01Libelle.jt1.doc
SPECIFICATIONS
Model type: Discus Launch Glider (DLG)
Skill level: Beginner builder; beginner/intermediate pilot
Wingspan: 47.2 inches
Length: 37-3/4 inches
Weight: 9.8 to 10.2 ounces
Construction: EPO foam and composite parts
Street Price: $120.00
TEST-MODEL DETAILS
Radio system: Hitec Aurora 9X; Hitec Minima 6L receiver; four Dream-Flight 4.3 gram digital servos; two 120mm servo extensions; Dream-Flight 4.8V NiMH 300 mAh battery
Ready-to-fly weight: 9.5 ounces
Flight duration: Varies depending on launch and lift
PLUSES
• Inexpensive DLG model perfect for beginners.
• Well thought out and engineered airplane.
• Ease of assembly and detailed instruction manual.
• Optional Flight Pack provides servos, extensions, and battery to match the aircraft.
MINUSES
• Vertical fin index hole in tail boom was misaligned.
Watching pilots fly Discus Launch Glider, or DLG as it is commonly referred to, has always intrigued me. While most may compare a DLG pilot to a discus launcher at the Olympic Games, and for obvious reasons, they also remind me of a pitcher at the mound. On the mound the pitcher carefully scans the field and accesses their opponent standing at the plate to determine just the right pitch to deliver and then comes the windup and release.
Similarly a DLG pilot, while holding their radio in one hand and the launching peg of their aircraft in the other, scans the sky both for other aircraft and thermal activity. Facing into the wind, the windup begins as they make a complete rotation releasing the glider directly into the wind and slightly above the horizon. The model streaks skyward, some capable of obtaining altitudes of over 100 feet. Once the apex is reached, the pilot levels the aircraft and the hunt for thermals is underway.
I have seen this repeated countless times as pilots fly their aircraft both for fun and also during competition and have always held an interest in trying it myself. This year at the Southeast Electric Flight Festival I had a chance to fly a Dream-Flight Libelle. After receiving a few tips, it was time to fly my borrowed aircraft. With a few launches under my belt, I felt like a pitcher who just achieved their first strikeout. There was a simple joy in being able to perform an acceptable launch, while not dropping the transmitter, and piloting the aircraft with the goal of keeping it aloft utilizing only the thermal currents of rising air. I was hooked, I had the try out and now it was time to get into the game!
Assembly
The Libelle comes neatly packaged and double boxed. Inside I found the parts to be complete and undamaged. Along with the basic model, I also received the Flight Pack, this $75 option provides four servos, extensions, and a battery. I also received the Wing Reinforcement Decals and Logos; a $10.50 option to increase the wing stiffness and durability. It includes four pre-cut wing reinforcement decals and logo sheet.
Prior to beginning the assembly process, I read the entire manual and found it to be well written with a lot of detail on building and flying the Libelle. It is filled with black and white photos to help complement its 25 pages of instruction. Beginners should have no problem with assembly because the manual covers the basics without assuming the reader understands how to complete the steps required to finish the model.
The process begins with setting up the radio and configuring the servos and servo arms. After configuring and testing the Dream-Flight 4.3 gram digital servos, it’s time to move on to the wing.
The manual recommends the use of medium CA for all steps requiring the application of glue. I chose instead to use Beacon Foam Tac, except as noted, as it provides a slightly longer working time and remains flexible even after it has cured.
The wing halves are attached using two plastic dihedral braces that fit into molded slots in the wing. As the name implies this sets the dihedral angle and strengthens the wing joint. They are glued into the left wing first, and then the right as the wing is joined together with the help of two alignment tabs and recesses.
The plastic wing centerplate is then pressed into the top of the wing and glued in place. It provides additional support to the wing joint and wing mounting bolts.
The next step is the aileron control horns which are inserted and glued into a recess in the underside of each aileron.
On the bottom of the wing, each aileron servo is provided its own pocket and channel to run the servo wire and extension to the center of the wing at the leading edge. The servos fit perfectly; however, I was concerned that the top of the servo arm might rub against the foam. To determine if I had enough clearance I tested the servos and found they moved freely. There was just enough room that a single piece of paper could fit between the top of the servo arm and the foam.
The channels for the servo leads and extensions are a nice touch, but I found the larger opening to accommodate the servo extension needed to be extended slightly. This could be because I was using the Dream-Flight servos and not the Hitec HS-35 and the length of the leads could be slightly different. I carefully extended each pocket until the servo extension seated into the wing.
If using the Wing Reinforcement Decals they are applied next. The four decals that are used are specific to not only the top and bottom of the wing, but also right and left. The ones used for the bottom have three holes punched into them to accommodate the launching peg, servo arm, and wing mount. The top two forgo the servo arm hole.
The instructions recommend misting the foam wing surface with a spray bottle filled with water and 4 drops of dish soap to allow decal to "float" into position. I would highly recommend using this method and it also would help to have a second person assist with this process. Once the decal was position, a combination of fingers, a squeegee, and some paper towels finished the process. If the decals are not used, it is recommended that Scotch tape is used to cover the servos leads and keep them from slipping out of the channel.
The supplied clevises for use with the ailerons, elevator, and rudder work well and only require that the sides be folded together to create a slot where the pushrod will be clamped using the supplied clamping screw. This provides for adjustments in the linkage to center the control surfaces.
