“HOW DO yOur models fly without RC?” That’s
a familiar question for most FF modelers. The short
answer is that the airplanes are designed and adjusted
to fly with no external control input. But how does it
really work?
Designing and adjusting an FF aircraft is a
balancing act. Fortunately, most adjustments are
speed-sensitive. Some, such as rudder, stabilizer, and
wing washin or washout, are more effective the faster
the model is flying.
Wing wash works much like movable ailerons, to control roll.
Washin means a positive incidence at that point on the wing relative
to the wing center, and washout indicates less incidence at that
point.
Other adjustments, including stabilizer tilt, CG location, and
engine thrust offsets, are more effective at slow speeds. By pairing
adjustments based on speed sensitivity, the model will essentially
fly itself.
A rubber-powered model might use downthrust and upstabilizer.
If it increases in speed under power, it will tend to nose
up. If the airplane noses up too steeply and approaches a stall, it will
slow. Then the downthrust will overpower the up-stabilizer and the
aircraft’s nose will drop slightly, preventing a stall. This is a
constant balancing act that is almost imperceptible in a properly
adjusted FF model.
FF airplanes have traditionally been “locked up,” with the flying
surfaces fixed during flight. Starting in the 1950s, movable surfaces
such as rudder (auto rudder, or AR) and stabilizer (variable
incidence tailplane, or VIT) were introduced as means to increase
the performance of Rubber or Gas models. Auto surfaces, controlled
by a clockwork or electronic timer, allow different phases of the
flight to be isolated and dealt with independently.
The high-speed climb would typically be trimmed with less
decalage, to reduce drag and prevent looping. Then the VIT would
move slightly, to increase decalage and improve the glide. Decalage
is the relative difference between wing and stabilizer incidence.
Although the auto surface-equipped model is mechanically more
complicated, adjusting it is simplified.
But many modelers continue to enjoy the challenges of adjusting
and flying a locked-up model without auto surfaces. Some events,
such as Nostalgia Gas and the recently introduced Classic Gas, do
not allow auto surfaces.
At the 2009 Nats, I watched Dan Berry fly his Nelson .36-
powered Marval 560 in CD Classic Gas. I wasn’t the only one
watching. The Marval’s designer, Marvin Mace, was sitting under
the shade of an umbrella, watching every flight.
The Marval was named a Model of the Year in 1993.
“The design evolved from Mark Valerius’s Rum Runner
design,” said Marvin. “The Marval name was used to acknowledge
my friendship with a fellow modeler who helped me get up to speed
after being away from modeling for 30-plus years.”
One hard-to-miss feature on Dan’s version of the Marval was the
large amount of left thrust in the engine.
“I’m guessing about 6°; you can see it from 100 feet away,” said
Locked-up Power models
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Free Flight Quarterly
• Building efficiently
Dan’s Marval is typical of the locked-up models flown in Classic
Power. The 725-square-inch Marvin Mace design uses a Nelson .36
engine.
Left: Dan Berry’s scaled-up Marval
features significant left thrust, to
help with launches in windy
weather. The split dowels attached
to the bottom of the wing assure
wing-fuselage alignment.
Larry Davidson cranks up the O.S. Max III in his scaled-up
Dixielander. The 1950s British design is becoming popular in
Nostalgia Power events.
November 2009 131
11sig5.QXD_00MSTRPG.QXD 9/24/09 3:53 PM Page 131
132 MODEL AVIATION
Dan. “It didn’t start out that way. I’ve
chopped the nose off twice to adjust the
CG.”
All of that left thrust didn’t seem to hurt
the climb; if anything, it helped on launch
consistency.
I asked Marvin about the use of left
thrust on his Marval.
“Normally, we put in about 3° left
thrust,” he said. “It means that when it gets
windy, it will still keep its pattern. If you
don’t have the left thrust, you don’t know
what the airplane will do.”
As with any FF aircraft, the launch is
critical. In wind, it can be the difference
between a max and a crash.
“Launch nearly straight up, about 10°
right of the wind,” said Marvin.
“Left thrust is the Texas cure for flying
in all that wind,” added Dan.
Marvin explained:
“The purpose of the left thrust is to keep
strong wind from capturing the model at low
speed immediately after launch and
throwing it off-pattern. This is especially
important since low-thrustline models with
pylons are launched to the right of the wind
and are very sensitive at low speed to wind
forces blowing against the pylon and the dihedral of the left wing.
“As the model’s speed increases, the effect of the left thrust is
lost, and it has little or no effect on other trim adjustments used on
the model. It is worth noting that 3° of left thrust has worked for me
in winds greater than 20 miles per hour.”
Full-size plans for the Marval are available from the National
Free Flight Society (NFFS). Check the Web site under “Shop” for
ordering information.
