I have this opening on my model and when I use the Patch command there is a slight tear on the sides and it’s not water tight. How can I have it closed successfully.
why would you want to close that? looks awesome already
in case those purple surfaces are not walls which is difficult to see on those pictures, then the following would apply: if you want a flat surface then just use the command edge surface and click on the 4 edges surrounding your wanted surface. if you want a closeable warped surface then use sweep 2 like seen below the yellow are the rails and the orange are the cross section curves.
if your purple surfaces are walls its slightly more complex and posting the file would help yourself that others can have a look.
Hi Mike - it looks like you can maybe just extrude that arc shape and trim the results with the edges of the object that you have.