This is how it starts. I have an idea and I start sketching and eventually (sometimes it can take awhile) there is an "ah ha" moment. Here we go.
I actually worked up something like this before several years ago, but I always thought I could do better. Now I have a good concept I like with what I think is good visual balance in shape and proportions. This was initially based an a MJ preliminary sketch as he worked his way towards the final design for the Enterprise.
The sketch in question was a saucer with a cylinder suspended beneath it and two narrow cylinders affixed atop. It was a very basic idea, but I'm trying to flesh it out.
From this I'll work up schematics and then move onto modelling it.
The basic background thinking is that this could be one of two earlier classes for either the Valiant
(which was lost at Eminiar 7) or the Republic
(referenced in "Courtmartial).
In this concept the nacelles are not affixed directly to the saucer as in MJ's sketch. Rather they are attached to a enlarged impulse section which houses main engineering. The support hull suspended below houses the shuttlecraft facilities as well as most of the support services.
This is something I photoshopped some years ago and gives a general idea as to what I'm working toward.
In any design I approach even as I tried to evolve it with some measure of logic I also try to work at it as if I'm designing a hero ship in order to get the right feel. I try for something that would look good if it had to be onscreen.