This product is an improved rubber band power glider, including an upper base, a lower base and a holding tube. The holding tube is fixed between the upper base and the lower base. The holding tube is equipped with a rubber band. The end of the rubber band is connected to a rod body, the front end is connected to a hook body, and it is connected to the propeller through the hook body and the sleeve. The advantage of the present utility model is that when the propeller rotates, the rubber band is restricted by the inner diameter of the holding tube and will not shake excessively, thus ensuring the smooth flight of the glider. In addition, since the holding tube can be made of lightweight and hard materials, such as plastic tubes, it is less likely to be damaged when landing, thereby extending the lifespan of the glider.

I. Detailed pictures of Accessories




Ii. Detailed packaging pictures

Iii. Clear large image of the finished product














Each box contains 270 pieces, with three inner boxes and three patterns, evenly assembled. It is an excellent choice for unified courses in school educational institutions
































            

Flight adjustment is the application of flight principles. Without the most basic knowledge of flight principles, it is very difficult to adjust the flight model well. Counselors should guide students to learn aviation knowledge and introduce the relevant basic knowledge based on their acceptance ability and in combination with the needs of production and release. At the same time, it is also necessary to prevent model aircraft activities from being turned into specialized theoretical courses.

I. Lift and Drag

The reason why planes and model planes can fly is that the lift of the wings overcomes gravity. The lift of the wing is formed by the pressure difference of the air above and below the wing. When the model is flying in the air, the air flow rate on the upper surface of the wing increases and the pressure decreases. The air flow rate on the lower surface of the wing slows down and the pressure increases (Bernoulli's Law). This is the cause of the pressure difference between the upper and lower parts of the wing.

There are two reasons for the variation in the flow velocity up and down of the wing: A. Asymmetric airfoil; B. The wing has an Angle of attack with the relative airflow. The airfoil is the shape of the cross-section of the wing. The wing profiles are mostly asymmetrical, with the lower arc being straight and the upper arc curving upward (plane-convex type), and both the upper and lower arcs curving upward (concave-convex type). Symmetrical airfoils must have a certain Angle of attack to generate lift.

The magnitude of lift mainly depends on four factors: A. Lift is directly proportional to the area of the wing; B. Lift is proportional to the square of the aircraft's speed. Under the same conditions, the faster the flight speed, the greater the lift force. C. Lift is related to the airfoil. Generally, the lift of an asymmetrical airfoil wing is greater. D. Lift is related to the Angle of attack. When the Angle of attack is small, the lift (coefficient) increases linearly with the Angle of attack. After reaching a certain limit, as the Angle of attack increases, the lift decreases rapidly instead. This boundary is called the critical Angle of attack.

The wing and the horizontal tail not only generate lift but also drag, while other components generally only generate drag.

Ii. Level flight

Horizontal uniform straight-line flight is called level flight. Level flight is the most fundamental flight attitude. The conditions for maintaining level flight are: lift equal to gravity and pull equal to drag.

Since lift and drag are both related to flight speed, if a model that was originally in level flight increases its horsepower, the pulling force will be greater than the drag, thereby increasing its flight speed. After the flight speed increases, the lift will also increase. If the lift is greater than the gravity model, it will gradually climb. In order to keep the model in level flight at higher horsepower and flight speed, the Angle of attack must be reduced accordingly. Conversely, in order for the model to maintain level flight under conditions of smaller horsepower and speed, the Angle of attack must be correspondingly increased. So, manipulating (adjusting) the model to the level flight state is essentially the correct matching of engine horsepower and flight Angle of attack.

Iii. Climbing

As mentioned earlier, when the model is flying level, if the horsepower is increased, it will switch to climbing. The Angle formed between the climbing trajectory and the horizontal plane is called the climbing Angle. Under the condition of a certain horsepower and a certain climbing Angle, a new force balance may be reached, and the model enters a stable climbing state (with both speed and climbing Angle remaining unchanged). The specific condition for a stable climb is: the pulling force is equal to the component of the resistance force that is applied backward (F=X + Gsinθ). Lift is equal to another component of gravity (Y=GCosθ). When climbing, part of the weight is borne by the pulling force, so a greater pulling force is needed, and the burden of lift is actually reduced.

