Control Line: Aerobatics
Frank McMillan, 12106 Gunter Grove, San Antonio, TX 78231
Line Care and Feeding
Since flying control line is what this precision aerobatics column is all about, some information on the care and feeding of the lines themselves is appropriate. I'll defer any comments on line lengths and trimming the airplane, etc., and focus on some rather basic hard-learned lessons. To paraphrase Bob Hunt's recent statement to me: the expert learns from his failures; the journeyman merely experiences the situation.
Before I discuss flying lines, let's look at the cable that connects them to your handle. As some of you may be aware, several expert fliers lost planes in the past two years because of cable failures at the handle.
In my view, only one type of cable is satisfactory for handle use, and that's aircraft control cable, which is designed for a similar application. Although I prefer the coated version, uncoated is also acceptable. This cable is designed for strength and flexibility; the flexibility is a key feature in my book.
Two sources for good cable are SST (Bob and Rollie McDonald) and Pro Stunt Products (Windy Urtnowski). Do not—under any circumstances—consider using such substitutes as leadout cable (too thin and it fatigues), picture cable (not strong enough), or bike cable (too thick and it fatigues). These types have all failed.
Another point here—and again the small details can be killer items—look where the cable exits the handle. This point must, must, must be flared or bell-mouthed. If it isn't, a stress point will eventually fracture the best cable.
Any time you bend metal (rear cables), it will eventually fatigue. I recommend that you change all cables in your handles every season, no matter how good they look or how much pull they sustain. Wire is cheap compared to the hundreds of hours and dollars invested in a competition plane. Remember: you saw it here; they always fail at the wrong time!
Line Types and Storage
Let's discuss the flying lines themselves. As we all know, they fall into two categories: solids and cable. The solids are stronger than cable, and by any rules, thinner solids are permitted against the various engine classes—i.e., .014 solids vs .018 cable in the larger class.
Performance-wise, the solids offer less drag and more positive control. But there are definite minuses associated with solids: they stick together on occasion—frequently at inappropriate times. The cables also have disadvantages: they are heavy and draggy. Note that drag goes up as a squared function; that's significant! I'll talk more about that in the future.
A basic point on storage of the lines: you really need a large-diameter reel, even for cable. The small 3-1/2-inch-diameter reels are not satisfactory, especially for solid lines. Either make one in the 4-1/2- to 6-inch range or buy one from Pro Stunt Products; these are the best available commercially.
Be very careful when reeling and unreeling the lines to ensure that the lines are straight and not twisted. Many times I've put a kink in a set of lines because I was in a hurry. Also, you might consider a pin arrangement that holds the lines and handle on the reel and prevents them from loosening. I use a pin through one side of the reel, through the eyelets or line clips, and into the other side of the reel. This positively locks the lines and handle in the reel without putting a strain on the lines.
Cleaning and Maintenance
It is important to keep the lines clean. Cleanliness is much more critical with solids, but both cable and solids perform better if kept religiously clean. Realize that as the lines get older, they are going to become more and more difficult to get and keep clean. Dirty lines will lock up more readily and more positively. You don't want that to happen; it ages you rapidly.
What should be used to keep the lines clean? For many years I used various types of alcohol, which works in dry weather. Throw in some humidity, and the alcohol will absorb moisture and you'll be in trouble—the big time! A lot of people use lacquer thinner; this does a good job of cleaning the lines, but since it evaporates quickly, it also tends to collect moisture on humid days.
Epoxy thinner does a good job of cleaning, as does acetone, but both tend to be hard on the lines. The best type of cleaner for continual use is a paint-prep degreaser, such as Prep Sol or Acetyl Clean. This type of automotive product also works well for removing fingerprints prior to painting. In wet weather it also absorbs moisture, but I still like it.
Benefits of Fresh Lines and Longevity Tips
Have you ever noticed how a nice, fresh set of lines makes a plane fly better? This happens for a variety of reasons. Obviously, cleanliness is one reason, and a fresh set of lines is initially easier to keep clean.
Another reason is that fresh lines are round and have less contact area; therefore they slide together more easily. Recall that for a large portion of your pattern, the lines have a twist in them that forces you to slide them together to apply control. In those short moments you create friction and wear. The lines usually overlap close to the plane and create a wear area that worsens as the number of flights pile up; eventually the wear area reaches a noticeable level.
It is possible to add to the longevity of a set of lines by swapping the lines end to end, plane to handle. This exchanges the wear points. Especially with solids, when you recognize a stickiness in the controls, some hunting, or the bottoms pick up a glint, dump those lines and put on a fresh set.
Summary
- Keep your lines clean. Wipe them down after every flight.
- Inspect your lines when you roll them out and when you finish each flying session. If there is any doubt about integrity, discard the lines.
- When you have used a particular set of lines for any length of time (around 100 flights), consider replacing them on principle. Your own safety, the safety of spectators, and that of the airplane depend on those lines.
Sources for Lines and Cable
- Pro Stunt Products, 9 Union Ave., Little Ferry, NJ 07643 — carries solids in bulk; polished medical-grade wire that seems to last longer and slide better.
- Riley Wooten at Lone Star Models, 1623 57th St., Lubbock, TX 79412 — bulk cable (1015 and 1018).
- GRW, P.O. Box 1011, White Oak, TX 75693 — bulk cable.
Try to buy in bulk, as this is the most economical approach.
Events / Notices
This year’s Vintage Stunt Championships will be held on April 3 and 4 in Tucson, Arizona. It’s been observed that the weather dramatically improves in April. Jo Ann Keville will again CD the contest. Write to 6109 E. Ivyglenn, Mesa, AZ 85202, or call (602) 985-3363 for information.
OTS Glow and Ignition will be on April 3, with Nostalgia on April 4. PAMPA rules will be used. Late word from Mike Keville is that pipes on the birds will be served upon as “going too far.” Mike says that the chances are good that he can attend.
Transcribed from original scans by AI. Minor OCR errors may remain.