Marvin’s follow-on design, the Super Marval 560, was featured
Free Flight Quarterly editor Sergio Montes was at the Nats from Australia, flying Coupe
and visiting with subscribers to the worldwide FF publication.
NFFS vice president and associate editor of Free Flight Quarterly,
David Mills, played host to Sergio on his visit to the US.
in a construction article in the June 2009 MA. The Super Marval,
designed for the AMA Gas event, utilizes timer-actuated auto
surfaces including auto rudder, VIT, and bunt. Bunt is a one-quarter
outside loop, activated by the stabilizer, to transition the model from
the near-vertical climb to glide.
At the Nats, Larry Davidson also flew a locked-up model. For
years, he had flown Russ Hansen’s T-Bird in all Nostalgia Gas
events. As in Classic Gas, only locked-up airplanes are allowed in
Nostalgia. Larry recently switched to George Fuller’s Dixielander
design.
“I have them in every size except 1/2A,” said Larry.
Nostalgia Gas rules allow only designs from the late 1940s
through 1956; aircraft can be scaled up or down to suit various
engine sizes. Larry flew a 550-square-inch version powered by a .29
O.S. Max III. The original Dixielander had a wing area of roughly
350 square inches for a .15-size engine. Covering was his usual
yellow-dyed Polyspan.
“That’s all I use,” said Larry. “It looks like tissue, but it’s a lot
stronger.”
The original Dixielander was noted for being easy to trim.
Larry’s scaled-up version was no exception.
“It’s the only airplane I’ve ever built that didn’t need any
adjustments,” he said. “It uses a lot of washin in the right main panel
and lots of washout in both tips.”
The original Dixielander used built-in adjustments, so it was
locked up the way it needed to be to fly right off the board. The wing
and stabilizer are both set at plus 3°, both wingtips are washed out
2°, and the right main panel is washed in 3°. The stabilizer is set
parallel to the right inboard wing panel, to give right glide turn.
The CG is located roughly at the wing TE. Glide adjustments are
made by shifting the CG slightly—never by shimming the stabilizer.
If necessary, power trim is adjusted by slightly shimming the wing
LE or TE.
Plans for the original 350-square-inch Dixielander are available
through NFFS plans. You can also find more information in the
August 2008 Duration column in MA and in Bob Stalick’s article in
the December 2007 NFFS Digest: Free Flight. Plans are in the
January-February 2008 Digest.
An important thing about locked-up Power models is that what
works for one type doesn’t necessarily work for all types. Both the
Marval and the Dixielander feature pylon-mounted wings with their
engines mounted on their fuselages. Pylon models are typically
flown to the right under power. High-thrustline models, such as the
11sig5.QXD_00MSTRPG.QXD 9/24/09 3:54 PM Page 132
T-Bird, have engines mounted almost in line
with the wings and are usually flown to the
left under power.
For more about trimming locked-up
Power models, see Don DeLoach’s
comprehensive article—“Beginning Free
Flight Power: A Journey”—in the 2004
NFFS Symposium.
Free Flight Quarterly: Sergio Montes, chief
editor of Free Flight Quarterly (FFQ)
magazine, was up from Tasmania to attend
the Nats. He flew in a few events and met
with some of his American subscribers.
FFQ is a worldwide FF publication.
Associate editors include Jean
Wantzenriether of France; Chris Stoddart of
Knoxville, Tennessee; David Mills of
Atlanta, Georgia; and Andrew Longhurst of
England.
Founded in 2001, FFQ offers in-depth
articles about a wide variety of FF topics.
These can range from technical papers about
aerodynamics to how-to pieces for Rubber
Scale. Articles about the history of FF have
included such designs as the Comet Zipper,
Wally Simmers’ Gollywock, and Rubber
Speed. In 2007, FFQ received an award
from the NFFS.
FFQ is available in a printed edition ($38
sent via airmail) or a digital edition ($18
available via download). Previous issues are
available as PDFs for PCs only; the cost is
$15 per year.
Also available are three collections: Bell
Henn’s Rubber Scale plans and articles, a
Coupe d’Hiver (F1G) survey, and “The
Great Gollywock Saga.” You can order
directly from Sergio using PayPal or by
sending a check to Chris Stoddard. More
information is available on the FFQ Web
site.
Building Efficiently: With all the other
demands of daily living, finding time to
build models can be difficult. Following are
a few suggestions to help you make the most
of your time.
• Start with a plan. Decide what model(s)
you would like to build. Research the
availability of kits, plans, supplies, and
accessories you will need to get started.
Make an inventory of materials you have
on hand, and then develop a shopping list.
It’s a good idea to check with mail-order
suppliers about availability, and then order
right away.
• Set up shop. Eugene Verbitsky, Ukrainian
F1C World Champion, once said, “First you
build the factory, then you build the
models.” While you are waiting for all of the
stuff you ordered to come in, take time to
organize your workshop.
