@lmuehrke, interesting simulation project you’re working on there! I think the problem with your geometry creation workflow is that somewhere in the process, only the faceted model is kept and the NURBS are lost. I had a similar situation in this thread: Collaborative simulation project? Multiphase flow around a boat hull. You can see this by the many, many small individually selectable faces of your model, which is probably only a couple of faces in SketchUp. So you basically seem to have here a STEP file that does not contain more information than a STL file.
Depending on what kind of CFD analysis you want to run there are different options now how to solve this. What kind of analysis do you want to run with the catamaran? A single phase flow of water around the bottom hull? A single phase flow of air around the top of the boat or a fully-fledged two-phase flow simulation including the air-water surface around the full boat? BTW there are also different public project of interest here:
I would recommend starting with a simple analysis, say a single phase flow if you agree. For this, a simple STL file of the part that you want to analyze is enough. So just export the model directly from Sketchup to STL and upload it to SimScale. Then you can use the “Automatic SnappyHexMesh for external flow” mesh operation to generate a mesh for the water domain around it. This analysis has the inaccuracy that it does not model the correct behavior of the fluid-water interface since this interface is artificially kept “straight”. But generally, I think starting with a simple analysis, getting that one right and then moving on to more complex is oftentimes a good choice in the very beginning.
Hope this helps as a first step!