Thunder Tiger Trainer 40 OBL ARF

By: Richard Landis and Barry Yarkon

This review is the deliberate collaboration of a very skilled RC flyer and modeler, Richard Landis and Barry Yarkon, a “beginning RC Pilot”. In addition to his long RC piloting experience, Richard also has a great deal of experience with electric power systems.

Barry’s introduction to R/C flying, as an adult beginner, contains several lessons for anyone of any age who is attracted to this sport and who wants to start off on the right foot. It didn’t always happen that way for Barry.

Lesson One:

Barry tried to fly a radio-controlled P-47D foamy with electric power before he had access to an AMA club and field. He quickly learned that flying a tail-dragger Warbird in too small a space was simply a recipe for disappointment. After one too many unplanned collisions with the surrounding trees and two bottles of foam-safe CAA used up, what remained of the Thunderbolt was retired to the Red Cross hangar.

Lesson Two:

Barry recovered the electronic components (receiver, micro servos and Lithium Polymer battery packs) from the P-47. Still not a member of a flying club, he chose a second airplane in which those same parts were useful. This was an intermediate, aerobatics-capable sport biplane, the Reactor Bipe EP.

The Reactor Bipe had small main wheels, complete with wheel pants that caught in the field’s grass. Again, the Reactor was also a tail-dragger. At this point Barry became a member of the Rockland County Radio Control Club (RCRC), an AMA chartered club in the lower Hudson Valley area of New York State. Barry found that, even after intensive practice on an excellent computer RC flight simulator using that same model biplane, that the biplane was too fast and too frisky for him to make much progress learning how to fly RC. He did notice it was a lot of fun for many of the other club members who volunteered to “check it out” at the field.

Lesson Three:

The common sense advice from experienced club members was for Barry to take a step back and learn to fly with a traditional trainer aircraft, one with a high-wing, flat-bottomed airfoil and tricycle landing gear. The Thunder Tiger Trainer OBL 40 ARF is a perfect match for their descriptions.

OUR PLAN

The underlying motive for this review is to see how successfully a beginner like Barry can assemble the Thunder Tiger Trainer OBL 40, install an electric power system, and then learn to fly RC. Could Barry make up for the lost time and earlier discouraging results by re-learning how to fly with a proper trainer?

Richard will be available during Barry’s assembly to answer his questions and afterwards, Richard will check out the build, its CG balance and then will test fly the Trainer. Richard will act as his flight instructor until Barry can solo with the Trainer.

That said, this review contains suggestions that may be helpful for builders of all skill levels. Read on to see how we made out....

Twelve years ago, Thunder Tiger of Taiwan purchased the former ACE R/C of Higginsville, MO. and incorporated into what is known today as ACE Sport Distributors, Inc. (www.ace sport.com). Ace provides retailers in the U.S. with airplanes, helicopters, cars, boats, engines and various other sport products down to the nuts-and-bolts aspect of the sport (which is where ACE R/C started 53 years ago).

Because Barry is relatively new to the sport, the Thunder Tiger brand was unfamiliar to him. He discovered that Thunder Tiger’s aircraft line is quite extensive. It includes Trainers, Gliders, Scale, Sport airplanes, Helicopters and Jets. Their smaller Park Flyer and Aerobatic aircraft have become famous. Ace even has a Tournament of Champions aircraft series that John Glezellis recently used to place 4^th at the XFC 2009. John was flying a Thunder Tiger TOC Extra 260 at this event.

It was comforting to find four Rockland, NY retailers listed on Ace’s website. After some minor confusion and a little trial-and-error, the box’s contents morphed into a great looking airplane. Fortunately, Barry did not need assistance beyond Richard’s expertise and the well-illustrated 28-page assembly manual, http://www.tiger.com.tw/product/4579-K10.html.

If you are a beginner considering buying a trainer aircraft, or if you are about to build the Thunder Tiger Trainer OBL 40, we suggest you download the manual and carefully cross-reference this review. Also, be sure to read the Sport Aviator articles, Building an ARF Trainer Parts 1, II and III.