Consider building fixtures, to improve
accuracy and speed construction. Rex
Hinson’s article, “Jigs and Fixtures: Don’t
Build Without Them” in the 2001 NFFS
Symposium illustrates a number of easy-tomake
fixtures. In the same Sympo, Aram
Schlosberg’s “Composite Outer Wing
Panels” shows several fixtures for
constructing carbon D-box wings.
Be sure to write exact information and
instructions on each fixture. This is
especially important on that most basic of
fixtures: the rib template. Include the
model’s name, chord size, and airfoil. I also
like to indicate how many ribs I need and
balsa thickness.
To make fixture pieces easy to find amid
workbench clutter, color them with paint or
marker.
• Keep it together. If you have ever visited a
hospital emergency room, you might have
noticed that the tools and supplies used for a
specific procedure are kept together in a
sterile package, ready for instant use. The
same idea can be used in the workshop.
Group all of the materials you need for a
specific task in a labeled container. I have
approximately a dozen boxes, each roughly 2
x 5 x 11 inches, set up for different modeling
“procedures.” One contains a set of taps,
corresponding drill bits, and tap wrenches.
Another box holds my F1B rudderbuilding
fixture, along with related rib
templates, tubular carbon spars, carbon TE
strips, and preselected balsa for ribs and
LEs—in short, everything I need to build a
rudder except glue, razor blades, and
sandpaper.
134 MODEL AVIATION
I also have boxes for small scraps of
thin balsa, thicker balsa (1/8 inch and up),
and plywood. It beats cutting up a full
sheet of balsa for a couple of wing
gussets.
• Set up a production line. Increase
efficiency by building several models at
the same time. The late Walt Rozelle once
told me that he would cut ribs for all of
the models he planned to build that year,
and then assemble wings, then stabilizers,
then fuselages. He covered all of the
airplanes at the same time.
• Make more than one. Instead of making
only the single part you need, consider
making a few extra at the same time.
Years ago, I set up my table saw to
make plywood stabilizer mounts—the
kind with the extra ears in front for
attaching the hold-down rubber bands. It
took only a few minutes more time and
approximately 50¢ worth of plywood to
make a lifetime supply.
When you are cutting ribs, make a few
extras and label them for future repairs.
• Power up. Adding power tools to the
workshop can save time and improve
accuracy. One of my favorites for
modeling is a router table.
I use a flush trim router bit that is
equipped with a ball bearing that is the
same diameter as the bit. I attach a
plywood pattern to a rough-cut piece of
balsa and trim to the exact size and shape
on the router. It’s great for cutting Rubber
model propeller blanks and solid-balsa
glider wings.
• Build with a buddy. Constructing a
model doesn’t have to be a solitary
activity. Consider working with another
modeler to “kit” parts for several aircraft.
This works best if you are building the
same design. Or use the opportunity to
teach or learn a new technique, such as
vacuum-bagging carbon components. And
it doesn’t have to be another FFer.
• Find the time. Try to spend at least a
few minutes in the workshop every day.
Use the time to select a sheet of balsa, cut
a few ribs, or glue in one or two uprights.
Omit one sitcom a night, and you’ll gain
more than 180 hours of building time a
year. It helps if your shop is set up so that
you can leave things out.
If you travel, take something to work
on at the motel. I’ve cut ribs, carved
propellers, and made rubber motors on
business trips. MA
Sources:
NFFS
www.freeflight.org
FFQ
www.freeflightquarterly.com
Edition: Model Aviation - 2009/11
Page Numbers: 131,132,134
Edition: Model Aviation - 2009/11
Page Numbers: 131,132,134
“HOW DO yOur models fly without RC?” That’s
a familiar question for most FF modelers. The short
answer is that the airplanes are designed and adjusted
to fly with no external control input. But how does it
really work?
Designing and adjusting an FF aircraft is a
balancing act. Fortunately, most adjustments are
speed-sensitive. Some, such as rudder, stabilizer, and
wing washin or washout, are more effective the faster
the model is flying.
Wing wash works much like movable ailerons, to control roll.
Washin means a positive incidence at that point on the wing relative
to the wing center, and washout indicates less incidence at that
point.
Other adjustments, including stabilizer tilt, CG location, and
engine thrust offsets, are more effective at slow speeds. By pairing
adjustments based on speed sensitivity, the model will essentially
fly itself.
A rubber-powered model might use downthrust and upstabilizer.
If it increases in speed under power, it will tend to nose
up. If the airplane noses up too steeply and approaches a stall, it will
slow. Then the downthrust will overpower the up-stabilizer and the
aircraft’s nose will drop slightly, preventing a stall. This is a
constant balancing act that is almost imperceptible in a properly
adjusted FF model.
