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World Models Extra 300 Electric Conversion

Battery Mounts:

This is always the most complicated part of an electric conversion - to allow for the proper CG location of the plane while affording a convenient placement of the batteries. Since the Zero typically takes a large 5lb gas motor to balance the plane, I knew that the batteries would need to be located as far forward as possible, since I’m using Lithium Polymer batteries (for light weight and high capacity), which weigh much less than Nicads or Nimhs. The complete motor/battery combo is just over 5 lbs.

The good news is that the Zero has a very large cowl within which will hold 3 battery packs. I used two  3s4p packs and one 4s4p pack. The 4s4p pack was mounted to the top of the firewall. Cut a hole through the fuse just above the firewall box. Mount a 3/8” light ply bed for the battery. Glue on a Velcro strip to prevent the battery from sliding and also attach a Velcro strap to hold the battery in place.

The two 3s4p packs were mounted to the side of the motor mount. Use 2 sets of 18” Velcro buckle style straps that will allow you to tighten down on both batteries at the same time. I mounted balsa blocks on the packs to ride on the motor mount brackets.

Cowl and Battery Hatch:

Mount the cowl and screw the brackets in place. I chose to cut the cowl in the front top area to make it easy to install the batteries. You may decide to choose some other configuration. Cut the hatch with a Dremel tool and a cut off disk. It works very well. This hatch hinges at the front and there is a latch at the top rear.

Mount the 24x12 APCe prop. You will need to ream this to 8mm. The Hacker C50 comes with a threaded shaft and collet style prop adapter. Insert the collet and back plate. Then slide the aluminum spinner rear plate. Use the right size brass adapter. Mount the prop and tighten in place with the nut. Attach the spinner adapter nut. Mount the spinner and bolt in place. The parts provided by Hacker and World Models work perfectly together. It’s a very clean setup.

Final Tests:

Before doing any tests, make sure that the brake is turned off on the speed control. The process is:

1 - turn off the Rx battery switch
2 - unplug one power battery
3 – turn on Tx and move throttle to full on
4 – plug in power battery, turn on Rx switch
5 – wait for beep, move throttle to off, wait for beep
6 – test motor to see if brake is off

When you do a ground test, I would suggest that you get help holding the plane. The thrust is substantial and the plane can easily get away from you. Please be very careful.

Also, remember that even if your Rx is off, once you plug in all three batteries, the system is armed. Stay away from the prop. Remember, this system provides more than 3 HP. It is very dangerous and startup is instantaneous. The other thing to remember is that this system runs at close to 70 amps and 38 volts. This is more than 2400 watts of power. Please be extremely careful. This is not a park flyer.

The flight performance of this plane is excellent. You will need less than ½ throttle to take off and climb. It has tremendous thrust. Throttle management is very important for overall system cooling and longevity. Remember to push the throttle all the way OFF on downlines. Any partial throttle uses power and causes heat build up. You will get longer, high performance flights through good throttle management.

The Zero is a remarkable performer. It handles almost as well as an aerobatic plane. Stall turns, snap rolls, big loops (inside and outside) can all be done with ease. The nice surprise is that this plane knife edges very well. It’s a beautiful plane in the air and a real crowd pleaser.

Enjoy the flight.


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