Thanks to you all!
Yes, the fin could be smaller - but then I will need more polygons to make it work. For this model I only used a cube and the Extraxtion and Sweep tools. The 'fine tuning' was done by selecting faces or edges and using the UM....
So this is really, really basic.
Will work through the rest of the Vertex model tools first before I start to make this model really work.
But I learned so much instead of going only through tutorials. So I guess the next step is something like a robot or so.....
Glad that I finally started with 3D - always seemed impossible to learn for me.
Jacqueline