Radio Control: Sport and Aerobatics
Ron Van Putte
Nats schedule and format
Well, guys wanted more fly times per day at the Nats — and they got them. With flying three days for each respective event, you should have no trouble getting at least six flights. That's the good news; the bad news:
- Sportsman/Advanced flies July 12, 13, 14.
- Expert/Masters flies July 15, 16, 17.
- Frequencies are allocated by class.
For some fliers the arrangement will be awkward — even impossible if a flying buddy is in Sportsman and you're in Expert, for example. Some people can only take off a few days for the Nats, and six days of Pattern may be too much. Having to change frequency will be more of an annoyance than a backbreaking expense, but some of us will gripe about it.
Another part of the good news is that you will find out much sooner how you are doing against the competition because we'll be flying nearly at the same time and should know our relative placing at least every other round. The size of the class will determine whether we face the same judges from round to round. For example, Expert will probably have a small enough number of entries to be flown in front of one set of judges; Sportsman will probably have to fly in front of two sets.
Pattern flying at the Lincoln Nats will be held from 1 to 8 p.m., so those of us who like to "shoot the bull" into the late night and sleep into the late morning will thrive on the Nats schedule. Needless to say, I'm thinking Lincoln already.
Writing and recurring topics
After a person writes a column like this for a while, there are "dry spells" with few ideas to write about. It's happened to me periodically over the past 12 years. When it does, I settle back and realize that every four or five years there's a large new crop of RC fliers who have entered the hobby. These fliers never read the columns from the early days of Model Aviation — not even ones from five or six years ago. That means ideas from a few years ago are still new to the recent group of fliers. For this reason, you'll read several different slants on the same topics over the years.
The dreaded Downwind Turn is a good example. I have no idea how many times in the past 12 years a reader or I have dragged up the downwind turn. No matter which side of the argument one is on, the problem exists; it's only our explanations of the phenomena that differ.
Downwind turn, Coriolis force, and energy
Coriolis force is another topic that is just as real, but with different explanations. The American Heritage Dictionary defines Coriolis force as "a fictitious force used to mathematically describe motion, as of aircraft or cloud formations, relative to a non-inertial, uniformly rotating frame of reference such as the earth." Simplistically, it is the apparent acceleration of an airplane to the east as it is flying from south to north in the northern hemisphere.
The airplane actually does go east of a north–south line, but it is because of the motion of the earth rather than the action of any force acting on it. However, one can dream up a force which accounts for the motion of an airplane flying northward (or southward) relative to a "fixed" earth.
Why bring up Coriolis force here? Partly to provoke some readers who I'm positive will insist that Coriolis force is real, but mostly to point out that many explanations of phenomena we observe don't have to be literally correct to be useful in flying RC airplanes.
For example, sooner or later a new pilot trying to perform stall turns will be told by an experienced pilot that a stall turn performed in a crosswind should be made into the wind because the wind helps the tail come around neatly. That explanation of the crosswind stall turn doesn't work. It's the wrong explanation because the airplane has no idea it's in a crosswind.
A simpler, more useful way to look at upwind/downwind-turn effects is to use conservation of total energy. Total energy is the sum of potential energy and kinetic energy. An airplane going downwind will be moving faster relative to the ground than the airplane going upwind because of the wind velocity; conversely, it's slower relative to the ground when going upwind. Kinetic energy is far higher going downwind than going upwind, so potential energy has to increase in the turn from downwind to upwind to keep total energy approximately constant. In other words, the airplane has to climb. If the turn is done rapidly, the climb must be rapid.
A real-world analogy: a fly buzzing around a car. If you drive straight at legal speed, the fly moves about relative to the car; sooner or later the fly moves to the front (downwind relative to the car) and then it may climb into the windshield and knock itself out. Simple when you understand basic physics.
Total-energy reasoning is a convenient way to look at some of these effects, but it does not by itself explain all the handling characteristics you observe in a crosswind stall turn.
Industry anecdote: The Incredible Name Game
It isn't often that you read about competing companies getting along well or agreeing on anything. I heard about a dilly of a potential problem which worked out well because both companies acted responsibly. A press release (edited) from the Sig Manufacturing Company describes the situation:
"The Incredible Name Game. During the course of bringing out any new product there always is a lot of trial, tribulation, and racking of the old brains to come up with a catchy new name. Hopefully, it will say something positive about the new product as well as being descriptive. We did, however, have a slight problem with the name of our new iron-on plastic covering material, UltraCote.
"We were going to call it that, tried it out, and even had the catalogs printed that way. Too bad, as you may have guessed from the mail order companies, both Sig and Carl Goldberg Models, unknown to each other, were both busily working on a new iron-on plastic covering material. The problem was we both picked the same great name, UltraCote! Now comes the fun part.
"We first found out about this just before the IM Show in Pasadena when we received some..."
Transcribed from original scans by AI. Minor OCR errors may remain.
