Homemade CFRP mid engine sports car

Spent most of the last week making lots and lots of little brackets for suspension mounts. Fitted the front suspension, went mostly ok, I was worried the inserts in the tub might have drifted a bit but everything seems in the right place. Still need to machine some brackets to lift the steering rack to the right height before i can fit that.

Also moulded one of the rear end inner panels. I used high temp resistant epoxy as will be close to the exhaust, this stuff is more viscous so has to be hand laminated, a messy job ! once i've moulded the other side too i'll post cure them both under an IR lamp. Need to make some inserts to fit under them before fitting.

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Chris Kouba

Supporter
Paul,

Fantastic work! Can you share more regarding how you locate/secure the suspension/rack/etc inserts when laying up the tub? That part of composite construction has always fascinated me- the application of point loads on sheet surfaces and how you get the metal and composite to remain reliably bonded. How is it done?

Chris
 
Thanks guys, Chris the main thing with the inserts is to get a large surface area, big enough so that the load to pull it through the CF is larger than the bolt strength (circumpherence of insert x thickness of CFRP x CFRP shear strength) . The biggest challenge i have is alignment, on a normal professional build all the holes would be machined on a big multi axis machine at the end, but since i don't have that luxury i used 3d printed frames to hold the pre-drilled inserts in place during the layup stage. post #64 shows some photos. The pockets in the tub surface for the wishbones also help mechanically lock the frames more or less in place too. This whole thing is not super accurate so there is a level of adjustment with oversized holes in the wishbone brackets too.
 
It is always absolutly amazing how clean your built is with such a DIY tecnology !!!!
congratulation to you and .... Kids !!!!
 
Thanks Michel !

progress update, finished the flanges between rear bulkhead and floor/sill on the cabin side. As these will be somewhat visible I moulded real parts and bonded & riveted them in. I find my 3d printer is great at quickly making small moulds. On the other side (engine bay side) i'll just wet lay some flanges.

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On the rear I have finished off the rear longitudinals. I bonded in metal inserts for the upper cross-members and engine mounts. The engine mounts took a lot of fine adjustment to position so that they sit properly against the inner panels, once positioned I wet laid some CFRP to secure them against the outer structure (tub) and to form a flange for the inner panel to join to. Then bonded the inner panels on, and then afterwards went over the lower edges with extra wet layup flanging.

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Next steps .. I want to mould the rear cross-members but there seems to be some kind of supply chain shortage of high temperature laminating epoxy. Instead I think i'll make the front nose box and maybe try test fitting the front and rear body panels, get hinges etc in place. After that, maybe doors or rear suspension pieces.

Some of you may be wondering why i've left it so late for getting an engine in place to ensure it fits, in truth this is because i'm very worried about future IVA rules (given how long a project this will be) and so am trying to keep my options open in case I want/need to switch this to some kind of EV project later down the line. I have many many many more areas I can work on before i hit a point of no return on powertrain options. Maybe by the time i am finally ready I can some kind of mr fusion power solution like from back to the future :)
 
Thanks Joel,
David - i don't find laying up with it itchy, but the dust from cutting or sanding can be. I do find that the fibres get everywhere though which is a pain.
Jim - The larger parts are made using vacuum infusion. Dry material goes in, vac'd down, then resin is pulled in and under the vacuum and fills the part.
 

Davidmgbv8

Supporter
I would love to see a wicked turbo diesel, that puts out great torque and would get great fuel mileage. Years ago I thought about getting a Fiero and dropping in a VW tDI to commute with.
 
end of 2022 update ..

Made and fitted the nose box, this serves as front crash energy absorption and will mount the radiator and front clip hinges. The sides are foam filled.

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Attached the rear body, made some CF support forks which bolt to the bodywork and then hinge to the lower rear body structure with rod end bearings.

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I was pleasantly surprised how well the rear body fitted against the mid upper body (I was certain that flex in the moulds would lead to distortion), but it matched pretty good. However .. my happiness was premature .. The rear body was not sitting straight, it would not have equally overlapped LH and RH rear tyres. When I bonded the mid body to the tub I was off by a few degrees. So .. I needed to do some 'aggressive adjustment' to the rear body, cut a slit and stretch the LH side by 10mm or so. Not a show stopper since i plan to fill/sand/paint it anyway, but annoying.

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Fitted the rear body stiffening braces. CFRP tubes, for the tube end fittings I tried a new process; compression moulded chopped CF fibre in a 3d printed mould. Turned out quite well, solid CF end lumps.

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Attachments

Continues to be one of the most interesting projects on the forum -
Seems like the perfect spot for radiators would be the two huge openings in front of the rear wheels (?) This will give some 'trunk' space up front and keep residual heat out of the passenger compartment.
 
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