Radio Control: Sport and Aerobatics
Ron Van Putte
Nats and RC Aerobatics rules
The Nats will be over by the time this appears; I'll be preparing the Nats RC Pattern report for publication. I hope everyone who went to the Nats had a great time and took away many pleasant memories. If you flew in the Expert class of RC Pattern, I hope you finished behind me!
It was reported in the Competition Newsletter (August issue) that the RC Aerobatics Contest Board final vote failed a rule proposal to combine Expert and Master into a single class called Open. Many thought Open would be adopted for 1988–89 based on the initial vote, but that did not happen. I expect a new proposal for the 1990–91 rule book that would create an Open class plus a beginner-level Turnaround class; if adopted, Advanced competitors would have a dual route to choose between the AMA pattern and the Turnaround pattern.
Anhedral in horizontal stabilizers
I've had several letters asking about anhedral (negative dihedral) in horizontal stabilizers, as on the Curare and Tiporare, and what anhedral does and why all airplanes don't have dihedral or anhedral.
There is no simple answer. Like most design features, anhedral involves trade-offs, and different airplanes face different compromises.
Basically, anhedral on the horizontal stabilizer produces two effects:
- It lowers the equivalent horizontal tail: the anhedral makes the tail behave like a flat tail that has been moved downward.
- It induces a more complicated aerodynamic effect: in a sideslip, it tends to roll the airplane in the direction opposite the sideslip — contrary to what one would normally expect.
Why use anhedral despite the adverse rolling tendency? It depends on the airplane. For example, you don't want the horizontal tail operating in the wing wake. Most wings produce a wake that is unpleasant for the tail, and a tail should be positioned above or below that wake. If fuselage-mounted placement would put the tail in the wing wake, anhedral can be used to drop the tail below the wake.
The adverse rolling effect can be used beneficially on certain designs: it can improve point rolls by adding just enough adverse-rolling moment to offset positive-rolling moments from other design features. Many airplanes do not need anhedral and some could benefit from dihedral on the horizontal tail instead.
I suspect Hanno Pretner discovered the Curare's anhedral improved point rolls — and perhaps he chose it because it looks neat.
A related anecdote: McDonnell‑Douglas test pilots used a simulator to evaluate the F‑4 Phantom II as the simulator varied the anhedral angle of the horizontal tail. The anhedral angle chosen for production was the one the pilots liked best — a pragmatic, pilot‑tested solution.
Letters and anecdotes
I waited for letters on Coriolis acceleration and fly‑stunning using conservation of energy; Frank Mock of Edwardsburg, MI, did not disappoint. He wrote (excerpt):
"I am writing as a member of the Panama City Beach (FL) and Edwardsburg (MI) chapters of the 'Save‑a‑Fly' organizations. I am appalled at your sadistic method of stunning flies. May I suggest you purchase a vehicle with a sunroof? When a fly appears, open the sunroof and increase speed to 75 mph. The potential and kinetic forces, in conjunction with the Coriolis acceleration, will drive the fly to the rear of the vehicle. Now turn the steering wheel hard to the right and slam on the brakes. The Coriolis cyclonic vortex action will spin the fly up and out of the vehicle."
Alicia Goode (De Quincy, LA) wrote, tongue‑in‑cheek, that her firm has developed an automated Pattern judging device that anyone with common sense and no Pattern experience can operate. To ensure "accuracy," it has only the following adjustment knobs: airplane, engine, pilot's halo, center, local quirks, and time of day. She said they were awaiting patent assignments. The only person I know from De Quincy is an old leg‑puller named Nat Penton, and the return address looked suspiciously like his.
Radio Control Duration — a proposed new event
Several years ago Glenn Gressens (Baton Rouge, LA) proposed a new event, Radio Control Duration. I agreed it was a good idea; he reports Radio Control Duration will be a provisional event in the 1988–89 AMA rule book.
As Glenn envisions it, Radio Control Duration is a Duration event that can be flown from small fields by sport RC fliers. Low weight and slow speed make it inherently safe. Aircraft processing and contest management can be handled with minimal manpower, and the event is promoted as a significant challenge for serious competitors within a relaxed, fun framework.
Key proposed limitations and rules:
- Maximum wingspan: 60 in.
- Minimum wing loading: 8 oz/ft² (projected wing area).
- Engine: stock Cox .049 cu in reed‑valve engine with the standard 8 cc fuel tank (as furnished with the Black Widow and Golden Bee engines).
- Propeller: two‑blade wood, plastic, or reinforced‑composite, maximum diameter 7 in.
- Format:
- The pilot has 20 attempts to make three official flights.
- Time starts when the airplane is launched and ends when it touches down.
- The touchdown must be made within the marked circles or the flight scores zero.
- Maximum time allowed per flight: 15 minutes (thus three flights have a 45:00 maximum cumulative time).
Glenn reported on a club contest (Baton Rouge RC Club). Most pilots were standard glider‑kit hobbyists; among 10 flights with the same engine, averaged elapsed times for three flights were 41:09, 37:49, and 37:14 out of a 45:00 maximum (the three‑flight total). Officiating was handled by a Contest Director with help from four timers; the same crew could have handled at least 20 competitors. It sounds like an enjoyable, relaxed form of competition for sport flyers.
If you want details on the new event in advance of the 1988–89 AMA rule book, contact:
- Glenn Gressens, 10224 Kenlee Dr., Baton Rouge, LA 70815. A SASE is appreciated.
Contact
- Ron Van Putte, 111 Sleepy Oaks Rd., Ft. Walton Beach, FL 32548.
Transcribed from original scans by AI. Minor OCR errors may remain.