FF airplanes have traditionally been “locked up,” with the flying
surfaces fixed during flight. Starting in the 1950s, movable surfaces
such as rudder (auto rudder, or AR) and stabilizer (variable
incidence tailplane, or VIT) were introduced as means to increase
the performance of Rubber or Gas models. Auto surfaces, controlled
by a clockwork or electronic timer, allow different phases of the
flight to be isolated and dealt with independently.
The high-speed climb would typically be trimmed with less
decalage, to reduce drag and prevent looping. Then the VIT would
move slightly, to increase decalage and improve the glide. Decalage
is the relative difference between wing and stabilizer incidence.
Although the auto surface-equipped model is mechanically more
complicated, adjusting it is simplified.
But many modelers continue to enjoy the challenges of adjusting
and flying a locked-up model without auto surfaces. Some events,
such as Nostalgia Gas and the recently introduced Classic Gas, do
not allow auto surfaces.
At the 2009 Nats, I watched Dan Berry fly his Nelson .36-
powered Marval 560 in CD Classic Gas. I wasn’t the only one
watching. The Marval’s designer, Marvin Mace, was sitting under
the shade of an umbrella, watching every flight.
The Marval was named a Model of the Year in 1993.
“The design evolved from Mark Valerius’s Rum Runner
design,” said Marvin. “The Marval name was used to acknowledge
my friendship with a fellow modeler who helped me get up to speed
after being away from modeling for 30-plus years.”
One hard-to-miss feature on Dan’s version of the Marval was the
large amount of left thrust in the engine.
“I’m guessing about 6°; you can see it from 100 feet away,” said
Locked-up Power models
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Free Flight Quarterly
• Building efficiently
Dan’s Marval is typical of the locked-up models flown in Classic
Power. The 725-square-inch Marvin Mace design uses a Nelson .36
engine.
Left: Dan Berry’s scaled-up Marval
features significant left thrust, to
help with launches in windy
weather. The split dowels attached
to the bottom of the wing assure
wing-fuselage alignment.
Larry Davidson cranks up the O.S. Max III in his scaled-up
Dixielander. The 1950s British design is becoming popular in
Nostalgia Power events.
November 2009 131
11sig5.QXD_00MSTRPG.QXD 9/24/09 3:53 PM Page 131
132 MODEL AVIATION
Dan. “It didn’t start out that way. I’ve
chopped the nose off twice to adjust the
CG.”
All of that left thrust didn’t seem to hurt
the climb; if anything, it helped on launch
consistency.
I asked Marvin about the use of left
thrust on his Marval.
“Normally, we put in about 3° left
thrust,” he said. “It means that when it gets
windy, it will still keep its pattern. If you
don’t have the left thrust, you don’t know
what the airplane will do.”
As with any FF aircraft, the launch is
critical. In wind, it can be the difference
between a max and a crash.
“Launch nearly straight up, about 10°
right of the wind,” said Marvin.
“Left thrust is the Texas cure for flying
in all that wind,” added Dan.
Marvin explained:
“The purpose of the left thrust is to keep
strong wind from capturing the model at low
speed immediately after launch and
throwing it off-pattern. This is especially
important since low-thrustline models with
pylons are launched to the right of the wind
and are very sensitive at low speed to wind
forces blowing against the pylon and the dihedral of the left wing.
“As the model’s speed increases, the effect of the left thrust is
lost, and it has little or no effect on other trim adjustments used on
the model. It is worth noting that 3° of left thrust has worked for me
in winds greater than 20 miles per hour.”
Full-size plans for the Marval are available from the National
Free Flight Society (NFFS). Check the Web site under “Shop” for
ordering information.
Marvin’s follow-on design, the Super Marval 560, was featured
Free Flight Quarterly editor Sergio Montes was at the Nats from Australia, flying Coupe
and visiting with subscribers to the worldwide FF publication.
NFFS vice president and associate editor of Free Flight Quarterly,
David Mills, played host to Sergio on his visit to the US.
in a construction article in the June 2009 MA. The Super Marval,
designed for the AMA Gas event, utilizes timer-actuated auto
surfaces including auto rudder, VIT, and bunt. Bunt is a one-quarter
outside loop, activated by the stabilizer, to transition the model from
the near-vertical climb to glide.
At the Nats, Larry Davidson also flew a locked-up model. For
years, he had flown Russ Hansen’s T-Bird in all Nostalgia Gas
events. As in Classic Gas, only locked-up airplanes are allowed in
Nostalgia. Larry recently switched to George Fuller’s Dixielander
design.
“I have them in every size except 1/2A,” said Larry.
Nostalgia Gas rules allow only designs from the late 1940s
through 1956; aircraft can be scaled up or down to suit various
engine sizes. Larry flew a 550-square-inch version powered by a .29
O.S. Max III. The original Dixielander had a wing area of roughly
350 square inches for a .15-size engine. Covering was his usual
yellow-dyed Polyspan.
