You have an excellent set-up wrongly used :-)!
The clue is in the "tension crease" that runs from above the reefing cringle (where the reinforcement patches are on the luff of the sail, diagonally aft and down to a point on your boom that isn't shown in your pic. Anytime you see a tension crease like that, you know you are doing something wrong!
No sense in being anything other than systematic in coming to grips with this "problem". Bring the sail all the way down and slip the
halyard off the headboard of the sail. Attach the "zero" end of a 50 foot measuring tape to the halyard. Now hoist the tape so it is chock-a-block with the sheave in the
mast crane and note (in your
maintenance log) the PRECISE reading of the tape at the upper side of the boom. Now knock off a foot from that measure. That reduced measure should be the length of your luff. If the luff of you sail is longer than that, it is wrongly dimensioned for the boat, and should be modified or, in the worst of cases, the sail should be replaced.
Now refer to the diagram GordMay so kindly gave you. The red line at the bottom is the fall of the topping
lift shown in red aft of the leach of the sail. In the diagram it is very properly led to the
cockpit.
Whenever you hoist or reef the sail, ALWAYS begin by starting the sheet and the vang below the boom, then take up six inches or a foot on the topping
lift so the weight of the boom is borne by the gooseneck and the topping lift and there is NO tension on the sail itself.
To reef, bring her
head to the eye of the
wind, start your sheet and vang, take up your topping lift, start your halyard and haul in you reefing lines (first or second as required). Now belay the halyard with a bit of tension on the luff. It should have been marked at the appropriate point where it comes to its cleat. Now start the topping lift so the boom-end is borne by the sail rather than the topping lift. Now fall 'er off to the desired point of sail and trim up your sheet and vang as required. Now tidy up any lines lying about.
In a C&C30 properly set up the entire procedure should take just about a minute from beginning to end, i.e., so little time that she won't even have time to fall her
head off the
wind before you are ready to fall off deliberately and let the sail draw again.
For now, that will get you off to a good start. You do NOT have to sail "to perfection" until you've got these fundamentals under your belt. When you have that, we can begin to discuss the use of Cunninghams and other devises used to perfect the sail trim.
Do not be misled by suggestions from people who use
roller furling. Doing so requires RADICALLY different techniques!
Bonne chance!
TrentePieds