The main halyard on our C27 jams when the sail is about 8 inches from being fulling raised. Of the past 8 times we've been out, only once (the second time out) have I been able to fully raise the main. The other seven times the main sail stops before reaching the top. No matter how hard I pull on the halyard, she doesn't budge. We end up sailing with a bit of slack in the sail near the boom. I don't know why she went up completely that one time. I'm guessing something might be stuck in the track. Barring that, what else might I be facing? Any suggestions? Any recommendations that don't start with "First, get a bosun's chair..."Paul