Found the following links describing the patent that 3DL falls under, and comparing the methods used by North compared to other sail manufacturers.
Full details are on this link (won't copy the text as it is one of the few things that are longer than Wouter's posts):
http://www.patentstorm.us/patents/6382120-description.htmlhttp://www.patentstorm.us/patents/6311633-description.htmlBut there is also this definition:
1. Sailmakers may shape, i.e., broad seam, the novel panels in the traditional manner. For added benefit, a selvage may be provided in the weaving process to also allow sewing (besides the increasingly prevalent gluing of seams).
For me, that definition is not necessarily true for 3DL. The shape of the sail is contrived from the mold and from laying of the yarn or fibres. The mylar film is only used to hold this in place. If they could, North would make this film the size of the whole sail as it would be lighter and produces less weak points, but that isn't conceivable or viable.
I know that Quantum up the road in Malaysia use broad seaming but the sails are made "3DL style". They have carbon and kevlar-fibre sections held together with mylar film, but the panels are about 1.5m to 2m wide and glued together. This way they get around the 3DL patent.
Macca made a Finn reference in an earlier post. That class requires broad-seaming. North get around this by essentially making a 3DL sail, then chopping it into panels, then gluing it back together to make broad seams.
Hope this helps.
