You may compose your bell from primitives such as partial spheres and/or tori;
you can use spline patches or a subdivision surface; or you can use one or more sweeps.
Here are some ways in which a bell shape might be composed (PPT).
You might first design a thin (mathematical) surface in the desired shape
and then thicken it by using the offset-surface capability in SLIDE,
or else you may define the complete bell surface explicitly (allowing to vary its thickness).
Make sure you end up with a viable B-rep for fabrication.
Create a SLIDE file with all parameters set to their preferred values.
Also, capture your design pictorially using a screen saver.
Try to get a tentative design done by Monday Sep. 26, so you can get some feedback.
Please e-mail me the final picture and your SLIDE-file before the deadline.
