대한민국 NO.1 RC커뮤니티 알씨원 :: BI SIDE Mechanical Setting

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BI SIDE Mechanical Setting

작성자: 박병준

조회: 141029 등록일: 2013-08-20

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<img width="675" src="/rankup_module/rankup_board/attach/bjair1/13825160780921.jpg">  <a href="http://www.rcuniverse.com/forum/electric-pattern-aircraft-385/11332318-bjcraft-biside.html">http://www.rcuniverse.com/forum/electric-pattern-aircraft-385/11332318-bjcraft-biside.html</a>   This is a draft for mechanical setting manual, so it shall be updated the contents including pictures and additional expanation.   About The Plane When I design Bi Side I paid attention to the weight of Bi Side to be within 5 kg with generally used battery  and equipments as the plane targeted for average flyers. As you know well it is very difficult for the factory to mass produce biplane within 5 kg so all the parts were made by using light materials. Especially the balsa we should use the lightest 20% of it, which causes many of inefficiency such as weakness in strength, difficulty of connection of pieces for broad pannel.  As a result the finished quality of surface of main wing is a little bit lower compare to that of ARF monoplane and can easily be twisted and less smooth as the materials are softer and thiner. The humidity of Zhuhai in China where the factory is located is over 70~90%, so the parts made of wood should be paid keen attention when you open the packages.  After your opening ARF box, you should dry the plane for a couple of days as the package unpacked making holes on the wrapping materials and avoid giving any press to main wing in the dry.     After being fully dried, if you check them, you may find some twisted parts (especially aileron)  These issues can be restored by ironing the film, at first you shall finish hinge job then wait for a couple of days to be fully released the effect of job, after that carefully iron the parts with less hot iron. almost of them shall be restored. Even though wood work is done well, during the iron job shape can be changed by pressure of ironing At factory before packing the plane we check each by each, if find the issue, reiron the very parts.  As the biplane has its own limit in weight and some other parts, I cordially request your understanding on these issues. Severe flaw beyond your understanding please contact with BJ Craft. Sellection of servo The servos developed recently were become very speedier and stronger because of their competitiveness,  Control feeling and flight feeling are mainly determined depending upon the performance of servo. Especially the feeling of Bi Side directly depends upon the performance of servo as it applys direct linkage system. The performance of servo became the important element which can change even the characteristics of aerodynamics of the plane. The sellection of elevator servo in Bi Side is very important as Bi Side has full moving horizontal tail. As a simple example the center of gravity has already been determined by the consideration of margin of stability when the plane is designed. But you tend to change center of gravity which is aerodynamically determined by the basic design of plane with your own feeling of maiden flight.  You tend to change center of gravity by your feeling of pitching in your maiden flight. If you feel that the pitching is unstable and over shooting, at first you reduce the throw and fly, if it is not improved, you move C/G to the forward. The feeling of overshoot happens in the case where too fast speed (relative to torque) servo is caused. In the case of high speed servo, when you input control you feel delay in the neutral zone by insufficient torque, after a monment, suddenly tracks the control position, the case of which is very similar feeling caused by tail heavy, in this case you tend to change C/G rather than to shorten the length of servo arm (5th gearfeeling in automobile) In a case you can improve the feeling of pitching but you can spoil the balance in other parts. AS the geometry of models designed by BJ Craft was calculated based on the aerodynamics and adjusted the detailed balance through test flight, if important elements like C/G is changed, whole balance shall be readjusted. The most important element of F3A servo is torque and resolution near neutral zone.   This means that the more the rotation of servo motor is in the same angle the more advantage you have and control feeling in flight is constant.   It is more advantageous for you to sellect the servo which has larger torque but slow speed than to sellect higher speed but lower torque. If servo has excellent resolution, larger torque and slower speed, it is very simple for you to increase speed of servo, you can do it by only extending the length of servo horn. That provides faster speed and more stable control feeling (3rd gear feeling in automobile) As servos sold in worldwide show similar performance in their limit of technology, the servo based on the torque shall be sellected from which has the ratio of torque and speed on/over 6 kg in torque and 0.20/sec in speed, or 8 kg in torque and 0.17/sec in speed, or 13 kg in torque and 0.15/sec in speed. As each servo has its own character, you shall sellect servo by your experience refering to the above. After maiden flight before changing C/G, change mechanical setting first (shorten servo horn as much as you can) Aileron By your favour you can use both of 4 servos and 2 servos (all kind of servos can be used)   The length of servo horn is 13mm, length of aileron horn is 30mm (the height from hinge line) 2 mini-servos were used for test flight (6.6 volt, 4.5 kg torque, 0.19/sec speed) which is necessary and minimum power to be able to use. In a case of 2 servos in the above specification,if you use longer than 13mm servo horn, you shall feel the change of neutral trim in the flight so 13mm length shall be the longest limit. In the above cases you can feel a bit slow snaproll(I like this)   If your servo has better torque, excellent resolution and good neutrality, use 17mm~20mm servo horn, then you can get faster snaproll speed. As main wing is short and roll rate is fast, if the speed of servo is too fast, you can feel over shoot control feeling. When you use 2 servos, recommended range of speed is on/above 0.17/sec~0.19/sec and 6 kg~4 kg range of torque.