“That’s all I use,” said Larry. “It looks like tissue, but it’s a lot
stronger.”
The original Dixielander was noted for being easy to trim.
Larry’s scaled-up version was no exception.
“It’s the only airplane I’ve ever built that didn’t need any
adjustments,” he said. “It uses a lot of washin in the right main panel
and lots of washout in both tips.”
The original Dixielander used built-in adjustments, so it was
locked up the way it needed to be to fly right off the board. The wing
and stabilizer are both set at plus 3°, both wingtips are washed out
2°, and the right main panel is washed in 3°. The stabilizer is set
parallel to the right inboard wing panel, to give right glide turn.
The CG is located roughly at the wing TE. Glide adjustments are
made by shifting the CG slightly—never by shimming the stabilizer.
If necessary, power trim is adjusted by slightly shimming the wing
LE or TE.
Plans for the original 350-square-inch Dixielander are available
through NFFS plans. You can also find more information in the
August 2008 Duration column in MA and in Bob Stalick’s article in
the December 2007 NFFS Digest: Free Flight. Plans are in the
January-February 2008 Digest.
An important thing about locked-up Power models is that what
works for one type doesn’t necessarily work for all types. Both the
Marval and the Dixielander feature pylon-mounted wings with their
engines mounted on their fuselages. Pylon models are typically
flown to the right under power. High-thrustline models, such as the
11sig5.QXD_00MSTRPG.QXD 9/24/09 3:54 PM Page 132
T-Bird, have engines mounted almost in line
with the wings and are usually flown to the
left under power.
For more about trimming locked-up
Power models, see Don DeLoach’s
comprehensive article—“Beginning Free
Flight Power: A Journey”—in the 2004
NFFS Symposium.
Free Flight Quarterly: Sergio Montes, chief
editor of Free Flight Quarterly (FFQ)
magazine, was up from Tasmania to attend
the Nats. He flew in a few events and met
with some of his American subscribers.
FFQ is a worldwide FF publication.
Associate editors include Jean
Wantzenriether of France; Chris Stoddart of
Knoxville, Tennessee; David Mills of
Atlanta, Georgia; and Andrew Longhurst of
England.
Founded in 2001, FFQ offers in-depth
articles about a wide variety of FF topics.
These can range from technical papers about
aerodynamics to how-to pieces for Rubber
Scale. Articles about the history of FF have
included such designs as the Comet Zipper,
Wally Simmers’ Gollywock, and Rubber
Speed. In 2007, FFQ received an award
from the NFFS.
FFQ is available in a printed edition ($38
sent via airmail) or a digital edition ($18
available via download). Previous issues are
available as PDFs for PCs only; the cost is
$15 per year.
Also available are three collections: Bell
Henn’s Rubber Scale plans and articles, a
Coupe d’Hiver (F1G) survey, and “The
Great Gollywock Saga.” You can order
directly from Sergio using PayPal or by
sending a check to Chris Stoddard. More
information is available on the FFQ Web
site.
Building Efficiently: With all the other
demands of daily living, finding time to
build models can be difficult. Following are
a few suggestions to help you make the most
of your time.
• Start with a plan. Decide what model(s)
you would like to build. Research the
availability of kits, plans, supplies, and
accessories you will need to get started.
Make an inventory of materials you have
on hand, and then develop a shopping list.
It’s a good idea to check with mail-order
suppliers about availability, and then order
right away.
• Set up shop. Eugene Verbitsky, Ukrainian
F1C World Champion, once said, “First you
build the factory, then you build the
models.” While you are waiting for all of the
stuff you ordered to come in, take time to
organize your workshop.
Consider building fixtures, to improve
accuracy and speed construction. Rex
Hinson’s article, “Jigs and Fixtures: Don’t
Build Without Them” in the 2001 NFFS
Symposium illustrates a number of easy-tomake
fixtures. In the same Sympo, Aram
Schlosberg’s “Composite Outer Wing
Panels” shows several fixtures for
constructing carbon D-box wings.
Be sure to write exact information and
instructions on each fixture. This is
especially important on that most basic of
fixtures: the rib template. Include the
model’s name, chord size, and airfoil. I also
like to indicate how many ribs I need and
balsa thickness.
To make fixture pieces easy to find amid
workbench clutter, color them with paint or
marker.
• Keep it together. If you have ever visited a
hospital emergency room, you might have
noticed that the tools and supplies used for a
specific procedure are kept together in a
sterile package, ready for instant use. The
same idea can be used in the workshop.
Group all of the materials you need for a
specific task in a labeled container. I have
approximately a dozen boxes, each roughly 2
x 5 x 11 inches, set up for different modeling
“procedures.” One contains a set of taps,
corresponding drill bits, and tap wrenches.
