Hello,
I am working on a small prototype for an RC airplane in a tandem wing configuration and I am having a control issue that I am hoping that someone can help me with.
This is a really small plane (9" wingspan and 3/8oz flying weight) with high camber wings to keep it flying slow. As you can see the rear wing has significant dihedral with bent-down wingtips to give it yaw stability. The front wing is slightly shorter in wingspan and has much less dihedral. The controls (elevons) are installed in the rear wings. I am trying to use this simpler setup to keep weight and complexity down.
I have performed some short flights with it and it feels like I have good pitch stability with acceptable roll and yaw stability.
The elevons give me very good pitch control, however roll control is another story...I get huge adverse yaw and some unwanted pitch down when trying to roll to the point that the plane yaws the opposite way than intended and I inmediatelly have to release the controls. I have build a couple of different versions on this airplane, positioning the ailerons closer to the body and also removing all "down" movement of the controls to see if I could minimize this adverse yaw but I have not had any luck. In fact I even get adverse yaw when there is no "down" movement at all in the elevons!
I know that tandem wing aerodynamics are very complex and my question is probably too simplistic, but...why am I getting so much adverse yaw? Also, is there any way to get good roll control using the current elevon configuration?
Thanks
Sportjet
I am working on a small prototype for an RC airplane in a tandem wing configuration and I am having a control issue that I am hoping that someone can help me with.
This is a really small plane (9" wingspan and 3/8oz flying weight) with high camber wings to keep it flying slow. As you can see the rear wing has significant dihedral with bent-down wingtips to give it yaw stability. The front wing is slightly shorter in wingspan and has much less dihedral. The controls (elevons) are installed in the rear wings. I am trying to use this simpler setup to keep weight and complexity down.
I have performed some short flights with it and it feels like I have good pitch stability with acceptable roll and yaw stability.
The elevons give me very good pitch control, however roll control is another story...I get huge adverse yaw and some unwanted pitch down when trying to roll to the point that the plane yaws the opposite way than intended and I inmediatelly have to release the controls. I have build a couple of different versions on this airplane, positioning the ailerons closer to the body and also removing all "down" movement of the controls to see if I could minimize this adverse yaw but I have not had any luck. In fact I even get adverse yaw when there is no "down" movement at all in the elevons!
I know that tandem wing aerodynamics are very complex and my question is probably too simplistic, but...why am I getting so much adverse yaw? Also, is there any way to get good roll control using the current elevon configuration?
Thanks
Sportjet
