Control Flutter and Hinge line gaps (Myth revealed)
06-05-2003 | 01:44 PM
#26
Senior Member
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Control Flutter and Hinge line gaps (Myth revealed)
Sealing the gap is not always necessary, but it is ALWAYS a good idea.
Think about this: When a surface is deflected upward, there is an area of high pressure generated on top, and a low pressure area generated below. This low pressure area acts like a vacuum cleaner and sucks air from the high pressure area through the gap. The bigger the gap, the more air passes through, and the more air that passes through, the less effect the control surface will have.
Unless you do it wrong, sealing the gap shouldn't put any extra strain on you servos (or at least, any strain they DO put will be negligible). Keep in mind that they may seem a little stiffer with a seal than without, but you are flexing the control surface with no wind resistance. So the slight tightness you may feel is nothing compared to the pressure generated by the rapid airflow over the surface when it is moving at 60 MPH.
Now, what to seal it with...
Virtually ANYTHING that will prevent the air on top from bleeding through to the bottom (and vice-versa) will work, but obviously, some choices are better than others. A strip of covering or trim sheet, and packing tape all work well, but I have used regular Scotch Tape also. The main thing is to get it close to the hinge so it interferes as little as possible with the surface's movement.
Think about this: When a surface is deflected upward, there is an area of high pressure generated on top, and a low pressure area generated below. This low pressure area acts like a vacuum cleaner and sucks air from the high pressure area through the gap. The bigger the gap, the more air passes through, and the more air that passes through, the less effect the control surface will have.
Unless you do it wrong, sealing the gap shouldn't put any extra strain on you servos (or at least, any strain they DO put will be negligible). Keep in mind that they may seem a little stiffer with a seal than without, but you are flexing the control surface with no wind resistance. So the slight tightness you may feel is nothing compared to the pressure generated by the rapid airflow over the surface when it is moving at 60 MPH.
Now, what to seal it with...
Virtually ANYTHING that will prevent the air on top from bleeding through to the bottom (and vice-versa) will work, but obviously, some choices are better than others. A strip of covering or trim sheet, and packing tape all work well, but I have used regular Scotch Tape also. The main thing is to get it close to the hinge so it interferes as little as possible with the surface's movement.
