Bayboos
Active member
Ever since I started to experiment with the Twin Twirl concept, there were two questions asked most often: "what are those rotors for, when there are wings?" and "what are the wings for, when there are rotors?" Al Foot - the designer of this plane - created a video of the wingless Twirl, answering the first of those; today I acidentally answered the second one.
The story: yesterday night I completed (sort of, more on that later) the build of my second Twin Twirl. This time I went much closer to the original plans, with carbon reinforcements and all; with only some minor exceptions. Those are derived from my experiences with the first prototype, which was way too weak and flexible (especailly in the tail section) regardless of installing various reinforcements and stiffeners. The main difference is 6mm Depron board used for the main fuselage, without any wooden elements except strut mounting blocks.
As usual, the only time in forseeable future with the weather good enough was just one day away when the plane still needed 1,5 day of work to be done. I couldn't let that one go, so I stayed late at night doing whatever I could to join all the parts together and hope the glue will cure before the morning.
During maiden flight both rotors failed one after the other, becoming stuck in one position due to the glue on axle braces not cured completely. Surprisingly, the plane remained fully flyable the whole time, with just a minor tendency to turn when one rotor was already stuck while the other one was still spinning. The flawn was quickly detected after landing and the rotors deemed inoperative; but with the fresh experience of controlled recovery I decided to give it a try and fly with the rotors removed.
As visible on the video, the plane was still flyable and controllable; yet the characteristics were substantially different. First of all, it required much more speed. Despite the AUW of only 150g, the wing is too small to provide enough lift without a lot of airflow. Second thing was the balance: to keep the plane level at less than full throttle, more than 50% up elevator input was required. Nonetheless the airplane was flying relatively stable (despite the wind) and the directional control seemed almost not affected at all. With full power (which isn't much in this setup) it was even capable of performing some aerobatics! With no power at all, the plane falls down like a brick (or multirotor without props).
Combining those observations with what Al Foot presented in his video, it can be concluded that with the rotors installed and operational, the Twirl's wings generate very little part of the total lift and add some (noticeable, but not required) directional stability; other than that it's just a matter of look with minor weight trade-off. But in case of rotor malfunction, those little wings can provide enough additional lift and stability to bring the plane safely back without any further damage; adding a fair amount of safety and reliability of this extraordinary flying machine.
The SPECS (basinc ones):
AUW - 150g (rotorless)
motor - 24g hexTronik 1300kv
battery - 450mAh 3s LiPo
2 x 5g servos, 6ch reciever with casing removed (only 3ch required)
Al Foot's videos can be found on his YT channel (still updated):
Al's YouTube channel
including the "Wingless Twirl" video:
The story: yesterday night I completed (sort of, more on that later) the build of my second Twin Twirl. This time I went much closer to the original plans, with carbon reinforcements and all; with only some minor exceptions. Those are derived from my experiences with the first prototype, which was way too weak and flexible (especailly in the tail section) regardless of installing various reinforcements and stiffeners. The main difference is 6mm Depron board used for the main fuselage, without any wooden elements except strut mounting blocks.
As usual, the only time in forseeable future with the weather good enough was just one day away when the plane still needed 1,5 day of work to be done. I couldn't let that one go, so I stayed late at night doing whatever I could to join all the parts together and hope the glue will cure before the morning.
During maiden flight both rotors failed one after the other, becoming stuck in one position due to the glue on axle braces not cured completely. Surprisingly, the plane remained fully flyable the whole time, with just a minor tendency to turn when one rotor was already stuck while the other one was still spinning. The flawn was quickly detected after landing and the rotors deemed inoperative; but with the fresh experience of controlled recovery I decided to give it a try and fly with the rotors removed.
As visible on the video, the plane was still flyable and controllable; yet the characteristics were substantially different. First of all, it required much more speed. Despite the AUW of only 150g, the wing is too small to provide enough lift without a lot of airflow. Second thing was the balance: to keep the plane level at less than full throttle, more than 50% up elevator input was required. Nonetheless the airplane was flying relatively stable (despite the wind) and the directional control seemed almost not affected at all. With full power (which isn't much in this setup) it was even capable of performing some aerobatics! With no power at all, the plane falls down like a brick (or multirotor without props).
Combining those observations with what Al Foot presented in his video, it can be concluded that with the rotors installed and operational, the Twirl's wings generate very little part of the total lift and add some (noticeable, but not required) directional stability; other than that it's just a matter of look with minor weight trade-off. But in case of rotor malfunction, those little wings can provide enough additional lift and stability to bring the plane safely back without any further damage; adding a fair amount of safety and reliability of this extraordinary flying machine.
The SPECS (basinc ones):
AUW - 150g (rotorless)
motor - 24g hexTronik 1300kv
battery - 450mAh 3s LiPo
2 x 5g servos, 6ch reciever with casing removed (only 3ch required)
Al Foot's videos can be found on his YT channel (still updated):
Al's YouTube channel
including the "Wingless Twirl" video:
