High-level, unlimited indoor aerobatics are the specialty of the house. Article and photos by Dave Lockhart. Featured in the Spring 2013 issue of Park Pilot.
One of the newest additions to the Twisted Hobbys lineup is the 32-inch Crack Yak-55 “Lite.” This model is lightweight and agile enough to fly in small gymnasiums, yet large enough to handle light winds if flown outdoors. Equipment needed to get the Crack Yak flying includes a 275-class motor (50-75 watts), 6-12A ESC, one 9-12-gram servo for the ailerons, two 4-6-gram servos for the rudder and elevator, a receiver and a 2S LiPo pack of 360-450mAh capacity. The Twisted Hobbys website offers all these items, and I chose the Twisted Hobbys Power Combo Digital Lite 32 package for the review, adding an older Spektrum AR6100 DSM2 receiver, and Thunder Power 2S 325mAh 65C LiPo. Twisted Hobbys recommends the use of Welder brand contact adhesive for the majority of the construction. CA adhesives can also be used. Most CAs are relatively brittle, although I did use CA for the servo-arm extensions and reinforcing thread, the landing gear and the axles.
Battery is a slip-fit into the fuselage. Elevator and rudder servos use carbon-fiber pushrods, held in place with small plywood guides.
The Crack Yak is built on a flat work surface. The manual, although only available online, has detailed, step-by-step instructions and photos. I didn’t print it out, but left the file open on my laptop, allowing me to zoom in on the pictures to see the small details. One of the early steps is installing the main-spar assembly. Multiple parts are involved, and several glue joints are made simultaneously. The instructions are very clear on how the spar is installed, although a thorough read before putting glue to the airplane is helpful. After doing a preliminary check on the CG, I realized that I could mount the ESC fairly close to the motor and solder the motor wires directly to the ESC. That made the installation cleaner and lighter with lower resistance to increase power and efficiency. I also removed the plastic case from the receiver to save that small amount of weight. When finished, my Crack Yak weighed 5.8 ounces, which was on the lighter side of the model’s advertised weight. The recommended control throws for sport flying are 20–30 degrees in each direction for all surfaces, with 30-45-percent exponential. The recommended starting point for the CG is 81.5mm back from the leading edge. With the recommended setup, I made the test flight at dusk one evening when the wind had settled to a whisper. I found the Crack Yak to be fully aerobatic without being too sensitive. Inverted flight required a noticeable but predictable nudge of down-elevator, and all the basic maneuvers — loops, rolls, snaps, spins, harriers, hovers — were easily accomplished. The next couple of flights were completed inside a large gymnasium. I moved the CG back to 84 mm, and switched to the 3D rates; roughly 60 degrees of elevator, 45 degrees of aileron and 50 degrees of rudder. With the more aft CG, only a touch of down-elevator was needed for inverted flight.
Dave hovers his Crack Yak during a demonstration flight at the North Penn Winter Blues Indoor Fun-Fly. Slow flight at any attitude is a Crack Yak specialty. This is an ideal indoor performer for advanced RC pilots.
Knife-edge maneuvers are as accurate as the pilot’s commands instruct. There is no maneuver that this airplane cannot perform.
On the 3D rates, the Yak livened up. It was easy to maneuver in small spaces, and the response to control inputs was surprisingly crisp for an EPP airframe. Throughout the day’s flying, I had a couple of midairs, but with the durability of the EPP, the Yak didn’t incur much more than a couple of minor scratches. The Twisted Hobbys Crack Yak-55 “Lite” is a versatile airplane with broad appeal. It offers a good combination of economy, durability, and indoor/outdoor performance — especially when it’s in the hands of a skilled pilot.
SPECIFICATIONS
Type: Full-kit aerobat Skill leve: Intermediate–advanced Wingspan: 32 inches Weight: 5.6 – 6.2 ounces Length: 31 inches Price: $78.99 Info: twistedhobbys.comFEATURES
• EPP airframe components with factory-cut hinging • Factory-applied, three-color trim scheme • Available in four color combinations • Carbon-fiber wing spars, pushrods and landing gear • Fiberglass motor mount • Plywood reinforcements, control horns • Oversized, fiberglass 3D servo arms • Included linkage parts and wheels • 51-page, photo-illustrated, online manual (PDF) • Power Combo Digital LITE 32-inch options kit (not included) comes with all the necessary equipment except the receiver and batteryArticle:
