The foil assembly is the aluminum extrusion that extends from the drum at the bottom of the forestay to the top of the forestay. It must have sufficient torsional stiffness so that it does not twist. The assembly is usually fixed at the bottom by a reef line or in the case of a Reef-Rite furler, by a locking pawl.
Many of the problems associated with roller furlers can be attributed to the design of the foil assembly. Perhaps the worst situation is having the luff tape of the sail pull out of the luff groove and jam part way up making it difficult to raise or lower the sail. Reef-Rite systems have twin oversize luff grooves designed to prevent this problem.
Another problem associated with foil assemblies is at the joints. At each joint, some kind of aluminium sleeve typically extends inside the foil above and below the joint. The sleeves are usually fastened to the extrusion with set screws.
The main problem with those joints is that if the set screws work their way out or if there is any play in the joint because of a loose fitting sleeve, the two sections of extrusion will work back and forth, and damage the sail. This scenario also is often the cause of breakage during removal at annual haul out.
With the Reef-Rite systems, the extrusion joiners, or sleeves, are machined from solid stock. They fit very snugly in the extrusion and accurately align adjoining sections. This assembly is extremely strong, resisting twist during use and greatly lessening the chance of damage during removal at annual haul out.
Finally, Reef Rite joiners are fastened to the extrusion with monel rivets and there is virtually no chance of the rivet coming loose or working its way out.