What is 3Di?

3Di™ is a unique, patented sailmaking technology that allows laminated sails to approach the balanced loadbearing and shapeholding of a rigid airfoil. 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.

What is a spread filament tape?

What we think of as an individual yarn or fiber in a sail is in fact a bundle of very small filaments, each less than the diameter of a human hair.
   
A spread filament tape is an individual filament bundle (yarn) that has been spread out until the individual filaments lie sideby- 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.
   

How is a 3Di sail made?

The illustration below shows how the ultra-thin spread filament tapes are arranged in layers and then thermomolded into a sail. Each color represent 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. Also note what is not shown... FILM. Because filament tapes make up the entire surface of the sail, film is not needed to form the 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.
 

Balanced distortion resistance?

Sail distortion of any type — stretch, compression, shear or shrink — has a negative effect on sail performance. Most sails concentrate on resisting loads in the stretch (tension) direction. But if you also restrict a material’s 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.
   

How are spread filament tapes made?

Spread filament tapes, the foundation of 3Di, are produced on North’s own “pregger”, a machine that spreads yarns into an ultra-thin layer of individual filaments, coats those filaments with adhesive and adds a backer.


1. The yarns* are drawn from a creel through bullet boards to keep them organized as they are fed into the “pregger” unit.

*UHMWPE (Spectra/Dyneema) yarns shown
   
2. In the pregger, the individual yarns are spread into a wide array of single filaments, merged with adhesive and applied to a paper carrier.
   
3. The spread filament array, adhesive and paper backer then travel through a 10-meter drying ramp where solvents are burned off and fumes evacuated. At the end of the ramp, the spread filament array is cut into thinner tape strips, rolled up and refrigerated.
4. The spread-filament tape rolls are then loaded into a multi-axis, computer controlled tape head attached to a bridge gantry.
   
3Di tape head applies each filament tape on a specified axis and cuts it into a specified length 5. The tape head applies each filament tape* on a specified axis and cuts it to a specified length.

*UHMWPE (Spectra/Dyneema) tape shown
   
  6. The different tape layers are joined on the mold with tapered scarf-like joints to ensure consistent sail thickness and strength. The laminate is then pressurized using a vacuum bag (shown) and then heat cured. Unlike any other sail laminate, no films are used.