SR batteries X610

Model Airplane News, Nov 1999 by Atwood, Tom, Post, Roger Jr

Cutting-edge ARF electric thermal floater

There's nothing like flying a well-behaved, thermal-grabbing sailplane, especially one that is large enough to linger in a thermal with that stately grandeur that only the larger span ships seem to evince. Is it that their size makes them less sensitive to minor turbulence? Is it that the sweep of their wings is simply easier to see at altitude? Whatever that elusive quality of greatness in soaring flight may be, the X610, the subject of this review, captures it.

If you like open-bay sailplane designs that float across the sky, as do I, imagine the following. Marry precision manufacturing to an ARF design and give it an 86-inch wingspan, just over 7 feet. Make the wing out of high-quality balsa and ply, and cover it with transparent Ultracote Lite so that the airplane is both pretty and easy to repair should you ever accidentally ding the wing.

To eliminate forever the challenge of escaping from a "boomer" thermal that threatens to pull your soaring machine beyond visual range, equip the sailplane with ailerons that can double as lift-killing spoilerons. Give it a light fiberglass fuselage and preassembled, built-up tail feathers. Add to this SR Batteries" endless quest to build customer loyalty and their obsessively meticulous quality control. Finally, equip the plane with an affordable, geared, sport power system that provides an aggressive climb-out using a 14X9.5 CAM prop. Using 8, SR 1300 Max cells, the plane has a wing loading of only 12 ounces per square foot and easily climbs to thermal-catching heights three times on a charge. Does this sound like a winner?

It's really just the proper matching of design, materials and power system-the product of years of experience within the modeling community-- paired with time-saving ARF construction in a package that raises the bar. I'm not saying this plane is going to compete with a competition sailplane, nor would you ever want to dive and yank this plane like you would a European FSb-style electric. But when I compare its performance with the many open-bay electric gliders I have built and flown since the mid-'80s, some under 2 meters in span and some over, none have shown the performance capabilities of this particular airplane.

ASSEMBLY

Aileron servos are mounted in fairly shallow bays (1/2 inch deep) using a technique I had not previously used. The SR instruction manual asks that you epoxy-seal the balsa floor of the bay (of course) and that you cover the area where the double-stick tape will be applied with Scotch tape. You are also advised to cover the side of the aileron servo (I used Airtronics* 94501 Microlite servos in conjunction with the Airtronics RD6000 programmable radio reviewed in our August '99 issue). SR owner Larry Sribnick assured me the adhesive qualities of this combination would work well in practice and minimize any challenges should I swap out servos. He was right. Clear plastic "windows" with slots for the servo arm are then simply taped down, and the servo arm and aileron control horn are connected by threaded rod with a nut-locked clevis at each end.

This approach worked just fine. If by chance you select any of the really tiny sub-micro servos for this application (the aileron loads are not high, as this is a slow floater), note that you may need to add some balsa posts to prevent "servo rock" (the slight rolling of a servo under stress that is entirely a function of the flexibility of the double-stick tape). No such problem with the 94501s.

Assembly of the model is simple and straightforward. Perhaps the most challenging task is the relatively simple threading of the servo wire extensions into the D-tube cavity of the outer wing panels so that the wires may be subsequently pulled through the servo wire opening into the servo bay for soldering to the servo leads. Not wanting to fish for the wire within the D-tube interior cavity as instructed, I tied a tiny weight (a bolt) to the end of a thread, inserted an outer tube section from an old flexible linkage system into the second interior wing bay through the predrilled holes, and then dropped the weight down the tube and let it fall out the hole leading to the servo bay.

FLIGHT PERFORMANCE

TAKEOFF AND LANDING

The obvious sailplane takeoff technique is the hand launch. For the climb-out, the X610's Sport System motor and 14x9.5 CAM propeller combination produces an aggressive climb rate for a large floater, but with a considerable left-tuming tendency. Accordingly, I needed right-aileron/rudder input to keep the model tracking straight in a fast climb.

To land the X610, use the same technique as you would with any other model: align the sailplane with the runway, use the elevator to control the airspeed and, if needed, use the throttle to gain a little altitude or to reach the runway. Do not stall it close to the ground because the X610 will drop-nose first-3 to 4 feet. Be sure to save some motor power to assist, if needed, in the landing.

When landing, if you have the ailerons work as spoilerons, you can kill the lift that would otherwise cause the glider to float down the runway. Without the spoilers deployed, it will soar on for a very long way in ground effect. It doesn't seem to want to drop those last few feet to the earth! When deployed, the spoilerons required the addition of some down-elevator trim.