Starting Control Line Combat
Annual 1960 Air Trails Hobbies for Young Men

Annual Edition 1960 Air Trails

Table of Contents These pages from vintage modeling magazines like Flying Aces, Air Trails, American Modeler, American Aircraft Modeler, Young Men, Flying Models, Model Airplane News, R/C Modeler, captured the era. All copyrights acknowledged.

According to this 1960 Air Trails magazine "Starting Control Line Combat" article, the contest event first appeared in the AMA (Academy of Model Aeronautics) rulebook in 1950. Hard to believe that was 72 years ago as of this writing. It's equally hard to believe it was only 8 years before I was born - ugh. Control line combat remains a very popular sport today, and is one of the relatively few aspects of the hobby which has not changed considerably. Engines have gotten more powerful and reliable, and building materials have improved, but the basic outline of the airframe is about the same. The story reports on combat rounds having up to five planes flying at once, duking it out for air superiority. Too bad there's not a video of it with all the flyers trying desperately to not become entangled in each other's lines or even keeping out of each other's way. There must have been a lot of smashed balsa after that event. Anyway, this article provides a lot of detail concerning all aspects of model construction, engine and fuel tank setup, and flying. Interesting fact: In the early days of control line combat, prolonged inverted flight was permitted, which meant closing speeds of a couple hundred miles per hour - what a mess that must have made during a head-on collision!

Starting Combat

Opinions may differ as to exactly when control line combat flying started its climb to popularity, but the event wasn't in the AMA rule book before 1950. With the upsurge of interest in yo-yo flying during the post World War II years it was inevitable that sooner or later several flyers would get into the same circle and chase each other.

As early as the 1947 Nats in Wichita, Kansas, a group of flyers put five ships in the air at once just for fun. What a show! Flyers were tripping over each others feet, models tangled wires and the rat fight ended in one grand mess.

Control-line's godfather, Jim Walker, flew three ships at once early in the game. In the 1948 Nats, young Dave Slagle flew two stunt ships at once. With streamers on both ships he succeeded in engaging himself in combat! Whew! Soon other modelers picked up the idea and before long combat flying and streamer cutting became a popular exhibition event. Then it was strictly for fun and a great crowd pleaser.

In the East, credit must be given to Sterling's combat team that toured contests flying the YAK-9 and P-51 kit ships. And so the trend was started, such events as Team Racing (and later Rat Racing) showed that the fun factor went up considerably when there was more than one flyer in the center of the circle.

The present AMA rules for combat are the outgrowth of several years of acute growing pains. The event's popularity has made some rules necessary that do not please all flyers. This is inevitable of course, but earlier, when prolonged inverted flying at 3-inch altitude was permitted, combat was mad, mad, mad, and model mortality was awful.

Space does not permit a rundown of the complete AMA combat rules here, but the important points relating to design and flying are: Maximum engine displacement permitted is ,36 cu. in. Flying lines must be 60 ft. from center of model to center of handle. Pull test is 20 times model weight. Each flyer permitted only two models and two official flights (attempts and unofficials detailed in AMA regulations). No flying inverted or less than 8 ft. altitude for more than one lap. Center circle is 10 ft. diameter. Streamers are 8 ft. long with 4 ft. string leader. Flight time is 5 minutes, scoring of "cuts" and "kills" must be done in shortest possible time. Points are deducted from score for time elapsing after starting. Two-minute starting time allowed, both ships must fly one level lap before starting combat. Unsportsmanlike or discourteous flying, deliberately causing crash or collision is cause for disqualification.

First and foremost the combat plane must be a full stunt ship, capable of good speed and high maneuverability, indeed most combat jobs are good stunt trainers. Attack and evasion tactics require quick response yet stable characteristics so that the flyer can watch his opponent's ship and still fly his own without having to pay much attention to it.

The combat ship therefore must be a light weight for speed and stunting. So far a big ship has been better than a small one. The largest engine permitted should be used, you want all the power you can get. Remember that the combat model is highly expendable, so although it must be rugged enough for high speed and air loads it should have a minimum of materials; construction should be simple and require a minimum of work and building time. Don't bother with a twenty-coat hand-rubbed finish. Enough dope to keep the oil out is all that is necessary. Fancy stripes and gaudy decals make a colorful model, but are wasted on a combat ship. Build 'em "quick and dirty" ... let's qualify that to not too dirty.

