4T FORTE™ Composite

No more film, no more glue!

In 2007, OneSails introduced the first continuous fibre sails built without the use of resin or glue, eliminating delamination issues at a stroke. Now OneSails goes a step further, by introducing 4T FORTE™ membranes made from exclusive Multi Micro Structure (MMS™) technology (patent pending).

The 4T FORTE™ composite structure incorporates high modulus fibres such as STR™ Solid Stripes, a new low stretch component of MMS™ technology which eliminates both glue and the mylar film, so often the weak element of a laminate sail. Using a multi micro layered structure, elements of the membrane are fused together in a cross linked, polymerised matrix resulting in a stable, stretch resistant, and durable sail. By doing away with both glue and mylar film these sails are significantly lighter than conventional laminate sails.

Not only is 4T FORTE™ intrinsically lighter than alternatives, but weight saving is enhanced by the fact that a 4T FORTE™ membrane does not need to be covered with extra woven taffeta fabric to protect it from UV or improve durability.

A core structural grid, constructed from high modulus fibre takes care of the principal loads, whilst oriented micro layers provide strength in other secondary directions. The entire skin is encapsulated between ripstop “shields”, which are UV, moisture, and mildew resistant.

The whole skin, with its continuous fibres, is vacuum cured in a heat activated cross polymerisation process. which fuses the components together so that every single element in the structure contributes to shape holding. As a result, a 4T FORTE™ sail membrane not only exhibits superior structural integrity, but the use of more efficient components creates a sail up to 25% lighter than film based alternatives.

4T FORTE™225R*325RREFERENCE: top mylar membranes
Structural yarns STR Solid Stripes™
High Modulus
STR Solid Stripes™
High Modulus
Color Black Black Clear film
Main structure modulus 210 245 210
UV stability proportion 1,6 1,9 1
*(225R suitable for boats up to 47')
4T FORTE™ styles325NREFERENCE: top mylar membranes
Structural yarns STR Solid Stripes™ High Modulus Carbon
Color Black Clear film
Main structure modulus 245 210
UV stability proportion 1,7 1
4T FORTE™220C*200E**320CREFERENCE: top taffetà membranes
Structural yarns STR Solid Stripes™ High Modulus STR Solid Stripes™
High Modulus
STR Solid Stripes™
High Modulus
Color Light grey Light grey Dark grey Different colors
Main structure modulus 210 190 245 210
UV stability proportion 1,5 1,5 1,5 1
*(220C suitable for boats up to 47')
**(200E suitable for boats up to 39')

OneSails 4T FORTE™ sails are simply the best sails available in the market in terms of quality, technology, shape holding and durability. These sails carry as standard a number of exclusive features that significantly increase their performance, lightness and ease of use:

  • Single piece sails without size limits
  • Composite laminate made by multi micro MMS Technology (Pat. Pending) layers structure vacuum fused together in a cross linked polymerised matrix
  • Thermo moulded process
  • Continuous STR Solid Stripes™
  • Soft corner finishing
  • OneSD™ microchip
  • Integrated reinforcements
  • Luff customized to mast/boom or headstay system
  • Integrated batten pockets
  • Dyneema leechline and footline
  • RBS epoxy "E-glass" battens
  • Batten pockets with easy V closure
  • Integrated spreader patches
  • Custom sailbag
Composite structure stand-by shape
Composite structure working shape

Composite warp-oriented intermediate layers are able to hold the loads of the core solid stripes’s frame and keep them in their original position resulting in perfect shape retention of the sail. The exclusive squared shape of STR Solid Stripes™ in MMS laminates increase the stability of the structure and results in a sail with a very smooth surface.
Mylar laminate stand-by shape
Mylar laminate working shape

The structural inconsistencies in a Mylar based sail result in distortions under load leading to reduced shape stability as the components bend and stretch.

The sail is shaped using a cross-cut base layer as a mould over which the composite layers are assembled. This process means that any designed sail shape can be accurately produced. Unlike most of the membranes in the market that are built with the use of resins or glue, 4T FORTE™ membranes are made by a vacuum cured heat-activated cross polymerisation process. This ensures superior structural integrity with no extra weight added to the sail. Furthermore the lighter specific weight of the micro layers compared to mylar film significantly decreases the overall weight by up to 25%.

After many years of carbon being the ultimate fibre in sailmaking, OneSails has introduced STR Solid Stripes™ with a better strength/weight ratio than carbon and a huge number of other advantages including being more robust, having higher tenacity and a full resistance to the harsh factors of the marine environment such as UV, temperature and moisture.

STR Solid Stripes™ High Modulus specifications

  STR Solid Stripes™ High Modulus CARBON High Modulus CARBON DYNEEMA TWARON High Modulus BLACK TECHNORA
Specific modulus (N/tex)
Load / weight ratio
UV stability
Flex loss
Creep free
Moisture resistance

OneSD™ technology for sail data broadcast.

Alongside the introduction of 4T FORTE™ sails, OneSails are the first sailmaker in the world to deliver sails with an electronic chip encapsulated in the membrane as standard.
The OneSD™ microchip will carry data which will help the end user and the OneSails network identify and monitor the sail over the course of its life. Simply place a suitable smartphone next to the chip and read the recorded identifier and design data.

A PRO version of the OneSD™ chip will shortly be introduced which will allow real-time recording of the sail's activity when linked to onboard systems. There are many possibilities, from hours exposed to UV, to the number of tacks and gybes experienced - all recorded with the aim of improving sail performance and the ownership experience.

'Green Sails' - certified ISO 14040 Life Cycle Assessment.

4T FORTE™ are the first “green sails”. Membranes and their assembly have been engineered for highest standards in terms of environmental impact and recyclable options. Glues, resins and solvents have been replaced by heat fusion and the base polymer is 100% recyclable in a standard waste separation process.

Why choose OneSails

1. Exclusive technology.
For over 10 years the OneSails design team have developed exclusive technologies to make one-piece continuous thread sails a reality for cruising and racing boats.

2. Performance.
Features like weight, shape control and deformation resistance means better performance compared to traditional panelled sails.

3. Quality.
Sails are designed and manufactured to the very highest standards from carefully selected components to ensure the very highest quality and durability. 4T FORTE™ membranes are exclusively made in Italy. All the assembly process is completely made in a unique factory ensuring the meeting of all the required standards.

4. Design.
The best sail shapes are the result of continuous analysis and experience. OneSails is at the forefront of the sailmaking industry, continually investing in research and development to ensure that the very best sail shapes are available. The success of this approach is confirmed by the vast array of racing trophies OneSails clients have won, competing at National, International and World Championship level.

5. Service.
A core activity for every OneSails Loft is providing first class service, support and assistance. As part of our service commitment, each OneSails Loft has a team of experts on hand to ensure that we can deliver on our service pledge. In addition to a growing number of principle lofts, the OneSails Group has an extensive network of service centres strategically placed worldwide's coast line.

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