The Jet 14 jib should “float” on the jib halyard, which is used to tighten the rig tension. (See an additional Rigging tip regarding Jib Halyard tensioning.) The jib cunningham, also called the jib cloth tension tightens the luff and brings the jib’s draft forward.
The jib cloth tension should be tightened just enough so that there are always very slight wrinkles in the luff (approximately 2” long, perpendicular to the luff) of the sail.
In very heavy wind you will want to add tension and make the luff of the jib smooth which brings the draft forward and opens up the leech of the sail.