CONTROL LINE AEROBATICS
Frank McMillan 12106 Gunter Grove, San Antonio, TX 78231
Introduction
Before we get back to our discussion on future technologies, we need to look back at the continually increasing popularity of the "trailing edge" of technology in Vintage Stunt.
Free flight really got it started many years ago. Mike Keville first pioneered the Vintage Stunt Championships in California, then in Tucson. We all know how popular these annual get-togethers have become. To balance the western venue, Tom Dixon has pushed for an Eastern Vintage Championships in the fall, versus the spring time frame in Tucson.
Vintage Control Line Championships
Now there's another contest on the Vintage scene, but it has a much broader format. Dave Platt and Jon Ramsden have formulated plans for the Vintage Control Line Championships. In addition to Old Time and Classic Stunt, they will be offering:
- Vintage Combat
- Team Racing (A and B classes)
- Vintage Speed
- Concours
The rule book they published for these events is available from Jon Ramsden, 730 Badger Dr. N.E., Palm Bay, FL 32905-5810; Tel: (407) 725-2399.
I've reviewed the rules, and they're set up for a lot of fun and good competition. The first annual event will be held October 1–2, 1994. Contact Jon for more information. (I'm getting out my old George Moir Rambler plans for Class B Team Racing.)
Fuels — a reminder
Before I get to the engines, there is one area that merits more words: it doesn't matter how good your model is or how well it performs if you don't have good fuel. Please review the column on fuels — nothing will eat your lunch quicker than a fuel problem.
Problems can be caused by an individual ingredient or by certain combinations. Many remember the nitro problem that caused modelers to use bad nitro, nitroethane as a substitute, and other contaminations. I've had problems with Klotz racing castor oil that was extremely viscous. Also, methanol can be contaminated by water.
I've only touched on what can happen. Symptoms can range from erratic heat-related runs to a severe drop in power. If you notice something funny and have changed fuel (can-to-can, brand, or mix), watch out.
Engines I've Used
The engines I've used during my Stunt career cover the gamut of those still popular today:
- Fox .35
- O.S. .35S
- ST .46
- ST .60
- O.S. .40FSR
- O.S. .45FSR
- McCoy .40
- O.S. .46VF
- ORS .40
- Several home-built specials
Most received extensive rework, although they all started out essentially stock. So I've had a firsthand view of what works and what doesn't. Some ran better than others, and some were outstanding under certain conditions — this is the first point.
Engine Characteristics and Setup
Many engines ran well under home field conditions, but unless you can make them run the way you want, when you want, almost every time, then you have work to do. There isn't a competitor who hasn't had his share of problems to work out; I know I have. All this puts a caveat on what is the best engine setup.
What good is having the state-of-the-art setup if you can't make it run? Modelers must answer this question for themselves. There has been much discussion of what is the best setup: a four-two break or a constant-speed high-rpm run? The classic versus the new generation.
Actually, this question ignores the fact that some of the piped operators set up a four-two break. Bob Hunt is one; I've got one running that way, and another is in the hard four-cycle. But the name of how you run your setup is not so important as how the engine works.
You want an increase in power under load (corners or climbs) and stable power downhill. The characteristics of the Fox .35 or ST .46/ST .60 are obvious; you can really hear them. With piped engines it is less obvious, but in the right setup it is definitely there.
The real goal is a reasonably constant, controlled maneuver speed without speedup. The control and the power you procure is the key. With more power, you need less break to produce the desired effect.
One of the major changes over the years that is reasonable to expect to continue is engine run improvement. Many times I've thought of the early Nationals I attended and the few competitors who had good runs. As I look at the later Nationals and the number of good runs with varied setups, the story is dramatic.
Certainly the exchange of information via PAMPA and the various magazines has made a contribution, but engine builders also have a lot to do with improving the product. I know that every engine I use in competition has been modified to a controlled set of parameters, for example:
- Chrome-plated sleeves
- Precise fits and timing
- High-quality bearings
- Improved heads
- Controlled clearances
Check PAMPA for the builders' advertisements.
New American Engines
The new trend on the engine scene is the appearance of American engines. The advantage is that they are specifically set up for Stunt; the fits, timing, and compression are configured for our needs.
The first engine to hit the scene was Willie Wiley's Winning Combat Motor reproduction. He produced a reproduction run last year, and I understand production units are now available. The engine is an AAC .40; it is conservatively timed (OPS .40-like), so it will work well in piped and non-piped modes. I only know of one extensively run engine; it's unpiped and is working well.
Randy Smith is assembling Precision Aero .40s, and they are absolutely beautiful. Henry Nelson does the critical machine work to his usual high standards. Randy is personally assembling the engines for each application. He has designed the engines to drop into such current installations as O.S. .46VF and some OPS .40 setups (of course, length will have to be adjusted with different extension lengths).
The third engine development is based on the 6.5cc K&B front rotor. Tom Lay has been working with Bob Whiteley to develop a piped .40. Bob is extremely enthusiastic about the consistency of the runs and the power. Bob, of course, has favored the high-rpm/low-pitch setup, so expect one like it.
The other approach is by Gary Tultz, who has been working with this engine for several years. Bill Werwage has been supporting him with tuned-pipe expertise, and they have this engine running in the four/two mode.
Another development that addresses one of the major problems of the ST .60/.46 engines is the limited availability of ABC cylinder/piston sets. The new engines are virtually bulletproof, while the STs have been somewhat vulnerable to ring and sleeve damage with hot runs.
I've had many hard runs on my first OPS while learning to run the piped setup, and now it is my best engine, with more than 600 flights. Its type of reliability and longevity should now be available with the ST. (Note that I'm referring to an essentially stock ST. I've extensively modified mine with a chrome sleeve and snap rings and have run for more than 1,000 flights without touching the engine. I'm hopeful that I've convinced John Hill to do a discussion of the ST .60 setup.) George Aldrich still had a couple of AAC .50s available.
Tuned Pipes and Mufflers
I haven't discussed tuned-pipe and muffler development yet. Despite the many changes over the last few years, much remains constant. The hot muffler for the ST .60 crowd seems to be a gutted Merco muffler that is not all that quiet but sounds powerful. For pipes, the leader is the Bill Werwage/Randy Smith Aeropipe in three- and four-chamber versions. There are also Bolly and Eather types in limited use.
There is no question that pipe development will go further. There is more work to be done on broader flange mechanical reliability and perhaps power. But don't get me wrong; it's pretty good now.
I believe the pipe's diameter needs to be slightly larger to increase the volume. Also, a lower-timed engine and the attendant shorter pipe will help performance by making the setup more friendly. Work is already underway in this area, and I'll report more on it.
Closing
Many new products will be tested at the Nats this year. The contest between the old and the new will probably be heightened, but when the wind blows, the real story will be told. My money is going with the piped setup!
Transcribed from original scans by AI. Minor OCR errors may remain.
