This is a problem I have presented before. I am trying to create hull plating.
I have simplified the object by chopping off the complicated area.
Now I want to shell to 0.3" to create the hull. However, even this highly simplified version of the original will not create a solid when shelled.
How can I get this to shell so I can 3d print it?
Problem82.3dm (10.7 MB)
If you use CurvatureGraph in Analyze menu, you can see some very funky joints and curves. I managed to shell the model with a 2mm external skin, but had the tip of the bow deck curved surface invert and some nasty surfaces towards the stern bulge out in a jagged manner.
I think the curves you used to generate the surfaces need rebuilding and where possible make them in long sweeps than make them up from jointed sections. I do a lot of 3D printing, so my approach here would be to print the ship in small sections and design it that way from the start than try and treat it as one huge entity. My old modest Mac struggled generating the shell in one piece.
If you’re printing a one piece, match the level of detail in the hull to that your printer can achieve, it maybe you can simplify the hull. I would be interested in hearing how and what you plan to print it on. 
I just tried exploding your model, joining smaller sections and shell small sections. You quickly find the problem areas in the model, and don’t get overwhelmed by the model as a whole.
Problem Bow.3dm (1.9 MB)
Look inside this model you can see curves are not in the right direction so the generated geometry is twisted. Others can better explain than me how to fix this, but I would explode and edit the surfaces manually to achieve what I wanted quickly. I used a 1mm internal shell for this part.
I think that the surfaces are built in the longest possible segments here.
The starting point is X/Y/Z coordinates giving a grid of frames and waterlines.
The problem throughout (and particularly at the bow and stern) is that the waterlines do not fit Rhino’s NetworkSrf. (If you use sweep2, there are ripples at every frame.)
I broke the frame/waterline model at the bow and stern and used radials
and some off vertical frames
Even if I just chop off a small, apparently simple piece it does not shell (to 0.3"):
Problem83.3dm (1.1 MB)
Problem84.3dm (1011.0 KB)
Here are a couple split down even more. I am trying to shell these to 0.3’, removing the top and vertical sides. None works.