SR Batteries: Bantam Monoplane & Bipe

Model Airplane News, Dec 2002 by Aberle, Bob

MODEL AIRPLANE NEWS

FLIGHT TEST

Easy-build, easy-fly electrics

SR Batteries' growing line of high-quality, electric-powered model kits has again been expanded with two backyard/indoor RC flyers. The new design-the SR Bantam-is available in both monoplane and biplane versions. Which to choose? The biplane has a lighter wing loading and will therefore fly at much slower speeds, so it's well suited to newcomers and Indoor pilots who fly in a gymnasium or auditorium.

THE KITS

The Bantams are nearly identical; the only difference is the inclusion of a second (lower) wing on the bipe. The CAD-- drawn designs have been precisely laser cut out of balsa and plywood without the usual burned edges, and it's nearly possible to build either kit without a hobby knife or a razor blade. The spars, leading edges, trailing edges, plywood formers and motor mounts are all supplied and laser-cut to the exact sizes. The included instructions are a work of art, and a firsttime builder shouldn't have any problem assembling either model. I built both kits for this review, spending part of approximately five evenings building the first and only four on the second (you get faster as you learn!).

Each kit comes with a bag of high-quality accessory parts such as wheels, wing dowels, control-rod keepers and landing-- gear-mount screws, so you won't have to shop around for a lot of extra hardware. Both the landing-gear wire and the control-rod wire are supplied as are control-- surface hinges and a simulated windshield. You'll need to buy a roll of covering material; one roll of the recommended Hangar 9 UltraCote Transparent Lite will cover the entire plane. You'll also need thin and medium CA.

Both Bantams were designed to use the same power and RC system as is supplied with the popular GWS Pico Stick and Tiger Moth ARF models; that's great for anyone who wants to build the kit after getting some experience on the ARF model. For those who don't already have this equipment, SR Batteries offers a power system package that includes a GWS IPS DXA motor geared 5.86:1, a GWS 9x4.7 orange plastic prop, an SR 7-- cell, 150mAh Ni-Cd battery pack and a Jeti SA speed control with BEC. These components come prewired with miniature JST connectors, so you don't need to solder; they're strictly plug and play.

In addition to the power system package, SR offers suitable RC system components, namely an MPI 6800 micro receiver and two MX50HP microservos. You'll also need at least a 3-channel radio and a battery charger.

ON THE BENCH

The 40-page instruction manual includes more than 100 detailed, clear photographs. I followed the suggested assembly sequence and didn't have any difficulty at all. In many places, the instructions read: "Don't glue anything yet!" or "Listen up." This is so you don't accidentally skip ahead in the assembly or build two left wing panels instead of a right and a left. The warnings are important, so be sure to read every word as you go along.

Motor mount. A unique item in this kit is the breakaway plywood motor mount. You first CA two pieces of laser-cut plywood together, then trim the assembly so that one end fits inside the molded-plastic motor housing while the other passes through a hole in the firewall and then into a hole in the first fuselage former. A single screw holds the motor mount in place. This is a very easy mounting method. If you use a connector to attach the ESC to the motor, it's easy to change motors, even right at the field. On a rough or crash landing, the motor mount will break away, usually saving the motor shaft and gears. Replacing the mount is also simple.

Pushrod installation. The control-rod scheme is really interesting. Place the provided 0.032-inch-diameter wire inside a thin-wall aluminum tube leaving a short length protruding at each end. Then attach the wire ends to the servo output arm and the horn to the control surface, and position the tube so that an equal length of wire protrades from both ends. Next, cement the tube to the wire. The tube acts as a wire stiffener and moves along with the wire. This works well and is simple and neat! Hinging. The new SR Gapless Hinge Tape included in the kit works much better than iron-on covering material and is quite durable. After covering your stab and elevators, position them with about a 1A2-inch gap using a few small pieces of masking tape. Cut a length of the hinge tape, peel off the protective backing and carefully apply it along the hinge line. Press down firmly, and you'll have a perfect hinge. The material is clear, so your covering material will show through. I plan to use this tape on all of my future models.

Covering. UltraCote Transparent Lite iron-- on covering has long been my favorite for small models. I have found that it's helpful to use two irons-one set on low heat (25 percent) to tack the covering to the wooden frame, and the other set at a higher heat (75 percent) to shrink the material and eliminate all of the wrinkles. Each SR kit comes with a volume from Larry Sribnick's series on modeling, "SR R/C Techniques." The Bantam kits come with "Basic Covering Techniques," which provides information that newcomers to covering will find especially useful. Battery access. With most electric-powered models, you need to remove the wing to access the battery pack for charging, but SR designed the Bantam so that a flat 7-cell, 150mAh Ni-Cd pack is accessible through a hole in the lower part of the firewall. The battery actually protrudes about lfi inch. I used hook-and-loop fastener to hold the battery in place. The battery cables are positioned so that they hang just below the motor and are accessible from the outside of the fuselage; you need only to disconnect the battery and attach your charger cable. You can also remove the pack and substitute a freshly charged one. To separate the hookand-loop fastener, I insert a 1/32-inch ply stick (the equivalent of a tongue depressor) between the fastener halves and work it upward inside the fuselage. Once the fastener has been completely separated, I remove the battery from the fuselage.