Sailing poorly upwind
So I'm by no means a great sailor. I don't know much or think about sail shape, I've never raced and don't particularly care too. But like most people, I pay attention to the boats around me and note how I'm doing in comparison. Usually I judge myself to be sailing just fine (meaning that I expect most boats to pass my Contessa 26 and when I match a C&C 25 or Catalina 30 I think "not bad").
But yesterday was bad. It was a bit gusty so I had opted for full main only (some other boats had the same, some had full rigs, many had a reef and a working Jib). My upwind performance was terrible with the biggest problem being my heading to the wind. I was tacking >100 degrees (perhaps ~115 on average) and nearly every boat that I could judge was sailing closer to the wind than myself. To the best that I could figure, the problem is that my leach and main in general just wasn't taught, it was typically flapping and even with lots of tension on the main sheet it never appeared taught. The main just appeared to be spilling a ton of air.
So I guess I'm asking what this indicates. First, my sails are original (1979) so I'm perfectly willing to believe they are stretched out if that's the most likely answer. But I'm also not sure I have the main adjusted properly. For example I've never adjusted leach line.