My friend's boat dock was missing a cap on one of the dock support pipes, so I offered to make one. The first cap was simple and fit well, but seemed rather mundane. The second cap has a recess for attaching a solar light.
A quick internet search yielded the pipe dimensions. The resulting fit is good - snug but easy to install and remove. The gaps between the cap and the pipe are to make fitting easier and to prevent vacuum or pressure since the other end of the pipe is in the water.
If he likes it, I will outfit all the dock support pipes with solar lights :-)
A smaller nozzle would make the outside smoother, but I did not see the need.
No post printing
It will live outdoors so I saw no value in sanding it smooth.
Used Autodesk Inventor
This is my first Autodesk design. It's pretty simple, but I'm just learning, so it was not quick. It is simply a round profile extruded to the required length, then a plane added and thickened on one end. The second part was just a modification of the first. Drew a circle on the closed end inside and out, then extruded the two circles to create a hollow tube in the cap. Then drew a plane on the bottom of the tube and thickened it. I wanted the end of the closed tube to print without supports so I beveled/radiused the flat end to minimize the flat section.