Hi
I would suggest IntelliCAD that you can download for free, It is one of
the best AutoCAD clones some even recon it better than AutoCAD and it
do offer import of various 2D and 3D formats.

Btw It is nice to see a fellow dane trying his luck on the web ,it seem
to be quite tradisional designs and proberly very tradisional plans and
there are a good collection of different boat types, nice to see.

P.C.