09Allusive.ht1.doc
[Headline: Horizon Hobby E-flite Allusive 2.2m ARF
[Subhead: A well-rounded sport sailplane]
[Author: Andy Griffith]
[Email: andy@customcutgraphix.com]
[Photos by the author]
[Sidebars within text]
[See a bonus video of the Allusive in the digital edition and online at www.ModelAviation.com.]
SPECIFICATIONS
Model type: Electric sailplane
Skill level: Beginner builder; intermediate pilot
Wingspan: 87.5 inches
Wing area: 546 square inches
Wing loading: 12.9 ounces per square foot
Wing cube loading: 6.6
Airfoil: Semisymmetrical
Length: 43 inches
Weight: 3 pounds, 1 ounce
Power system: .15-size brushless outrunner motor; 40-amp brushless speed control
Radio: Four-channel minimum
Construction: Balsa-sheeted, foam-core wings; fiberglass fuselage; built-up V-tail
Covering/finish: White, black, and yellow UltraCote covering; white painted fuselage
Street price: $329.99
TEST-MODEL DETAILS
Motor used: E-flite Power 15BL 950 Kv outrunner
Battery: E-flite 3S 2,200 mAh 30C LiPo
Propeller: 12 x 8 folding
Radio system: Spektrum DX9 radio; Spektrum AR6260 receiver; two Spektrum A5030 Mini Digital Aircraft Servos; two Spektrum A7020 Digital Wing Servos
Ready-to-fly weight: 3 pounds, 1 ounce
Flight duration: Varies depending on skill and weather conditions
PLUSES
• Nicely finished fiberglass fuselage.
• Easy and quick to assemble.
• Fun to fly.
• Simple control setup offers easy assembly for beginners.
• High contrast between the top and bottom of the wings for excellent visibility.
MINUS
• Model needed some weight added in the tail to balance at the recommended location.
The Allusive has slightly more than a 2-meter wingspan and uses a reasonably priced power system. The only special requirement for the radio system is support for V-tail mixing, which is available on most radios sold within the last 10 years. Assembly time is only a few hours and it can be put together at the field in minutes.
The Allusive comes with straight, fully sheeted wings with foam cores that appear strong without being heavy. The wings only feature ailerons. There are no flaps or spoilers—saving weight and complexity. The ailerons are factory hinged with covering material, and there is a cutout for the aileron servo.
The wings are joined by an 8mm-thick carbon wing rod that protrudes approximately 3 inches into each wing, along with two smaller carbon-fiber antirotation pins on each wing panel. When attached, the wings have a slight dihedral angle.
Despite this being the norm with the glider crowd, some modelers still cringe when they see me attaching the wings on a nice glider with vinyl electrical tape. This is a well-accepted practice and works perfectly.
The fuselage is nicely laid up and painted fiberglass with no visible seams. In the front of the fuselage there is a factory-mounted wooden tray to install the servos and hold the battery. The radio compartment is topped with a snap-in fiberglass hatch that provides easy access to change out the flight battery.
The Allusive features a V-tail with mixed elevators and rudders. The most common question I hear when people see a V-tail is whether the steering function works like ailerons or rudders. The correct term for the control surface is “ruddervator” and as the name implies, the surfaces function as rudders and elevators. The stabilizers and ruddervators on the Allusive are built up, prehinged, and use carbon joiner rods that go all the way through the fuselage for a solid assembly.
The control system consists of rudder, ailerons, elevator, and throttle. The ailerons can be attached to a Y harness or individual channels. The ruddervators are mixed using the V-tail mixing feature available on most computer radios.
The power system is composed of a 40-amp speed controller that spins a .15-size electric motor and a 12-inch folding propeller. There aren’t many parts, so getting it into the air quickly shouldn’t be a problem.
Construction
E-flite manuals are among the standard by which I judge others, and the Allusive’s instruction manual is no exception. It is well illustrated with clear photographs and leaves little to chance. There were only a few minor details that the manual failed to mention, and I will discuss them.
I used Zap brand thin and medium CA, Pacer Z-Poxy 15-Minute and 30-Minute epoxy, and Z-42 threadlocker to assemble the Allusive. All are available from Frank Tiano Enterprises. Always ensure that you have adequate ventilation when using modeling chemicals. The older I get, the more sensitive I am to CA fumes.
The first step in assembling the Allusive is to install the four control horns. I used 30-minute Z-Poxy for this task. Prepare the control horns by removing the shine from the gluing surfaces. I have an assortment of emery boards purchased from dollar stores that last for months of review builds, and work perfectly for this and other modeling tasks.
After the control horns have been prepared, test-fit them and mix the epoxy. You can use blue painters tape to mask off the area so you don’t make a mess with the epoxy. When the glue is mixed, use a toothpick to pack the holes and install the control horns. Remove the tape and clean up any stray epoxy with isopropyl alcohol. Nothing looks worse on white covering or fiberglass than yellow epoxy fingerprints!
