RADIO CONTROL SOARING
Mike Garton 2733 NE 95th Ave., Ankeny IA 50021 E-mail: [email protected]
Theme
This month's theme is electronic components for large gliders. I compare several high-end transmitters, including the new Multiplex Royal Evo 12-channel synthesized transmitter, the Profi 4000, and the Stylus. I also provide information about the Multiplex 12-channel IPD receiver and the ElectroDynamics amplified optoisolator for long servo leads.
Requirements for large gliders
Unlimited gliders typically have "full-house" controls, meaning six servos with rudder, elevator, two ailerons, and two flaps. Using a computer radio allows the pilot to create complex control mixes. These often include:
- Camber: all four wing servos change their neutral position together.
- Crow (butterfly): flaps down and ailerons up for landing.
- Snap-flap: moderate amounts of up-elevator produce small amounts of down-camber.
- Aileron-to-rudder coupling.
- Inboard flaperons: flaps deflect as additional ailerons.
Some of the larger Unlimited and Scale gliders are even more complex, with three flaperons per wing side. Scale sailplanes often have a nose release for aerotowing. When retracts and spoilers are added, it pushes the limits of most RC transmitters.
Multiplex Profi 4000
For years, the Multiplex Profi 4000 has been the king of high-end transmitters. It has 12 fully proportional channels, all of which are equal in resolution, speed, and flexibility. This transmitter has as many as 99 model memories.
The Profi design's biggest imperfection is its lack of emphasis on ergonomics. The Germans often use "cocktail trays" to hold their transmitters with neck straps. Keeping the transmitter small with built-in hand grips was obviously not a priority. It is 9.375 inches across the face.
However, the ergonomic issue is easy to overlook if you fly large and/or complex Scale gliders. Having the flexibility to program 12 channels any way you can imagine is well worth it for these models.
Multiplex Royal Evo
The Royal Evo line is Multiplex's latest offering. It is available in nine- and 12-channel versions. Single-frequency and synthesized versions are available. I bought an Evo 12 synthesized transmitter and have been using it for most of my flying this season.
The Evo is an evolution of the Profi. Much-improved ergonomics for handholding are evident. The Evo transmitter is 7.5 inches wide and weighs 33 ounces compared to the Profi 4000's 51 ounces. For reference, the Airtronics Stylus weighs 45 ounces. The lower part of the Evo transmitter is sculpted with comfortable handgrips. The LCD display has adjustable tilt and contrast.
The Evo's antenna can collapse into the case, extend straight out, or extend out angling up and to the left. Why would someone want to make the antenna angle up and to the side? These types of antennas are most efficient when they are perpendicular to the line of sight between the airplane and the transmitter. Often, pilots fly with the transmitter antenna pointed right at the model, which gives the weakest possible transmitter signal. The Evo's offset option helps eliminate this phenomenon.
How easy is the Evo to program? I don't think "easy" fits very well, but I do like it better than the Profi 4000 and the Stylus. Templates are already in the memory for common cases. The Evo software gets high marks for its consistency and layout. A user can quickly get to a menu by pressing its button on the face of the transmitter.
By consistency, I mean that you can function well after learning a simple system or process. As an analogy, consider towns that are laid out in a grid with logically numbered streets. These towns are much easier to navigate than those with skewed streets and unrelated names. In RC-transmitter software and city layouts, consistency minimizes the need for memorization.
I was uncomfortable with Evo programming until I read Joedy Drulia’s excellent Evo tutorial. It is available free online in Adobe PDF format, with a link from the Multiplex website. You can print the document if you choose.
The Evo comes with a manual in the box, but the online tutorial is a great addition. It was 100 pages when I read it last and has been growing. The illustrations are excellent. There is a flowchart that tells you what to do and in what order.
Even more icing on the cake are the tutorial's glider-specific instructions. There are chapters on "programming full-house sailplanes" and "programming electric RES sailplanes." Specific examples show how to program selectable crow (butterfly) braking, a discus-launch momentary preset, and other advanced glider-related features.
