90 M ODEL AVIATION
his jack switch is ideal for a small
sailplane or a park flier. The miniature
switch weighs one gram, and is used
as an on/off switch and a battery-charging
connector.
You turn the switch on by removing a
small external telephone plug, and turn it off
by inserting the plug.
The onboard batteries can be charged
when a battery charger is connected to the
plug. Having the charge connector
accessible on the outside of the fuselage can
be a real advantage—especially if the
fuselage is packed full of electronics.
Standard connectors are wired to the
switch, allowing the receiver or battery to
be removed easily.
The jack switch and its telephone plug
can be purchased by mail order for $1.50,
excluding return postage.
Make a
Lightweight
n Robert Boyce Switch
The completed switch harness is shown at the bottom. The plug at the top is used as a charger connector and on/off switch.
The purchased switch and plug. The penny is shown for size comparison—it’s small!
I have encountered no reliability in more
than two years of operation.
The switch can be mounted directly to the
side of the fuselage or it can be incorporated
into the aluminum servo mount described in
the September 2000 Model Aviation.
If you are going to mount the switch
directly in the fuselage, reinforce the inside
of the fuselage with a 1/2-inch-diameter
washer made from 1⁄32 plywood.
Before you begin construction, study
Figure 1 and decide which option you
prefer. The primary difference is that the
wire harnesses exit the sides of the switch in
Option 1, and they exit the back of the
switch in Option 2.
Option 2 is probably the best choice,
because it allows a heat-shrink sleeve to be
slipped directly over the switch and leads.
However, it has the disadvantage of
requiring a greater distance across the
fuselage for clearance.
If you select Option 1, use a thin coating
of epoxy to insulate the terminals.
construction Details: Drill a 5/32-inchdiameter
hole in the fuselage and
temporarily mount the switch there.
Temporarily insert and route the batterywire
harness from your existing battery plug
to the switch. Extend the wires 11⁄2 inches
beyond the switch, and snip the leads. Be
sure that the wire harness is disconnected
from the live battery before snipping.
In a similar fashion, route the receiver
harness and extend its leads 11⁄2 inches past
the switch, and cut off the excess.
Remove the switch and the wire
harnesses, and trim the ends of each wire
to match the corresponding solder tab on
the switch.
Refer to the drawing and select the
Option you will build.
Strip 1/2 inch of insulation from each
wire and twist its bare wire strands together.
Depending on the version you choose,
cut and slip the 1⁄8-inch-outside diameter
(OD) or 3⁄16-inch-OD heat-shrink coverings
over the wire harness (see Figure 1).
Flux and tin the three switch solder tabs
fairly close to the switch.
Twist the bare wire strands of the two
negative leads together. Wrap these two
negative strands 3⁄4 turn around the
corresponding solder tab, and flux and
solder the strands close to the switch.
In the same way, flux and solder the
remaining two bare wire strands to their
corresponding switch solder tabs.
Trim each of the bare wire strands and
switch-solder the tabs flush with the solder
joint. Dip a Q-Tips® swab in alcohol and
remove any excess flux.
If you are building Option 2, cut a piece
of 1/2-inch-OD heat-shrink covering to a
length of 5⁄8 inch and slip it over the jack
switch and leads. Complete this portion of
the switch assembly by shrinking the tubing.
If you selected Option 1, also coat the
solder tabs with a thin coat of epoxy.
February 2001 91
Figure 1
Photos by the author Graphic Design by Jill Ann Cavanaugh
Remove the two vertical wire hold-down
tangs on the charger plug’s negative solder
tab by snipping the horizontal tab just ahead
of the vertical tangs. Flux and tin the inside
surface of the negative solder tab and the
outside surface of the positive tab.
Snip the wires of the charger harness
to a length of two inches. Strip a 3⁄16-inch
length of insulation from each wire,
twist its strands together, flux and tin
each lead.
Slide the wires through the plug’s
plastic case and slip a 3⁄8-inch length of 1⁄8-
inch-OD heat-shrink covering over the
negative wire.
Push the positive lead through the
solder tab hole so its bare wire is pointing
outward, and flux and solder. Flux and
solder the negative bare wire lead to the
inside of the solder tab. Clean the excess
flux off the two terminals.
Slide the heat-shrink covering over the
entire length of the negative solder tab
and shrink it.
Complete the charger plug by coating
the metal threads and solder tabs with
epoxy prior to screwing the plastic sleeve
onto the charger-plug assembly.
Use an ohmmeter to check the wiring
of your finished switch compared to the
schematic. Be sure to check wiring with
the charger plug in and out (off and on).
Do not perform these tests with the
harness connected to the battery.
Install your finished switch assembly,
charge your battery, and go fly. MA
Sources:
Jack switch (1312-0001) and its mating
telephone plug (1312-00003):
Try your local electronics supplier.
