Large introductory science courses are isolating for many students, and reducing this isolation is an important factor for student retention in college. Active learning courses often build community among students as an explicit goal, but many commuter or non-traditional students have limited on-campus time. Online discussion forums provide one tool for engaging students with each other outside of class time. This study uses social network analysis with forum data from an introductory physics course to examine students' positions in the class discussion network and link it to their final course grades. We find that, contrary to expectations, there is no strong correlation between forum network centrality and class outcomes. Possible reasons for this mismatch and future refinements to the model are discussed.