Is there a way to disable the show Grid permanently on Filemaker 13?
Are you trying to disable them on a hosted solution? The setting (VIEW > GRID > SHOW GRID) will not stick on a hosted solution. In the case of a hosted solution you need to temporarily stop sharing it, make the change above, and then share it again.
If it is not a hosted solution then simply toggling the SHOW GRID option above will do it for you.