You'll need to measure, as we don't have any way of knowing what dimensions are for a sink in a 2018 Coachmen Catalina 26 BHS.
So long as your sink measures 10" long x 14" wide, 11" long x 13-1/4" wide, or 12" long x 14" wide, you can use the Camco Sink Mate RV Polyethylene Cutting Board # CAM43857. view full answer...
Yes, the Adco SFS AquaShed Cover is actually going to work better for you than the Adco All Climate Cover. The reason for this is that the AquaShed is better suited for wet climates with warm weather and high humidity whereas the All Climate is more for climates with heavy snow and wind. The All Climate has a thick tyvek top panel which will not be as breathable as the triple-layer top panel on the AquaShed.
If you can let me know what floorplan you have on your 2017 Coachmen Catalina... view full answer...