The next step involves installing the servos in the wings. You prepare the servo tray by prethreading the servo mounting holes and hardening the threads with thin CA. When that is done, the mounts are epoxied into the wings. Pull strings are included for the servo wires and they assist in pulling the extensions to the wing root.
Here’s a detail the manual missed: the servo-mounting screws need to be shortened by a few millimeters or they will be too long and will go through the sheeting. I used a rotary tool and ground approximately 2mm off each screw before installing it.
When assembling the control linkage, although electric gliders produce little or no vibration, I used threadlocker on the jam nuts after the servo was installed. The radio configuration was completed.
Plastic servo hatch covers are provided for the aileron servos to reduce drag and protect the linkages. The hatch covers are cut to shape using scissors designed for RC car bodies, then secured using clear tape provided in the kit.
Installing the V-tail is next. The provided carbon pins go all the way through the fuselage and end up flush with it. There is a left and right stabilizer with the stabilizer pins offset from each other. I used 15-minute epoxy and blue painters tape to keep the stabilizers against the fuselage while the epoxy cured.
Clean up any excess epoxy with alcohol. Don’t skimp on the glue to save weight—the Allusive needs weight in the back anyway. The entire assembly is solid and the tail ended up perfectly aligned without any tinkering.
When the tail glue is dry it is time to install the tail servos and control rods. Prethread and harden the threads before mounting the servos. The pushrods are installed next. A 90° bend is placed in the pushrod where it attaches to the servo and it is then cut to length. Final adjustment is made on the control surface end when the radio setup is done, then threadlock the jam nuts.
I set up my Spektrum DX9 and bound it to the 6260 receiver. When configuring the DX9 or DX18 there are V-Tail A and V-Tail B choices in the wing-type menu. To get everything moving in the proper direction, the Allusive uses V-Tail B and I set the wing type to dual aileron servos.
I also enabled the Throttle-Cut function so I could disarm the motor with the flick of a switch. This is a safety feature that I recommend using on any electric model if your transmitter allows.
Powering my Allusive is the E-flite Power 15 motor mated to a 40-amp E-flite brushless speed controller. The first step in installing the motor is to reverse the motor shaft. The instructions for the motor detail this procedure. I have an old drill that I installed in my drill press with the shank sticking down, and used the drill press to press the shaft through. This minimizes the chance of damaging the motor bearings.
You can also use piece of 2 x 4 or similar wood on the shaft. I don’t recommend striking the motor shaft directly with a hammer.
Install the motor bolts with a dab of threadlocker on each screw. Because the shaft is reversed, you also have to reverse the motor rotation. If you hook up the three wires from the ESC to the motor per their color code, all you have to do is switch any two of the wires. Black to black, red to blue, and blue to red will give you the proper rotation.
The instructions show the ESC being mounted under the servo tray. In what is likely a difference between the prototypes and production kits, the hole in the servo tray isn’t big enough to get the recommended ESC under the floor. This was an easy fix that required using a sanding drum in a rotary tool to enlarge the front opening in the plywood tray. Enlarge the opening enough to slide the ESC into place.
After installing the ESC, I programmed it per the instructions prior to installing the propeller. The only option that needs to be changed on the ESC is setting the propeller brake (option 2) to Hard Brake mode so that the propeller fully stops when power is removed.
The 12 x 8 folding propeller is installed next. I sanded the roots of the blades where they go into the propeller hub to eliminate the mold flashing. This ensures that the propeller blades smoothly fold backward.
There is a proper orientation to the propeller hub and the notches go toward the front and allow the spinner to seat properly. The optional E-flite 40mm aluminum spinner enhances the front of the Allusive.
The only remaining steps are final assembly and balancing the model. The carbon-fiber antirotation pins are glued in one at the time and I recommend sanding a slight radius on the end of the pins. This will help them slide into place in the fuselage when you install the wings.
When I put the 2,200 mAh battery into place and sat the Allusive on my balancer, I was in for a surprise. This is the first glider with a fiberglass fuselage that I have built that came out nose-heavy.
The best I’ve ever been able to achieve is balancing a glider without nose weight with careful component selection and location. I relocated the receiver under the wing rod and installed a 1,800 mAh battery and the Allusive was still nose-heavy.
I resigned myself to the fact that I would have to add dead weight. To use the least possible amount of weight, I added small pieces of lead to the tail until I achieved balance at the recommended spot with the 2,200 mAh battery all the way forward. This would give me a little room to swap batteries or slide the pack back if I felt it was still nose-heavy. When I determined that I needed slightly more than an ounce of weight, I measured that out in lead shot.
After drilling a hole in the tail cone aft of the stabilizer rods, I placed the balls of shot in a few at a time until they were all in the tail cone, and used medium CA to secure it. Some baking soda and a drop of thin CA filled in the hole and made the modification nearly invisible.
