Not quite sure what spacio-mechanical skills are, CB, but I'm guessing that maybe like me, you have a 'white noise generator' in your arm, scrambling signals and preventing your hand from drawing what's in your brain?

If so, it sounds like you would find a tile-mapper useful. Check out Viewingdale, Dundjinni and Dungeonforge (the ones I'm familiar with - there are others). You just place pre-drawn, pre-scaled objects on a grid, adjusting the layout until you get something you like. The objects are generally designed by someone else who knows what components are needed and you just add them from a menu. If you want somwething more artistic, you could use the finished tile map as a template for drawing a more freestyle map.

Tilemappers are particularly good for rectangular forts and castles.