Kulot914 New Reader
6/29/23 9:16 p.m.

So as we all know most used material in supercar chassis is CARBON FIBER but I do have questions regarding the manufacturing and design of it ,there's a bunch of FORMULA SAE,car brand assembly lines videos on youtube and it just shows the process of it being assembled and it isn't that detailed I wanna know the design aspect of a monocoque chassis how is it designed like if its hollow or there is bracing inside the chassis and likewise to vintage le mans cars that uses aluminum monocoque chassis.

so feel free to drop any info you have about the DESIGN ASPECT of BUILDING A MONOCOQUE CHASSIS

78CobraII Reader
6/30/23 2:47 a.m.

There are lots of carbon fiber projects that can be done at home by a hobbyist, but designing and building a carbon fiber monocoque supermarket chassis is not one of them.

The college SAE projects are usually done with lots of University Engineering Department resources and corporate support.

Even the small CF projects on YouTube involve multiple types of fabric, resins, mold-making, vacuum bagging, curing ovens, etetcand weeks of effort. Scale that up to a full monocoque chassis and you are looking at an industrial scale project.

Kulot914 New Reader
7/3/23 4:50 a.m.

we run a body shop that works all types of composites and metals and even then theres no harm in trying yes i know money wise is a problem but we shouldnt worry about that I am here just to ask if there is any internal structures INSIDE the monocoque chassis not about the SAE's or other projects


7/3/23 7:22 a.m.

In reply to Kulot914 :

I have often had the same thoughts about carbon tubs: How do you make structural attachment points for stuff like suspension or even interior bits that need to bolt to the carbon?

In my grassroots vision, I would be making a bathtub shaped structure with a tunnel down the middle and attaching metal subframes front and rear for suspension and drivetrain. So perhaps not a true Carbon car, but an easy shape to make. Unless you are going to use pre-preg I don't see this as being the impossibility that 78cobraII sees. 

They make boats out of carbon all the time so it is not impossible. I am guessing that any buried metal is either molded in place during the build or glued in using one of the miracle epoxies that are available to glue cars together.

Lotus made a Fiber Glass monocoque called the Elite way back in the 60s and actually sold it to the public. Probably as close to a shed built car as you would want.

I follow a person on YouTube building a large catamaran. He also does a channel on building stuff with composites. Might be worth a look.  


TJL (Forum Supporter)
TJL (Forum Supporter) Dork
7/3/23 8:07 a.m.

Look up pictures of wrecked supercars. Many have a carbon fibre monocoque. Its super strong until it isnt, then its splintered fabric. 

as far as i know/have seen( and i havent really studied it), the boxy structure of the monocoque is the only structure. 

TurboFource HalfDork
7/3/23 9:47 a.m.

There is a e-fiberglass supercar build that has portions bonded into for such things, he explains his choices etc and is pretty interesting ... just search for Arete Supercar 

paddygarcia GRM+ Memberand HalfDork
7/3/23 10:17 a.m.
78CobraII Reader
7/3/23 12:05 p.m.

I made an assumption that the monocoque would need to be a large object with minimal joints and connections for maximum strength (supercar?). This implies a large-ish vacuum oven to process in one go.

Back in the 80's I read that Ford Racing created the Capri and Mustang IMSA chassis from CF because they had access to a Ford Aerospace vacuum oven.

I guess that you could create an over-sized oven from recycled cooking ovens, scrap sheetmetal, and old fiberglass home insulation  Grassroots-style though...

TurnerX19 UberDork
7/4/23 3:24 p.m.

In reply to 78CobraII :

The oven has to be very precisely controlled, although the temperatures are not excessive, the volume is the problem. The home built airplane industry has mastered the construction process, but the design loads of a road car require deeper structures than a wing or a true full monocoque fuselage. The Lotus bobbin is the magic for low load attachments. Bonded in dedicated load distribution plates are common for higher loads. The larger the structure, the slower the resin cure time you need during the layup process, or you need many skilled helpers for a brief flurry of activity. This is a big conundrum for the home builder, as slow resins mean longer hotter oven time.

To the O.P., The presence of internal webs and baffles varies a lot, but yes they exist. This is not yet a mature technology. I have dabbled a lot, with varied success, and the more I do the more I don't know. In the end, no 4 wheeled driver carrying vehicle will ever be a true monocoque regardless of material, because you need too many holes for minor things like wheels, and the driver. The fact a car is only a semi-monocoque structure is a semantic point of serious consideration.

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