Similar to level flight, to maintain a stable climb under a certain climb Angle, a proper match of horsepower and Angle of attack is also required. Breaking this match will prevent maintaining a stable climb. For instance, an increase in horsepower will lead to an increase in speed, lift, and the Angle of climb. If the horsepower is too large, it will cause the climbing Angle to keep increasing, and the model will climb along an arc-shaped trajectory. This is a common phenomenon of overturning.

Iv. Gliding

Gliding is a flight without power. When gliding, the resistance of the model is balanced by the components of gravity, so gliding can only fly diagonally downward. The Angle between the gliding trajectory and the horizontal plane is called the gliding Angle.

The condition for stable gliding (with both the gliding Angle and speed remaining constant) is that the resistance is equal to the forward component of gravity (X=GSinθ). Lift is equal to another component of gravity (Y=GCosθ).

The gliding Angle is an important aspect of gliding performance. The smaller the gliding Angle, the farther the gliding distance at the same height. The ratio of the gliding distance (L) to the descent height (h) is called the gliding ratio (k). The gliding ratio is equal to the cotangent gliding ratio of the gliding Angle and is equal to the ratio of the lift to the drag of the model (lift-drag ratio). Ctgθ=1/h=k.

Gliding speed is another important aspect of gliding performance. The larger the lift coefficient of the model is, the smaller the gliding speed will be. The greater the load of the model wing, the greater the gliding speed.

When adjusting a certain model aircraft, the main methods are to raise and lower the adjustment plates and move the center of gravity forward and backward to change the wing Angle of attack in order to achieve the purpose of changing the gliding state.

V. Torque Balancing and Adjustment Methods

Adjusting the model requires not only the balance of attention but also the balance of torque. Torque is the rotational effect of force. The center of rotation of the model aircraft in the air is its own center of gravity, so gravity does not exert a rotational torque on the model. Other forces, as long as they do not pass through the center of gravity, will exert a torque on it. To facilitate the analysis of the model's rotation, the rotation around the center of gravity is decomposed into rotations around three hypothetical axes, which are perpendicular to each other and intersect at the center of gravity. The axis that runs through the front and back of the model is called the longitudinal axis. The rotation around the longitudinal axis is the rolling of the model. The vertical axis that runs through the top and bottom of the model is called the vertical axis. The rotation around the vertical axis is the deflection of the model's direction. The axis running through the left and right of the model is called the horizontal axis, and the rotation around the horizontal axis is the pitch of the model.

For adjusting the model, four types of torques are mainly involved; This is the lift moment of the wing, the lift moment of the horizontal tail wing. The tensile torque of the engine; The reaction torque of the power system.

The lift moment of the wing is related to the pitch balance. The main factors determining the lift moment of an wing include the longitudinal position of the center of gravity, the wing installation Angle, and the wing area.

The lift moment of the horizontal tail fin is also the pitch moment, and its magnitude depends on the tail boom, the installation Angle of the horizontal tail fin and the area.

If the tension line does not pass through the center of gravity, it will form a pitch moment or a directional moment. The magnitude of the tension moment is determined by the tension force and the distance the tension line deviates from the center of gravity. The reaction torque of the engine is the transverse (rolling) torque, whose direction is opposite to the rotation direction of the propeller. Its magnitude is related to the power and the mass of the propeller.

The pitch moment balance determines the Angle of attack of the wing: increasing the head-up moment or decreasing the head-down moment will increase the Angle of attack. Conversely, it will reduce the Angle of attack. Therefore, the adjustment of pitch moment balance is of the utmost importance. Generally, the use of lifting and lowering adjustment plates, adjusting the installation Angle of the wing or horizontal tail fin, changing the upward and downward inclination Angle of the tension, and moving the center of gravity forward and backward have not been achieved.

The directional torque balance is mainly adjusted by the directional adjustment plate and the left and right inclination Angle of the tensile force. The lateral moment balance is mainly adjusted by the ailerons.

 Check the calibration and hand-throw test flight

I. Inspection and correction

 

After a model aircraft is fabricated and assembled, it should be inspected and necessary corrections made. The items to be inspected are the geometric dimensions and the position of the center of gravity of the model. The general method of inspection is visual inspection. For greater accuracy, some items can also undergo some simple measurements.