The Airplane

Photo Courtesy of Thunder Power Taiwan

Designed for both glow and electric power, this is the newest addition to the family of eight Thunder Tiger Trainer models. It is a prefabricated ARF (Almost Ready-to-Fly) meant for beginning model pilots like Barry. “OBL” is short for Outrunner BrushLess motor. [For beginners: “40” indicates the approximate size of a model aircraft based upon the size of the appropriate 2-stroke glow engine. The GP-42 engine has a displacement of 0.396 cu. in. and is recommended for “.40-size aircraft,” hence the “40” in this trainer’s name.

The Tiger Trainer is available in two structurally identical models, the 4579-K10 for glow engine power systems and the 4579-K11 for electric motor power systems. The glow-powered version is also reviewed in Sport Aviator’s On The Flight Line Section as the Thunder Power Easy Trainer Plus.

The K10 airplane (TTR4579-K11) is meant for glow engine power and it contains extra parts to facilitate the use of either of two suggested glow engines: the Thunder Tiger GP-42 or the F54S 4-stroke. These parts include: 300cc. fuel tank and full accessories; and an adjustable engine mount with hardware.

For electric power, the K11 (Prod. No. TTR4579-K11) airplane comes instead with Thunder Tiger’s Ripper OBL36/11-40A brushless outrunner motor (No. 2368), an ACE BCL-40A Electronic Speed Control (ESC) (No. 8027), and an OBL motor mount (No. AS6458).

So, if you prefer to set up your Thunder Tiger Trainer with a glow power system, then specify the 4579-K10 and add the appropriate engine. If you prefer to set up your Trainer for electric flight, purchase the 4579-K11 model. Your retail dealer can advise you.

Authors Note: The K10 (glow) model was provided for this review. We preferred to electrify it by setting aside the glow power parts and installing an ElectriFly RimFire 35-36-1200 brushless outrunner motor and an ElectriFly Silver Series 35A SS-35 brushless ESC from Barry’s other airplane. The motor mount is a Great Planes GPMG1255 Medium Motor mount. We were not able to test the Ripper OBL36/11-40A brushless outrunner motor (No. 2368) and ACE BCL-40A electronic speed control combination but their specifications are similar.

Photo 2

Photo 3

The Thunder Tiger Trainer OBL 40 came packed in an attractive, sturdy box with all of the parts thoughtfully bagged and packed. See Photos 2 through 5. Photo 6 shows an exploded view of the kit’s parts (courtesy Thunder Tiger Taiwan).

Photo 4

Photo 5

Even the little super magnet that will hold down the access hatch was sealed into its own corner of one parts bag. There was no “hangar rash” and no shipping damage. We did discover that the nose gear mount was missing. Richard fabricated a nose gear mount for the steerable nose wheel.

(Ed. Note: This was supposed to have been the K-11 version but the K-10 was sent instead as the K-11 was not yet in stock. The K-10 nose gear mount is part of the engine mount and therefore was absent once that mount was eliminated. If you are converting a K-10 to electric power use Du-Bro bearing blocks number 156 and steering arm number 155.)

Photo 6

Photo Courtesy of Thunder Power Taiwan

We were also pleased with the handsome, streamlined design of the Tiger Trainer OBL 40 – white with a screened four-color scheme and matching side-stripes. Quality of construction was obvious from its drum-tight film covering (not a wrinkle or a bubble) to the extensive use of sheeting in both the fuselage and the wing halves. The entire top section of the fuselage is a white plastic molding that was permanently bonded to the balsa and plywood sides and bulkheads at the factory.

We learned from the manufacturer that the covering material used is "OPP" a form of Biaxially-Oriented Polypropylene (BOPP) film. Thunder Tiger was not able to specify a retail brand of covering, so if you need to do repairs or construction on your Tiger Trainer OBL 40, try speaking with the dealer you purchased it from or any one of Ace’s listed dealers. One such brand, Solarfilm, is available in the USA and is compatible with BOPP films according to the manufacturer, Solarfilm Ltd., UK.

Barry would like to share this anecdote with you. While he was doing some of this research via the internet, he was pleasantly surprised to have an email sent to Thunder Tiger Support at 10:30pm on a Monday evening from New York, answered within a few minutes! Turns out that Thunder Tiger Taiwan is almost exactly 12 hours ahead of New York time, for them it was 10:30am the next morning (Tuesday).

