So while I was looking around to see if I had that ship building excel spreadsheet, I came across something I did a long time ago. I sat down and wrote out every single stat given for every single ship. I calculated volume as length*width*(height=width*2) it's not a perfect guess by any measure, but it's consistent and a "rule of thumb". If someone wants to more carefully calculate the estimated volume of each ship and let me know by PM, I'll gladly take it, but if it's a consistent measure that it doesn't matter.

Ship Type Crew/Volume Space/Volume
GC 4.42 3.25
BC 14.29 10.74
C 14.28 12.06
LC 29.72 29.71
F 75.62 117.69
R 63.76 142.59
T 24.03 50.09

Hopefully the above table comes out reasonably well. What I've noticed is that the bigger ships (GC especially) suffer from extremely poor crew to volume and space to volume ratios.

Rather than start say ok, lets scale everything to a raider and get totally borked stats, I think maybe exploring a "fluff" explanation, examining 40k tech to explain these.

My thoughts are:

1.) Bigger ships have more automation, necessitating less crew/volume

2.) Bigger ships have more redudancy, and are hence more durable. (maybe scaling up hull integrity further?)

Any other thoughts or questions?

I've had a great number of impromptu I-forgot-my-notes games set in the underdecks of my players' ships. Many larger vessels, by virtue of their great age and incredible size, have entire subdecks that nobody from the crew has even been to; be they service tunnels for the ship's less-critical functions or a design oversight that's been copied by rote ever since (original enginseer responsible for design forgot to include a drop-off button for level 128c in the elevatus and now it's only accessible via a series of hatches and easements through the walls) or more sinister events in the ship's past, where a previous captain was forced to seal something away in one of the holds, unable to remove it from his ship but unwilling to let the crew know what was truly in there with them.

HeavensThunderHammer said:

How about this for a thought… It's not that bigger ships have smaller crews, but that Grand Cruisers have proportionally smaller crews.

The Grand Cruiser write-up in Battlefleet Koronus suggests that these vessels were, at the time they were created, highly advanced. They possessed technologies that have since been lost in the wider Imperium. Look how fast a Repulsive Class Grand Cruiser can move in realspace - it's incredibly fast for a ship of its size. Grand Cruisers have fallen out of favour because their advanced technologies can no longer be maintained by a modern Imperium which has lost the skills to operate them safely. This explains why so many Grand Cruisers are lost in the warp - and end up in chaos fleets.

This suggests that Grand Cruisers probably DID have more automation, as you suggest, requiring smaller crews.

This paradigm - that chaos tech is older, more advanced, but more unreliable than "modern" Imperial tech - sits neatly alongside a lot of chaos legion equipment, like the ripper cannon and dreadclaw drop pod. If 41st Milenium Imperial tech is a shiny new AK47, Chaos tech is an old dirty, badly maintained M-16; arguably better, and with more advanced features, but more prone to catastrophic malfunction.

Lightbringer said:

But the hard numbers indicate that as a ship gets bigger, it needs proportionally less crew. This is true simply from Raider to Cruiser, and then GC's get rediculous. I like your fluff idea, but I think something else needs to be added to factor in for the majority of ships the Imperium uses.

Errant said:

Great idea too.

For a moment I thought this would be another thread about how the ship's densities were so low that they would float on water in some cases… LOL

BaronIveagh said:

Good god man, why did you just remind me of that? Noo…. NOw I must update my spreadsheet and ***** about that too….

BaronIveagh said:

Why wouldnt you expect that?