Experimenting: Model making

My early experiments on cardboard before moving into metal sheet. I found it hard to think of ways to join two differently cut cylinders or cones. How to calculate the exactly right circumference, and what if the rim needed be oval shape?? Realised that it had become quite mathematical for me.. spent hours on online forums, where math experts explains formula's that aren't so easy to figure out, especially if it has been 15 years since the last time calculating complex formula's in secondary school! Needed to cogitate something more straightforward. These shapes has become too complex for my taste, I have realised that what I am after, is more ascetic.  

Cylinder with oblique rim and edge 

Hybrid cylinder. The main vessel carries smaller one on its side. 

Low cylinder with oblique rim

    Oblique truncated cylinder