i somehow dont think i will get anywhere near the kind of weight where traction becomes a problem.

With a roll cage in place the inner crash structure is just "additional" to the roll cage and hence dead weight.  The cage along provides sufficient protection to meet FIA protection levels so more than good enough for a track car.

unibody autos
the cosmetic skin of the weld on panels are not structural panels.
25 years collision repairs i know what i am speaking of.
bolt on panels no issue make from CF. as for the inner structure i would not go nuts with a hole saw on it.
also consider if you make vehicle too light then you have traction issues because less ground pressure for tire grip.

good luck and nice pics!


scott

CarbonFiberCreations

My car has already been through the SVA test as it was built from a new customised shell for 4wd so is technically registered as a kit car and was given an age related plate for the donor parts that were used.

the rules are a bit funny.  Had i converted an old ford puma to 4wd wether i used a new shell or not, id end up on a Q plate because the rules say you must use a new and unmodified monocoque to retain the original vehicles identity.  However as i was creating a new vehicle identity, it didnt matter what a new shell looked like as it is considered on its own merits and the allocation of age related, new reg or q plate is solely determined by the mix of new or old componants.

strange how you can end up with 2 identical cars, one on a q and one on a age related plate all because one tried to retain the original ID.

Although these days under IVA i wouldnt be able to call it a "ford puma" but something else on the reg documentation as it wasnt  manufactured by ford so i cant claim it is.  They are a bit more hot on that these days. indeed it happens quite often with rally cars that you buy a kit conversion off the manufacturer and it has to go through IVA if it isnt homologated in other ways to be road legal between stages. Not so common these days but in the late niineties it was very common.

the joy is with kit cars or any one offs, there are no "manufacturers specifications" for type approval so much of the componants (and things you later modify) fall outside of the scope of the rules as they cannot be considered "altered from manufacturer specification" when no such specification exists!!

As you are making significant changes to the standard chassis, technically you stand a very high risk of requiring an IVA to be road legal and you will end up on a q plate.

I dont have a chassis jig or a engineering workshop to do that myself.

Would you not be better building a space frame in CDS or chromoly and then using an entire composite shell.  Have a look at some pro-mod / pro-stock door slammers for inspiration.

its mostly for trackdays and because i can. Its possible so why not??

All of my panels will have kevlar in the mix somewhere to stop break up of the panel in a crash and reduction in fragmentation and splinters flying around.

In terms of replacing the floor panels, ive already considered additional bars to the roll cage, eg sill bars, cross floor bars etc.  The floors will the last bits done as they are the hardest.  It may turn out easier once i get that far to have the complete sills cut out and replaced with largish diameter tube then have the floor between tunnel and sill tube cut out that way and it fabricated just like a cage.

Depending on how flexible my local scrappy is, i might buy half a shell cut where i need it and strip it in the back yard, or strip down a scrap yard shell over a few days.  Those panels are luckily small enough to do on the kitchen table and relatively simple shapes to mould so ideal when the summer fades away and im stuck in the house in the evenings.

If its being used in regulated motorsport have you checked what limitations the current and any proposed regulations place on removing/replacing material?
These mods would not be allowed in rallying but may well be ok for what you intend.
Taking material out behind the B pillar is pretty safe as its behind the safety cell, lots of scope for just removing material on the inner skin and also getting rid of material higher up has a CoG advantage as well as weight.
For the panels you may want to think about including some kevlar in the mix - roof, rear quarter, door, front wing, bonnet and boot are all good candidates for weight saving, particularly in modern cars.
Personally I'd leave the floor as is (at least from B pillar forwards) the contours in the pressing still give a fair amount of strength for torsional rigidity and also side impact protection.

Sounds interesting and looking forward to seeing further photos.

Stuart

I dont doubt the roof is rigid especially when bonded on 4 sides. However, even fairly stiff thin flat panels for a car side and roof would flex if there was no other support or connection to the body. Ie you could put your hand on the B pillar and probably visibly flex the body work as a whole.

By me retaining the internal frame work but in composite, it would be at least as stiff as the original thin pressed steel but with massive weight savings.

i work for a bmw approved bodyshop here in oz i can garantee that the carbon roofs on m3's are pretty rigid! bmw are also testing an electric 1 series at the minute thats built just using aluminium and carbon fibre in the structure