Another box holds my F1B rudderbuilding
fixture, along with related rib
templates, tubular carbon spars, carbon TE
strips, and preselected balsa for ribs and
LEs—in short, everything I need to build a
rudder except glue, razor blades, and
sandpaper.
134 MODEL AVIATION
I also have boxes for small scraps of
thin balsa, thicker balsa (1/8 inch and up),
and plywood. It beats cutting up a full
sheet of balsa for a couple of wing
gussets.
• Set up a production line. Increase
efficiency by building several models at
the same time. The late Walt Rozelle once
told me that he would cut ribs for all of
the models he planned to build that year,
and then assemble wings, then stabilizers,
then fuselages. He covered all of the
airplanes at the same time.
• Make more than one. Instead of making
only the single part you need, consider
making a few extra at the same time.
Years ago, I set up my table saw to
make plywood stabilizer mounts—the
kind with the extra ears in front for
attaching the hold-down rubber bands. It
took only a few minutes more time and
approximately 50¢ worth of plywood to
make a lifetime supply.
When you are cutting ribs, make a few
extras and label them for future repairs.
• Power up. Adding power tools to the
workshop can save time and improve
accuracy. One of my favorites for
modeling is a router table.
I use a flush trim router bit that is
equipped with a ball bearing that is the
same diameter as the bit. I attach a
plywood pattern to a rough-cut piece of
balsa and trim to the exact size and shape
on the router. It’s great for cutting Rubber
model propeller blanks and solid-balsa
glider wings.
• Build with a buddy. Constructing a
model doesn’t have to be a solitary
activity. Consider working with another
modeler to “kit” parts for several aircraft.
This works best if you are building the
same design. Or use the opportunity to
teach or learn a new technique, such as
vacuum-bagging carbon components. And
it doesn’t have to be another FFer.
• Find the time. Try to spend at least a
few minutes in the workshop every day.
Use the time to select a sheet of balsa, cut
a few ribs, or glue in one or two uprights.
Omit one sitcom a night, and you’ll gain
more than 180 hours of building time a
year. It helps if your shop is set up so that
you can leave things out.
If you travel, take something to work
on at the motel. I’ve cut ribs, carved
propellers, and made rubber motors on
business trips. MA
Sources:
NFFS
www.freeflight.org
FFQ
www.freeflightquarterly.com
Edition: Model Aviation - 2009/11
Page Numbers: 131,132,134
“HOW DO yOur models fly without RC?” That’s
a familiar question for most FF modelers. The short
answer is that the airplanes are designed and adjusted
to fly with no external control input. But how does it
really work?
Designing and adjusting an FF aircraft is a
balancing act. Fortunately, most adjustments are
speed-sensitive. Some, such as rudder, stabilizer, and
wing washin or washout, are more effective the faster
the model is flying.
Wing wash works much like movable ailerons, to control roll.
Washin means a positive incidence at that point on the wing relative
to the wing center, and washout indicates less incidence at that
point.
Other adjustments, including stabilizer tilt, CG location, and
engine thrust offsets, are more effective at slow speeds. By pairing
adjustments based on speed sensitivity, the model will essentially
fly itself.
A rubber-powered model might use downthrust and upstabilizer.
If it increases in speed under power, it will tend to nose
up. If the airplane noses up too steeply and approaches a stall, it will
slow. Then the downthrust will overpower the up-stabilizer and the
aircraft’s nose will drop slightly, preventing a stall. This is a
constant balancing act that is almost imperceptible in a properly
adjusted FF model.
FF airplanes have traditionally been “locked up,” with the flying
surfaces fixed during flight. Starting in the 1950s, movable surfaces
such as rudder (auto rudder, or AR) and stabilizer (variable
incidence tailplane, or VIT) were introduced as means to increase
the performance of Rubber or Gas models. Auto surfaces, controlled
by a clockwork or electronic timer, allow different phases of the
flight to be isolated and dealt with independently.
The high-speed climb would typically be trimmed with less
decalage, to reduce drag and prevent looping. Then the VIT would
move slightly, to increase decalage and improve the glide. Decalage
is the relative difference between wing and stabilizer incidence.
Although the auto surface-equipped model is mechanically more
complicated, adjusting it is simplified.
But many modelers continue to enjoy the challenges of adjusting
and flying a locked-up model without auto surfaces. Some events,
such as Nostalgia Gas and the recently introduced Classic Gas, do
not allow auto surfaces.
At the 2009 Nats, I watched Dan Berry fly his Nelson .36-
powered Marval 560 in CD Classic Gas. I wasn’t the only one
watching. The Marval’s designer, Marvin Mace, was sitting under
the shade of an umbrella, watching every flight.
The Marval was named a Model of the Year in 1993.
