Is this what you are trying to achieve?
Not exactly but it is definitely very cool. I was wondering if the thinning ending was also possible.
What I’m trying to achieve is a tightly wrapped spiral like the ones on the photos. I want to make rolls like those for some models and I really have no idea how.
With no gaps between the tube sections.
Here I enlarged the diameter before doing both sweeps and made the inner end a full spherical radius. Overlapping the sweep does work.