Anything less than a hot running engine is a real drag when the fight is on. Your engine should start easily and run like the well-known watch. Fuel tank and lines must be clean, tank should be at least 2 1/2 to 3 oz. capacity for 5-minute flight depending upon engine. Any good stunt tank will do the job. Veco (Froom) tanks are popular. Tank center should be level with needle valve and firmly mounted to prevent foaming and poor fuel flow. Some engines tend to run rich in air even when leaned-out on the ground. Pressurization can help this problem. Cap vents with length of fuel line beveled at 45° with bevel facing forward. Experiment with different propellers to get best running and top speed. For .35 engines, 10"D-6"P, 9"D-8"P and 9"-7"P are preferred.

Simple beam mounts for the engine are best, these should be hardwood. Pine and bass crush easily at mount bolts because of vibration. Use birch or maple if possible. The engine beam mounts should extend well back into the structure for maximum strength needed to tie wing and fuselage together. The control system should be rugged. If possible, the bellcrank should be mounted on an engine bearer, not on a flimsy bit of plywood stuck on balsa fuselage side or wing rib. The engine bearers and bell-crank mount should form the strongest part of the model since combat ships are subjected to a pull test of 20 times the model's weight. Plenty of combat flyers are eliminated by the pull test during processing-before they even get to start an engine. The strength of bellcrank mount should extend throughout the control system. Use a 3/32" dia. wire push rod where you would ordinarily use 1/16" dia. wire. The elevator horn should be at least 1/32" thick aluminum, brass or steel, the latter being preferred be cause it stands up better under engine vibration. Make good strong wraps and eye ends on lead-out wires from bell-crank. If you like to use regular flying wires and simple handle, there are ready-to-use lines available made by Pylon. If you use a U-Reely control handle be sure the reel lock works properly.

Like any other high performance model, the combat ship should be built with as accurate alignment as possible. This applies particularly to wing structures, since warped surfaces. cause erratic flying. A warp that causes the model to bank into the circle is particularly troublesome and can cause loss of control during tight maneuvers. Proper balance is also very important for a good flying combat ship. Center of gravity should fall between 20% and 25% of wing chord. Models with regular tail surfaces can balance at 25% but flying wings should balance at 20%. Of course the bellcrank pivot and leadouts should be located behind C.G. position. Rearward C.G. position will cause model to turn into circle, while forward C.G. will make model too stable and make maneuvering sluggish.

Since combat flying is conducted in all kinds of windy weather, a few degrees outward offset of the engine thrust line will help keep the model out on the end of the lines where it belongs. Engine thrust offset is more effective than rudder offset so the rudder can be mounted straight ahead, its main function anyway is to provide a place to attach streamer. Add a bit of weight to outside wingtip to help compensate for leadout and flying line weight. Don't use spinners on a combat model, they add unnecessary weight, some cause vibration and a prop change is time consuming when a spinner must be fitted during a re-start. Even though they may have a very short life, balance propellers carefully. As manufactured, props sometimes need careful trimming or sanding to balance exactly because of varying wood density or uneven varnishing.

Although the green beginner has on occasion jumped into combat competition and wiped out the old hands, this is not often the case. Flying a hot combat ship in the same circle with others takes a little getting used to for most yo-yo-fliers, so a little ground school should precede soloing in competition. Practice the stunt pattern to gain confidence and get to know your model thoroughly first. Fly in windy weather to learn how your model behaves under extreme conditions. Then try flying with your friends two at a time and later with three in same circle. Practice chasing tails (without streamers); don't try for kills or near misses at first. Get used to the footwork needed to pass each other and following each other around in the air. As your proficiency gains put streamers on your ships and have at it. If you are a club flyer, all the better. You can practice with fellow members.

When flying in competition you and your helper should be a real team. He should have your engine starting down pat, so that he can re-start for you without your having to leave the center of the circle. Hand launching is best way to get a combat ship into the air, since wheels are seldom used. A light ship with big engine will practically fly off your hand without much of a push. Have your helper familiar with launching your ship VTO or HTO. Do not hold full up during launch or you are liable to lose a helper. A hot ship will turn in its own length at low speed and whango, right back at your helper's back. When landing, try to put your ship down close to your helper so he won't have to chase around the circle.

Stick with a proven ship design, build duplicates of the same model so that a new design won't come as a complete surprise to you in competition. Some flyers like conventional types while others like the flying wings; fly which ever you like best after trying out different designs. If you are flying two different ships be sure flying lines and leadouts add up to 60 ft. on both. There are numerous good combat model kits available such as T-square, Bandit, 1/2 Fast III, Omega and Quicker.

Posted September 24, 2022