13.3. Main rotor setup - part 1

13.3.1. Main rotor blade balancing using the KSJ-528 blade balancer

It is important to balance the main rotor blades because this reduces vibration. Reduced vibration will make hovering easier, increase the flight time because less power will be wasted, and will reduce gyro drift and allow the gyro to function more efficiently.

There are multiple ways to balance the blades, but this method works best for me so far. It minimizes the amount of tape used and we avoid disrupting the airflow where the blades generate the most lift by putting most of the tape near the bolt holes and the CG.

Be sure to use ELECTRICAL tape to balance the blades. Regular transparent tape is not heavy enough. Electrical tape weighs about 0.1 gram per 2.5cm (1 inch).

13.3.1.1. Step one: Matching the CG

  1. Remove the blade holder posts from the balancing tray of the KSJ-528.

  2. Make sure the balancing tray balances evenly when nothing is on the tray. If necessary, use the setscrews to balance the tray.

  3. Place one blade in the KSJ-528 tray and delicately shift the blade left or right across the balancing tray until the blade balances.

  4. Mark the balance point with a felt tip pen. The balance point is the point where the center line on the balance beam touches the leading edge of the blade tip.

  5. Repeat for the other blade.

  6. Stack the rotor blades, then insert a bolt through the hole to align the blades perfectly. Check if the CG of the blades match within 1/16th of an inch (1.5mm).

  7. If the CGs are close enough, go to Step two: Matching weight

  8. Determine which blade has CG farthest away from the mounting bolt hole.

  9. Move the CG of the blade closer to the bolt hole by placing placing 1-2 inches of electrical tape on the underside of the blade next to the leading edge near the bolt hole.

  10. Measure the CG on this blade again and mark the new CG location.

  11. Go to step 6

13.3.1.2. Step two: Matching the weight

  1. Determine which blade holder posts fit your blades, then mount them on the balancing tray.

  2. Make sure the balancing tray balances evenly when nothing is on the tray. If necessary, use the setscrews to balance the tray.

  3. Mount the blades on the blade holder posts and make sure both blades balance and are perfectly horizontal.

  4. If the blades do not balance, put a small strip of electrical tape on the underside of the lighter blade at the CG point next to the leading edge of the blade.

  5. Add or remove tape on the lighter blade at the CG point until the blades balance.

13.3.1.3. Step three: Optimizing tape usage (optional)

  1. If you applied tape to only one blade or less than seven inches of tape were used in steps one and two, you can skip this step.

  2. If one blade has a large amount of tape near the bolt hole and the other blade also has a large amount of tape on the CG, then you should definitely perform this step.

  3. On the blade with tape near the bolt hole, remove all the tape.

  4. On the blade with tape at the CG, remove the tape and discard half of the tape. Reapply the other half of the tape to the blade but at a point halfway between the CG and the tip.

  5. Go back to Step One: Matching the CG and rebalance. The blades should require less tape to balance this time.

13.3.2. Blade grip tension adjustment

  1. Loosen the main blade grip bolts so the main blades move freely.

  2. Hold the helicopter so the right side or left side is facing down.

  3. Turn the main rotor hub so the blades are parallel to the ground.

  4. Tighten the blade grip bolts just enough so the blades won't droop much when the heli is lightly shaken. If you overtighten the main blade grip bolts, then the main rotor blades will not straighten out at full headspeed and this will cause vibration.

    If you have too many boom strikes later, you can tighten the blade grip bolts after running up the heli to full headspeed to ensure the blades have straightened out.

13.3.3. Flybar paddle setup

This step is not necessary for the Corona since it is already performed by the instructions in the construction manual. The tilt of the flybar paddles should match the tilt of the swashplate. This is done by adjusting one flybar paddle at a time.

  1. First, make sure the flybar paddles are parallel to each other. This can be done using the KSJ-624 paddle gauge or just by visual inspection. If the paddles are not parallel to each other then loosen the paddle mounting screw or setscrew and twist the paddle and retighten the screw.

    If you use the KSJ-624 paddle gauge on a micro heli, the weight of the paddle gauge will twist the paddle and change the pitch by a few degrees. To avoid this, hold the heli so the flybar is perpendicular to the ground and then sight along the edge of the paddle gauge down to the ground. This will prevent the weight of the gauge from twisting the paddle.

  2. Next, rotate the main rotor so the main rotor blades are aligned with the body, e.g. one points forward and the other points backwards.

  3. Pick one flybar paddle, and lower it slightly so it almost obscures the swashplate. Now align the outer edge of the flybar paddle with the top of the swashplate. It should be level with the top of the swashplate. If the paddle is tilted relative to the swashplate, then this should be fixed by shortening or lengthening the linkages between the swashplate and the flybar paddles

  4. Now rotate the rotor head 90 degrees so the flybar paddles are aligned with the body. Check the same paddle against the top of the swashplate again. It should still be aligned.

  5. Repeat the last two steps for the other flybar paddle and make sure it is aligned with the top of the swashplate at two different angles 90 degrees apart.