The fuselage and tail assembly starts with gluing the elevator and rudder servos in place. For this step, I used CA by applying a drop through all four mounting tabs. The servos fit securely and the servo wires are easily routed under the servo mounts to the receiver.
The horizontal stabilizer can then be mounted using a nylon bolt and the elevator pushrod attached. It is important when attaching the Z bend ends of the elevator and rudder pushrods to their respective servos to ensure the pushrod is under the servo arm to allow for proper clearance once the canopy is attached. The manual also provides direction in the proper orientation of the elevator and rudder clevises to prevent any binding.
The vertical stabilizer/rudder has a groove in which to mount the tail boom. Located in the groove is a foam index tab that mates up with the opening in the tail boom for proper alignment. Unfortunately, the cutout in my tail boom was off center resulting in the stabilizer not mounting square.
Because of this issue, I opted to use 5 minute epoxy to allow for additional working time so that I could ensure proper alignment. I lightly sanded the tail boom where it contacts the stabilizer and then glued it in place.
Since the vertical stabilizer/rudder contacts the ground when landing, I followed the recommendation in the manual to add a small strip of clear tape over the tail boom and onto the fin for added strength.
The wing attaches to the fuselage with two nylon bolts; the longer of the two is used for the forward hole. A molded foam channel in the fuselage, underneath the wings leading edge, ensures the servo wires are not pinched and are routed to the receiver location.
The Libelle has adequate room for the radio gear and flight battery, but it is by no means spacious. Just like the rest of the aircraft, this area is well thought out and provides a recessed area for the battery and its wires run through a channel. The receiver and wiring also has a dedicated space.
I opted to use the Hitec Minima 6L receiver, one of two recommended receivers in the manual. Due to its end pin orientation, it was easily mounted in the forward location. I also oriented the receiver so that the connection for the battery was on top for easy access. Servo tape was used to keep it in place. The 6L has two, six-inch antenna wires. I ran one on the outside of the fuselage and the other inside the aircraft.
Three steel balance weights, a total of a half-ounce, were used to obtain the CG at 5mm behind the wing spar at the sides of the fuselage. One weight was affixed in a cutout below the battery and the other two on each side of the battery fully forward.
High rate control surface deflections for ailerons, elevator, and rudder were used. Since I fly most of my aircraft on high rates, I opted not to program low rates.
The carbon fiber launching peg can be installed in either wingtip, depending on the pilot’s preference. Mine took a little sanding with the included sandpaper to get it to fit, but it stays put and can be removed if needed.
Finishing
The Libelle is like an artist’s canvas with the EPO foam wing and tail ready to accept a splash of paint, colored tape, or even some Sharpie art. My goal was to keep the Libelle as light as possible, so I opted to forgo adding color with one exception.
While the canopy attaches firmly with the included magnets, I did witness one launch that shed the canopy and battery turning the Libelle into a tail-heavy Free Flight model.
To ensure that didn’t happen to mine, I opted to wrap the canopy with blue painters tape after powering the radio. This provides a little added color to the black and white model and the security of knowing the battery will stay put. The almost unmeasurable added weight simply assists with the CG.
Flying
I decided to start simple and no mixes or flaperons were used. I did; however, utilize a neck strap to ensure that my best toss of the day wouldn’t be my Hitec Aurora 9X transmitter!
The first three launches were made overhand, into the wind, standing atop of a small hill. These launches were used to trim the model for straight and level flight. A total of five clicks of up trim was all the Libelle needed, no adjustment to the ailerons or rudder were required.
Transitioning into discus launch, I followed the instructions in the manual allowing the glider to hang freely from the launching peg and fully extending my launching arm horizontally. All launches were made into the wind, releasing the glider at an angle of just slightly above the horizon.
As the Libelle left my hand and streaked skyward on my first discus launch, it took with it any nervousness or apprehension. The thrill and excitement I had experienced flying DLG at SEFF had returned.
While the Libelle is easy to fly, it also challenges you to throw it higher and to keep it aloft longer. In the air, I was comfortable with the responsiveness that the high rates provided. The high rate elevator can be a little touchy, if you’re not smooth with your inputs, which can easily be resolved with a little expo. Loops are easily performed after a slight dive and then applying full up elevator.
The rudder authority is good and the model can be comfortably flown without the use of the ailerons. Pushing the aerobatic capability further, the Libelle is also capable of rolling maneuvers, either rolling inverted or complete rolls. Just be sure to give yourself a little room until you’re comfortable with its responsiveness and slight loss of altitiude.
Just like when launching, the Libelle is best landed into the wind giving the control surfaces the most authority. It can also be caught in flight, if you are comfortable doing so. Even though the vertical fin extends below the tail boom and contacts the ground on each landing, I have yet to have an issue. I often opt to catch the Libelle which also helps.
Conclusion
The Dream-Flight Libelle is thoughtfully engineered to provide beginner’s an inexpensive option to experience the thrill of soaring and the hunt for thermals. Using your own body and launching technique to propel the aircraft skyward is uniquely challenging and thrilling. The challenge continues as you silently try to stay aloft as long as possible with the help of upward rising air.
The servos and battery that Dream-Flight recommends and sells have performed flawlessly and is a perfect match for aircraft. If you have an interest in soaring, either discus launch or slope, the Libelle is certainly a good choice.
Jay Smith
[email protected]
MANUFACTURER/DISTRIBUTOR
Dream-Flight
(805) 845-1803
www.dream-flight.com
Sources:
Hitec RCD
(858) 748-6948
www.hitecrcd.com
