BiSide design notes 

When designing the Bi Side I paid close attention to the weight of the plane, with the aim of creating something that falls under the 5kg weight with the standard equipment favoured by the average flyer.

As we know all too well, it is something of a challenge getting our mass-produced factory Biplanes within the 5kg limit so the BiSide was made using the lightest possible materials.

The balsa wood we use is always from the lightest 20% and this threw up the design problems of strength of the structure and connecting the pieces to the wider panels. 

As a result this, the finished quality of the main wing surface is more difficult to control compared to that of the ARtF monoplanes and can sometimes be twisted and less smooth as the materials are softer and thinner.  

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 to when opening the packages. 

After opening your ARtF box, you should dry the plane for a couple of days immediately after unpacking, making holes on the wrapping materials whilst avoiding putting any pressure on the main wing while it dries.  After being fully dried, if you check them, on some rare occasions you may find some twisted parts (especially aileron) 

These issues can be restored by ironing the film, at first finish the hinging of the aileron then wait for a couple of days to be fully released the effect of job, after that carefully iron the parts with a cooler hot iron and almost always any twist will disappear.

Even though much attention is paid to the woodwork and quality is assured during the ironing the shape can be changed by the pressure of the iron.

At the factory before packing the plane we carefully check each part, if we find any issues these parts are re ironed.

  As the biplane presents particular challenges to meet the weight limit we respectfully request your understanding on these issues.

Any severe flaw beyond your understanding please contact Bondaero or BJ Craft.

Selection of the servos

The servos developed recently have become very much faster and stronger and the feeling of control in flight is mainly determined by the performance of servos.

This is especially true with the Biside as it employs a direct linkage system.

The performance of the servos becomes the important element which can change even the characteristics of the aerodynamics of the plane.

The selection of elevator servo in Bi Side is of particular importance as the BiSide has a full moving horizontal tail.

As a simple example the centre of gravity has already been determined by the consideration of the margin of stability when the plane was designed. Each pilot will tend to change the centre of gravity which is aerodynamically determined by the basic design of plane to their own preference after the maiden flight. 

The centre of gravity is often changed in accordance with the pilot’s feeling of pitching in the maiden flight.

If you feel that the pitching is unstable and over shooting, first reduce the throw and fly, if

it is not improved, then move C/G to the forward.  

The feeling of overshoot happens in the case where too fast speed (relative to torque) servo is used.

In the case of high speed servo, when you input the control you feel delay in the neutral zone by

insufficient torque, after a moment the servo suddenly tracks the control position, this situation produces a very

similar feeling to that caused by the plane being tail heavy, in this case you tend to change C/G rather than to shorten the

length of servo arm thus reducing the throw (5th gear feeling in a car)  

Changing the centre of gravity can improve the feeling of pitching but you can spoil the balance in other areas.

The geometry of models designed by BJ Craft has been calculated based on the aerodynamics and adjusted following the detailed balance after many test flights, if important elements like the centre of gravity is changed the whole balance can be thrown out.

The most important element of a F3A servo is torque and resolution near the 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 select a servo which has larger torque but slower speed than to select higher speed but lower torque.

If the servo has excellent resolution, larger torque and slower speed, it is very simple for you to increase the speed of the 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 car)

Servos sold worldwide show similar performance limits.

 A servo selection based on the torque and speed combination below is recommended for the elevator.

 on/over 6 kg in torque and 0.20s/60deg,

 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 characteristics select the servo of your preference and experience referring to the above.

 After the maiden flight before changing C/G, change mechanical setting first (shorten servo horn as much as you can)


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