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World Models Giant Scale Spitfire

The GS Spitfire is an excellent electric conversion. At 14.5 lbs all up, it is light and powerful. The plane will out run many smaller planes and has outstanding vertical performance. It has enough power to hover at half throttle (although as a scale plane the control surfaces are too small to do this very long). The flight characteristics are excellent. Combined with the power, this Spitfire makes for an exciting aerobatic performer.

Specs:
Hacker Brushless Motors : C50-14XL Acro, 6.7:1 gear ratio, APC-electric, 20x15 prop, 10 series 4 parallel Lithium Polymer cells from Thunderpower
AUW (all up weight) : 14.5 lbs
Static Thrust : 20 lbs
Current : 68 amps
Flight Time : Full Aerobatic 13 mins
Conversion Parts:
Power system : Hacker motors are available from www.hackerbrushless.com
Speed control : Master 77 Series from www.hackerbrushless.com
Mounts : Hacker /AeroModel Motor mount www.hackerbrushless.com
Batteries : 10s4p Lipoly - www.thunderpower-batteries.com
Prop : APCe 20x15 - www.apcprop.com

Conversion Process:

The ARF is very complete and easy to assemble. Follow the instructions for basic assembly. The only modification I made was to place the rudder servo in the throttle servo location to move the CG forward.

Motor Mount:

I used the Hacker- AeroModel motor mount. Measure the length required by locating the cowl onto the firewall. You will need to stretch out the front mount to the last mounting holes to make it as long as possible. Locate the mounting holes on the firewall by aligning it with the cowl. Duct tape the motor mount in place and slide the cowl to see if it is centered. When you find the correct location, mark the holes on the firewall.

You need to order the C50 front plate and an extra set of side brackets for more stiffness.

You will need bolts and blind nuts to mount the motor bracket. I would suggest 4mm. The mounting hardware that comes with the plane could be used but is unnecessarily large and heavy for an electric motor (no vibration).

Once the motor mount is bolted into the firewall, mount the motor. Make sure you use blue Locktite on the mounting screws. Also, remember to use all 8 mounting screws. To prevent vibration, use nylon cable ties - one on each side - at the rear of the motor. Make sure you tighten each side evenly. This reduces motor vibration from large props.

Battery Mounts:

This is always the most complicated part of an electric conversion. Fortunately, the Spitfire has a secondary chin cowl section that makes an ideal battery hatch. The batteries must be located as far forward as possible for proper CG.

 

Cut a hole below the firewall and mount a 3/16ˇ¨light ply bed for the battery as shown below.

 

 

Glue on a Velcro strip to prevent the battery from sliding and also attach 2 Velcro straps to hold the battery in place. You will need to cut a hole in the hatch as well as in the main cowl just below the spinner as shown below. You also need to cut a large hole in the fuse just behind the wing to allow the cooling air to exit.

 

You will need to make a "Y" connector to the speed control to connect together the 2 battery packs in series. I have added an additional female Dean Ultra connector as a safety switch. It is mounted to the side of the cowl and the switch is closed with a male connector that is shunted (solder a wire across the male connectors and cover with electrical tape or heat shrink tubing). I leave this switch open while connecting the batteries and closing the hatch. Once the plane is turned over and ready to fly, the male connector (shunt) is inserted into the female connector and the motor is armed. I donˇ¦t like flipping the plane over with a large prop near my face. Even if the Rx is off, itˇ¦s best to be sure that the motor cannot switch on by accident.

You will need to place the batteries as far forward as possible to have the CG at the correct location. I also mounted the receiver battery on the motor mount to keep this weight forward as well.

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 the 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.

The Spitfire is a joy to fly. It will take off on half throttle in less than 50 feet. You really need to apply the throttle slowly to have a scale takeoff. Ground handling is excellent. You just need a little up elevator to keep the rear wheel on the ground as you pick up speed.

Once in the air, the Spit is great fun. It handles like an aerobatic plane with its speed, thrust and maneuverability. You will have no problems doing huge loops ˇV both inside and outside. Four point rolls, stall turns, inverted flight and even knife edge are easy. On knife edge, it will pull hard to the belly so be prepared to apply a lot of up elevator. I like to fly the plane with medium elevator, high rudder and high aileron.

You can actually hover this plane on ½ throttle for a little while. The scale control surfaces don't give you much authority but hovering looks a bit silly anyway so you don't need to do this very long. It makes it very easy to do your stall turns very slowly.

The Spitfire has flaps for landing but they are not necessary unless you have a short runway. It will glide in very smoothly and requires very little input to land properly. The landing gear is short and stiff and not prone to bending on landing so the plane will bounce if you come in too fast. However, there's no need to land very hot because of the low wing loading. You should not have any problems with stalling the plane. It will mush forward slowly.

Enjoy your flying! You will amaze your friends.

 

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