Radio Technique George M. Myers
EACH TIME that I discuss this column with someone I hear the same request: "Say something for the beginner." Usually, the guy talking isn't a beginner! Upon further investigation we find that a new crop of beginners sprouted this spring, and they're making all the old mistakes. This explains the request. Well, what can you say to the beginner who shows up with radio and model in hand with the request "Help me fly it?" or words to that effect? I have an idea: Read the instruction manual. The experienced modeler has been reading the magazines and talking to people for a long time. That's how he's got so smart. He has also been flying a lot; that's how he got so proficient. The beginner can get information by reading, and by discussing the points that he doesn't understand with someone who does. Proficiency comes with well-planned and well-executed practice. (There's no gain in practicing mistakes.)
The experienced pilot begins with a pre-flight inspection: Is the radio working and the ground-range adequate? (The instructions which came with your radio tell you how to measure it, and what to expect.) Do the control surfaces move in the proper directions? Proper direction is a convention. People have standardized the convention so that they can fly one another's airplanes. I find that the convention that gives the most trouble to beginners is the practice of moving the lever on the transmitter up toward the top of the box in order to make the model come down. People entering the hobby expect the airplane to move the same way that they push the control levers, something left over from the games in the Penny Arcade. OK, beginners, you now know that it works the other way, because it comes from the situation in which a guy sitting in a real airplane decided that he wanted the airplane to descend when he pushed the control stick away from him. Rudder is almost never connected wrong, but nosewheel steering frequently is. That's because it has to move opposite to the rudder; it works right because it's on the opposite end of the airplane. Ailerons never seem to give any problems in comprehension, but they get hooked up backwards when the servo is in the bottom of the wing because the beginner doesn't expect the reversal that happens when the wing is turned over and placed on the fuselage. Now you know what to look for.
Next on the list of potential problems is fastenings. In general, one should bolt his engine down with as many bolts as there are mounting holes provided, and the bolts chosen should fill the holes completely. This means #4-40 for engines to .15 cu. in. size, #6-32 for engines .15 to .40, and #8-32 for .40 to .61 in most cases. Some people go up one screw size for greater security. Nylon wing bolts usually described in the plans use two 1/4-20 bolts for .60-sized airplanes; two 3/16 or #10-28 bolts for .40 airplanes; #10-28 for anything smaller. Of course, engines smaller than .049 have their own smaller sizes and don't carry RC gear very often.
Two birch dowels the same diameter as the bolt go in the front wing holes and into holes in the plywood fuselage in cases where the wing is held by rubber bands. Use dowel sizes above to retain the wing and use two #64 (1/4" wide) bands per pound of the weight of the airplane, running fore-and-aft. For a cross form, add bands crossing the way just to make sure others stay on the job.
Servo mounting screws are usually provided with the radio, but they get lost. Replacements should be #2 x 3/8" long pan-head sheet-metal coarse-thread screws. These screws must not clamp down on the plastic case of the servo, but should pass through soft rubber grommets that provide vibration isolation in flight, and will release the servo in a crash. The screws should be holding onto servo rails; cut some hard wood, never balsa. Spruce rails 1/4 x 1/2 x 36" are available at most hobby shops and work well; cut to fit the fuselage and retain with epoxy glue. In a bad crash the rails will pop free before any damage is done to the servo.
Battery and receiver should be encased in at least 1/2" thick foam, and that should not be compressed if you expect any vibration isolation. The switch, if mounted on the airplane structure, must have plenty of slack. Otherwise you will be tearing up some wires in a crash. 3-48 screws are the usual size for switches and charging jacks.
Control surfaces should be securely mounted with enough hinges to prevent flutter, and with a proper gap. Even the "experts" have trouble with this. Use the minimum that will provide free motion of the control surface over its working range. The working range is much smaller than you think, usually plus and minus 15 degrees, so you can keep those gaps very small (1/32"). How many hinges do you need and what size? This one is harder to answer, because there are so many variables. For a starter, you must have at least two hinges per control surface, and they should be as big as you can make them. The best way is to cut slots into the control surface and the mounting surface and fit the hinge in place. Then push a pin or toothpick through each tab of the hinge, perpendicular to its surface, and glue it in place. The only way to insure good hinge action on any given surface? The best answer I can give is "only as many as you need to keep the surface from flapping between the hinges." This works out to one every 8 inches on a strip aileron on a wing for a .60 pattern airplane. An overly wide gap, combined with too few hinges, invites flutter and loss of control in flight. The only way to stop it is to slow down, if you can.
The final consideration for this issue is pushrods. The 1/16" music wire is standard for connections to servos and control horns. It should not extend more than 3 inches from the hole in the plastic control horn or servo wheel, because long wires are too flexible, and promote control surface flutter. Fill the space between the wires with 1/4 x 1/4" balsa pushrod, 5/16" diameter dowel, or similar material. If you prefer NYROD or similar plastic pushrod, make sure that it is securely fastened at each end, and at several points along the way if possible.
My thanks go to Scott McAfee for suggesting the theme for this column first. Scott is the editor of the LIDS (Long Island Drone Society) newsletter The Flyer.
(My address is 70 Froehlich Farm Road, Hicksville, N.Y. 11801.)
Transcribed from original scans by AI. Minor OCR errors may remain.
