Hacker-Model Extra 330SC EPP ARF
Written by Tom Sullivan
Large, yet lightweight, aerobat
Photos by Tom Sullivan
As seen in the summer 2016 issue of Park Pilot.
Type: 3-D/sport ARF
Skill level: Intermediate
Wingspan: 47.2 inches
Wing area: 519 square inches
Weight: 24 ounces (without battery)
Needed to complete: 250- to 400-watt brushless outrunner motor; 40-amp brushless ESC; 3S 1,500 to 2,500 mAh LiPo battery; four-channel radio/receiver
Equipment used: ElectriFly RimFire 400; Castle Talon 25 ESC; ElectriFly 3S 2,200 mAh 30C LiPo battery; APC 11 x 5.5E propeller
>> EPP parts
>> Preprinted fuselage, wing, and horizontal stabilizer
>> Carbon-fiber pushrods and struts
Chances are, if I asked you to describe an aerobatic electric-powered 3-D model, something such as a profile model with a wingspan of less than 24 inches would come to mind. Well, this review might open your eyes to something similar, but different in several ways. Because space is short, let’s get started.
The model I’m reviewing is an Extra 330SC EPP ARF, made by Hacker-Model and distributed by Tower Hobbies. Not unlike other small 3-D profile models, the Hacker-Model Extra is made from tough EPP foam that is almost unbreakable.
Other similarities include that it requires a micro four-channel system and it comes preprinted from the factory in an eye-catching yellow, blue, white, and black color scheme. However, where it differs is in its size. The 330SC has a 47.2-inch wingspan and a length of more than 48 inches—all of this in an airframe that only weighs 11/2 pounds when complete.
When I opened the box, I found that there are few parts for such a large model. This is because, in part, the wing, stabilizer, and vertical fin are cut in such a way that the control surfaces (ailerons, elevator, and rudder) are attached. No hinges are required, and as a bonus, there are no hinge gaps.
Another nice surprise is that the 330SC utilizes a full fuselage, not a profile. This makes it stiffer and allows all of the radio and power gear to be mounted inside for a more scalelike look.
The included cowl and canopy are vacuum-formed plastic and will require some trimming. With all of this foam and plastic, there are still a few laser-cut wooden parts that will make up the box where the motor is mounted. The kit also includes all of the hardware needed (wheels, landing gear, pushrods, control horns, etc.).
The brightly preprinted foam airframe and low parts count allow the Hacker-Model Extra to be assembled in a couple of evenings.
Assembling the Extra 330SC isn’t difficult, but if you’re considering this as your first EPP ARF, you might have some trouble. The steps aren’t hard and the manual has a wealth of photos and diagrams to help with assembly, but it uses techniques that require some experience to have success.
Assembly starts with joining the two wing halves, then cutting openings for the carbon-fiber spars, servos, and servo wires. The manual recommends that all be cut with a sharp knife, but I had better results with my soldering iron.
To ensure straight cuts, I used a 48-inch aluminum ruler, which made a great guide. When satisfied with the cuts, I glued in the carbon-fiber spars with foam-safe CA, and chose to install the servos with hot glue instead of CA adhesive.
To finish the wings, the control horns are installed and then the pushrods are made to the correct length and attached.
Next up is constructing the motor box from the laser-cut wooden pieces. Some care is needed. Be sure to dry-fit everything before gluing. The mount is designed to have some right thrust, so the parts must be correctly put together. A mixture of medium CA glue and 5-minute epoxy holds the entire assembly together. When cured, the motor box is mounted to the fuselage’s firewall, and the landing gear stiffener is installed with more 5-minute epoxy.
While the epoxy is curing, work moves to the back of the fuselage, where the servo locations need to be measured and cut. A sharp hobby knife makes short work of this, and then the rudder and elevator servos can be attached (I used hot glue instead of CA).
When all of the glue is cured, an unusual step is required. It involves splitting the bottom half of the fuselage so the wing can be inserted. If you use a sharp, new blade, the cut will be clean and virtually invisible after everything is glued back together.
Installing the one-piece wing in the fuselage requires you to cut and bend a portion of the fuselage. It seems scary at first, but use a new #11 blade and the cut will disappear when everything is glued back into place.
After inserting additional carbon-fiber spars into the stabilizer, the vertical fin and rudder are glued into place, and then the control hardware is installed.
Next, the motor is installed so the cowl can be fitted. The manual shows the cowl extending over the top of the fuselage, but I had no luck getting that to work. I ended up carefully trimming some of the foam so the cowl could be properly seated.
Now the landing gear is attached. Foam is included to add wheel pants and covers to the landing gear. Because I planned to fly the Extra from grass fields, I chose not to add the wheel pants and covers so the aircraft would have better taxiing ability.
The final steps are to measure and cut the top battery hatch, and then attach the clear canopy.
Between the canopy and the cowl is a hatch with a quick 90° release. This allows access to the radio installation, but also covers the battery compartment.
When all finished, I was pleasantly surprised that this 330SC weighed in at 11/2 pounds—3 ounces lighter than noted in the manual. The center of gravity was also spot-on, so I programmed my radio to match the recommended control surfaces and was ready to fly.
As you might be able to tell in the photos, I chose a small baseball field complex for the Extra’s maiden flight. After double-checking everything, I throttled up and hand launched the 330SC into the wind. Not knowing what to expect, I found the airplane to be docile for its size, with plenty of control “feel” at any speed.
It is extremely aerobatic and able to handle almost everything I tried to do, but I wouldn’t call it precise. It is great fun to throw around in the sky and it doesn’t need a lot of airspace in which to fly.
When in inverted flight, the 330SC requires little down-elevator to fly level—it’s close to a neutral design in any attitude. You will need more throttle to hold altitude in rolls, rolling loops, and knife-edge flight. It requires some work, but with practice, it does a good job.
For an EPP design, the Hacker-Model Extra 330SC is quite a large aircraft. But with that larger size comes an extremely wide flight envelope that can be flown in smaller spaces. It’s just as much at home performing crazy 3-D maneuvers as it is in slow flight. And for the price, it’s hard to beat having this much fun on a 3S 2,200 mAh LiPo battery pack.