190results about "Rotary propellers" patented technology

The invention discloses a ship propeller energy-saving rectifying device with diversion wings, and particularly relates to the technical field of ships, the ship propeller energy-saving rectifying device comprises a ship body, a driving rod is arranged at the rear end of the ship body, a propeller is arranged at the rear end of the driving rod, and a plurality of diversion wings are fixedly installed on the outer wall of the driving rod in an annular array mode. An L-shaped fixing support is arranged above the driving rod, the L-shaped fixing support is installed on the rear side of the ship body, a rectifying mechanism is installed at the bottom end of the vertical position of the L-shaped fixing support, the rectifying mechanism comprises an annular flow guide cover, and the propeller is located on the inner side of the annular flow guide cover. According to the ship propeller energy-saving rectifying device with the flow guide wings, through the synergistic effect of the flow guide wings and the rectifying mechanism capable of being dynamically adjusted, the inflow condition of the disc face of the propeller is improved, pre-rotation and non-uniformity of water flow are effectively weakened, and therefore the propelling efficiency of the propeller is improved, and fuel consumption and operation cost are reduced.

Methods and systems are provided for nautical stationkeeping of free-floating objects. In one example, a method includes adjusting translational motion of a body freely floating in water by rotating the body. The translational motion may be adjusted, for instance, to maintain the body within a geographic area. In certain examples, the adjustment of the translational motion may be realized via a Magnus effect induced by rotating the body. The body may be configured as, for example, a free-floating object such as a wave engine.

A ship propulsion machine (1) includes a propeller (2), an engine (4) configured to rotate the propeller (2), the engine (4) serving as a first power source, a motor (17) configured to rotate the propeller (2), the motor (17) serving as a second power source, an inverter (19) configured to control driving of the motor (17), an engine drive shaft (21) connected to a crank shaft (6) of the engine (4), a motor drive shaft (22) connected to an output shaft (18) of the motor (17), a transmission shaft (23) connected to a propeller shaft (3) provided with the propeller (2), and a power switching mechanism (24) configured to switch a connection mode of the engine drive shaft (21), the motor drive shaft (22), and the transmission shaft (23) to switch a power source for rotating the propeller (2) between the engine (4) and the motor (17).

A variable toroidal propeller (10) is proposed, comprising a hub (12) and toroidal propeller blades (14) connected to the hub (12). The hub (12) is configured to operably couple the blades (14) to an actuator (44), and the blades (14) are configured to deform when the actuator (44) is operated.

A kind of assembly method of paddle hub, the method includes the following steps: first step: repair sliding block inner hole, the gap value of the outer circle of crank pin on crank disc and inner hole meets the inspection standard;Second step: repair sliding block and the sliding block groove on piston rod, so that it meets the requirement;Repair groove sliding block or sliding block groove until the gap value meets the inspection standard;Third step: the paddle shell is connected with hollow support, then install crank disc, fix the crank pin on the upper end of crank disc, then sliding block is sleeved on the outer circle;Fourth step: piston rod drops into the paddle shell, after sliding block enters sliding block groove, make the vertical movement stroke of sliding block and crank pin be synchronous with piston rod drop, piston rod stops descending after descending to appropriate position, then fix crank disc;Fifth step: other parts in the assembly of paddle hub.The design sets the test index between crank pin, sliding block and piston rod to improve the operation accuracy of mechanism.Therefore, the assembly quality of the paddle hub of the design is high.

The application provides a scalable propeller hub cap fin for a ship, and belongs to the field of ship propulsion. The application solves the problem of poor energy-saving effect of a traditional cap fin in the whole voyage. The application comprises a propeller hub, a plurality of blades which are uniformly distributed on the propeller hub, a propeller hub cap which is arranged at the rear end of the propeller hub, a plurality of fin blades which are arranged one by one and correspond to each blade, all the fin blades are in sliding connection with the propeller hub, and a hydraulic adjusting device which is arranged in the propeller hub cap and is used for driving each fin blade to extend out of the propeller hub or retract. The application is mainly used for changing the running state of the propeller.

