MEASUREMENT COMMITTEE –10 November 2003 Item: 14 DRAFT ISAF GUIDE TO SAIL MATERIALS This paper is aimed at giving guidance on sail materials and construction methods for those classes which wish to place controls on these issues. Background......................................................................................................1 Construction of a Sail ...................................................................................1 Exclusion of Sail Materials from a Class ......................................................2 Recommendation:............................................................................................3 Appendix A - Fibres that can be found in Sail materials...................................5 Background Construction of a Sail The Equipment Rules of Sailing (2001-2004) define some basic principles regarding the construction of a sail. These are: G.1.3 Ply : A sheet of sail material G.1.4 Soft Sail : A sail where the body of the sail is capable of being folded flat in any direction without damaging any ply other than by creasing. G.1.5 Woven Ply : A ply which, when torn, can be separated in to fibres without leaving evidence of a film. G.1.6 Laminated Ply : A ply made up of more than one layer. G.1.7 Single-ply Sail : A sail, except at seams, where all parts of the body of the sail consist of only one ply. The majority of classes then go on to specify in their class rules, the material of the ply and, in some cases, control the method of the construction of the sail. Many classes used the IYRU Sail Measurement Instructions, (last published in 1986), as a guide to definitions concerning sails. In particular, it contained a default prescription which prohibited sail material that shows evidence of a DRAFT Page 1 of 14 MEASUREMENT COMMITTEE –10 November 2003 Item: 14 film when torn. Accordingly classes which specified, “Sails shall be made and measured in accordance with the IYRU Sail Measurement Instructions”, prohibit Mylar sails. The Sail Measurement Instructions have been superseded by the Equipment Rules of Sailing (ERS) and the Standard Class Rules (SCR) and no longer contain this default and accordingly any restrictions on permitted sail material need to be specified in the class rules. Further sail definitions can be found in the ERS and in Appendix B of this document. Exclusion of Sail Materials from a Class Class Rules are a means for Class Associations to limit development, control costs and therefore ensure fair and safe sailing. Where sail materials are concerned, class rules may restrict the permitted materials to be used whilst racing. As many existing class rules were written before the introduction of modern sail materials, they do not extend to the full market of materials that they are intended to cover. Below are examples of rules used to restrict wording and how some sail materials aren’t covered. “Polyester” refers to the following materials only: Polyethylene Terephthalate (PET), Polyethylene Napthalate (PEN) and all of the associated Trade Names including Dacron, Terelene, Teteron, Trevira, Diolene and Pentex. Examples of some classes that refer to Polyester as the only permitted sail material are the Optimist and J-24. The essence of these class rules is to allow woven materials only and to exclude expensive high performance materials. However, Class Associations should note that Pentex is classed as a polyester which is a high performance material that falls under the basic polyester definition. “Aromatic polyamide” refers to the following materials only: DRAFT Page 2 of 14 MEASUREMENT COMMITTEE –10 November 2003 Item: 14 Poly p-phenylene terephthalamide and all of the following associated Trade names including Kevlar. An example of a class that refers to Aromatic Polyamides is the Soling. Here the essence is to restrict the use of aramids in the class. The wording used is probably too definitive and does not include other aramids such as Twaron and Technora which are referred to as aromatic copolyamides. “Polyamide” refers to the following materials only: Nylon, Poly p-phenylene terphthalamide, and all of the following associated Trade names including Kevlar, Twaron and Technora. Examples of some classes that refer to Polyamides are the Soling and the 470 Class, and is used in reference to the spinnaker only. The wording used is too vague with many other modern materials falling into this category such as Kevlar, Twaron and Technora. It was presumably originally intended only to allow for Nylon to be used in spinnakers as well as polyester. “Polyethylene Terephthalate” or “PET” refers to the following materials only: Polyethylene terephthalate (PET) and all of the following associated Trade names including Dacron, Terelene, Teteron, Trevira and Diolene. An example of a class that refers to PET is the J-80 Class. This is very specific wording and refers to single type of sail material. Some classes have tried to ban certain sail material types but have used incorrect wording and “loopholes” have appeared in the rules. Some sail materials