 

The visual inspection method is to observe whether the geometric dimensions of the model are accurate from three directions of the three views. When looking at the direction from the front, mainly check whether the upper reverse angles on both sides of the wing are equal. Whether the wing is twisted or not; Check if the rear wing is skewed or twisted. The side view direction mainly examines the installation angles of the wings and the horizontal tail and the difference in their installation angles. The upward and downward inclination Angle of the tension line. When looking down, mainly check if the vertical tail fin is skewed. The left and right inclination Angle of the tension line; Check if the wings and the horizontal tail are skewed.

 

For small models, the center of gravity is generally checked by the fulcrum method. A point is selected to support the model. When the model is stable, this fulcrum is the position of the center of gravity.

 

If any major errors are found during the inspection, they should be corrected before the test flight. If the error is small, it may not be corrected for the time being, but one should be aware of it and further observe it during the test flight.

 

Ii. Hand-thrown test flight

 

The purpose of hand-throw test flights is to observe and adjust gliding performance. The method is to hold the fuselage (the center of gravity of the model) with the right hand, raise it above the head, keep the model level, tilt the nose forward towards the wind direction by about 10 degrees, and throw the model in a straight line at an appropriate speed along the fuselage direction. The model then enters an independent gliding flight state. The hand-throwing method should be practiced many times. It is necessary to correct all kinds of incorrect methods. The more common problems include: the model tilting left and right or the machine head tilting upwards. The release is not a straight line from back to front, but an arc around the base of the arm. The release direction is not along the fuselage forward but upwards. The release speed is either too fast or too slow.

 

After release, if the model glides smoothly at a small Angle in a straight line, it is normal flight. A slight turn is also a normal state. When any of the following abnormal flight postures occur, adjustments should be made to bring the model to a normal gliding state

 

1. Wavy flight: The gliding trajectory undulates like waves. It is generally called "light head", meaning the center of gravity is too far back. This statement is correct but not comprehensive enough. In fact, all cases where the overhead moment is too large or the overhead moment is too small, resulting in an excessively high Angle of attack, will cause wavy flight. The adjustment methods are as follows: A. Push rod (pull down the lifting adjustment plate); B. Forward shift of the center of gravity (head counterweight); C. Reduce the installation Angle of the wing; D. Increase the installation Angle of the horizontal tail wing (with the same function as the push rod).

 

2. Dive: The model rushes down at a large Angle. It is generally called "heavy head", but this description is not comprehensive enough. All situations where the head-up moment is too small and the head-down moment is too large, resulting in a too small Angle of attack, will cause the model to dive. The adjustment methods are as follows: A. Pull rod (lift the adjustment plate upwards); B. Shift the center of gravity backward (reduce the counterweight of the aircraft head); C. Increase the installation Angle of the wing; D. Reduce the installation Angle of the horizontal tail wing (with the same function as the pull rod).

 

3. Sharp Turn and downward rush: The model makes a sharp turn to the left (or right) and rushes downward. The reason is that the directional torque is unbalanced or the transverse torque is unbalanced. The specific reasons are mostly the unequal lift on the left and right caused by the wing twist or the directional deflection moment formed by the longitudinal deflection of the vertical tail wing. The consequence of the fuselage bending left and right is the same as that of vertical tail deflection, and it may also cause sharp turns and downward surges. The adjustment methods are as follows: A. Turn the steering wheel in the opposite direction (pedal the rudder); B. Correct the wing distortion (equivalent to pressing the lever to control the aileron).

 

The principle of operating an aircraft or an advanced model aircraft is the same as that of adjusting the model, which is to change the state of torque balance. Primary models generally do not have these rudder surfaces, so the adjustment can only be achieved by changing the shape of these aerodynamic surfaces. There are three methods:

 

A. Heating and shaping: Rotate the part that needs adjustment to a certain Angle by hand and heat it simultaneously (such as blowing air, hot air, baking, etc.), and hold it for a certain period of time to deform it. This method is applicable to paper, blow-molded paper and wood chip components. Generally, the larger the turning Angle, the higher the temperature, and the longer the holding time, the more deformation will be adjusted.

 

B. Contraction and deformation: Apply an appropriate concentration of permeable oil to one side of the wing surface that needs to be adjusted. This side will contract as the permeable oil solidifies, causing the wing surface to intersect.