“The design evolved from Mark Valerius’s Rum Runner
design,” said Marvin. “The Marval name was used to acknowledge
my friendship with a fellow modeler who helped me get up to speed
after being away from modeling for 30-plus years.”
One hard-to-miss feature on Dan’s version of the Marval was the
large amount of left thrust in the engine.
“I’m guessing about 6°; you can see it from 100 feet away,” said
Locked-up Power models
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Free Flight Quarterly
• Building efficiently
Dan’s Marval is typical of the locked-up models flown in Classic
Power. The 725-square-inch Marvin Mace design uses a Nelson .36
engine.
Left: Dan Berry’s scaled-up Marval
features significant left thrust, to
help with launches in windy
weather. The split dowels attached
to the bottom of the wing assure
wing-fuselage alignment.
Larry Davidson cranks up the O.S. Max III in his scaled-up
Dixielander. The 1950s British design is becoming popular in
Nostalgia Power events.
November 2009 131
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132 MODEL AVIATION
Dan. “It didn’t start out that way. I’ve
chopped the nose off twice to adjust the
CG.”
All of that left thrust didn’t seem to hurt
the climb; if anything, it helped on launch
consistency.
I asked Marvin about the use of left
thrust on his Marval.
“Normally, we put in about 3° left
thrust,” he said. “It means that when it gets
windy, it will still keep its pattern. If you
don’t have the left thrust, you don’t know
what the airplane will do.”
As with any FF aircraft, the launch is
critical. In wind, it can be the difference
between a max and a crash.
“Launch nearly straight up, about 10°
right of the wind,” said Marvin.
“Left thrust is the Texas cure for flying
in all that wind,” added Dan.
Marvin explained:
“The purpose of the left thrust is to keep
strong wind from capturing the model at low
speed immediately after launch and
throwing it off-pattern. This is especially
important since low-thrustline models with
pylons are launched to the right of the wind
and are very sensitive at low speed to wind
forces blowing against the pylon and the dihedral of the left wing.
“As the model’s speed increases, the effect of the left thrust is
lost, and it has little or no effect on other trim adjustments used on
the model. It is worth noting that 3° of left thrust has worked for me
in winds greater than 20 miles per hour.”
Full-size plans for the Marval are available from the National
Free Flight Society (NFFS). Check the Web site under “Shop” for
ordering information.
Marvin’s follow-on design, the Super Marval 560, was featured
Free Flight Quarterly editor Sergio Montes was at the Nats from Australia, flying Coupe
and visiting with subscribers to the worldwide FF publication.
NFFS vice president and associate editor of Free Flight Quarterly,
David Mills, played host to Sergio on his visit to the US.
in a construction article in the June 2009 MA. The Super Marval,
designed for the AMA Gas event, utilizes timer-actuated auto
surfaces including auto rudder, VIT, and bunt. Bunt is a one-quarter
outside loop, activated by the stabilizer, to transition the model from
the near-vertical climb to glide.
At the Nats, Larry Davidson also flew a locked-up model. For
years, he had flown Russ Hansen’s T-Bird in all Nostalgia Gas
events. As in Classic Gas, only locked-up airplanes are allowed in
Nostalgia. Larry recently switched to George Fuller’s Dixielander
design.
“I have them in every size except 1/2A,” said Larry.
Nostalgia Gas rules allow only designs from the late 1940s
through 1956; aircraft can be scaled up or down to suit various
engine sizes. Larry flew a 550-square-inch version powered by a .29
O.S. Max III. The original Dixielander had a wing area of roughly
350 square inches for a .15-size engine. Covering was his usual
yellow-dyed Polyspan.
“That’s all I use,” said Larry. “It looks like tissue, but it’s a lot
stronger.”
The original Dixielander was noted for being easy to trim.
Larry’s scaled-up version was no exception.
“It’s the only airplane I’ve ever built that didn’t need any
adjustments,” he said. “It uses a lot of washin in the right main panel
and lots of washout in both tips.”
The original Dixielander used built-in adjustments, so it was
locked up the way it needed to be to fly right off the board. The wing
and stabilizer are both set at plus 3°, both wingtips are washed out
2°, and the right main panel is washed in 3°. The stabilizer is set
parallel to the right inboard wing panel, to give right glide turn.
The CG is located roughly at the wing TE. Glide adjustments are
made by shifting the CG slightly—never by shimming the stabilizer.
If necessary, power trim is adjusted by slightly shimming the wing
LE or TE.
Plans for the original 350-square-inch Dixielander are available
through NFFS plans. You can also find more information in the
August 2008 Duration column in MA and in Bob Stalick’s article in
the December 2007 NFFS Digest: Free Flight. Plans are in the
January-February 2008 Digest.