If the supplier cannot provide the items,
purchase a small (6 x 8.5-inch) padded
mailing envelope. Take the envelope to the
post office and pay 60¢ of return postage.
Self-address the unsealed envelope and
insert $1.50.
Put this envelope inside a sealed
envelope addressed to Gateway
Electronics Inc. of Colorado, 2525 North
Federal Blvd., Denver CO 80211, Attn:
Dan Duryee.
Wire harnesses with attached connectors,
glues, plywood, hobby tools:
Available at your local hobby shop
Heat-shrink covering, solder, flux, wire
strippers, miscellaneous items:
Radio Shack
Robert Boyce
5741 S. Crestbrook Dr.
Morrison CO 80465
92 M ODEL AVIATION
IN A PREvIOUS column, I emphasized
that Pattern often leads to innovation by
builders and manufacturers. I don’t think
that is the only place where innovation
occurs; it just happens often in competitive
situations. I thought you might find some
engine developments interesting.
YS and O.S. have produced fuel-injection
type systems for their 1.40 engines, and they
were flown at the 2000 AMA Nationals; Chip
Hyde flew the YS prototype and Jason
Shulman flew the O.S.
Chip and Jason made it through to
represent the US in next year’s Federation
Aeronautique Internationale (FAI) World
Championships in Ireland. (Jason had a midair
and did not finish the contest with his engine,
but what I saw looked very good).
The YS injection system is a variant of its
proven pressurized tank and fuel regulator
system. The engine receives the right amount
of fuel to produce the most power at any
given throttle position.
The O.S. system involves the
computerization of the fuel delivery that is
linked and matched to the exhausttemperature
sensor.
Although these systems are fitted to the
Eric Henderson, 303 Shady Ln., Marlton NJ 08053; E-mail: [email protected]
RADIO CONTROL AEROBATICS
David Cepas with an O.S. 1.40 engine squeezed into a 1994 Omen. This combination
took David to an NSRCA Masters District I Championship.
Patty Baiano with beautiful color scheme—looks good and wins. The TAI-JI is showing up at more and more contests.
top-of-the-line two-stroke and four-stroke
engines, they do indicate the direction in
which engine technology could be heading.
The result of these systems is that the
engines receive the correct amount of fuel
when it is needed. “Normal” model engines
have the inherent weaknesses of 19thcentury
carburetor design.
The Spitfire was no match for the Me
109 until the Merlin V12 engine was fitted
with fuel injection. The injection system
allowed the pilot to point the airplane in any
direction without losing power.
These new systems change the power curve
available to the Pattern pilot. They run
relatively huge propellers of 17 and 18 inches
in diameter. This allows 11-pound models to go
vertical on not much more than half-throttle. It
also makes the models extremely quiet.
The ability to go the same speed up and
down is now at the pilot’s fingertips, so to speak!
These engines may or may not be available
to the public by the time this column goes to
print, but the promise of this type of
technology reaching the sport flier is out there.
Imagine flying a model and never having to
touch a needle. The fuel is supplied to the engine
by a computer; only air comes in the carburetor,
and the throttle is smoothly responsive. Not a
burp or a bip! Your airplane is no longer as
constrained by a less than 1:1 gravity-conquering
capability. It’s not that far away.
Another quieting aspect of these engines
is that they all use soft mounts. Pattern pilots
learned a long time ago that if you isolate the
engine from the airframe, you get a quieter
airplane and much less wear on your
servos/linkages.
These soft engine-mount developments are
available now—and not just for the big engines.
Recently, the Central Hobbies ad showed a
whole range of mounts for smaller engines.
Merle Hyde (Chip Hyde’s dad) has produced a
whole series of mounts for the sport engines.
These mounts are extremely effective,
and they will improve relations with
neighbors surrounding your flying field.
Supporting the US Team: I have been reliably
informed that Dave Guerin will be the US FAI
Pattern team manager in 2001. This bodes well
for our chances; we have the talent in the team,
and now we have added the technical knowhow
and wisdom of a Pattern expert.
February 2001 93
Super-quiet ES carbon pipe in Hydeout. Measures 40 inches from spinner to stinger.
The ES carbon pipe shown from another
perspective.
Dave Guerin models have won each class at
the AMA Nationals, with almost a clean sweep
the past three years. Dave’s airplanes have been
flown successfully at World Championships
and at Tournament of Champions events.
Please contribute to the success of this
team; it costs a great deal to ship the pilots
Continued on page 97
February 2001 97
and the equipment across the Atlantic Ocean
(and to bring them back). Send your
donation to AMA Headquarters and mark it
“US Pattern Team Fund.”
Flying the Maneuvers: I have a series of
48 maneuvers planned for this section of the
column. If there is a particular maneuver
you would like to see, please drop me a line
and I will include it sooner.
This month I will examine a maneuver
that looks simple, but has a high degree of
hidden challenge: the Triangle Loop.
