How do I set up these jib car sheet holder thingies?

[DEAN2140]

Moving the car back is wrong unless you want to depower the jib. This will tighten the foot but loosen the leach causing it to break off and lose the wind. This is similar to easing the vang on your main; the boom comes up and the wind is spilled out of the leach.

[smj]

Plenty of YouTube tutorials on this subject.

[Brioche]

As often is the case there are several methods of getting the jib sheets properly positioned for your boat and sails. Another method I didn't see mentioned yet is to compare the shape of the leach and foot of the jib. Moving the sheeting block forward will increase tension on the leach, flattening it, and ease the tension on the foot, giving the sail a deeper shape. Moving the block back tensions the foot and flattens the bottom of the sail, but eases the leach and allows air to spill from the middle of the sail. Generally you want a position that is midpoint between these extremes.

[wholybee]

Originally Posted by DEAN2140

Moving the car back is wrong unless you want to depower the jib. This will tighten the foot but loosen the leach causing it to break off and lose the wind. This is similar to easing the vang on your main; the boom comes up and the wind is spilled out of the leach.

Unless your leech is tight and the foot has too much shape. Then you should move the car aft.

The subject too complicated to have rules like "it should be moved forward." What to do depends on the sail, the boat, and the conditions. Libraries of books have been written on sail trim.