Photo 7

Photo Courtesy of Thunder Power Taiwan

Back to the Tiger Trainer. Construction was laser square and Thunder Tiger’s concern for quality showed in the extensive use of model grade plywood bulkheads and hardened points. There is also an attractive red spinner and backplate. According to Ace’s website, the MSRP for the K10 Trainer is US$150. and the K-11 is $199. Considering the K-11 arrives with an outrunner motor and ESC, the $49 extra is a great deal.

Photo 8

The broad wing seems to have a modified flat-bottomed airfoil of about 13-14% with a constant chord of 11 inches. Photo 8 shows the Tiger Trainer airfoil.

Photo 9

Each of the wing halves has 8 ribs and is generously sheeted top and bottom for 7” out from the root edge and for 5” in from the neatly beveled wingtips. The full-length ailerons are beveled where they hinge into the trailing edge of the wing and each aileron has 18 circular lightening holes (¾” diameter, see Photo 9). There is even a clear plastic wing protector that slips over the center trailing edge and an included strip of white covering tape to hide the wing join seam, no heat gun necessary.

Richard and Barry chose the 6-channel Futaba 6EX 2.4 GHz transmitter and matching R606FS receiver. This Futaba system is reasonably priced ($220) for a beginner and avoids interference problems and their potential shoot-downs. A new RC pilot already has enough challenges to contend with and really doesn’t need the extra one of frequency interference.

The ESC used has a battery elimination circuit (BEC) built in. The receiver and servos will get their power directly from the motor battery without the need for a separate receiver battery pack. The motor battery is composed of two 3S 1P 2100mAh 20C Lithium Polymer battery packs in series for a 3S 2P power system (2 3-cell battery packs wired in parallel).with Deans connectors for on-board power that were used with my biplane. Barry already has a PolyCharge4 field charger and two Equinox LiPo balancers for these batteries.

Photo 10

Photo courtesy of MPI Maxx

Safety arming switch: Just recently, Barry had a safety incident at the field when he retrieved an electric-powered model that had landed on the runway and someone else inadvertently jiggled the transmitter throttle stick starting the electric motor [that would not happen with a glow engine]. This type of accident-waiting-to-happen can be avoided by installing an arming switch between the flight battery and the ESC. He chose to use an MPI Maxx Products International #6970 High Current Arming Switch with Dean’s connectors, pictured in Photo 10. It will mount into the fuselage side and cut-off power to the entire system when the red/black arming plug is pulled out. In Photo 10, the left-hand image is disarmed and the right-hand image is armed.

Servos: Using an electric power system eliminates the need for a throttle servo because the “throttle” function is handled by the ESC. Three Futaba 3010 servos were used to power the aileron, rudder, and elevator surfaces. A single aileron servo activates both the right and left ailerons simultaneously and it is hidden from view within the fuselage when the wing is attached. Also, a 6” (or 9”) servo extension cable will connect the aileron servo to the receiver to allow enough slack for easy wing removal and attachment when traveling.

Questions often come up on the forums, when a builder’s radio system has more channels than necessary for the four basic controls, about adding flaps to a model and about separating the two ailerons onto two different channels to allow for differential mixing.

Thunder Tiger rightly warns: “Please assemble your model exactly according to these instructions. Do not attempt to modify or change the Tiger Trainer OBL in any way as doing so may adversely change its flying characteristics.” We decided to build according to plan for this review knowing that once Barry masters the Tiger Trainer OBL 40 as is, we can revisit these questions and consider adding either or both of these more advanced capabilities in the future.

(Ed. Note: As regular readers of Sport Aviator know, I strongly favor using flaperons when the airplane uses twin aileron servos. I even installed flaperons in a HobbiStar 60 MK III in an article in the Pri-Fly Section. But the Thunder Tiger Trainer really doesn’t need flaperons although installing them, which is a lot of work on this airplane, would allow adjusting the ailerons to compensate for adverse yaw. Mechanical adjustments are possible as noted in the Midwest Aero-Star Review. )