The utility model discloses a paddle antifouling device based on an ultrasonic module, which comprises a double-paddle propeller and an ultrasonic cleaning device arranged in a ship body, two symmetrical direction adjusting blades swinging independently are arranged at the tail end of the double-paddle propeller, and a swinging antifouling blade is further arranged at the tail end of the ship body. The top of the antifouling blade is linked to an ultrasonic cleaning device in the ship body through a rotating shaft, a cavitation groove and an impact groove which are symmetrical are formed in the two side faces of the antifouling blade, an electrically-controlled rotating paddle is arranged in the cavitation groove, and an ultrasonic generator is arranged in the impact groove. After the ultrasonic cleaning device is improved, the damage to the propeller is reduced; ultrasonic waves are transmitted into water by taking the rotating paddle on the antifouling blade as a medium to cause vibration, so that a cavitation phenomenon is generated, bubbles after being buffered are broken and attached to the surface of the propeller, and the damage is smaller; the antifouling blades can also play a certain role in propelling and redirecting the ship body; and the propeller is additionally cleaned under the assistance of direct-flushing sound waves or high-pressure water flow.

The application discloses a longitudinally foldable water-air dual-purpose propeller, and belongs to the technical field of cross-medium aircraft propulsion, comprising a new-configuration hub, a longitudinal folding mechanism, a limiting structure and a down-bending propeller blade with a preset down-bending angle; the configuration of the propeller enables the down-bending propeller blade to be completely unfolded to form a first working configuration through centrifugal force in air, and the down-bending propeller blade to be passively folded and limited to form a second working configuration through hydrodynamic lift in water; the longitudinally foldable water-air dual-purpose propeller can automatically complete mode switching according to the difference between working media without any active control mechanism, and can maintain high efficient propulsion performance in both media.

Described herein is a rotor blade assembly (100) and a method for generating a lift in a fluid installation. The rotor blade assembly includes an arcuate rotor blade (102) that is configured to be rotated about its axis Y. One or more motion transmitting members (106, 114, 116) are provided that connect the arcuate rotor blade with at least one power generating member (104) for transmitting torque from the arcuate rotor blade to the at least one power generating member (104). The fluid incident on the arcuate rotor blade is caused to flow over a first leading edge L1 of a rotor blade towards a central rib R of the rotor blade (102). This fluid flow is then caused to flow along the central rib R of the rotor blade towards a stem section of the rotor blade from where the fluid exits, thereby causing rotation of the rotor blade.

This invention relates to the field of marine propulsion technology, specifically to an auxiliary propulsion structure for electric ships. The structure includes a ship hull, a propeller mounted on the bottom of the hull, and rotating rods fixedly connected to both sides of the hull. An auxiliary propeller is mounted on each rotating rod. Through an idling cooling mechanism, when the water inlet is above the water surface, causing the drive rod to drive the auxiliary propeller to idle, the idling cooling mechanism opens an emergency water path. This allows pre-stored cooling water from the tank to be precisely delivered via drip pipes to the junction of the drive rod and the bearing. This directional dripping forms a water film at the friction interface, providing immediate lubrication and drag reduction, as well as rapid heat absorption and cooling, preventing high-temperature wear, deformation, or sintering of components. Compared to traditional unprotected designs, this mechanism is fast-responding and highly targeted, minimizing damage to core components during idling and ensuring reliable operation of the auxiliary propeller in complex waters.

The invention discloses a propeller hub of a marine water-based hydraulic controllable-pitch propeller device. The propeller hub is fixedly connected with a propeller shaft through a shaft flange bolt and is fixedly connected with an oil cylinder through a propeller hub body and an oil cylinder screw; the pistons are connected with propeller shafts through piston rods; the blades are fixedly connected with the crank disc through blade root screws; a cavity A is formed between the left side of the piston and the oil cylinder, a cavity B is formed between the right side of the piston and a supporting base of the propeller hub body, a cavity C is formed between a sliding block disc of the piston rod and a propeller shaft, a blade root bearing is arranged on the blade, the crank disc and a blade root hole part of the propeller hub body and is made of a water-lubricated composite material, and the end face, matched with the propeller hub body, of the crank disc is subjected to ceramic spraying cladding. The piston and the oil cylinder are sealed by adopting a GSF glyd ring adaptive to a water medium; a reversing stop device is arranged in the piston; and discharge holes are respectively formed in the propeller hub body and the crank disc. The device is applied to a water medium hydraulic controllable-pitch propeller device, pollution caused by leakage of a mineral hydraulic oil controllable-pitch propeller device is thoroughly solved, and the sealing requirement of the device is lowered.

