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This article provides a really good look at
how varied model airplane designs can be for a defined contest event - in this case Free
Flight Rocket, Jr. Jet PAA-Load and PAA Load Jet. Wing, fuselage, and tail outlines,
pylons or not, sub-rudders, and engine mounting locations are all over the map,
figuratively speaking. "Jet" as used here refers almost universally
to the Jetex engines that were popular at
the time. Jetex motors, fuel, and accessories were imported from England and distributed
in the U.S. by Aristo-Craft Distinctive Miniatures, in Newark, New Jersey.
Jetex rocket engines were quite popular with model airplane, boat, and car builders
through the early 1970s, at which point the fuel supplies began to disappear. Most Internet
sources posit that
Imperial Chemicals
Industries (ICI) ceased making the fuel pellets due to a combination of liability
and regulation issues. ICI, based in Scotland, manufactured the Jetex fuel pellets from
a measured blend of guanidine nitrate, 2,4-dinitroresorcinol, potassium nitrate (aka
saltpeter), iron oxide, kaolin, and asbestos.
Free Flight Rocket, Jr. Jet PAA-Load and PAA Load Jet
"Rocket'' Their Way to Success
Rocket free-flight and Jet PAA-Load events at the last National Contest produced a
great number of original designs. Most were functional, both in configuration and structure.
There were some radical deltas and flying wings, but while their performances were creditable
they were not substantial enough to get into the top brackets.
The favored adjustment technique, used by most winners, began with a right spiral
climb, which steepened into a near vertical climb after the second fuel charge cut in.
Then the model would roll into a left turn glide pattern.
To obtain such a pattern, slight left rudder was used in conjunction with a tilted
stab. Upon launching, the models were usually banked to the right, and the engine thrust
did the rest.
More thought and care went into the design of models for the Jet PAA-Load events than
in the rocket F. F. events. Which proved that if imagination and effort are required
in design, the American modeler is well qualified to do the rules justice.
Constructionwise, it appeared that a trend had already been developed. The Jetex "50"
powered entries leaned heavily towards all-balsa construction, with exceptions in the
Junior Jet PAA-Load event, where some built-up designs were in evidence.
One reason for the absence of small built-up free-flight rocket designs was the inability
of many to "heave" them in launching as is possible with more sturdy all balsa types.
However, there were a few ambitious exceptions here, too.
At the time the Nationals were being held, Jetex fuel appeared to be the critical
problem. Because of import taxes on the chemicals in the "Red-Spot" fuel, it became impossible
to price it within a reasonable range of the model builder, thus new fuel had to be developed
very quickly. With it were born many new problems calling for further refinements in
fuel and modifications of the engines to use the higher power of the new fuel to better
advantage.
Despite these difficulties winners were using a Jetex design engine and fuel. The
latest Jetex fuel is considerably improved and lower in cost.
With regard to engines and fuel there were a few interesting steps some of the expert
modelers were taking to insure maximum performance. For example, Ted Gonzoph, Philadelphia,
Pennsylvania, used silica jell to keep the pellets from absorbing moisture. He also used
a silica-base compound as a sealing agent for the engines. All this adds to the engine
life as well as the power output. Others were inclined to be somewhat secretive about
their efforts.
PAA-Load designs ran as high as 180 sq. in., while some free-flight "rockets" for
the same size engine had only 120 sq. in. An appreciable difference, but one expected
in view of the different design and performance qualifications. A few models featured
augmenter tubes.
The models as a rule were designed for one event; few combination rocket and PAA-Load
jet design showed promise outside of Joe Foster's first place rocket design, which featured
a conversion on the fuselage for PAA-Load jet.
Some are currently experimenting with folding wing designs, which are retracted to
smaller dimensions with power-on, and snap out to full span after the engine cuts-off.
Flaps are another means of getting the best climb and glide combination.
Analyses of 22 Designs
Information on many interesting entries at the last National competition selected
and drawn by Paul Del Gatto follows this pattern (all powered by Jetex-made engines):
1) Free-flight "Rocket" design (1st place, Jr. event) by Steve Benko, Lakewood, Ohio
Flite Masters; PAA-Loader "150" engine; spans 30"; 28" long; angular set-up of wing and
stab, 2 degrees-zero degrees; dihedral (from fuselage), 1", 4"; center of gravity 70%
back from leading edge; "3/8" sq. body.
2) Jet PAA-Load by Jim Breunig, Minneapolis; "150"; spans 32"; 26" long; two-zero,
3/4"r 3"; 70%.
