It is my belief there are too many variables to use a "standard scope" for anchor rode, but I do remember 7:1 as Chapman's recommendation. We have a 35# CRQ with 300 ft of chain and since most of Narragansett Bay is quite deep, we frequently anchor in 40 to 50 ft of water, even a bit deeper at times.
In most situations, I let out 200-250 ft in 40-50 ft, with a 5:1 scope. This seems more than adequate, especially compared to 280-350 ft using a 7:1 scope.
True Blue . . .
sold the Nauticat