I have embarked on making an undertray running the whole length of my car. I was just going to use plywood but I got ambitious and found some cheap(ish) kevlar.... I made a few practice bits using vacuum bagging. It is not as easy as the interweb tends to suggest and I messed up a few parts. But having just about succeeded with a dashboard I decided to make the front section...pictures below.

First I used a wooden board to mark out the mounting points. I put aluminium inserts in the board and bolted it to the car to test. I then put a Polypropelene sheet over that and drilled through. Inserts were turned up out of Aluminium (7075T6 - bar ends from ebay). I used the remainder of the sheet to form the edges of the mould and then uses wax (the yellow stuff) to make a fillet. This is what the mould looked like once the part was out.

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I then used carbon fibre and Kevlar to laminate. This was by far the biggest thing I have done with composites and it took nearly 2 hours to lay up - all the time I was paranoid it would start to go off. Between the laminate I used PVC foam to provide reinforcement. This is good stuff - I was able to sand and shape the edges to match the wax fillet and to make it easier to lay over the fabric by rounding the edges.

I then stuck the whole thing in a vacuum bag


Front splitter/undertray

It leaked! I had run out of the breather fabric and had not covered all the sharp edges. Much gum tape later and it held a reasonable vacuum. Small problem was that it was now 10pm - family a little ratty that I refused to turn off the vacuum pump all night - on the bright side the cat did return today..

The moment of truth last night

First off with the bag and peel ply


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Then out of the mould - small problem whilst the part just fell off the polypropelene (no wax at all) I had bonded the polypropelene with hot melt glue around the outside. The excess fabric was shall we say very well bonded....I cut it off with a dremmel. After that it just popped out. What appear to be scratch marks are actually just sticky masking tape that I wrapped around a ruler to prise the part out. It polished off (phew).


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I have done a rough trim so far - I had to use the cutting disc in the angry grinder. I then fitted the support frame just to make sure that it would fit. It did!


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I am really pleased. I know that a front splitter is generally considered a disposable item and so Carbon fibre is a bit OTT but hey so is the rest of the car. All the materials together were just over one build your own sportscar.

I will bond this section to the next 1m wide section using glass reinforcement so that as and when it gets bashed to bits ripped off etc I can just saw off the front and make another one. Now I just need to find somewhere to put the mould.

I will put some helicopter tape on the underneath to see how long that lasts..

Good work

Nice effort! That is carbon - not Kevlar (unless you have sandwiched the Kevlar under the carbon?)...

If you make another, I would suggest you try resin infusion - your part will be higher quality (fewer voids) and it is likely to be lighter (less resin rich than hand laminating/vacuum bag).

Good job!

Too scared to try infusion! I get too many leaks. The laminate is carbon x 2/kevlar x 2 /carbonx2. Cutting Kevlar is such fun...

nice work very cool

Looks great

thats awesome, I know who'll Ill be ringing when I need one...

@ TIMMY

Could you make one at work?

Nice work - it encourages me to do some bits of my own in carbon.

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Originally posted by omega0684
@ TIMMY

Could you make one at work?

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quote:

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Originally posted by twybrow

quote:

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Originally posted by omega0684
@ TIMMY

Could you make one at work?

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Yes mate - my boss is very receptive to little side projects (he has a kit car himself)... We are moving into our new building (office + workshop) next month, so the projects will pick up after then!

And I just took an enquiry for us to design and build CF wheels (automotive) - hmmmmm!

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That looks nice! I'd be worried about infusion on such a flat wide piece personally, because I've never done it, any tips add to how to ensure a complete infusion up to corners etc?

PS hope you are wearing appropriate PPE when cutting/grinding carbon!

[Edited on 27/5/13 by coyoteboy]

Errrm cutting in the garden and keeping my mouth closed??? More seriously I must get some masks and glasses - I did get some bifocal safety specs which are very good for machining (you can read a micrometer) but.....sat on them.

Carbon fibres, especially those cut with a grinding tool rather than a saw and water, produce fibre dust with similar properties to asbestos.

http://www.aerotherm.co.uk/the-hidden-dangers-of-carbon-fibres

Oh dear

That said given that most of my education was in post war portacabins I am probably screwed anyhow. That and I worked in a garage for years blowing out the brake dust and working alongside the sprayer blasting out 2 pack....... No, I know I will get some masks.

Don't worry, I've done the same too before it was pointed out to me by a H&S manager at a place of work - there must be millions of us!

Probably not a problem but worth taking reasonable precautions.