RADIO CONTROL SCALE AEROBATICS
Michael Hurley, 11542 Decatur Ct., Westminster CO 80234; E-mail: [email protected]
I know most of us don't fly giant models for our Scale Aerobatics (SA) fix.
But the big airplanes—especially performance-oriented big airplanes—require more attention in building and setup than their smaller counterparts, and information about these monsters is kinda hard to come by. So from time to time, I'll try to shovel you as much technical info as I can dig up.
I fly 35% and 40% SA models, and all of them require multiple rudder, aileron, and elevator servos. One of my airplanes has provisions for 12 servos to control just three functions: roll, pitch, and yaw!
Even with a 10-channel radio and two receivers, some of those servos are going to have to be ganged onto one channel without the ability to individually control each servo with computer mixing.
In a perfect world you would just Y-harness the servos together, adjust the linkages while the surface is centered, and you'd be off and flying!
That was the case just a few short years ago, and you can pretty much still get away with it now if you want to stick with analog servos.
But for those of us who want to take advantage of the speed, precision, and torque of today's digital servos, things just became much more complicated.
JR's digital DS8411 has fast become the servo of choice for large-scale aerobatics pilots, touting unrivaled torque, speed, and accuracy in one amazing standard-size package.
I did some tests with a servo jigged into a specially built protractor and an in-line ammeter. These servos are so strong that they do not budge more than 2° beyond where the signal tells them to stay.
A noticeable increase in battery drainage and heat buildup begins as the servos are forced ever harder off the prescribed mark, so much so that a failure of one component or another is a possibility if left to strain.
You may say, “So if I use digital technology, they should be all the same and I should have no problem, right?”
Wrong! Of the 40 DS8411 servos I tested, approximately three of them matched the servo I picked for my control (reference servo).
I'm not talking about matching the centering of the servo. I'm talking about measuring complete linearity throughout the entire sweep of the arm, so when two servos are Y-harnessed together to work on the same solid surface they do not fight each other throughout the range of motion.
With a digital servo, it only takes approximately 2° of variation for things to start getting ugly. My 40 test servos varied as much as 20° in extreme cases, but most had roughly 6° of variation from one servo to the next.
I called JR Tec support to learn its stance on how to deal with this scenario, and the company's position was to measure and adjust linkages and output arm locations to find a combination that works together.
However, in my testing, linkage adjustments only really fix one direction from the center in certain circumstances.
If one servo has a total travel of 125° and the other has 118°, whatever adjustment you make must have the ability to reverse itself as the whole combination travels past center.
You can adjust linkages to work to the left or to the right, but not in both directions. If you randomly choose two servos to work together on a solid surface, you may be asking for trouble.
Pay careful attention to quicker-than-expected battery drainage, heat buildup in the servos themselves, or heat buildup in any other electrical component, including the wiring, receivers, and batteries. Even surface oscillation at neutral could be an indication of trouble.
My remedy was to remove all the servos from my airplanes, and measure and match them with specific output arms so that no Y-harnessed servo pair varied more than 1° throughout the entire sweep.
Then it's just a matter of matching up the linkages at center, and off you go.
New Product: Clamp Locks from J'Tec
A new item from J'Tec that I installed in my latest SA project has turned out to be one of the cleanest little additions I've come across.
They are Clamp Locks, and they are designed to hold almost any plumbing you can imagine in a model aircraft, from fuel lines to assorted electrical wiring.
- Clamp Locks are made from a soft, pliable material that won't chafe and makes for quick placement or removal of the material you want to locate, yet they're strong enough that the wiring or tubing won't come loose.
- They glue into place with cyanoacrylate (CyA), and you don't have to replace them each time you service the model.
- They're convenient, neat, and they do the job well.
I really liked these little gems, and I plan to integrate them into all of my models.
Contact J'Tec at (805) 487-0355 or see the company on the Web at www.j-tec.com.
New Aerobatic Competition Format: Extended Flight Envelope (EFE)
Along with standard Precision Aerobatics, I'm very interested in a promising new format some people are developing.
It is designed to test and push the skills of those hot 3-D demo pilots you see from time to time at the bigger Giant Scale events.
These pilots seem to defy the limits of aeronautics as we know them, flying in a stalled manner, hovering still in the sky, and maneuvering with little or no apparent forward motion.
The first contest of this type will be held this fall. Event Contest Director Owen Maupin (Box 2038, Collegedale TN 37315; Tel.: (423) 396-4638; E-mail: [email protected]) sent me the following announcement.
"Do you enjoy flying or watching big RC (Radio Control) airplanes torque rolling, performing harriers, elevators, waterfalls, blenders, and more, mixed in with some of the hardest aerobatic sequences imaginable?
If your answer is yes, then this new style of competition is for you!
It's called 'EFE', which stands for 'Extended Flight Envelope.' This new format is different from IMAC competition because it has 3-D requirements at every level. There are three levels to compete in, plus the Freestyle competition.
- Level one requires a competent level of aerobatic flying skills and the ability to fly some basic 3-D maneuvers such as harriers and elevators.
- In level two, you will need to perform all the above in addition to flat spins, knife-edge spins, negative waterfalls, and some difficult aerobatic sequences.
- Level three combines all the above, plus torque rolls, blenders, and high-alpha rolling circles along with some of the hardest aerobatic sequences imaginable.
Then, last of all, there's the Freestyle competition, where only the best of the best can win. The sky (and the ground!) is the limit.
This new competition format came about as a result of numerous conversations between Bramwell McClory and myself (Owen Maupin). We wanted to see a new form of competition that encompassed 3-D flying as a requirement.
As a result, Bramwell developed this new format called 'EFE.' The first EFE event of this kind to be scheduled is District V's Tennessee Valley EFE Aerobatics Contest. The contest will be held at the Flying Horse RC Modelers Club in Apison TN, just outside of Chattanooga. The contest dates are Oct. 5-7, 2001.
If you would like to compete or just come and watch, eat, and have a great time, join us at the Tennessee Valley EFE Aerobatics Contest. For more information about EFE and other EFE events to be held, go to www.gsal.org."
Owen tells me that people from across the country, and even a few people from outside the US, are signed up to fly at this event. It should be an exciting first experience that I hope to attend if opportunity permits.
As always, if you have any input or ideas for this column, or news about new products that pertain to SA, please contact me. Tks. MJA
Transcribed from original scans by AI. Minor OCR errors may remain.
