The Stack is one of the fundamental components in OpenVSP and is useful for modeling various geometries requiring a buildup approach rather than setting a known total length. The Stack places cross-sections relative to the preceding section by prescribing translation and rotation for each. By default, Stacks set a free design policy which means that each section may be placed anywhere in your model to create exceptionally complex geometries including engines, flow-through components, fuselages, wings, landing gear, rockets, projectiles, screws, paths, … the applications are almost endless.
One of the most common uses of a Stack is to parametrically vary a body based on the assembly of individual sections. For example, you may begin with a baseline fuselage configuration and wish to vary individual section length or size to examine a design space. A Stack enables the designer to quickly set individual section lengths for the cockpit, cabin, and tail without computing the percent length stations for each as would be required with a Fuselage component.