The IFS evolved from the FFR which was inspired by the Screeher but One Sails were more inspired to create a more versatile sail. The Screecher is a great sail but it's really dialled in for reaching. The FFR (previous post), evolved as a hybrid to fill in between a Screecher and a Asymmetric Spinnaker. The IFS takes the hybrid theory in another direction.
Integrated Furling System refers to having the sail constructed from Structural Membrane that is capable of supporting the entire rig load. The structural fibres spread the load across the whole sail instead of having only loaded corners in a more conventional cloth sail.
Distributing the load in this manner allows for the removal of what is normally a large diameter luff rope/torque line. The luff rope on THE IFS is now only 4mm instead of 8. What this means to the sail flying characteristics is, the luff now has the ability to fly instead of being restricted. With the luff being able to project ahead of the boat efficiency is increased and it flies more like a Spinnaker than a 'rigid' sail.
This component of the sail makes it easy more versatile than a 'normal' Screecher.
We've found that the IFS operates with reduced halyard tensions in comparison to the rigid Screechers. This is a big plus on longevity for sail and halyards! But the real value is in being able to dial in the draft/camber of the sail by using the halyard tension.
On a tight fetch the halyard is loaded, you can carry the sail to within 5-7 degrees of the upwind heading that you can achieve under jib alone.
Coming down to broad reach angles, easing the halyard about 10-15cms will yield about 5-10 degrees more downwind angle - that's the plus!
The other bonus, made from Structural Membrane with loads calculated for each boat, the sail will retain its shape for its entire lifetime. The shape is fixed in and doesn't alter across the wind range - unless you play with the halyard tension!
Higher performance. Longer life!