The utility model relates to the technical field of underwater robots, in particular to a propeller composite wheel with a convertible underwater motion state for an observation and maintenance robot. A propeller outer wheel is installed outside the pressure-resistant hub, a buoyancy adjusting device is installed between the propeller outer wheel and the pressure-resistant hub, a sealing partition plate is installed in an inner cavity of the pressure-resistant hub, air holes are formed in the surface of the pressure-resistant hub, the buoyancy adjusting device is communicated with the first sealed cabin through the air holes, and an exhaust pump is installed in the first sealed cabin; a driving motor is mounted in the second sealing chamber, gas between the buoyancy adjusting air bag and the first sealing chamber in the pressure-resistant hub is exhausted through the exhaust pump, the size of the buoyancy adjusting air bag is changed, and rapid and repeated adjustment of'zero buoyancy-negative buoyancy 'of the propeller composite wheel is achieved. The underwater robot can be used as a propeller, a roller and a walking foot so as to adapt to a complex underwater operation environment, so that underwater observation and maintenance operation are completed, and the environment adaptability is high.

The utility model provides a new energy leisure ship, which is characterized by comprising a ship body, a ship body, a ship body and a ship body, the ship body is made of light materials and comprises a cabin bottom and a deck, and at least part of the cabin bottom and at least part of the deck define a containing space. The power system comprises an oar and a motor which are arranged in the containing space, the oar is provided with a rotatable oar blade, the oar blade is located on the outer side of the cabin bottom, and the motor is in transmission connection with the oar to drive the oar blade to rotate; the energy system comprises a power supply arranged in the accommodating space and a power generation device arranged on the deck, and the power generation device is electrically connected with the power supply; the power generation device is configured to generate power using natural resources including light energy and / or wind energy. By arranging the power generation device, natural resources can be utilized to generate power, electric energy is supplemented in real time during sailing, the cruising ability is further improved, and meanwhile carbon emission is avoided.

The invention relates to a water sport device, in particular a foilboard, comprising a floating body (4), preferably in the form of a floating board, and a foil device (6) which is secured to the floating body (4) by means of a retaining device (8), wherein the foil device (6) arranged on a link (10) of the retaining device (8) has at least one, preferably at least two foils (16), and the foil device can be transferred via the retaining device (8) from an idle and / or starting position close to the floating body (4) into an operating position below the floating body (4), wherein, in the operating position and during a forward movement, due to an uplift force caused by the foil device (6), the floating body (4) can be transferred into a position in which it is spaced apart from the surface of the water, wherein at least one propulsion device (50) is provided which has at least one motor designed preferably as an internal rotor, which can be controlled by means of a control unit and which is provided for propelling the water sport device and designed in particular at least partially as part of the foil and / or retaining device (6, 8) or arranged on one of these or between these.

The utility model provides a ship vortex elimination fin type paddle based on an energy-saving flow guiding device, and relates to the technical field of ship paddles, the ship vortex elimination fin type paddle comprises a propeller hub, a vortex elimination hub and a hub cap, the vortex elimination hub is in a circular truncated cone shape, and the outer diameter of the end, close to the propeller hub, of the vortex elimination hub is larger than that of the end, close to the hub cap, of the vortex elimination hub; the outer diameter of the end, close to the propeller hub, of the vortex eliminating hub is consistent with the diameter of the end, close to the vortex eliminating hub, of the propeller hub, the outer side face of the hub cap is a spherical surface, the outer diameter of the end, close to the propeller hub, of the hub cap is consistent with the outer diameter of the end, close to the hub cap, of the vortex eliminating hub, and the outer edge line of the hub cap is tangent to the outer edge line of the vortex eliminating hub. The propeller hub, the vortex eliminating hub and the hub cap are arranged, the diameter of the joint of the propeller hub and the vortex eliminating hub is consistent, water flow is smoother from the outer surface of the propeller hub to the outer surface of the vortex eliminating hub, the outer edge line of the hub cap is tangent to the outer edge line of the vortex eliminating hub, and the water flow is smoother from the outer surface of the vortex eliminating hub to the outer surface of the hub cap; and the joint of the propeller hub, the vortex eliminating hub and the hub cap is prevented from bearing larger load.