It may just seem to be an extension of
the Square Loop, featured last month; it has
corners and straight lines, and it takes the
model in a loop back to where it began.
So where is the challenge?
It’s in the angles. You don’t have to be
a competition Pattern pilot to be
challenged by angles. These maneuvers
are there to test us all.
The Triangle Loop is composed of one
90° angle and two 45° angles. This
maneuver is best visualized as a right-angle
triangle standing on its apex.
The first line is pulled at a center point that
you choose. (In a contest, it would begin on
the centerline right in front of you). This line
has to draw at a 45° angle. It is hard to draw
this line freehand on a piece of paper, and it is
equally hard to do with a model.
Draw the 45° line for two or three
seconds before you pull another corner. The
inside angle will be 45°, but the model will
actually pull 135°. Now the airplane is
inverted and parallel to the ground.
A huge mistake, which is the most
common one, is to pull a 60° angle and
make the first line much too steep.
The third corner is a 45° that makes you
pull another 135°. This pull directs the
airplane back toward the point where your
maneuver began.
The last 45° pull brings the model
back to level, upright flight. The
maneuver is complete when the airplane
is flying level again.
The first and last corners make the 90°
of the perfect right-angle isosceles triangle
you have just drawn in the air.
Now let’s look at what can go wrong,
and where the challenges are lurking. By
now you should have a friend, or several
friends, who will be more than willing to
critique your efforts.
The first challenge is getting those 45°
corners and lines right. There is no easy way
to tell if you pull two wrong, but equal lines;
the maneuver will seem right, but your
“peanut gallery” will let you know.
A tough line to hold is that top, inverted
one. Then there is the “gotcha” line.
Assume you got all the angles right, but
went a little too short or too long on the
top line. What happens is that your model
is visibly short of, or over, the center when
it’s time to level out.
Continued from page 93
RC Aerobatics Only many, many hours of practice can
program you to do the Triangle Loop
correctly. It is really not that hard to do, and
using a distant centering device, such as a
tree, will allow you to more accurately judge
how long to fly the inverted section.
Please remember that pulling the radius
of the corners takes time, hence distance.
This has to be factored into how long you
draw those straight lines.
The Triangle Loop is pretty to watch
and to perform, but it is much more
difficult to get right than, say, a Square
Loop. The four-sided loop has obvious
symmetry requirements, and it is nowhere
near as obvious when the pilot draws a top
line that is too long.
Good judges will catch the error, but you
can fool them! All judges will catch the
asymmetry in the Triangle Loop!
Schedule designers always seem to
throw in a Triangle Loop. They also love to
put rolls and snap rolls in the straight lines.
There have been Triangle Loops with
one negative snap on the top line, and ones
with full rolls and 1⁄4-rolls on the top line.
Really tough Triangle Loops have 1/2-rolls
on the up and down 45° lines, to spice it
up even more.
Feedback on my wind-correction advice
has been mixed. Some actually bemoan
being given this knowledge, and state how
much happier they were before they were
informed of this requirement!
The need for headwind correction seems
intuitive for most pilots. Crosswind
correction—not so much.
In the Triangle Loop, you need to pull
the up-line slightly shallower than 45° to
compensate for the headwind drift, and
slightly steeper on the 45° down-line. This
is a sophisticated correction, and it may
even be lost on the casual observer.
However, it is a good practice, and it
really helps you hit the center on the
completion of the maneuver.
Crosswind correction comes in two
forms: straight-line correction—the usual
small amount of rudder—and slightly
lowering the wing panel facing the wind.
With either method, you need to make sure
the wings are level and the nose is pointing
straight before you pull a 45° corner.
Technically, it is 45° at the bottom
corners and 135° at the two top corners.
When pulling these corners, any entry errors
will become painfully apparent. Nothing
shows a heading error like a 135° corner.
The good news is that you can fix your
heading while you are pulling the corner. If
you are holding in left rudder and you pull
with the nose pointedto the left, you can
apply right rudder as you go around the
corner and come out straight. Then you will
need to reapply the left rudder, to fight the
wind again.
The goal is to start and finish the
Triangle Loop in the same spot in the sky.
When you can do that in front of all and
sundry on the flightline, call the National
Society of Radio Controlled Aerobatics
(NSRCA)!
For more information on maneuver
descriptions, rules, and downgrades, check
out NSRCA.org-related Web sites.
Boldly go … If you have a model that is
larger or heavier than AMA contest rules
permit, but would like to try Pattern before
you “buy” into it, give it a go!
Just for grins, call the Contest Director of
an event you see in Model Aviation or on
NSRCA.org, and explain that you are
interested, but not correctly equipped. Ask if
you can fly it anyway.
You will most likely be welcomed with
open arms—especially if you tell them I
sent you. If you are not, call me. MA
