RC JETS 2013/07 Building projects at the Toledo R/C Expo

How could Greg Wright trump his first Flite-Metal F-100? How about with
his latest F-100D covered in camouflage? Its detail, paint, and realistic
weathering must be seen up close to be appreciated.
Bob Bush’s Skymaster A-4 is detailed and perfectly weathered. Underneath
is an engineering masterpiece—full hydraulics, designed and built by Bob,
for landing gear retraction, speed brakes, tailhook, and flaps.
Building projects at the Toledo R/C Expo
by Jim Hiller
[email protected]
The 2013 Toledo Show is over, and it was again an exciting place for modelers.
For us Northerners it was a great place to take a break from our winter building
and see our friends from throughout the region.
The turbine-modeling industry is not strongly represented at the Toledo R/C Expo.
Its representatives prefer to attend flying events to show off the latest products, but
don’t let that
keep you away.
Jet modelers
were all over
the floor
helping friends
in the industry,
bringing out
the latest
projects to
display, and of
course, taking
in the sites and
visiting.
Radio
manufacturers
showed up in
full force, with
Futaba, JR, Spektrum, Hitec, Airtronics, and XPS all attending and showing the latest
products—new toys for the boys (and girls)!
On the show tables, Terry Nitsch brought out his latest Scale model, a Skymaster
F-86, painted in the deep black of the Sabre Dance. It was named Best Finish at the
Toledo Show.
Terry’s model is complete with the functional LE slats, and we look forward to his
thoughts on the effectiveness and flight characteristics of flying the F-86 with slats.
The model is ready for test flights.
Greg Wright, from Aurora, Illinois, brought his latest building project, an F-100D.
This is a sharp and well-detailed Scale model. The attention
to detail and craftsmanship make this one sweet model and
deserving of the Best Jet award at this year’s show.
This is Greg’s second F-100. His first F-100 is also an
outstanding model built with aluminum Flite-Metal, then
skinned with titanium in the hot section. The new F-100D
is finished in a camouflage paint scheme with the correct
amount of weathering. Some areas are worn through to reveal
the aluminum. Greg is a talented builder.
The largest jet model on the table was Curtis Wade’s
Tomahawk Designs Hawk. Curtis stepped up big time with
his winter project, which is a large model set up with enough
power to kick out the performance. Curtiss had it ready for
test flights, which were scheduled for the following weekend.
The engineering feat of the show, however, has to be Bob
Bush’s Skymaster A-4. He is back with a Navy aircraft this
time. For those who don’t know Bob,
he has been flying the same U.S. Air
Force Thunderbirds F-100 Super Sabre
for a long time, wearing out three AMT
turbines.
He surprised us all by showing up
with a Scale Navy A-4. He did an
exceptional job of weathering this
model. Navy airplanes are workhorses,
not pristine and clean as is his F-100.
Bob is a man of many skills. He
engineered, designed, and built his
own hydraulic system in this A-4, then
installed it in the airframe in a manner
that makes it easily accessible for
maintenance.
Not only is the landing gear retract
system hydraulic actuated, but he also
uses the onboard hydraulic system
to power the gear doors, tailhook,
speed boards, and flaps. That’s a lot of
hydraulics!
The brakes use an air cylinder moved
by a JR 8411 servo to provide air
pressure for braking. An air pump is not
required to fly.
A standard turbine fuel pump,
powered by an 1,800 mAh LiPo battery,
serves as the hydraulic pump. The
maximum operating pressure is set by
a Robart pin-type onboard pressure
indicator. As the pressure increases, the
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Terry Nitsch is back with
a beautiful Skymaster
F-86, fully detailed for
Scale competition. It has
operating LE slats for lowspeed
handling. Terry is a
master at flying Sabres.
pin extends and makes a
microswitch shut off the
hydraulic pump to avoid
overpressurizing the
system.
The hydraulic control
valves are commercial
units moved by individual JR 8411
servos—a bank of five—and located
behind the A-4’s removable nose cone.
There is one set each for the individual
systems operated by hydraulic power.
The operating concept of hydraulics
is to run the pump to move oil to the
actuator cylinder to move something.
The control valves route the oil to the
appropriate actuator cylinder and return
oil from the backside of the actuator to
the oil reservoir.
Bob uses an RC car fuel tank as his
oil reservoir. After the actuator cylinder
reaches its limits, the pressure in the
system rises until the Robart pintype
indicator moves out and hits the
microswitch to shut off the hydraulic
pump, completing the cycle.
This sounds simple, unless you’re
Bob Bush. He believes so strongly in
his basic hydraulic system that he is
using it to control five different items.
Those include five control valves and
two hoses out to each actuator cylinder,
three landing gears, three gear doors, two
speed brakes, two flaps, and one arrester
hook. It also has 11 actuator cylinders
with two hoses each, or 22 hoses, routing
from the nose of the aircraft back to the
actuator cylinders.
The last item in Bob’s hydraulic system
is an accumulator tank that provides a
last chance to drop the landing gear if the
hydraulic pump fails. This pressurized
source of hydraulic oil in the tank is large
enough to allow one extension of the
landing gear. It’s a luxury that pneumatic
systems don’t have.
How well does the backup system
work? Bob demonstrated the hydraulics
so often at the Toledo Show that he
exhausted the battery, so he seized
the moment and showed how the
accumulator tank successfully lowers
the gear without the hydraulic pump
running. It worked like a charm.
A potential problem with the
hydraulic system is finding a way to
disconnect the hoses from the wings
when they are removed for transport,
without getting excessive air in them.
This requires air to be bled out of the
system.
Bob has a solution. He found a
connector valve with a ball-check system
to prevent the oil from leaking when
disconnected. The system is located on
the fuselage side of the connectors.
On the wing side of the connectors,
he joined the two hoses to keep the
oil in the wing cylinders from leaking
out, which is slightly more difficult
than disconnecting a normal pneumatic
system.
Bob took time at the Toledo Show
to explain the components required
to make his hydraulic system. The
movement of the landing gear with
hydraulic actuation is the same as in
full-scale aircraft. The scale gear takes
approximately 3 seconds to retract.
I look forward to seeing Bob fly his
new A-4 as hard and as often as he flies
his F-100. He will truly test the system’s
durability and reliability. Bob knows he
wants to fly his A-4 many times a day
with little or no maintenance, which is
what he had in mind when designing
and building his hydraulic system.
SOURCES:
Jet Pilot’s Organization
www.jetpilots.org
Toledo R/C Expo
www.toledoshow.com
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