Provided is an evaluation system comprising a removal means which removes fouling from a surface of a propeller of a vessel, a determination means (412) which determines a fouling degree of the surface of the propeller before the fouling is removed and surface roughness of the propeller after the fouling is removed, and an output means (46) which outputs the fouling degree and the surface roughness.

The application provides a wear-resistant and antifouling propeller and a preparation method thereof, and belongs to the field of coating. The propeller surface is provided with a wear-resistant and antifouling iron-based amorphous alloy coating formed by thermal spraying of iron-based amorphous alloy powder. The wear-resistant and antifouling iron-based amorphous alloy coating has an antifouling ion release channel. The antifouling ion release channel is formed by the communication of a plating layer metal plated on the surface of the iron-based amorphous alloy powder, and the antifouling ion release channel is in a three-dimensional and stereoscopic communication state. The melting point of the plating layer metal on the surface of the iron-based amorphous alloy powder is lower than the melting point of the iron-based amorphous alloy powder, and the preferred plating layer metal is Cu. The amorphous coating is prepared on the surface of the propeller by using the copper-coated amorphous powder as raw material and ultrasonic flame spraying, and the amorphous coating contains an antifouling ion three-dimensional transmission channel. The amorphous coating has excellent wear resistance and antifouling performance. The method has a simple process, can be practically applied in industry, and has a good application prospect in the field of high-erosion marine antifouling and corrosion prevention.

The utility model relates to the technical field of underwater robots, in particular to a motion state change device for an underwater observation and maintenance robot. The propeller composite wheel is installed at one end of the composite wheel position conversion device, and the other end of the composite wheel position conversion device is installed on a main body frame of the robot. The outer edge of the propeller composite wheel adopts a blade design, the propeller composite wheel can be used as a propeller, a roller and a walking foot under the action of a driving motor and a speed reducer, and a mounting bracket rotates in a horizontal plane by driving an outer rotor II; the outer rotor I is driven to enable the composite wheel position conversion device to rotate in a vertical plane relative to the assembly mounting and fixing flange, so that the position of the propeller composite wheel in the robot is changed, and the composite wheel position conversion device is matched with the propeller composite wheel for use to realize rapid and repeated adjustment of'zero buoyancy-negative buoyancy 'of the propeller composite wheel; change of floating / crawling / walking state switching of the robot is the core of state switching and walking functions of the robot.

There are included: a motor contained in a top cover; a vertical shaft that is rotationally driven by the motor, the vertical shaft being contained in an extension casing; and a propeller that is rotationally driven by the vertical shaft, the propeller being provided at a gear casing. A heat exchanging member is provided that is positioned below an anticavitation plate and above a propeller shaft that rotationally drives the propeller, and inside the heat exchanging member, a cooling oil channel member is provided that cooling oil for cooling the motor flows through.

The present invention relates to a ship flow control system having a pre-swirl flow control fin, wherein a swirl flow is generated opposite to the propeller rotation direction such that the ship propulsion efficiency is improved without increasing cavitation and hull fluctuation pressure occurring in the upper portion of the starboard of the ship. The ship flow control system comprises a flow control fin installed in a curved portion of the stern of the port side of the ship positioned in front of the propeller so as to be inclined toward the lower side with respect to the basic flow direction of seawater, thereby inducing the seawater flow direction to face the lower side of the propeller. By generating a swirl flow in the counterclockwise direction, which is opposite to the propeller rotation direction, such that the ship propulsion efficiency is improved without increasing cavitation and hull fluctuation pressure occurring in the upper portion of the starboard of the ship.

The utility model belongs to the technical field of marine propellers, and particularly discloses an adjustable marine propeller which comprises a shell, a plurality of blades are arranged on the outer side of the shell, and an adjusting assembly is arranged in the shell. The adjusting assembly comprises a driving part and an adjusting part, the adjusting part comprises a sliding block, the outer end of the sliding block is fixedly connected with a plurality of connecting blocks, one end of each connecting block is connected with a rotating rod, and one end of each rotating rod is connected with a rod body; the driving assembly comprises a hydraulic cylinder, the hydraulic cylinder is located in the shell, the output end of the hydraulic cylinder is fixedly connected with a push plate, and the interior of the shell is fixedly connected with a connecting rod. Through the arrangement of the adjusting assembly, during high-speed navigation, the pitch angle of the blades can be dynamically adjusted according to the water flow resistance and the engine load; the effects of reducing the water flow resistance of the propeller and reducing the load of the propeller motor are achieved, and the problems of heating and power loss caused by high-rotating-speed overload of the propeller motor are effectively solved.

