Hi vektor. That is some really clean modeling. May I ask what software you are using, as well as if you are using NURBS (my suspicion) or polygonal modeling? You may have talked about that before, and I apologize if it is a FAQ.
I'm using 3ds Max 2009. Methods of choice include polygonal modeling with extensive Sub-Ds, lots of spline-based extrusions and lathes, free-form deforms, etc. I have dabbled with NURBS but never enough to become truly proficient with it and haven't used it at all on this model.
This ship falls into a rather unique category in terms of which modeling methods are most suitable for it. Some models, like the original TOS Enterprise, are best constructed with very simple methods like lathes and extrusions, with more advanced techniques used to add the details here and there. For a ship like the Grandeur however, lathes and extrusions are virtually useless for the major shapes. It's organic enough that it's almost like building a character model rather than a mechanical object, but it requires just enough regularity and symmetry that you can't go completely free-form. I suppose it's a lot like modeling a car, though I've never actually done that so I can only speak conceptually.
On the Grandeur, virtually the entire secondary hull and nacelle struts are a single Sub-D object. Same goes for the nacelles themselves. Another single-piece Sub-D is most of the superstructure on top of the saucer, flowing back into the impulse engine housings and around underneath into the various shapes surrounding and in front of the neck section. The saucer itself, believe it or not, was built from a lathed spline, then tweaked into its characteristic egg-shape with a combination of Xform and FFD (Transform and Free-form Deform) modifiers. I did try a couple of times to build it entirely with Sub-Ds, but it turned out to be about the same amount of work to create the basic shape with a lathe and I wound up with a lot fewer faces to boot.
The techniques I use depend entirely on the specific part I'm trying to make. Even then, I can't claim to necessarily be doing it the best way as I am essentially self-taught at all this, which is one of the reason I still don't do much with NURBS.
When you say spline based modeling, do you mean creating a spline and then converting to editable-poly and then doing the extrude or lathe? Or can you some how extrude a spline without converting?
I just don't know how you model all of those curves and corners and have a clean mesh with surface subdivision, and then to make each part fit together smoothly after modeling. I model almost exclusively with polygon and subdivision and have not had enough time to venture into other techniques like I want to. I would not have even thought about trying to model something like that with those techniques but I guess it can be done.