As the Fireball has evolved over the years from spinnaker launcher tubes to spinnaker bags, so too has the jib fairlead system changed from deck mounted fairlead tracks to systems that are now inside the cockpit. This evolution has been in part because the move to bag boats has left less real-estate on the foredeck for positioning jib fairlead tracks, and in part because of the other advantages that cockpit (floor) sheeting systems provide.
There is nothing fundamentally wrong with deck sheeting systems, and some fast boats still use them. The typical system is a single track that the fairlead slides on, with a pinlock to hold it in its selected fore/aft position. This track is generally about 10.5 inches out from the centreline of the boat, but if you measure several boats you'll see some of variation in this. In an effort to provide adjustment of the slot, some boats will have a second track placed in parallel with the first, and about 2 inches further outboard. There are also fancier "H" track systems seen on occasion. One of the drawbacks of deck sheeting is its weight - those tracks are heavy. And they are limited in adjustability.
When the first innovators migrated to cockpit sheeting, they simply moved the fairlead tracks from the deck to the floor. This gave plenty of room on the foredeck for large spinnaker bags, but made the boat a bit of a cats- cradle for the crew to pick his way through when tacking. And they still didn't have much adjustability of the slot. Modern systems have come a long way since then, with systems that provide great adjustability and low weight. A less obvious advantage of cockpit sheeting is that, with the clew of the sail being further from the fairlead, the sail will "pant" when hit by a heavy gust and slightly twist off and depower itself. This automatic response makes the boat easier to sail in heavy air conditions.
Cockpit sheeting is probably the way to go if building a new boat, and should be considered when refitting an older boat. But before you go converting from deck sheeting to cockpit sheeting, here are some things to keep in mind.
1. Cut of the jib: Explanation deleted!
2. Aft edge of the foredeck: Explanation deleted!
3. Location of the turning block: Explanation deleted!
4. Decoupling Effect: Explanation deleted!
In the remainder of this article I will attempt to describe some of the cockpit sheeting systems that are in use today. The first system (Figure 3) is simple, flexible, light, and inexpensive....