At Windwing in Berkeley, CA, we worked closely with Tom and Jim to develop and optimize the WindWeapon and we became their production supplier. The swept dihedral geometry is a primary design feature that I suggested to Tom to solve some initial unwieldy problems. This geometry seems natural by viewing the versions since built by others (including the inflatables,) but took a few prototypes to get right in the beginning.That video was filmed 30 years ago !!
The purpose for the geometry is multiple:
1) Maximize the square area since the system is limited by rider stature and their ability to reach and hold the wing overhead in a flying position and rotate it to vertical in a sailing position.
2) Improve upwind sailing VMG by orienting the upper wing half more perpendicular to the higher wind velocity aloft without dragging the lower wingtip in the water.
3) Position the CE such that the rider could handle the forces in balance like a windsurfing sail without fatigue from pitching moment.
4) Stability while airborne to improve control.
Tom was an energetic, enthusiastic innovator with a dedicated passion for flying and a pleasure to work with.
CG