A "safety pilot" doesn't log anything, ever, in a single pilot aircraft. Not even when he's an "official" safety pilot
Hold on a second : Under FAR 61.51, if the safety pilot is a required crewmember, and he is responsible for the safety of flight, he does log PIC time. The example that springs to mind is the safety pilot when the pilot in the left hand seat is doing instrument approaches or holds under the hood.
...or you have a 60kg instructor.
I've always preferred the 60 kg instructors. They never shouted at me, and they were fun to look at.