would have made up an aluminum monocoque tub, but held togetther with CF tape instead of rivets. To have done another run of chassis in this way would have probably been way too time-consuming to be cost effective, and to invest in proper series-production moulds would have been incredibly expensive in tooling costs.
Davi said:
If the TVR is a wet lay CSM then IMO moving to woven glass and epoxy VIP would yield massive weight savings without any stiffness penalty - just getting a fibre ratio nearer 70% than typical wet lay CSM of 30%, epoxy having 3 times the specific tensile strength of polyester plus the additional strength of the woven glass. Add in some well thought out core material...
Agreed! Those techniques would result in a very substantial weight reduction. But even then, the cost would be pretty scary if you were having the work done for you. And there is still the potential problem of egtting access to the moulds, unless the Chimp/Griff generation tooling and moulds have been sold off to someone helpful?I'm not usually one for the 'brute force and ignorance' approach over weight reduction and handling as a means of making a car quicker, but in this case I have to say that it would make a whole lot more financial sense to ditch the Rover V8 and fit a Chevvy LS7, instead of messing about re-moulding the bodyshell.
Sam_68 said:
I think that it's mainly that the costs spiral when you get into professional production techniques of complex components with vaccuum baggings and autoclaves, with highly paid, skilled staff. There's a world of difference between a simple moulding for a non-structural panel or a wing, or whatever, and a chassis, where you have to be moulding in hardpoints in precisely jigged positions.
The chassis on my Westfield was one of the prototype batch, effectively made up of individual flat panels with a honeycomb core, rather as you would have made up an aluminum monocoque tub, but held togetther with CF tape instead of rivets. To have done another run of chassis in this way would have probably been way too time-consuming to be cost effective, and to invest in proper series-production moulds would have been incredibly expensive in tooling costs.
Of course, some very valid points there - also a very interesting construction method for the chassis you have... I can see an easy adaptation of my CF chassis design to take advantage of that to save on moulding The chassis on my Westfield was one of the prototype batch, effectively made up of individual flat panels with a honeycomb core, rather as you would have made up an aluminum monocoque tub, but held togetther with CF tape instead of rivets. To have done another run of chassis in this way would have probably been way too time-consuming to be cost effective, and to invest in proper series-production moulds would have been incredibly expensive in tooling costs.
Sam_68 said:
Agreed! Those techniques would result in a very substantial weight reduction. But even then, the cost would be pretty scary if you were having the work done for you. And there is still the potential problem of egtting access to the moulds, unless the Chimp/Griff generation tooling and moulds have been sold off to someone helpful?I'm not usually one for the 'brute force and ignorance' approach over weight reduction and handling as a means of making a car quicker, but in this case I have to say that it would make a whole lot more financial sense to ditch the Rover V8 and fit a Chevvy LS7, instead of messing about re-moulding the bodyshell.
Can you not try and loose some weight somewhere else? I took a lot of sound deadening off my lotus which saved a few kilo's.
Is the TVR standard i.e. got all the factory interior, lighter seats will save a few kilos.
Carbon copies would be pretty wicked and look good if exposed but expensive.
Is the TVR standard i.e. got all the factory interior, lighter seats will save a few kilos.
Carbon copies would be pretty wicked and look good if exposed but expensive.
Gassing Station | Kit Cars | Top of Page | What's New | My Stuff