With the tutorial in hand, the Evo's learning curve wasn't nearly as steep as it was for the Profi 4000 or the Stylus.
While using the Evo, I fell in love with the digital trims and their display in the LCD. I can look down at the transmitter and immediately tell the state of the four primary trims (graphically on the LCD). When I quit flying a model for the day, I do not need to worry about positions of mechanical trims; I just turn it off or change model memories. The next time I come back to that sailplane program, the trims will be right where I left them.
Another neat trim feature is the audible-feedback option. It can beep with each click, with a different tone when you cross the center point. With the beep option turned on, you can center the digital trim while flying without looking at the transmitter.
The Profi and the Evo have cases that are easy to open without tools: you just push two spring-loaded buttons on the top to unlock and open the case. The Evo has many more cool design features that I do not have space to elaborate on here. I think the Evo 12 is the best high-end radio available for gliders. It can handle thermal-duration-style models and complex Scale sailplanes with ease.
The Evo cannot do everything the Profi can, but it can do most of it. The Profi's 13-point curves have been replaced with five-point curves in the Evo. The Evo hardware (switches and levers) is less expandable. Pilots who fly something very complex and want the ultimate in hardware and software flexibility should still consider the Profi.
Airtronics Stylus
The Airtronics Stylus transmitter with glider card seems tailored specifically for American thermal-duration-style flying. Although it has eight channels, the most complex templates are geared toward models with four wing servos. Controlling two tail servos plus six wing servos independently is not an option.
You can use a Y-harness in the airplane to make the inboard flaps operate together. It is easy to accommodate a tow release and/or retracts. The Stylus programs are great for gliders with as many as six total (four wing) control surfaces and an extra binary function or two, but they are lacking if your glider is more complex.
Long servo leads and noise isolation
In large sailplanes, it is usually easiest to mount servos extremely close to the control surfaces. This minimizes the weight and slop of the control linkage. Aileron leads, for example, usually approach half the wingspan in length, which can be 2–3 meters. The long wires create two problems: voltage drop and their tendency to act as antennas that feed unwanted radio noise back into the receiver. One little black box can solve both issues.
The Pow'R Bus Pro from ElectroDynamics uses separate power buses to isolate servo noise and loads from the receiver. The receiver can use its own battery while the servos use a larger, higher-voltage battery. The servo signal is transferred to an optical signal to cross over onto the other power circuit. It is then converted back into a normal signal and amplified before it leaves the black box.
The box can isolate as many as six channels (choose the ones with the longest leads). There is also a socket for expansion if you need to isolate more servos. At roughly $80 retail, the Pow'R Bus Pro is relatively cheap insurance for a large, expensive glider.
Multiplex 12-channel IPD receiver
A 12-channel transmitter cannot be fully utilized without a 12-channel receiver. The Multiplex 12-channel IPD receiver has built-in capability for redundant batteries. You can use one four- to six-cell pack or two five-cell packs.
If a large-scale glider has a multi-thousand-dollar replacement cost, a redundant battery on the receiver is probably worth it. The funny servo connector with a single wire loop in the picture is a jumper to select battery configuration.
Quoting from the website, "The IPD circuit provides 'Intelligent Processing' to filter out unwanted signals and assures crystal clear, glitch-free reception." In layman's terms, the receiver will ignore interference, assuming that the interference does not look like a valid signal.
This technique has proven extremely effective at reducing glitches. The receiver also has a fail-safe mode. You can program the receiver to lower your flaps and turn gently if it has not received a valid signal for the last 0.5 second.
MA
Sources
- Multiplex (distributed exclusively in North America by Hitec RCD) — www.multiplexusa.com/
- Airtronics — www.airtronics.net/
- ElectroDynamics — www.electrodynam.com/
Transcribed from original scans by AI. Minor OCR errors may remain.
