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Author: Subject: fiberglass vs aluminium
kastrato

posted on 27/6/08 at 05:00 PM Reply With Quote
fiberglass vs aluminium

Hello all!
I was wondering if a thin aluminium sheet is lighter that a fiberglass panel of similar size.
Thanks in advance





MK INDY fireblade

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mr henderson

posted on 27/6/08 at 05:02 PM Reply With Quote
It's going to depend on how thick the different materials are. For instance- 1.5mm aluminium would be the same weight as 6mm birch plywood

I don't have any figures for grp I'm afraid.

John

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kastrato

posted on 27/6/08 at 05:08 PM Reply With Quote
Thanks for the reply.
I was thinking to remove a couple of fiberglass bodywork panels off my car and replacing them with thin aluminium sheet (something like 1mm thick ones)
By doing this I think the car will be braced structurally and also will be lighter.
I am not sure about the lighter bit though that is why I am asking.
Also I was planning to paint them so they will weight a bit more than bare aluminium.
I hope this makes any sense





MK INDY fireblade

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BenB

posted on 27/6/08 at 05:34 PM Reply With Quote
I think the main problem in answering that question is it depends very much on unknown factors

- Thickness of aliminium sheet
- Grade of ally
- Resin used in GRP (polyester or epoxy)
- Type of matt used (CSM/woven/one thick sheet/ multilayer thin sheet)
- Forces applied to panel (twisting, pulling, bending)
- Method of attachment of panel to bodywork

However, all things being equal, most GRP bodywork panels are fairly non-structural polyester GRP. Replacing with aliminium (if you sikaflex and rivet it) will introduce some structural rigidity into the chassis for the same weight (or even a little less than GRP).

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BenB

posted on 27/6/08 at 05:35 PM Reply With Quote
And that's ignoring the fact that the care and attention in the way GRP has been laid up, bubbles removed etc can make a huge difference to the strength of the final piece....
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scoop

posted on 27/6/08 at 06:11 PM Reply With Quote
Are they stressed panels? If so go the ali way and bond and rivett. What you gain in weight will give you more rigidity. We are only talking tiny amounts in any respect. Are you racing it?
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tomblyth

posted on 27/6/08 at 06:25 PM Reply With Quote
just dont have that bacon sandwich and cup of tea before you race!
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martyn_16v

posted on 27/6/08 at 07:02 PM Reply With Quote
quote:
Originally posted by tomblyth
just dont have that bacon sandwich and cup of tea before you race!


Blasphemy!






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smart51

posted on 27/6/08 at 08:47 PM Reply With Quote
Fairly thin GRP (1 layer of 600 GSM plus gelcoat) is going to weigh 1.5kg per square metre minimum, about the same as 0.6mm aluminium. The bodywork I'm making is about 2.7 kg /m2 or the same as 1mm aluminium.
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907

posted on 27/6/08 at 09:33 PM Reply With Quote
Originally I was going to fit fibreglass front mudguards and rear wheel arches to my car,
then after having a bash (pun intended) at making my nose I decided to make ally guards and arches.

According to the kitchen scales, the Lolocost front guards that I had bought
and the 16g ally ones I made were exactly the same weight.

I will of course have reduced the ally down to 30g by the time I have polished them.

Cheers,
Paul G






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RK

posted on 28/6/08 at 02:48 PM Reply With Quote
I just bought some rear arches from a guy in the States. In order to fit the 13" wheels correctly, he added these overhanging flanges to the arch itself so it matches the contour of the wheel. They are HEAVY! Any 1 - 1.3 mm ally would be way lighter I am sure.

I am considering calling Carbon Mods again, since the front wings are so nice - and light. Hey what's a few extra hours of work for a nice car?

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kastrato

posted on 29/6/08 at 12:49 PM Reply With Quote
The car is only a trackday car never meets the road. All the interior is made out of carbon fibre plus wings etc.
The bodywork is the standard MK fibergrass panels.
So to make sure if I understand correctly
the ali side panels dont weight significant less but offer rigidity to the chassis.
So I shall go for it then..





MK INDY fireblade

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sebastiaan

posted on 1/7/08 at 09:09 AM Reply With Quote
Maybe you should have a look at usign dibond, a sandwich panel with two 0,3mm aluminium skinplates bonded to a PE core. My car has 2mm total bidond sides which weigh next to nothing. (and a flippin' heavy pinto ;-))

Look here

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kastrato

posted on 4/7/08 at 05:08 PM Reply With Quote
thanks for the reply do you have any ppics of that material fitted on your car because the website haven't got any pics





MK INDY fireblade

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:{THC}:YosamiteSam

posted on 5/7/08 at 02:22 PM Reply With Quote
i had to raise the boot box floor on my dax and after cutting the fibre glass off and replacing with 1.2mm ally i couldnt believe how much lighter it was! felt bout half the weight... far far lighter but can be hard to work into shapes specially curves
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mr henderson

posted on 5/7/08 at 02:44 PM Reply With Quote
quote:
Originally posted by :{THC}:YosamiteSam
i had to raise the boot box floor on my dax and after cutting the fibre glass off and replacing with 1.2mm ally i couldnt believe how much lighter it was! felt bout half the weight... far far lighter but can be hard to work into shapes specially curves


Quite often the fibreglass on kits is a lot thicker than it needs to be. I think this is probably due to the use of chopper guns for laying up the grp. It's quite easy for the operator to lay it on really thick, he just keeps on spraying

John






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kastrato

posted on 5/7/08 at 09:41 PM Reply With Quote
Thank you very much all of you.
You been really helpfull. I will proceed then to remove the side panels and replace them with ali ones.





MK INDY fireblade

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