Why does Beowulf not tell unferth of hruntings uselessness?

There are 2 ways you could go with this. You could say that Beowulf didin't tell him

because he wanted to behave honorably and not cause any more unnecessary tension between them. However, you could also say that he didin't tell him because he didin't want Unfreth to have the satisfaction when he finds out that hrunting put beowulf's life in danger. I mean Unferth never liked Beowulf so he could have given the sWord to Beowulf knowing it wouldn't work. Just a theory :) Hope i help u!