In simplified technical terms, 3Di is a flexible composite membrane built from pre-impregnated spread filament tapes applied in multiple axes and thermo-formed on a 3D (3DL) mold.
A spread filament tape is an individual filament bundle (yarn) that has been spread out until the individual filaments lie side-by-side, forming an ultra-thin tape that is then combined with adhesive and applied to a paper backer.
Shown here is a pre-preg carbon/UHMWPE (Spectra/Dyneema) spread filament tape approx. 35 microns thick.
SHOW ME HOW IT'S MADE
Each color represents a different ply (layer ) comprised of filament tape(s).
The tapes can be any length and oriented in any direction, allowing unprecedented precision in matching sail structure to predicted loads in the sail.
Note that all reinforcements in a 3Di sail (blue layers) are applied as an integral (internal) part of the sail laminate.
With 3Di technology, designers have such precise control over the disposition and orientation of material within the sail, they can come far closer to achieving the holy grail of sailmaking... BALANCED RESISTANCE TO DISTORTION IN ALL DIRECTIONS.
Most sails concentrate on resisting loads in the stretch (tension) direction.
But if you also restrict a materials ability to compress in the nonload, or bias direction (see illustration), you concurrently enhance resistance to stretch in the loaded direction.
We call this balanced distortion resistance. Balancing resistance to both stretch and compression means less change in sail shape as the boat moves through waves and changing wind pressures.
This is why we call 3Di airfoil technology. It comes closer to matching the performance of a rigid airfoil than any other sailmaking technology.