are not considered in any of the above wording, including PBO, Spectra, Dyneema, Vectran, Carbon Fibre and Cuben Fibre. Recommendations: Classes are recommended to use the terms as defined in the Equipment Rules of Sailing, which minimises the chance of mis-interpretation. Below is a list of recommended wording and the sail materials they will allow. DRAFT Page 3 of 14 MEASUREMENT COMMITTEE –10 November 2003 Item: 14 Polyethylene Terephthalate refers to the following materials: Polyethylene Terephthalate (PET), and the associated trade names including Dacron, Melinar, Melinex, Terelene, Teteron, Trevira and Diolene. Polyester refers to the following materials: Polyethylene Terephthalate (PET), Polyethylene Napathalate (PEN) and the associated trade names including Dacron, Melinar, Melinex, Terelene, Teteron, Trevira, Diolene and PENTEX. Aramids refers to the following materials: Poly p-phenylene terephthalamide and all of the associated trade names including Kevlar, Twaron and Technora. High Performance Polyethylene (HPPE) refers to the following materials: Spectra and Dyneema and all associated types and trade names. Liquid Crystal Polymer refers to the following materials: PBO and Vectran and all associated types and trade names. Carbon Fibre refers to the following materials: Carbon Fibre and all associated types and trade names. Cuben Fibre refers to the following materials only: Cuben Fibre and all associated types and trade names. As there are so many different variations on the chemical structure of a fibre and so many different trade names it is very difficult to include all associated fibres without writing out a complete list. DRAFT Page 4 of 14 MEASUREMENT COMMITTEE –10 November 2003 Item: 14 Appendix A - Fibres that can be found in Sail materials Below is a list of some of the different fibres that may be found in modern sail materials. However, it should be noted that in the majority of cases the fibre name is only a trade name and does not represent the actual properties of the fibre. There are several chemical groups into which these fibres can be split. They are; POLYESTERS, NYLONS, POLYETHYLENES and ARAMIDS. Where a description is given in italic it is a direct quote from the Federal Trade Commission list of Rules and Regulations under the Textile Fibre Products Identification Act. Below is a diagram illustrating the different chemicals and the families they are derived from. DRAFT Page 5 of 14 MEASUREMENT COMMITTEE –10 November 2003 Item: 14 Polyester: “A manufactured fibre in which the fibre-forming substance is any long-chain synthetic polymer composed of at least 85% by weight of an ”ester” of a substituted aromatic carboxylic acid, including but not restricted to substituted terephthalate units, and para substituted hydroxyl-benzoate units.” Polyester is the most common fibre used for woven sail material. Its properties include good UV and flex resistance, as well as being relatively inexpensive. Traditionally white in colour although it can easily dyed to suit the sailmaker’s demands. A proven fibre for durability, polyester has over recent years been replaced by higher modulus fibres, such as modern aramids, for most racing applications (where class rules permit). Woven Dacron, Polyester laminates and Polyester spinnaker cloth are all products made from this versatile fibre. Polyester fibres are also called by other manufacturers brand names of Dacron, Terelene, Teteron, Trevira and Diolene. The standard woven polyester weave can come in two forms. The first is balanced plain weave sail material, where the warp and the fill have the same amount of crimp. This induces a tight weave which is stretchy along both the warp and the fill but not so along the bias which is held by the interlock between the fibres. The second is a highly orientated weave where the crimp is limited to the warp fibres. This produces a cloth which is stretchy along the warp and the bias but not along the fill. Dacron®: (Polyethylene terephthalate) or PET. Dacron is the original polyester fibre and was first introduced in 1953 by Dupont. This fibre is the foundation of traditional woven sail material. Dacron fibres are also used in cruising laminates and Polyester laminated sailcloth where the use of DRAFT Page 6 of 14 MEASUREMENT COMMITTEE –10 November 2003 Item: 14 expensive, low stretch, aramid fibres is not necessary. The chemical structure for PET is shown below: This can be further broken down into its chemical groups by closer analysis of the structure. The ester group is represented by the chemical structure of This is the backbone of all polyesters and is present in the chemical make up of both PET and PEN. The ethylene group is represented by the chemical structure of This is the linkage part of the structure which is also represented in the structures of both PET and PEN. The ester groups in the polyester chain are polar with the oxygen atom having a negative charge and the carbon atom having a positive charge. The positive and negative charges of the different ester groups are attracted to each other.