Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H9/00—Marine propulsion provided directly by wind power
  • B63H9/04—Marine propulsion provided directly by wind power using sails or like wind-catching surfaces
  • B63H9/06—Types of sail; Constructional features of sails; Arrangements thereof on vessels
  • B63H9/067—Sails characterised by their construction or manufacturing process

Definitions

• the present invention relates to a sail as described in the claim hereafter.
• the purpose of the invention is to enhance a sail's properties so that a greater forward thrust of the sailing boat can be achieved than with a similarly sized, conventional sail.
• the invention is based on at least one flap fixed behind battens that stiffen the back part of the sail, and which can be tightened perpendicular to the plane formed by the sail.
• the invention is based on flaps fixed in the vicinity the luff of the sail, that are raised whenever eddies are formed at the luff.
• characteristic to the sail pre ⁇ sented in the invention is what is said in the claim part.
• the invention increases the total efficiency of the sail, and a greater lift is achieved.
• the fluid dynam ⁇ ic drag is decreased especially in situations where the wind direction is changing rapidly.
• a sail described in this inventions is relatively cheap to manufacture. Although primarily meant for boats, this kind of sail can be applied to all wind driven vehi ⁇ cles, such as windsurfers and land or ice crafts.
• Figure 1 is a side view of one implementation of the invention for a sail.
• Figures 2 and 3 show a sectional views of the same sail, illustrating the behaviour of the sail in dif ⁇ ferent flow situations.
• Figure 4 is an enlargement of fig. 3.
• FIG. 5 represents another implementation of the invention.
• Figure 6 is a sectional view of fig. 5.
• Figure 7 shows a performance comparison, as tested in the wind tunnel, of a conventional sail vs. a sail as described in this invention.
• FIG. 1 shows a sail 10 as described in this invention, fitted into a mast 1.
• the foot of the sail would be fastened into the boom.
• the sail 10 is formed by a soft membrane made of sailcloth, stiffened in its rear edge by battens 3a - 3c. The battens help to keep the sail in shape under the pressure of the wind. Flaps la and lb are sewn on both sides of the sail.
• the flaps la and lb are fastened to the sail only in their front edge and can be lifted freely at their rear end to an angle restricted by a stopper 5, .Another, movable flap 2 is sewn into the leech of the sail.
• the flap can be formed by sewing the rear ends of the battens 3a - 3c some 5 cm into the sail 10. In conventional sails battens 3a - 3c are sewn all the way to the leech.
• the foremost flaps la and lb and the leech flap 2 work in different wind conditions as follows.
• the leech flap 2 deflects the airflow strongly from the surface of the sail 10, and pressure rises on the windward side of it. On the leeward side, airflow is accelerated, resulting in a decreased pressure, hence increased suction. The flap 2 thus considerably increases the sail's lift.
• the flaps la and lb in the front part of the sail function alternately, depending from which side the wind hits the sail 10.
• a so-called separation bubble is formed on the windward side of the sail 10.
• the flaps la and lb are equipped with preventers that keep them from overturning completely.
• the upraised flap la or lb forms a hinder to the reversed flow which is directed to the sail 10.
• the leech flap 2 increases the total force of the sail and the forward flaps la and lb decrease the drag.
• a sail presented in the invention equipped with the flaps,increase the Power by 10 to 40%, as compared to a conventional sail.
• Results from the windtunnel tests are shown in Figure 7.
• the lift coefficient CL and the profile drag coefficient CDp of a conventional sail were compared to the values obtained with the type of a sail presented here.
• Figure 7 shows clearly how the lift is increased at all angles of attack. The differences in the profile drag are smaller, but it seems that the effect of the forward flaps is to more or less compensate the extra drag due to the leech flap.
• An appropriate width for the forward flaps is approxi- mately 2% of the sail width, and for the rear flap 0,5% - 1,5%.
• the forward flaps can be in several rows, as in Fig. 4 and 5.
• the width of the leech flap can be varied by fixing the the battens at different places in their pockets. In this manner power can be adjusted from light winds (lots of power) to stronger winds (less power) .
• Forward flaps can be in several rows, and they can cover the height of the sail only partially 6. The aerodynamic efficiency is increased slightly by adding several rows, but so is the manufacturing cost. Flaps 6 can be divided approximately 1 m long pieces so that they act independently at various heights. A sys ⁇ tem consisting of small independent flaps 7 would probably be the most efficient, but the cost of such a system can be far greater than the one presented in Fig. 1.
• the leech flaps 8 can be sewn on both sides of the sail 10. In this case the battens come normally all the way to the leech.
• the flaps 8 on both sides must have their own leech line 9, that permit the flap on the windward side to be raised off the sail from its rear edge.
• the invention presented here work on all kinds of sails that form a wing-like profile under the pressure of the wind. Usually, on boats these are the mainsail and the jib.
• the leech flap can also be fit ⁇ ted into sails without battens, as long as the materi- al used for the sail is stiff enough to allow the flap to be bent more than the leech normally would. Then it is advantageous if the material used in the flaps is more flexible and lighter than the one used for the sail.
• the leech of the sail can be stiffened with an extra layer of cloth, or possibly with a line at the junction of the leech and the flap.
• the sail can be manufactured using the same sewing and gluing techniques as for conventional sails. Sail materials do not limit the use of the invention, either. Since different types of sails may be fixed into the the rig in different ways, the con ⁇ struction of the leech flap and its control lines may vary in different types of sails. The solutions described above can be combined in dif ⁇ ferent ways to achieve desired aerodynamic properties.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Wind Motors (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8542375

Family Applications (1)

Country Status (2)

Citations (4)

• 1995
  • 1995-04-28 FI FI950216U patent/FI2031U1/fi active
• 1996
  • 1996-04-25 WO PCT/FI1996/000226 patent/WO1996033908A1/en active Application Filing

Patent Citations (4)

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