A sail membrane impregnated with nanomaterials results in a surface structure especially suited for sailing with wind astern, which can thus be used for the making of spinnakers and gennakers according to its German inventors in U.S. Patent Application 20100000456.
Uwe Stein (Heinsberg, DE) and Heiner Schillings (Heinsberg, DE) manufactured a sail membrane of woven synthetic fiber fabric which is provided with microroughness in the form of intersecting groove families or sets arranged so as to achieve a density of 5 to 25 grooves/mm and deposited on or integrated into the fabric structure. The sail is characterized by hydrophobization achieved by means of perfluoropolyalkylene and a nanoparticle coating.
The sail membrane is impregnated with a nanoparticle layer aimed at improving the membrane's water repellency. Its water absorptiveness can be significantly reduced in this way and the sail remains dry even when in use.
The sail is covered with a continuous coating of a water-repellent agent--as well as a coating intended to reduce the permeability to wind which can be dispensed entirely over the sail so that altogether a considerable reduction in weight of both a dry sail and of a sail in use at a given time is achieved.
The term "sail membrane" means any woven fabric made of synthetic fibers suited for and/or employed in sailmaking. Such sail membranes are, in particular, intended for the making of sails used (also) when sailing with astern wind. The fabrics may be manufactured from fibers of a single type such as, for example, polyamide fibers, polyolefin fibers and polyester fibers but may as well comprise mixed systems. Said fabrics may be coated in a manner known per se with a view to reducing or eliminating their permeability to air and, as a rule, are hydrophobized. To bring down their permeability to air the fabrics may also be rolled and/or treated thermally, for example by fusing a fiber with a low melting point of a mixed fabric consisting of various synthetic fibers.
Especially preferred materials are polyamide (Nylon-6.6), polyester as well as polyethylene (Dyneema™ and/or Spectra ™).
The sail membrane has a groove density within a groove family ranges between 5 and 25 grooves/mm corresponding to a groove crest spacing of 200 microns to 40 preferably 8 to 20 grooves/mm corresponding to a crest spacing ranging between 125 microns and 50 microns.
The amplitude of the grooves, i.e. the height of the valleys between two crests up to the crest top preferably amounts to 25 to 75% of the crest spacing of a groove family and in particular 40 to 60%.
Essentially, the all the grooves of each family extend parallel to each other and, to all intents and purposes, may be arranged on the fabric in any conceivable orientation and direction. However, preferred is a diagonal arrangement at an angle of 45 degrees in relation to the warp or weft filaments, +/-15 degrees. Especially preferred is an essentially diagonal arrangement at 45 degrees because such an extension is best suited to cover up the irregularities of the fabric.
Microroughness in the form of at least two parallel extending groove families may be integrated into the fabric structure in any desired manner, for example by printing, weaving in, applying rows of nanoparticles or by rolling-in methods. Especially preferred is the calendaring method using a structuring or groove roller.