The invention discloses a bionic shaftless rim thruster and a full parametric modeling method thereof. The bionic shaftless rim thruster comprises a bionic conduit, an inner ring, a first bionic propeller blade, a second bionic propeller blade and a third bionic propeller blade, an inner ring is arranged in the bionic catheter and attached to the interior of the bionic catheter. A first bionic propeller blade, a second bionic propeller blade and a third bionic propeller blade are arranged in the middle of the long axis of the inner ring; the first bionic propeller blade, the second bionic propeller blade and the third bionic propeller blade are coaxially arranged; the first bionic propeller blade, the second bionic propeller blade and the third bionic propeller blade are arranged at intervals of 120 degrees. Blades of the bionic rim thruster are of a unique bionic whale fin structure, thrust is provided through a rotor, tip vortexes are effectively reduced due to the appearance characteristic, and the bionic rim thruster plays an important role in improving the thrusting efficiency of a propeller. And the edge of the propeller is also provided with a unique bionic structure, so that the hydrodynamic efficiency of the propeller can be effectively improved.

The invention discloses a pre-rotation flow guide cover for a marine energy-saving device and the marine energy-saving device, and the pre-rotation flow guide cover comprises a base which is of a rotary body structure and is provided with a flow guide curved surface; the arc-shaped guide pipe is fixed to the base and is coaxially arranged with the base, and a water flow channel is formed between the inner wall face of the arc-shaped guide pipe and the flow guide curved face; one end of each full-width pre-rotation guide vane is positioned on the inner wall of the arc-shaped guide pipe, and the other end of each full-width pre-rotation guide vane extends to the base; one end of each half-range pre-rotation guide vane is positioned on the inner wall of the arc-shaped guide pipe, and the length of each half-range pre-rotation guide vane is smaller than that of each full-range pre-rotation guide vane; the multiple full-width pre-rotation guide vanes and the multiple half-width pre-rotation guide vanes are sequentially arranged at intervals along the inner wall of the arc-shaped guide pipe. By means of the flow guide cover, a flow guide cover structure capable of achieving multi-stage pre-rotation can be constructed, the flow guide curved surface and the inner wall face of the arc-shaped guide pipe are used for applying first-stage pre-rotation to incoming flow, the full-range pre-rotation guide vane can achieve large-scale rectification on the incoming flow, and the half-range pre-rotation guide vane can conduct fine repairing on speed distortion of a local wake flow area.

The utility model discloses a double-body foldable underwater explorer, which relates to the technical field of underwater operation auxiliary equipment and comprises a floating body component, a platform, an underwater operation cabin, a positionable connecting mechanism, a lifting adjusting mechanism and a control component. The underwater operation cabin is detachably connected with the floating body assembly through the positionable connecting mechanism, the underwater operation cabin can keep the underwater preset depth under the action of the positionable connecting mechanism, and the lifting adjusting mechanism is installed on the platform, connected with the underwater operation cabin in a matched mode and used for driving the underwater operation cabin to ascend and descend so as to switch the operation state and the navigation state. The control assembly is installed on the platform or the floating body assembly. The floating body assembly bearing platform is adopted and matched with the independent underwater operation cabin, underwater preset depth fixing of the operation cabin is achieved through the positionable connecting mechanism, safety and comfort are improved, and production and assembly difficulty and transportation and storage cost are greatly reduced by being detachably folded and matched with the portable wheel set.

The invention relates to a vehicle water navigation control method and device, computer equipment, a computer readable storage medium and a computer program product, and can be applied to the technical field of vehicles. The method comprises the steps that water depth information of a wading area where a vehicle is located and wheel torque information of the vehicle are obtained; under the condition that the water depth information is larger than a preset water depth threshold value and the wheel torque information is smaller than a preset torque threshold value, the vehicle is controlled to enter a water sailing mode; a first propeller control instruction of the vehicle is generated according to the gear signal and the pedal signal of the vehicle in the water navigation mode; and according to the first propeller control instruction, the rotation direction and the rotation speed of a propeller arranged on the vehicle are controlled so as to control the vehicle to sail on the water. By adopting the method, the accuracy of vehicle water navigation control can be improved.

