SR batteries X610

Atwood, Tom

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 14×9.5 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.

HIGH-SPEED PERFORMANCE

The X610 was designed to be a floater, and it does float very well, so this category doesn’t really apply. If it is dived-power off-it can pick up quite a bit of speed. But it’s a floater, so don’t dive it expecting a high-speed flyby like an F5B ship does; you will only endanger the aircraft by exceeding its design speed.

LOW-SPEED PERFORMANCE

At one point during the test flights, with the model pointed directly into the 8-knot–gusting to 12-wind, its ground speed was zero– no perceptible forward movement. It can catch thermals and “hang” in the air with tremendous stability.

Many modelers who fly sailplanes without spoilerons have lost them during efforts to avoid the powerful lift of large thermals. This is the electric glider that you can explore “boomer” thermals with. Because of its spoileron capability, you need not worry about its floating up and away; no need to fear that with this grand ship. The power-off stall produces a nose drop as previously noted. To recover, neutralize the elevator and add power, there was no tendency for the wing to drop.

AEROBATICS

The X610 is designed to be an intermediate electric sailplane and is therefore not set up to produce the wild gyrations of an aerobatic craft. It will do gentle loops, spins and barrel rolls (lots of rudder required), take care to avoid building up excessive speed during a dive.

If your rudder thumb has lain dormant for a number of years, either wake it up or use a computer radio that allows the rudder to be slaved to the ailerons. If you slave the rudder to the aileron stick, I recommend that you use 100 percent rudder deflection. Also, program some aileron differential into the setup by using either the end-point adjustment (EPA) percentages or the aileron differential function in your radio. The adverse yaw that is created by improper aileron deflection, i.e., in the absence of differential, will initially yaw the model a direction that’s opposite that of the intended turn.

The model isn’t pitch sensitive, so a little extra elevator throw wouldn’t be a problem. Use as much rudder throw as you can get out of your rudder servo. The manufacturer states that the X610 may be flown as a 3-channel airplane (no rudder), but it recommends the use of the rudder. I concur without the rudder to help with the model’s turning, the mild response on ailerons alone will be an issue.

The X610 can be flown in moderately windy conditions, but be sure to save some power to help you get out of a jam (if you’re in mild chop, you don’t want the motor to cut off near the ground). The model is extremely light, and turbulent air can toss it around in the air unexpectedly.

–Roger Post Jr.

The other end of the thread was attached to the servo wires (see photo). I just pulled the wires through by pulling on the thread. Then I cut the servo connectors off the end of the servo leads and soldered the leads to the extension wires and used heat shrink tube in accord with standard practice.

SR provides beautifully engineered epoxy and glass control horns for the ailerons, rudder and elevator (see photo). I at first mistook these fairly thick, rugged fixtures for some type of semi-opaque phenolic. They are designed for modelers who will be using a programmable radio like the Airtronics RD6000. SR also supplies a second set of more conventional looking horns for modelers who will be using standard 4-channel, non-programmable radios. Whatever your radio type, you will be able to create aileron differential either mechanically with the conventional horns (thoroughly explained in the manual), or via your programmable radio using the custom-built SR hardware.

Mounting the elevator servo was easy, although I did rasp out a slight cavity in the upper extreme inner “lip” of the balsa former that separates the back of the fin sidewalls. I wanted to absolutely guarantee 1/8 inch clearance for the elevator pushrod. Very carefully install the tiny custom-designed elevator control horn because if you recess it farther aft than the instructions say, you can cause subtle problems in the geometry of the setup.

Installing the rudder servo is a real snap, as the mounting rails on which the servo tray is to be glued have been preglued to the inside of the light glass fuselage. You simply mount the servo on the tray, place it roughly in position, center the servo, and connect the supplied linkage to the rudder horn and servo. Center the rudder and then glue the tray down. A snap. Interestingly, SR advises not piling the epoxy on to strengthen the bond between the preglued firewall and the nose; better to have that firewall slip loose if you accidentally impact the nose of the ship than crack the fuselage. Attaching the motor to the firewall is a real breeze. Three small bolts do the trick. The sport system motor, planetary gearbox, Jeti* speed control, fuse and Sermos connectors come preconfigured, mounted and soldered. That is a real convenience. The hub, prop and spinner assembly is simple and sure. Setscrews are used to mount the yoke to the motor shaft, and the spinner is mounted to the yoke via interior screws that are threaded through the underside of the yoke.

Three nylon bolts hold the center wing panel to the wing saddle, one of which you need to prepare. That is a simple matter of drilling a hole in the aft portion of the panel and through the fuse cross panel at that point, and then mounting a blind nut underneath to accept the nylon bolt. The outer wing panels are connected by short steel joiner rods that slide into preinstalled joiner tubes. Small steel guide pins ensure perfect alignment.

The ailerons, elevator and rudder are all hinged with highly adhesive, strong, clear SR gapless hinge tape (developed by SR with 3M for this purpose). The manual is clear and well illustrated. So, you can see, the airplane is quite easy to build.

CONCLUSION

The result exudes quality. It utilizes an SD 3021 airfoil and is not really designed for high-speed aerobatic flight. For the traditional U.S. sport modeler who likes to fly floater-style gliders, it is a step ahead in materials, workmanship and performance. Despite the relatively inexpensive motor drive system, it climbs with enough power to require torque correction (i.e., a bit of right aileron coupled with right rudder). When landing, the X610 wants to hang in ground effect seemingly forever, so the spoilerons are an immense help (see “Flight Performance”). And it takes very little time to assemble because all the really time-consuming work has been taken care of, right down to installing a fuse in the power system. In my opinion, this all represents genuine progress.

Sopwith Baby Sea Scout

Stretch: conference acknowledgements