(Normal or aileron servo is better) 0.1/sec in speed needs above 10 kg torque, in a case of 4 servos you can sellect depending on the above instance.(4 servos, 3kg/each shall be enough) The sellection of aileron is not sensitive issue you can sellect it by your experience. If you feel that unstable roll is developed and/or unstable vibration develops in wing tip, you should change the sevo which has larger torque but slower speed or change mechanical seting  Rudder Directly use 1 servo. The length of servo horn is 20mm, that of Rudder horn is 15mm-20mm Servo used for test plane is 6.6 volt, 13 kg in torque and 0.17/sec in speed. I felt that capacity of servo is proper. As the rudder is larger than other pattern planes, torque of servo should be larger, the throw of rudder should be the largest as long as it doesn't touch to stab when servo moves 140%. Torque of servo for test plane has no room, servo capacity for Bi Side is recommended 15kg in torque, 0.19/sec in speed, if 0.15/sec in speed, 20kg in torque is needed. Elevator Use 1 servo. the sellection of servo does very important role in flight setting and flight feeling as the stab is full moving style. The length of servo horn is 17mm and that of stab horn is 45mm. The capacity of servo used for test plane is 6.6 volt, 13kg torque and 0.17/sec speed, if you place recommended C/G at 130mm, pattern flying is possible at 80% throw. You must machanically adjust the length of servo horn on trying test flight, desirable length shall be the point that the throw of servo is to become above 70%. You can get more stable and constant pitching control feeling, if you should machanically set control throw which is necessary for F3A pattern flying when the servo moves 100% With the condition of my servo setting, the elevating of Bi Side was considered without necessary use of EXP, maiden flight shall be done on 80% D/R(travel)throw and 0% EXP. It is very important to use 0% EXP for flying tail plane as the character of EXP program is unstable (especially battery, humidity） To make a full moving stab which is aerodynamically possible to excute 0% EXP, BJ Park tested various kind of full moving stab finally got a present full moving stab for Bi Side. Despite the full moving stab, you shall surprise that it is very dull in neutral in spite of EXP0%. If you do mechanical setting properly, You can do all things including control linearity more easily than conventional elevator as design was considered aerodynamically. If the speed of servo is too fast and torque of that is too large, the pitching causes overshoot and you may feel as if tail is heavy. in this case it is better for you to further shorten the length of servo horn before change of C/G. Sellection of propeller. You may think that Bi Side is biplane so its drag shall be larger and speed be slower, but not, it has almost no drag and speed goes up instantly. You have to be carefull to sellect propeller as propeller is biger and powerfull reltive to the size of plane, basically must be sellected the smallest prop that you can use with your power.   Accordingly you must secellect the propeller which has wide blade and lower pitch. Propeller can be determined by the motor to be used but I recommend you to choose the propeller which has the lowest pitch and can be used for the motor sellected. Some cases you may choose 3 blades propeller. F3A NeuMotor and 21*12w propeller was applied to the test plane, if you want to be stable side thrust, smaller dia and lower pitch is less variation. Test setting was so overpower in full throttle that I adjusted it 60% at full throttle. You should find out the prop which makes linear throttle curve with your motor. Sudden change of throttle curve can spoil pitch yaw roll stability. Basic setting for biplane should be mild throttle control to follow linear curve in proportion to the variation of speed.  Check list before maiden flight   As Bi Side targeted the flyers who can easily set it and participate in competition using Bi Side, to match the purpose, I allowed the margin of C/G and that of stability. The recommended C/G of Bi Side is 130mm same as designed C/G considering that the plane is biplane and allowed that stability margin is bigger than maneuverability margin. This point is a bit nose heavy position in design point of view, as biplane is under the process of improvement, present basic stability was set at a bit forward C/G. After seeing the elevator trim situation gained by your maiden flight with the conditions that I recommended above such as C/G and neutral position of stab, you can find out your circumstance, based on your circumstance you should do your onward flight setting (Flight setting to be published shall be made based on this result)        The basic settings in factory are as following.  Thrust:right 3 degree up 0.5 degree, lower main wing +0.5 degree, upper main wing 0 degree, flying tail 0 degree. C/G shall be checked as that mark with pen at 130mm on the bottom of lower wing and lift plane by finger. The 130mm spot in the pic is the position that wing spar passes.   The center position of flying tail shall be checked as shown on the pic.  If your confirmation of servo setting, C/G and center position of flying tail described in the above is finished, start the maiden flight of your Bi Side.