My smaller models are a good way to get familiar with the construction methods of most of my ships. I follow these principles:
Usually the sides (running fore/aft) clip the ends (across the ship). For 0.5 mm (0.020″) styrene, this means the sides will be slightly more than 1.0 mm (0.040″) longer than the corresponding base. This means a good method to build a cabin is to glue the ends to the base, making sure they are aligned, and then glue the side to the base and ends. This will keep things reasonably square.
Most bases and decks are doubled to provide more strength gluing surface. Most large hull skins are doubled for a different reason: it is easier to bend/stretch 0.5 mm (0.020″) styrene than 1.0 mm, and get it to stick to the curves of the bulkheads. The second layer also reinforces the curves. On some large hulls, the skins may be tripled or more.
Most roofs are doubled, with one inside piece the same size as the base, and an outer piece that is larger and will clip the ends and sides.
Interior reinforcements are generally 1.5 mm less tall than the sides and ends, leaving room for the doubled base and the inner roof.
Many times I use 0.6 mm for tolerances instead of 0.508 mm. This may leave some edges slightly proud. This is easily sanded off.
I often reinforce joints with scraps squares such as the chads from doors and windows, or just squares and triangles I cut from excess stock.
Most hull skins align along the bottom of the ship. With small ships, beginning at the bow and working back often works best. With larger ships, positioning the skins and then working from the middle outward may be best. Use lots of making tape.
Smaller ships will now use longitudinal spines rather spine-and-bulkhead construction. This method is easier to build and probably stronger.
I am phasing out large resin cast pieces. They are just too expensive and inefficient. Bows can be constructed more easily of styrene; rounded sterns may be better in wood. Besides, I’m getting better at cutting full-length skins: e.g., the heavy cruiser Portland-class (not yet announced).
Except for rare cases, I’m limiting cuts to 36″ long, so that longer hulls will have to be spliced. With the tremendous drag (and wear) that styrene places on a cutting blade, longer pieces have a diminishing chance of success
The ideal cut for these kits is that the pieces are just barely hanging on, with the barest of styrene thickness, making them simple to pop out. But styrene is not uniform, so sometimes I cut all the way through, and sometimes not quite enough, and sometimes both on the same sheet. I hate it that cutting styrene is more an art than a science, but so be it for now.
I work in millimeters rather than inches. It is just so much easier. N scale is roughly 2 mm to one foot (actually 1.905. but that doesn’t matter for small increments). Z scale is 72.72727 . . .% of N scale. If I design for 0.5 mm styrene in N scale, then Z scale should work for 0.375 mm without a lot of tolerancing, especially if I use 0.6 mm slots for 0.508 tabs.