4T FORTE™ Composite

OneSails 4T FORTE™
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™ 115R 215R REFERENCE: top mylar membranes
Structural yarns twaron STR Solid Stripes™ High Modulus carbon
Color grey grey clear film
Average weight gr/sqm 325 300 355
Main structure modulus 118 245 210
UV stability proportion 1,6 1,9 1
4T FORTE™ styles 215N REFERENCE: top mylar membranes
Structural yarns STR Solid Stripes™ High Modulus carbon
Color grey / clear clear film
Average weight gr/sqm 270 355
Main structure modulus 245 210
UV stability proportion 1,7 1
4T FORTE™ 110C 210C REFERENCE: top taffetà membranes
Structural yarns twaron STR Solid Stripes™ High Modulus carbon
Color grey grey different colors
Average weight gr/sqm 410 375 490
Main structure modulus 118 245 210
UV stability proportion 1,5 1,5 1

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

Smart sails - 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.


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Mer information

Mer information

4T FAQ Q: What are the fibers used in 4T FORTE™ ? A: 4T FORTE™ uses either Ultra High Molecular Weight Polyethylene (STRHM) or black aramid (Twaron HM) fibers as primary load bearing structural members Q: Does 4T FORTE™ delaminate ? A: Delamination is defined as the loss of bonding between the layers of a composite. This occurs when the glue or resin used to keep these layers together loses its adhesive properties due to polymerisation, aging, etc. 4T FORTE™ uses no glue or resin whatsoever, the bonding between the many layers of the composite structure is achieved by means of thermoplastic infusion under pressure at high temperatures, and therefore cannot delaminate. Q: How many layers is 4T FORTE™ made of ? A: The patented MMS™ (Multi Micro Structure) 4T FORTE™ is made of, is custom designed for every application. Generally speaking, the number of layers is between 12 and 19 in most cases. Q: What is a Multi Micro Structure? A: 4T FORTE’s patented MMS™ (Multi Micro Structure) can be defined as a stratified flexible composite structure where each component contributes to support the primary structure of the sail (the load-bearing fibers grid). Within MMS™ there are components which act as bonding agents, sealing layers, multiaxial micro-meshes, protective shields and structural members. Q: How can 4T FORTE™ be recycled ? A: 4T FORTE™ is by far the sail construction method with the highest percentage of recyclability (meant as the possibility of getting back to the raw components at the end of the product’s life cycle) currently on the market. This is achieved through the selection of components which are recyclable in the first place. 4T FORTE™ has also recently been ISO certified as the lowest CO2 emission sail production system in the World.

Q: How is the sail given its three dimensional shape ? A: In the most classical and accurate way, by joining the horizontal (crosscut) panels of the base layer in the first stages of production. Q: Is 4T FORTE™ built on a mould? A: Yes and no. A flexible thermo-active mould is used in the lamination phase of the production process to ensure perfect matching of the sail’s three-dimensional shape while all of the many structural components are permanently bonded together. Q: How are the individual layers put together ? A: 4T FORTE™’s several structural components, from the primary load-bearing yarns, secondary load-bearing multiaxial scrims, to external abrasion protection layers, are bonded together by thermoplastic infusion under vacuum pressure at high temperatures. Q: What is the warranty on 4T FORTE™ ? A: Every 4T FORTE™ sail comes with a three-year warranty against delamination (conditions apply, see warranty documents for details). Q: How can 4T FORTE™ be so light and strong at the same time? A: Because, thanks to the MMS™ system, every component of 4T FORTE™ contributes to its structural integrity, and there are no elements which add to the weight but very little to the strength, like mylar films, taffetas, glue or resin. Q: What does “FORTE” exactly mean? A: “Forte” is an Italian word meaning “Strong”. But also: solid, rugged, robust, muscular, determined, forceful, intense, talented, …

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