Quote:
Originally posted by MiCkLe
When I checked the blades, I saw a small area of the plastic cover on the tip of the blade coming off so I stuck it back with instant glue.
I tried flying my heli again...but it wasn't as stable as before... like... the rudder was shaking a bit. |
Gluing something down near the edge of the blade (I supposed it was near the edge as "the plastic cover on the tip of the blade") will have two effects:
1- add a slight increase in weight to that blade, hence the blades, if perfectly balanced before, might not be so balanced now, hence the oscillation you're seeing
2- the gluing might not be as smooth a surface as it was before. Hence the aerofoil has lost it's smooth laminar surface and airflow over that part of the aerofoil won't be as clean as it was before. So there's be a little loss of lift. Hence this will cause a slight disymmetry of lift, and that too will cause oscillation.
Just to relate a story as an analogy:
I remember when I was hovering a full sized helicopter once and suddently (goodness knows where it had come from!!) this huge ball of tinfoil was caught in my rotor's air current, it went up into the air, then back down through my rotor system (near the edge of the disk).
The tinfoil ball was history, but everything seemed OK with the helicopter, so I continued my flight.
But there was a slight oscillation, same frequency as the RPM of the main rotor.
When I landed, what had happened was a piece of the tinfoil was around the leading edge of one of the three rotors.
This was enough to spoil the lift on that section of the blade, thus causing disymmetry of lift.
(I considered it might also because the blades weren't in balance anymore, but it was only a small piece of tinfoil so it wouldn't have made much difference)
08-11-2003, 08:14 AM