 

C. Shaping of the frame. Fix the wing surface on the frame as per the adjustment requirements to achieve the purpose of changing the shape. It is generally used in combination with heating or applying paint. This method is applicable to the adjustment of the wing surface of the framework type.

 

 Hand-thrown straight-line distance subject

 

 

I. Three flight modes

 

This event involves a round-trip hand-thrown flight distance competition under the condition of a limited width. There are three factors that determine the score: A. Throwing technique; B. Gliding performance of the model; C. Linear flight performance of the model. There are the following three flight modes:

 

Natural gliding straight-line flight: The release speed is the same as the gliding speed of the model. After release, the model glides along the gliding trajectory in a straight line. The flight distance depends on the release height and the gliding ratio, generally ranging from 6 to 10 meters.

 

2. Horizontal forward straight-line flight: The release speed is slightly greater than the model's gliding speed. After the release, the model first advances horizontally in a straight line for a certain distance and then transitions to natural gliding. This method may increase the distance by 2 to 5 meters compared to natural gliding.

 

3. Climb forward dash straight flight: Release at a greater speed and with a smaller release Angle. After the release, the model climbs up in a straight line at a small Angle and then glides. This method may increase the gliding distance by more than 5 to 10 meters compared to natural gliding.

 

The first method has a lower score, but it is easy to master and has a high success rate. The latter two methods have a longer flight distance, but the technical difficulty of release and adjustment is high, and the success rate is relatively low. Because (a) the direction deviation is directly proportional to the flight distance. After increasing the flight distance, the probability of the model flying out of the edge line increases (the score is invalid after flying out of the edge line). (b) The forward rush, especially the climbing forward rush, is prone to causing the model to stall and rush down or change course and fly out of the sideline. Therefore, in order to achieve good results, it is necessary to learn more about flight adjustment knowledge, improve physical fitness and apply throwing skills proficiently.

 

Ii. Model Adjustment

 

Gliding performance. Gliding performance is the foundation for flying a large straight-line distance. Two issues should be noted when making adjustments. One is to minimize drag to the greatest extent. The model surface should be kept smooth, the components should be streamlined (including counterweights), the front and rear edges should be ground into a circular shape, and the wing surfaces should be flat without distortion, etc. Reducing drag can increase the lift-to-drag ratio, that is, the gliding ratio can be increased.

 

The second point is to adjust to a favorable Angle of attack. The Angle of attack is controlled by the lifting adjustment plate. The lift-to-drag ratios of models with different angles of attack are different. The favorable Angle of attack has the largest lift-to-drag ratio and the longest gliding distance at the same altitude. After normal gliding, it is still necessary to fine-tune the lifting adjustment plate to find the best rudder position.

 

2. Counterweight of the model. Many people have the impression that the heavier the model is, the less it can fly. In fact, that's not the case. The gliding ratio of the model is independent of its weight. On the other hand, the smaller the weight of the model, the less kinetic energy it has, the smaller its ability to overcome resistance, and the smaller the throwing distance. The same principle applies to the fact that a light straw cannot be thrown far. Therefore, for the model of the hand-thrown straight-line distance project, within the range permitted by the rules, the weight should be appropriately increased to enhance the kinetic energy of the model.

 

3. The rigidity of the wing. The initial velocity of the hand-thrown model is relatively large, and the wing is subjected to a large bending moment, which makes it prone to deformation or even flutter, thereby affecting flight performance. For this reason, be careful during the production process to prevent creases from appearing on the wing surface. If the rigidity is still insufficient, it should be appropriately strengthened. The method is to apply glue at the junction of the wing root and the fuselage. Alternatively, reinforcing materials (such as adhesive tape) can be pasted on both sides of one side of the wing root.

 

4. Adjustment for straight-line flight

 

The ideal straight-line flight is when the model has neither directional unbalanced moments nor transverse unbalanced moments, that is, the vertical tail has no deflection Angle (the neutral position of the direction adjustment plate), and the left and right wings are completely symmetrical (without the function of ailerons). This situation not only has the least resistance but also can adapt to changes in speed.

