The Ultra Bond System
For modern racing materials, the Ultra Bond system is the way to go! It is a high tech adhesive (think super-duper, incredibly strong hot glue) developed in 1995. We get ours through Dimension Polyant.
There are several clear advantages to using Ultra Bond:
There is no slip/creep/stretch in the seam. Two pieces of material Ultra Bonded together have the same properties as a single piece of material with no seam in it
The seams themselves are much smoother - no needles holes or little clumps of thread to get in the way
Ultra Bond seams are stronger than the actual sail material
We have used the Ultra Bond system on hundreds of sails, including Randy Smyth's trimaran designs, an Olson 40, a Columbia 30, and Hunter's own S27.9