This utility model belongs to the field of underwater robot technology and discloses an underwater inspection and survey robot, including a support frame, a control box installed inside the support frame, a camera installed inside the control box, an extension plate installed inside the support frame, a mounting bracket installed on the lower surface of the control box, an outer shell fixedly connected to the mounting bracket, the outer shell being located on the lower surface of the control box, a cross-shaped component fixedly connected inside the outer shell, a motor body fixedly connected to the outside of the cross-shaped component, a filter plate rotatably connected inside the outer shell, a connecting rod connected to the output end of the motor body, a fan blade connected to the other output end of the motor body, and a cutting component fixedly connected inside the outer shell. This utility model achieves underwater propulsion by the motor driving the fan blade, and the other end drives the filter plate to rotate via the connecting rod. The filter plate blocks debris and prevents accumulation, effectively reducing the interference of debris on the components.

A vortex inducer is applied to the pressure face of a propulsion rotor blade. The vortex inducer defines an aft face located forward of the trailing edge of the blade. In operation, the vortex inducer generates a primary vortex behind its apex, which induces a counterrotating secondary vortex through viscous coupling at the trailing edge. The secondary vortex accelerates and deflects the suction face wake, enhancing overall blade performance. The system is applicable to propellers, helicopter rotors, prop-rotors, fan blades, and marine propellers.

The invention discloses a cavitation-erosion-resistant medium-entropy alloy coating as well as a preparation method and application thereof, and belongs to the technical field of functional alloys and surface strengthening materials. The chemical formula of the cavitation-erosion-resistant medium-entropy alloy coating is CoCrNiNbx, x ranges from 0.6 to 1.0, and the atomic ratio of the coating ranges from 0.6 to 1.0. Under a phase change mechanism triggered by Nb regulation and control, the cavitation-erosion-resistant medium-entropy alloy coating with an FCC + Laves double-phase structure is obtained through accurate control over the Nb content, balance of strength and toughness is achieved, the FCC + niobium-rich Laves phase is continuously distributed in the cavitation-erosion-resistant medium-entropy alloy coating, impact loads are effectively dispersed, crack propagation is blocked, and the cavitation-erosion-resistant performance of the coating is greatly improved. In an ultrasonic cavitation experiment, the cumulative mass loss of a cavitation-resistant medium-entropy alloy coating sample with x equal to 1.0 is only 2.8 mg, the average loss rate is 0.2333 mg / h, the cumulative mass loss is increased by about 26 times compared with that of a 316L matrix, and the average loss rate is increased by about 20 times compared with that of a sample without Nb.

The utility model discloses a novel corrosion-resistant propeller, which relates to the technical field of propellers, and comprises a mounting sleeve, blades, a support connecting cylinder and a limiting piece, the mounting sleeve is a cylinder body with two open ends, the mounting sleeve is provided with a stepped clamping groove, one end of each blade penetrates through the side wall of the mounting sleeve and is integrally provided with a limiting part, and the limiting part is clamped in the stepped clamping groove; the supporting connecting cylinder and the installation sleeve are coaxially arranged and located in the installation sleeve, and a plurality of supporting blade plates distributed along the circumference of the axis of the supporting connecting cylinder are fixed to the outer side of the supporting connecting cylinder. Therefore, the connecting area of the propeller blades and the mounting sleeve is greatly increased, the structural strength of the installed propeller blades can be improved, the defects that an existing corrosion-resistant propeller is insufficient in overall structural strength and prone to deformation can be overcome, meanwhile, the detachable performance of the corrosion-resistant propeller is reserved, and maintenance is convenient.

The invention describes a device for reducing the propulsive power demand of a watercraft, in particular a vessel, and arranged in front of the propeller of the vessel in the direction of water flow, comprising a flow guide surface, in particular a nozzle ring or partial nozzle ring, at least one inner fin protruding from the flow guide surface; and at least one outer fin protruding from the flow guide surface, where when the device is mounted on the watercraft, one end of the inner fin is fixed to the flow guide surface and the other end is attached to the watercraft; one end of the flow guide surface outer fin is attached to the flow guide surface, the other end of the flow guide surface outer fin forms a free end, and the at least one inner fin and / or the at least one outer fin are / is made of a composite material.