 

B. In fact, the model usually always turns. The reasons are no more than the asymmetry of the wings (in most cases, the wings are twisted), which generates a roll torque, or the vertical tail has a deflection Angle, which generates a directional torque. When encountering such a situation, it is easy to identify the cause and "prescribe the right medicine" to achieve a straight-line flight close to the ideal. We call this adjustment method the "direct adjustment method".

 

C. There is another adjustment method. For instance, due to the twisting of the wings, a torque causes the model to roll to the left, and the component force of the lift to the left makes the model turn to the left. In this situation, instead of directly correcting the distortion of the wing, a bit of right rudder can also make the model fly straight. This adjustment method is called the "indirect adjustment method". Although indirect adjustment can also achieve linear flight, this kind of linear flight has drawbacks: first, it increases drag and reduces gliding performance; Second, it is difficult to adapt to changes in speed. Many models can basically maintain a straight line in the first section but turn and yaw in the second section. The main reason for this is mostly indirect adjustment.

 

Therefore, the "direct adjustment method" should be adopted as much as possible to avoid the "indirect adjustment method".

 

5. Methods to overcome forward stall

 

As mentioned earlier, forward rush and forward rush climb can significantly improve flight performance, but at the same time, there are risks of stall downrush and stall steering. Therefore, overcoming forward stall is the key to improving performance.

 

The measure to overcome forward stall is to improve pitch stability. The specific approach is to appropriately move the counterweight forward to shift the center of gravity, and at the same time, increase the installation Angle difference of the wing and the horizontal tail accordingly to maintain pitch balance. In this way, when the model's forward thrust head-up wing gradually approaches stall, the horizontal tail, due to its small mounting Angle, has not yet stall. The horizontal tail still has sufficient lowering moment to enable the model to enter gliding.

 

Another way to overcome forward stall is to fly with a smaller Angle of attack. Facts have proved that the larger the Angle of attack, the more likely it is to stall and rush down; the smaller the Angle of attack, the less likely it is to enter a stall and rush down.

 

Stall turning is caused by wing distortion. When the wing is distorted, one side of the wing must have a larger installation Angle (the other side becomes smaller). When approaching stall, this half of the wing will stall first, causing the model to tilt and turn. The defect of the indirect adjustment mentioned earlier is particularly manifested in this situation, so the distortion of the wing must be thoroughly corrected.

 

Iii. Throwing Skills

 

After the model is adjusted, the flight performance is entirely determined by the throwing skills. Good techniques can fully leverage the flight performance of the model and even make up for some of its flaws. So, it's not just a matter of throwing it in. You need to practice repeatedly to master the key points

 

1. The actions of running up and throwing should be coordinated to keep the model stable. Avoid shaking and drawing arcs.

 

2. Appropriate release speed. The release speed is not fixed. Different adjustment conditions, different flight modes, and different wind speeds and directions require different release speeds. Strive to do as you please and be accurate without error.

 

3. The appropriate Angle of release. Generally, when gliding naturally, the release should have a very small negative Angle. The release Angle of the horizontal forward charge is generally zero degrees (horizontal). Before climbing, there should be an appropriate positive Angle (elevation Angle) on the opposite side.

 

4. Release point and direction: If the model is flying in a completely straight line, in a windless condition, the athlete should release the shot directly forward from the midpoint of the take-off line, as this will have the highest success rate. But in fact, the majority of the models are turning, and the situation of crosswind release is also the majority. Smart athletes are good at using changes in the release point and direction to correct deviations caused by crosswind and model shifts. For instance, if a right-turn model is released right in the middle of the take-off line, it may fly out of the edge line from the right. If it also encounters a wind on the left, the situation will be even more serious. If we change the method - the release point is selected on the left side of the take-off line, and the release direction is consciously deviated to the left. In this way, the first half of the model might fly out of the left line in the air, while the second half might circle back and land on the field, making the score valid.

 

5. Wind and Throwing Timing: Wind has both unfavorable and favorable effects on flight. For example, a tailwind can increase the flight distance. Headwinds reduce the flight distance, while crosswinds sometimes intensify yaw and sometimes reduce it. Wind is usually in gusts, with wind speed and direction constantly changing. One should be good at seizing the best opportunity to make a move. For instance, when the wind is favorable, it's good to make a move in an instant when the wind is strong; when the wind is against, it's good to make a move in an instant when the wind is weak.