Radio Control
Sport/Aerobatics
Ron Van Putte
ALMOST ALL of us use nickel-cadmium batteries in our airborne battery packs. As is usually the case in anything that is in common usage, there are many different ways that they are used and abused. The treatment of nickel-cadmium batteries varies about as much as individual modelers vary. I'm sure you know at least one guy who will try to get away with flying without recharging his batteries because he didn't fly the previous weekend or only had a flight or two. Then there's the guy who has his batteries on charge all week from flying session to flying session.
Nickel-cadmium batteries have been attributed with all sorts of mysterious characteristics, such as "memory," and you can carry on an hour's conversation with almost any R/C-er on the "care and feeding" of nickel-cadmium batteries. Much of the discussion about them is caused by their unusual discharge characteristics. The voltage under load is not an indication of the condition of the battery, unless the voltage is very low, because the output voltage is so nearly flat over most of the useful life of the battery.
Many crashes have been blamed on battery failure. For some pilots, it is almost as popular as blaming a crash on radio failure. I think that a substantial number of the crashes we blame on battery failure are really pilot error, not in the air, but in the workshop. Improper care of batteries in the workshop may result in as serious a crash as forgetting which way to push the stick. Unfortunately, the characteristics of an improperly cared for battery pack are often the same as those of a battery pack which is getting ready to fail.
There are several things that RC modelers can do to avoid most battery problems. One should always charge batteries before flying, regardless of how little flying was done during the previous flying session. It is a good idea to discharge the battery pack if it wasn't used very much. One way which has worked for many is to leave the radio on for a while (3 to 4 hours). Of course, one can use one of the commercially available systems like Flite Life.
All of our precautions will have little effect on actual battery failure. The most common mode of battery failure that I have observed is a short circuit through the cell. The cell shows no voltage and a resistance of 2-3 ohms. Fortunately, this type of failure is usually detectable on the ground or in the air and generally doesn't cause a crash with the new 3-wire servo systems. The servos slow down and an observant modeler can usually spot what has happened and, unless the pack has been used a lot, there is enough voltage to run the receiver to get the airplane back to the ground.
Lately, I have noticed many nickel-cadmium cells which were dead before they were ever used. Since the cells were from a usually reputable firm, it has been quite a shock. My explanation of the cause of the new cell failure is a guess: When the new hand-held calculators came on the market, their great popularity substantially increased the demand for the nickel-cadmium batteries which power them. The push to manufacture more batteries caused production quality control to suffer. After all, when you can sell all you make, why bother with high quality control? Besides, calculators don't crash and if a cell fails it can always be replaced, free if the calculator is under warranty.
As the contest season approaches many of us are planning to head out on the contest trail. As is my habit, I plan to encourage others to come in with me going to contests. For me, competition is what it's all about. I never fly better than in a contest. The excitement of putting my ability on the line against others has the effect of improving my concentration and flying skill. Besides, it's great to sit around and talk with the other contest goers. I have many memories (and plan to have many more) from contests that I treasure all my life.
For those who have never competed in a contest, a Fun Fly is a great way to get started. Fun Fly events should be designed to appeal to fliers of all ability levels and not require competition airplanes. A typical list of events might be: Le Mans Start, Most Spins, Slalom, Taxi, Most Loops, and Abbreviated Pattern.
Le Mans Start: The flier places his airplane on the runway ready to go, except that the prop nut and propeller are removed. The flier carries the prop nut balanced on the end of the starting line to his airplane, installs the prop and nut, starts the engine and takes off, all in as short a time as possible.
Radio Control: Sport/Aerobatics
The Most Spins event starts as soon as the airplane breaks ground. The pilot has 90 seconds to do as many spins as possible. I recall Greg Kieliszk (2nd in Class A, 1974 Nats) getting 61 spins with a Rimfire/Webra 40 RC combination!
The next flight starts out with the Slalom Taxi. An L-shaped pattern of balloons, flags, or styrene blocks is laid out on the runway, each about 10 feet apart, and the pilot tries to take his airplane through the course in minimum time. Time is added for missing a gate or hitting a "pylon."
The airplane is then taken off and Most Loops starts when the pilot is ready. He loops the airplane as many times as he can in 30 seconds.
All the events are getting the pilot ready for competition by getting him used to pressure and excitement, but the one which is most like a pattern contest is Abbreviated Pattern. Half a dozen maneuvers from the Class A pattern are selected. These might include Take-off, Straight Flight Out, Procedure Turn, Straight Flight Back, Immelmann Turn and Landing Perfection. Generally, the judges coach the pilots and tell them what is expected of them. The really experienced pilots often have the good grace to fly most of the maneuvers inverted!
There are other events which can be included that meet the basic Fun Fly requirements: fun to do, not dangerous to airplanes or spectators and not requiring a special airplane. Perhaps full blown pattern competition isn't what you're interested in, but you may just find that competing in a Fun Fly is what you've been looking for. Try it...
For the past two months I've been testing a new item on the market called the Glo-Daptor from C-C Avionics. It is a "black box" which you attach to your 12-volt starter battery by two wires and clips (provided). You attach a glow starter cord (not provided) to it and the glow plug is inserted in the side of the box. A small wrench which fits in the side of the box is used to adjust the glow plug so it functions normally. When attached to the 12-volt battery and connected to the glow plug, the Glo-Daptor only draws about 3 ma, so you don't have to disconnect it while you're at the flying field. It works great! I like it and you might too.
Have you ever heard of a T-nut? I have been using them for years and you might like to make up a set for yourself. The radio manufacturers have been telling us not to tighten down on the servo grommets or seat them on vibration isolation grommets or the grommet will be lost. This works fine if you are using a commercial tray which has a hollow post which fits through the grommet. All you have to do is push the servo on the posts, place washers on top of the grommets and run screws down into the posts. However, if you like to make your own servo trays from 1/8" plywood, the T-nut may be what you need.
Buy some 1/8" aluminum pop rivets about 1/4" long and remove the nails. File them down until they'll just fit through the servo grommet, then tap them with a 2-56 tap. Drill 5/64" holes in the tray where the servo is to mount. Push the T-nuts into the grommets from the top and screw 2-56 binding head screws up into them from the bottom of the board. Now you can tighten the screws as tight as you like without compressing the grommet at all. By the way, you can get 2-56 binding head screws at radio-electronics parts stores.
All of us who are pattern competition fliers now have an organization analogous to what the free-flighters, Q-controllers and pylon racers have had for years. The National Society of Radio Control Aerobatics is alive and well. Thanks to Rhett Miller, Sr., the NSRCA is on its way toward doing things for the pattern fliers through the AMA. The organization has a newsletter — the K Factor; a new president, Joe Bridi; and a Constitution — published in the March K Factor. Only $4/year will make you a member. To join us write to the secretary/treasurer, Mrs. Sally Brown, at 8534 Huddleston Dr., Cincinnati, Ohio 45236.
If you have any info, pictures, drawings for this column, my address is Major Ron Van Pulte, 12 Connie Dr., Shalimar, Fla. 32579. Nominal payment is made for drawings and pix used in the column.
Transcribed from original scans by AI. Minor OCR errors may remain.
