............I need to set the tension on our jib. Does anyone know the specification for the tension?........
Not aware of any specification. The shape of the jib is controlled by the fore and aft location of the jib leads, luff tension, sheet tension and headstay tension. Below are some general comments
jib leads...........used to control the top and bottom shape of the jib. The middle of the jib is not as affected by lead position as much as it is with sheet. Once the sail is trimmed to the appropriate spot on the lower spreader, adjust the lead to make the top and bottom look right. Moving the lead forward will make the upper leech more closed and the foot rounder. Moving the lead aft will make the upper leech more open and the foot flatter
J/105 Tuning Guide | North Sails You also might this article helpful:
A Foolproof (and Simple) Way to Set Jib Leads - Practical Sailor (practical-sailor.com)
luff tension.............on the leading edge of the sail is controlled by jib halyard. The principal effect of luff tension is to position draft in the sail. Increased luff tension moves draft forward. Decreased luff tension moves draft aft
5.2 - Genoa Trim — UK Sailmakers. If you want to optimize it, tension should be less in light air to give the sail a fuller, more powerful shape, and more taut in stronger winds. Good discussion in this thread on jib halyard tension:
Dumb Jib Halyard Question...can it be TOO tight? | SailNet Community
Sheet tension.............is the most important control for adjusting the jib once the draft is set. Trim the jib as hard as possible without slowing the boat down too much. The jib needs to be played in conjunction with the main and the helmsman’s steering. The sheet tension will change with each change in the wind speed
J/105 Tuning Guide | North Sails
Headstay tension...........affects the the overall camber of the jib
J/105 Tuning Guide | North Sails.
Overall discussion on jib triimming might be helpful:
Jib trimming: a balancing act (yachtingnews.com)