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Free Flight Action
January 1975 American Aircraft Modeler

January 1975 American Aircraft Modeler

January 1975 American Aircraft Modeler - Airplanes and Rockets3 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.

Materials and methods for free flight aeromodeling have changed significantly since this "Free Flight Action" column appeared in the January 1975 issue of American Aircraft Modeler magazine, but the enthusiasm has not. Carbon fiber tubing now constitutes a large portion of modern free flight duration model airframes, electronic timers have replaced mechanical wind-up timers (and even dethermalizer fuses), electric motors have joined (but not replaced) glow fuel engines, and lighter and stronger covering has supplanted tissue and/or silkspan and dope. More efficient airfoils, and wing, empennage, and fuselage planforms combine to produce new record flights in all competitive classes. Even modern weather detection and forecasting is being used to predict the best moment for launching. You've come a long way, baby.

Free Flight Action

Free Flight Action, January 1975 American Aircraft Modeler - Airplanes and RocketsBob Meuser on FF Sport

Jetex Breakthrough: Far too often, I've seen an expert fail three successive times to get his Jetex 150 engine to ignite. We have often pondered the problem at club meetings. Larry Parsons suggested some sort of electric igniter. But getting the lead wires through the case was a problem. Some sort of miniature ceramic feed-through brazed into the sides of the case, a heating element connected between them, could perhaps provide a solution. But nobody ever did it. Years passed. Larry didn't give up; there had to be a simple solution.

Jetex Engine Ignitor Solution, January 1975 American Aircraft Modeler - Airplanes and RocketsWhenever I see a beautifully elaborate solution to a design problem, I know I'm looking at the signs of defeat. Great designs usually look as though an idiot could have dreamed them up in two minutes. The solution Larry finally came up with, and his son Dave put into practice, has the right look. A stainless steel heater wire - nichrome might be better - loops around a notch in a piece of fuel pellet. No feed-throughs are used; the heater wires are simply brought out between two thin gaskets which are substituted for the standard gasket. At a recent contest, Dave's engine ignited every time. He used the same piece of heater wire all day.

Ugly Duckling Free Flight, January 1975 American Aircraft Modeler - Airplanes and RocketsNATS Winning Mini-Unlimited: The Unlimited Rubber-Powered Model rules permit 300 sq. inches of wing area, and such models frequently carry nearly half a pound of precious Pirelli rubber. However, much smaller models often perform disgustingly well. The Ugly Duckling (shown in the three-view) is one such model, having won the Senior Unlimited Rubber event at the 1973 NATS for Robert Zeigenfuse, with a score that would have taken second place in the Open Age Group event.

Designed by Robert's father, Gerald Zeigenfuse, the Ugly Duckling was originally designed to be flown with old 80-gm. Wakefield motors. The rules were changed. With twice the rubber of a present-day Wakefield, and less gross weight, the performance potential of such a plane is obvious; no small-field model is this! The greatest problem with small unlimiteds is keeping them in sight for the period of a max. The original model, built by Gerald in 1964, placed first in every contest in which it was entered.

When Robert got to the age for serious competition and wanted to build an Unlimited, the Ugly Duckling was the obvious choice. Robert made his NATS-winning flights, incidentally, using a 1973-vintage Filatti rubber, the kind that barely turned the prop and was scarcely of sufficient quality for strapping on wings. (The Fillatti rubber currently sold is as good as good old Pirelli, according to some tests.) However, it takes more than a well-built model of good designs to win; proper adjustment is an essential ingredient. Robert spent most of the afternoon preceding the Unlimited event at the NATS test-flying his model. That took lots of leg-work because of the fierce wind, but the effort paid off.

Unlimited Speed Free Flight, January 1975 American Aircraft Modeler - Airplanes and RocketsRubber-Powered Speed Contest: Charlie Sotich, fastest gum-bander in the Midwest, won the IMAC-sponsored speed meet with a speed of 50.5 mph. That's a hair short of Jim Charlie Sotich's rubber-powered racer covered the 200 ft. course in 2.7 sec. (50.5 mph] to win the IMAC-sponsored Speed contest. McCracken's speed made at the 1973 NATS, but Charlie hasn't finished developing his model yet.

Here are the specs: 24" span, 34.5" fuselage length, 7" plastic prop, 2.78 oz. gross weight, of which about half is rubber. The lightweight dolly, which uses the bottoms from foam coffee cups for wheels, falls off after takeoff. CG must be well forward - 6% of the chord back from the leading edge - to keep the model from zooming up. Solid balsa wing and tail, and built-up fuselage are employed. The model has been flown on eight strands of 1/4" Pirelli wound only to two-thirds capacity. Charlie hasn't broken a prop yet.

"There is still much testing to do," he says. A rubber speed model must be light - not more than about 4 oz. per 100 sq. inches of wing area - and should have a prop diameter no larger than one-third of the wingspan. It should be driven by plenty of rubber.

The Illinois Model Airplane Club meet was held according to the NFFS rules: 200-ft. course, 100 ft. wide; model must take off from a table; model may not rotate more than one turn in flight; no dimension may exceed 36".

Charlie has been experimenting with a variety of plastic props, some of uncertain heritage: one from England, another from France, a 7" Testers prop from an ROG kit, among others. He suggests that the 9" Peck Polymers prop might be good if cut down to about 7". He felt that the original solid 3/32" sheet balsa wing was a little too flexible, and has constructed a light stick-and-tissue wing only 3% thick. We hope he completes his experiments before the NATS, and shows up with a real sizzler for the NFFS-sponsored unofficial Rubber-Power Speed event.

Tatone Timer Modification, January 1975 American Aircraft Modeler - Airplanes and RocketsTatone Timer Modification: From the prolific pen of the old gadgetmaster himself, Bob Hatschek, comes America's answer to the high price of European multi-function timers. It won't pop up the tail for dethermalizing (a fuse DT can be used for that) but it will give time-sequenced actuation of autorudder, autostab, and engine cut. If 1/32" wire is used for the arms, and the bent ends of the arms are nearly touching, the time delay between functions is about one-half second. For a longer delay, a knee can be bent into one arm to better separate the ends. The rudder and stab lines can be hooked up to the same arm for simultaneous actuation.

Tadpole Free Flight, January 1975 American Aircraft Modeler - Airplanes and RocketsThe lever on the left side goes to the flood-off device. Those on the right may be connected in either order, depending on whether the rudder or autostabilizer is to be actuated first. The disk position is shown just before actuation of the flood-off device.

The modification can be made to either a Tick-Off or Flood-Off timer, either the new models or the old, as the stock faceplate is to be discarded anyway.

Tadpole: Designed by el maestro George Xenakis to A/1 Towline Glider specifications, the Tadpole is one of those simple, ugly beasts that has a special knack for finding thermals. One was flown to first place at the 1974 U.S. Free Flight Championships by Greg Xenakis, and established a National Record as well. The wings on the original series of models employed Jedelsky all-sheet construction. These proved to be too weak, and had to be reinforced with spruce and plywood. The newer series employs sheet balsa for the rear half of the wing, and built-up construction for the front half. This promises to be both stronger and stiffer in torsion.



Posted February 11, 2023

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