3) Jet PAA-Load by Robert Walters, Maspeth, N.Y. (Bklyn. Skyscrapers); "150"; spans
32"; 23" long; two-zero; 1 1/2", 3 1/2"; 75%.
4) Jet PAA-Load by Henry Cole, Palo Alto, Calif.; "150"; spans 36"; 27 3/4" long,
three-zero, 1", 3"; 55%.
5) Jet PAA-Load by George Ostrowski, Whiting, Ind.; "150"; 30 1/2" span; 24" long;
two-zero; 2"; 75%.
6) Jet PAA-Load by C. O. Wright, Topeka, Kan.; "150"; spans 36"; 25 1/4" long; two-zero,
1", 2 1/2"; 50%.
7) F-F Rocket by Albert Lynch, Jr., Chicago Prop Nutz; "150"; spans 26 1/2" 27" long;
2.7 oz loaded; one-zero; 5/8", 2 7/8"; 70%; sheet balsa fuselage, triangle cross section
back from wing l.e.
8) Junior Jet PAA-Load (5th place) by Stephen Stackhouse, Levittown, Pa.; Jetex "50B";
spans 24"; 15" long; two-zero; 3/4", 3 1/4"; 75%; canopy from plastic glow plug pkg.
9) F-F Rocket by Charles Sotich, Chicago Prop Nutz; Jetex "100"; spans 22 1/2"; 27"
long; one-zero; 1/2", 2 1/2"; 75%; good performer, popular club design.
10) F-F Rocket (4th place) by Joe Morrissey, Ozone Park, N. Y.; "150"; spans 27";
20" long; one-zero; 2 3/4"; 60%; Warren truss fuselage silhouette, sheet balsa covered
from nose to back of pylon.
11) Junior Jet PAA-Load by John Vikesland, Cedar Rapids, Iowa; "50B"; spans 16 1/2";
16 1/2" long; two-zero; 1/2", 1 5/8"; 50% root chord; wing, stab swept 15%; canopy from
plastic g.p. pkg,
12) F-F Rocket by Ted Gonzoph, Philadelphia; "150"; 27 1/2" span; 22 1/2" long; two-zero;
1 1/4", 4"; 60%; built-up sheet balsa fuselage.
13) Junior Jet PAA-Load by Steven Benko, Lakewood, Ohio, Flite Masters; "50B"; spans
20"; 18" long; zero-zero; 1", 3"; 65%; dummy boxed in, cabin from small plastic blister.
14) F-F Rocket by Fred Steffens, Jr., Champaign, Ill.; "150"; spans 22"; 25" long;
three-zero; 2 1/2"; 60%; Czepa-type wing.
15) Jet PAA-Load (2nd open) by Joseph Pusateri, Bethpage, N.Y., L.I. Gas Monkeys club;
"150"; spans 36"; 30 1/2" long; three-zero; 3/4", 2 3/4"; 60%; 1/16" sheet wing tip plates.
16) Jet PAA-Load (1st open) by Capt. Lee Waldrop, USAF, Wright-Patterson AFB, Ohio;
"150"; spans 36 1/2"; 27 3/8" long; two-zero; 1", 4"; stab dihedral, 3/4"; 80%.
17) Jet PAA-Load by Paul Bartel, Garfield Hts, Ohio; "150"; spans 36"; 28 3/4" long;
two-zero; 3 1/2; 60%.
18) Junior Jet PAA-Load by Randy Jones, Decatur, Ga.; "50B"; spans 22 1/2"; 18 1/2"
long; 1.5 oz loaded; 1 1/2-zero; 2 3/8"; stab dihedral, 1/4", 1 1/4"; 45%; cabin from
plastic g.p. pkg.
19) Jet PAA-Load by Joe Foster, San Jose, Calif.; "150"; 36" span; 22 3/4" long; two-zero;
4 1/2"; 50%.
20) Jet PAA-Load by Charles Bedwell, Whiting, Ind.; "150"; spans 36"; 24 1/4" long;
two-zero; 4"; 50%; air scoops on fuselage sides, shortened augmenter tube.
21) Jet PAA-Load by Tom Keister, Duncan, Okla.; "150"; spans 36"/ 26 1/2" long; one-zero;
3"; 50%ยท,
22) Jet PAA-Load by Ted Gonzoph, Philadelphia; "150"; spans 36"; 26 1/2" long; two-zero;
1", 4 1/2"; 70%.
Posted July 14, 2018
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