Easystar Adventures

The Multiplex Easystar is one of my oldest airplanes. Yes, this is a photo of me with the same plane I still fly after 20 years. The Easystar is an amazing design. It has been copied many times, including by the Hobby King Bixler which came years later, but has never been matched. The Easystar flies significantly better than any of the imposters and has no need for ailerons to compensate for poor handling characteristics.

The Easystar is a natural candidate for all sorts of experiments. It has gentle handling, a pusher motor, and lots of internal space. I liked the plane so much I actually bought a second.

The goal was to design a plane capable of being flown at night. In my local area, it was commonly windy during the day and calm at sunset. This was a problem because the airplane would get hard to see just as the other flying conditions became ideal.

It didn't take long to decide that strip LEDs would be the best option for this project. These particular LEDs run on 12 volts and are very bright. They are so bright that I need to be careful to keep the plane faced away when I plug it in. Conveniently, a Dremel sanding tool has the same width as the light strips which made it really easy to carve shallow trenches into the bottom of the wing. The LEDs were glued in the trenches and clear tape covered them up.

Once the LEDs had been mounted, I needed to connect them all to a power source. I decided to use a small 3s 730 mAh battery from another small airplane. This battery will power the lights for about 30 minutes. All the plugs were JST and joined in the Easystar's central compartment. There is an RC switch in the circuit that allows the lights to be switched on or off with the transmitter.

The removable wing proved to be a little trickier to wire than the rest of the plane. I simply bored two holes through the plane from just under the wings to the inside compartment. Everytime the wing is attached, the wires are fed through this hole. The system works fairly well but isn't all that elegant.

The modified Easystar is fully UFO worthy. The only small flaw I found is that the light's battery lasts ~30 minutes but the flight battery lasts ~35 minutes. The pilot just needs to be aware enough to set a timer before taking off. The airplane is very easy to fly while it is overhead but can be a little tricky to land. It is hard to see if I fly directly toward myself. Overall, this project was a big success. I really enjoy flying this airplane right around sunset when it is easy to see with the lights but would be just slightly too dark otherwise.

The project was actually pretty simple. I made a banner out of a white trash bag. It was attached to a wooden dowel on one side and free on the other. The wooden dowel was weighted on the bottom to keep the banner upright in the air. It didn’t require much weight, just a couple fishing weights did the trick. The dowel was tied to a single line with a washer on it.

One important design feature was the ability to release the banner. This was useful in the air to make landing easier. It also could be used if something went wrong, although I never had any issues with the banner. The washer simply looped onto a servo arm to hold the banner in place. If the servo arm was pointed up wind, the banner would stay locked in place. If the servo arm actuated to point downwind, the washer slipped off and the banner fell away.

The servo for holding the banner was attached along the tail boom behind the motor. This was a convenient location because it was easy to attach the servo and there was no danger of the banner catching in the propeller. The servo was positioned so the strong also wouldn’t wrap around the horizontal or vertical stabilizer.

Taking off the plane with the banner was actually very easy. The Easystar is a hand launch plane, so the banner needed to be carefully placed in front of whoever threw it into the air. Other than that, just throw the airplane like normal and away it goes.

The handling of the airplane with the banner was poor. While the Easystar normally flies very nicely, the banner caused some problems. The banner attachment at the tail reduced the tail effectiveness which made the airplane sluggish in every axis. Thankfully, the Easystar had so much control authority to start that this degradation didn’t cause any safety issues. A giant banner also produces drag so the plane required more power to stay up. Overall, big success.

This modified Easystar was my first ever VTOL project. I started working on this right after the first serious Quadplane update was added to Arduplane in about 2015. The main purpose of this project was to experiment and learn about VTOL airplanes. This was definitely a learning experience. I had no real performance goals although I was hoping to fully tune the airplane for autonomous flight.

I was still in college during this time and wanted to keep the costs fairly low for this project. I bought 4 small drone motors with 8 inch propellers for the VTOL system and used a Pixhawk for the flight controller. I normally flew the Easystar with a single 3s 2000mAh battery but decided to use two batteries in parallel for a combined 3s 4000mAh battery. The motors were mounted on carbon fiber rods glued into the wings. The center of the 4 motors overlapped with the airplane CG. All the extra wiring, battery, and structure doubled the weight of the airplane from just over 2lb to 4.2lb.

Although the Easystar is a versatile design, it is not a great base design for a Quadplane. It became instantly clear that the wings were too flexible. The foam airplane was not designed for the high weight and the wings did not have nearly enough torsional stiffness. Yaw control was nearly non-existent at first. The twisting of the wings would cancel the torque of the motors until I reversed the spin direction of all the motors. The hovering propulsion system was also undersized for the system. The motors could lift the airplane, but the battery would drain in about 5 minutes, and the motors would be very hot.

Tuning the airplane in hover actually wasn’t too hard. I accepted soft and sluggish control and didn’t bother trying to fix it. I learned quickly that using the pusher motor is essential for maintaining position in hover. A normal quadcopter tilts to move around. If an airplane tilts the nose down to move forward, it will generate negative lift at the same time. This makes it basically impossible to fly forward with any real speed. Worse, a sudden gust of wind from the nose will cause the autopilot to correct by lowering the nose to hold position. This positions the wings at a negative angle which causes the whole airplane to get pushed down. I had this happen and the whole plane was pushed 10ft down into the ground in less than a couple seconds. Thankfully, there was no damage.

I did finally succeed in getting the airplane to takeoff, transition to forward flight, fly around, then transition back to land. I never fully tuned the autopilot for navigation. The battery life was too short for this to make any sense. The transition was very smooth and simple. The transition felt very similar to a normal takeoff or landing.

The lessons learned from this project were eventually applied to the Vertigo project. Vertigo uses carbon reinforced wings with extensive structural reinforcement to create an extremely stiff structure in torsion. Vertigo also uses 16 inch propellers which have 4 times the disk area despite the airplane weighing slightly more than twice as much. This dramatically increased the efficiency and reduced the wiring losses. Despite the overall poor performance, this project served as a steppingstone as intended.

Matthew Warren

Lights

Banner

EasyQuad VTOL