It's hard to know things like this won't work unless you have a lot of experience with failure. One thing is that you've got areas of the edge between the side and the bottom that transition from tangent to not tangent. This is always a problem for features like thicken and shell. The software has to make or extend an edge where previously only a single surface with no internal edges existed. This is generally just not going to work or at least very unlikely to work. To make a real shell on this, I would just go ahead and finish everything up with surfaces, including the edge at the front of the hull. If you can enclose it with surfaces and make a solid out of it (mirrored, prow, transom, top deck), it has a better chance of shelling. And you might take that transitioning edge out and accomplish that some other way. Either make the whole edge tangent or not tangent. In a real ship, this edge would have a more engineered shape, it would not meander so much. To control that you might consider a guide curve.