F.5.1 Primary Structure

Explanation

F.5.1.1 - The Primary Structure has to be made of a combination of approved materials. Most of these materials will be pre approved, but in some cases it is appropriate to use materials that are not explicitly pre approved (alternative materials). As long as adequate documentation is provided for these materials, and the chassis member in question is permitted to be constructed using these alternative materials. All of the material selection resources for tube chassis is summarized in F.3.2 Tubing Requirements: 

Notice how most chassis structures have alternative materials permitted for their construction, which allows monocoque teams to replace these structures with their monocoque fiber material equivalent. The Main Hoop, Main Hoop Bracing, and Shoulder Harness Mounting Bar are required to be constructed out of steel tube no matter what kind of chassis a team is building. This is a safety requirement because the Main Hoop and these surrounding structures are the primary driver protection structures in case of a rollover. They would also be subjected to the brunt of the force if a rollover occurred. 

The Composite Material bullet point references F.4 Composite and Other Materials which is an entire section of the chassis rules about how to safely acquire, document, and test composite materials to prove they are safe before using them to construct the chassis. Using composite materials on the chassis creates a new sheet on the SES that has to be filled out and is significantly more complicated than it's tube frame equivalent. 

F.5.1.2 - The chassis design must meet all material requirements highlighted in F.5.1.1 (the rule directly above this one). 

If Alternative Materials are selected to be used, they must demonstrate F.2.3 Equivalence in the SES. This means that if an alternative material is used to construct a chassis structure, there has to provided documentation proving that it is just a strong/ functional as the pre selected steel tubing material in the context of it's application. 

Connections used as part of the chassis design must also follow a specific set of rules. 'Connections' is a broad term referring to fasteners such as bolts, threaded fasteners, and tabs. 'Connections' also refers to adhesives. Reference F.5.4 Fasteners in Primary Structure for more information about appropriate use of fasteners, and F.5.5 Bonding in Regulated Structure for more information about adhesives.

 F.7.8 Attachments refers to rules about appropriate methods of attaching the tube structures to composite panels on monocoque chassis, and this rule is not directly relevant to tube frame chassis.