Closed | Today with our composite toys we have many tools how to set up proper deflections on all controllable surfaces (flaps, ailerons, elevator, rudder etc.). We play with speed polars at computers with sophisticated simulation software, we cope with secret setups from top pilots etc. We play with millimeters, on elevator perhaps with tenths of millimeters.
I was just curious what’s going on for example with trailing edge of standard F3B model at launch phase. For me it was big surprise to find out that if you setup e.g. 12mm deflection, just after model release from hand you can have there only 50% of expected setup.
There are many factors which influence these no load/load setups:
- Arm ratio (servo arm, driven surface arm)
- Arm stiffness
- Strenght of servo (do you really believe in servo Ncm parameters specified by producers? After some measurement me definitely not)
- Stiffness of wing skin where your servo is glued
- Stiffness of hinge
- Servo looseness
- Global wing stiffness
… I’m sure somebody will find other weak points
Don’t be fooled, same phenomena you can experience when switching to speed phase, snap flaps etc. Thanks to above mentioned factors you can see that your expected reflex 1,5mm (Trailing Edge up) is actually nearly triple. There is really expected suction effect.
Having in my hands some RDS systems, this shouldn’t be always 100% cure for above mentioned troubles. Well designed classic pushrod system can withstand a lot and can be very reliable but RDS is perhaps the best way to go today.