When the Allusive was done, I hooked up my E-flite wattmeter and headed outside for a power system test. With a fully charged battery, the 40-amp ESC and 12 x 8 folding propeller pull 37 amps and make 387 watts at full throttle. This equates to 129 watts per pound, which should provide plenty of climb rate.
I set up the control throws as recommended in the manual, which is easy because they provide a template at the rear of the manual to set the throw. No exponential was indicated in the manual but I set mine up for 20%. One thing mentioned in the manual and worth repeating is to verify that the combined elevator and rudder input doesn’t overdrive the servo or control surfaces on the V-tail.
Flying
At the flying field, insert the wings, plug in the aileron servos, and secure the wings with a strip of vinyl tape on each side and you’re ready to go.
I sometimes take perfect flying days for granted, but it was another great day when it was time to test-fly the Allusive. With the battery fully charged, I headed to the flightline.
My goal for the first flight was to determine if any down-elevator mix was needed for throttle and to see whether I needed to move the CG to obtain the performance I wanted.
With the Allusive pointed into the wind, I advanced the throttle and gave it a straight-and-level toss. The Allusive quickly gained speed, so I pointed the nose approximately 50° up and advanced to the throttle to full. The aircraft climbed with good authority and little pitching up, even at full throttle.
I cut the throttle at approximately 150 feet and settled the Allusive into a nice glide to trim it out. It still felt slightly nose-heavy and required a few clicks of elevator trim to slow down. No aileron or rudder trim was needed.
I pushed the nose over and the Allusive picked up speed and made a pleasant whistling sound. I did a loop and felt that the elevator response was almost perfect. Combine aileron and rudder and turns will look nicely coordinated.
You can also put the Allusive up on a wingtip and turn tight without the airplane stalling. If you force the Allusive into a stall, it simply breaks forward and resumes flying as if nothing happened.
I took the Allusive back up to roughly 350 feet and cut the throttle and headed off in search of thermals. The S3021 airfoil works well over a wide speed range.
The Allusive likes flying slightly faster than the Mystique, but I suspect there is room to move the CG back, which would slow it down. At the recommended CG, the slight extra speed is what I expected from the increased wing loading compared to a pure thermal aircraft. Despite the Allusive’s “hot-liner” look, it reacts to and works lift well.
While in a thermal, the Allusive turns tightly and climbs well. It’s not a Radian or a Mystique, and I probably wouldn’t choose the Allusive if I wanted to strictly look for thermals, but it will hold its own working lift.
Thermal hunting isn’t what I pictured when I first saw the Allusive, so I wanted to see how it flew going fast and doing some aerobatics. With a good launch, I shut the motor down and pointed the nose toward Earth. I tried a couple of rolls, and when moving quickly, the roll rate is brisk. As the aircraft bleeds off energy and slows down, the roll rate decreases. Even at slow speeds, the aileron response remains crisp. Loops look great and at the recommended throws, even full up-elevator won’t cause any snapping tendency.
Under power, the Allusive will zip along nicely. I estimate straight-and-level speed in the 80 mph range. In a dive, however, the Allusive is as fast as any of my EDF jets and maybe faster. Those have been clocked in the 125 to 135 mph range, so I estimate that the Allusive was flying a similar speed.
The Allusive performed full-speed dives and flybys with no indication of flutter or other control problems.
Everyone at the flying field loved the downwind full-speed runway passes with the Allusive. The aircraft will fly inverted but requires roughly half of the available down-elevator to maintain level inverted flight. Under power or out of a dive, the Allusive will do outside loops but they are bigger than inside loops.
Landing a slippery glider such as the Allusive, without any flaps or spoilers, requires some getting used to. A long, flat approach is needed, but after a few passes I was getting the hang of it. Before the weekend was over I was consistently landing it in the same patch of grass between our runway and the pilot stations.
I don’t want to imply that it’s difficult to land, because it isn’t. The Allusive slows down nicely and settles into the grass without any problems, it just needs a longer flat approach than the spoiler-equipped Mystique RES or the larger, flap-equipped Mystique.
Conclusion
The Allusive is a blast to fly. It can be flown quickly under power, but get it up high and let the propeller fold back, and speeds can easily exceed 120 mph (probably higher; I didn’t have a radar during flight testing). Even with that capability, the Allusive remains docile and easy to fly, unleashing that speed only when called upon.
Although the Allusive isn’t designed to be a floater, it will slow down and work both slope and thermal lift. Everyone I handed the transmitter over to had a big smile on his or her face while putting the Allusive through its paces, and everyone who watched it wanted to know more about it.[dingbat]
—Andy Griffith
andy@customcutgraphix.com
MANUFACTURER/DISTRIBUTOR:
E-flite
(877) 504-0233
www.e-fliterc.com
Horizon Hobby
(800) 338-4639
www.horizonhobby.com
SOURCES:
Spektrum
(800) 338-4639
www.spektrumrc.com
