The Big-D Rocket gets its name from the D12 engine which powers it. Although the current design is for use with a D12-3 or D12-5 engine, I have provided the step file which will allow for complete scalability to fit your engine choice.
Beyond scalability, I put a focus on modularity. The engine cap is threaded and acts as a retainer for the fins. Each fin is separate from the rocket body and utilize a slot accessible from the bottom.
I have test printed this model and found that ASA is best for the nose cone, fins, and tube. The main body/base and engine cap are best printed with carbon fiber-polycarbonate or PLA+.
Everything except for the main body/base can be printed without supports.
I also have a single body version for those with printers more than Z-390mm Link > https://thangs.com/model/6873
STL Files by request