Many Thanks TIG,
You've answered my question. There is no wall thickness for the hull. This was originally a paper model that I originally designed on Autocad, then,... once I discovered Sketchup,... I made a model of it. Download the original paper model at http://jleslie48.com/terrestrialvoyager/terrestrialvoyager.htm

Please, while on a rant,... you.. and many of the others that post regularly, posts have helped people like myself, IMMENSELY...I use Sketchup to draw everything from machine guard design for Contractors..., to packing line layouts for the company I work for..('cause Sketchup is cheap compared to Autocad 3D,... which I would never get a capex for).

Thanyou
Andrew

On this model can I,...or how do I, stop the edge of the deck being seen as a line on the outside of the hull?
Honestly I can't work out how to stop the edges being seen from the outside.
Thanks,
Andrew

For the sledge hammer approach, I use the push pull tool also, then intersect with model tool.
I have to do a bit of cleaning up afterwards, but it usually gives a fairly good result. Latest use attached.
( I have Fredo's tools though and should probably learn to use them.)

http://www.flickr.com/photos/53607031@N05/6627192419/in/photostream

Cheers,
Andrew