In light winds, you want the sail as flat as possible or almost so. In other words, you have to fiddle with it to get the most optimum position. You also have to use your outhaul because you don't want much belly in the sail because very light wind doesn't have the power to get around the sail.
8 knots of wind is not light winds but I'll bet your boom vang is so loose that you're spilling wind off the top 1/3 of the sail. Like I said, next time you go to the boat just hoist the mainsail at the dock and don't touch the boom vang. Look up the sail and see if the top is open. Here's what you're looking for. Form your right hand in a salute and then turn your fingers only to the right. See how the top opens!! Now turn your finger back to the left, as if you were cranking on your boom vang, and see how it closes thus causing the sail to power up from top to bottom.
On the "set it and forget it" with the boom vang or the outhaul and jib fairleads or any of your controls, your setting is right for one point of sail and wind condition and wrong for all others.
I know there are a lot of sail trim controls but think of them as "levers" you have to push or pull to fine tune and tweak your sails (engine). Once you get the hang of it, it becomes fun. Now it's a chore
8 knots of wind is not light winds but I'll bet your boom vang is so loose that you're spilling wind off the top 1/3 of the sail. Like I said, next time you go to the boat just hoist the mainsail at the dock and don't touch the boom vang. Look up the sail and see if the top is open. Here's what you're looking for. Form your right hand in a salute and then turn your fingers only to the right. See how the top opens!! Now turn your finger back to the left, as if you were cranking on your boom vang, and see how it closes thus causing the sail to power up from top to bottom.
On the "set it and forget it" with the boom vang or the outhaul and jib fairleads or any of your controls, your setting is right for one point of sail and wind condition and wrong for all others.
I know there are a lot of sail trim controls but think of them as "levers" you have to push or pull to fine tune and tweak your sails (engine). Once you get the hang of it, it becomes fun. Now it's a chore