An important thing about locked-up Power models is that what
works for one type doesn’t necessarily work for all types. Both the
Marval and the Dixielander feature pylon-mounted wings with their
engines mounted on their fuselages. Pylon models are typically
flown to the right under power. High-thrustline models, such as the
11sig5.QXD_00MSTRPG.QXD 9/24/09 3:54 PM Page 132
T-Bird, have engines mounted almost in line
with the wings and are usually flown to the
left under power.
For more about trimming locked-up
Power models, see Don DeLoach’s
comprehensive article—“Beginning Free
Flight Power: A Journey”—in the 2004
NFFS Symposium.
Free Flight Quarterly: Sergio Montes, chief
editor of Free Flight Quarterly (FFQ)
magazine, was up from Tasmania to attend
the Nats. He flew in a few events and met
with some of his American subscribers.
FFQ is a worldwide FF publication.
Associate editors include Jean
Wantzenriether of France; Chris Stoddart of
Knoxville, Tennessee; David Mills of
Atlanta, Georgia; and Andrew Longhurst of
England.
Founded in 2001, FFQ offers in-depth
articles about a wide variety of FF topics.
These can range from technical papers about
aerodynamics to how-to pieces for Rubber
Scale. Articles about the history of FF have
included such designs as the Comet Zipper,
Wally Simmers’ Gollywock, and Rubber
Speed. In 2007, FFQ received an award
from the NFFS.
FFQ is available in a printed edition ($38
sent via airmail) or a digital edition ($18
available via download). Previous issues are
available as PDFs for PCs only; the cost is
$15 per year.
Also available are three collections: Bell
Henn’s Rubber Scale plans and articles, a
Coupe d’Hiver (F1G) survey, and “The
Great Gollywock Saga.” You can order
directly from Sergio using PayPal or by
sending a check to Chris Stoddard. More
information is available on the FFQ Web
site.
Building Efficiently: With all the other
demands of daily living, finding time to
build models can be difficult. Following are
a few suggestions to help you make the most
of your time.
• Start with a plan. Decide what model(s)
you would like to build. Research the
availability of kits, plans, supplies, and
accessories you will need to get started.
Make an inventory of materials you have
on hand, and then develop a shopping list.
It’s a good idea to check with mail-order
suppliers about availability, and then order
right away.
• Set up shop. Eugene Verbitsky, Ukrainian
F1C World Champion, once said, “First you
build the factory, then you build the
models.” While you are waiting for all of the
stuff you ordered to come in, take time to
organize your workshop.
Consider building fixtures, to improve
accuracy and speed construction. Rex
Hinson’s article, “Jigs and Fixtures: Don’t
Build Without Them” in the 2001 NFFS
Symposium illustrates a number of easy-tomake
fixtures. In the same Sympo, Aram
Schlosberg’s “Composite Outer Wing
Panels” shows several fixtures for
constructing carbon D-box wings.
Be sure to write exact information and
instructions on each fixture. This is
especially important on that most basic of
fixtures: the rib template. Include the
model’s name, chord size, and airfoil. I also
like to indicate how many ribs I need and
balsa thickness.
To make fixture pieces easy to find amid
workbench clutter, color them with paint or
marker.
• Keep it together. If you have ever visited a
hospital emergency room, you might have
noticed that the tools and supplies used for a
specific procedure are kept together in a
sterile package, ready for instant use. The
same idea can be used in the workshop.
Group all of the materials you need for a
specific task in a labeled container. I have
approximately a dozen boxes, each roughly 2
x 5 x 11 inches, set up for different modeling
“procedures.” One contains a set of taps,
corresponding drill bits, and tap wrenches.
Another box holds my F1B rudderbuilding
fixture, along with related rib
templates, tubular carbon spars, carbon TE
strips, and preselected balsa for ribs and
LEs—in short, everything I need to build a
rudder except glue, razor blades, and
sandpaper.
134 MODEL AVIATION
I also have boxes for small scraps of
thin balsa, thicker balsa (1/8 inch and up),
and plywood. It beats cutting up a full
sheet of balsa for a couple of wing
gussets.
• Set up a production line. Increase
efficiency by building several models at
the same time. The late Walt Rozelle once
told me that he would cut ribs for all of
the models he planned to build that year,
and then assemble wings, then stabilizers,
then fuselages. He covered all of the
airplanes at the same time.
• Make more than one. Instead of making
only the single part you need, consider
making a few extra at the same time.
Years ago, I set up my table saw to
make plywood stabilizer mounts—the
kind with the extra ears in front for
attaching the hold-down rubber bands. It
took only a few minutes more time and
approximately 50¢ worth of plywood to
make a lifetime supply.
When you are cutting ribs, make a few
extras and label them for future repairs.
• Power up. Adding power tools to the
workshop can save time and improve
accuracy. One of my favorites for
modeling is a router table.
I use a flush trim router bit that is
equipped with a ball bearing that is the
same diameter as the bit. I attach a
plywood pattern to a rough-cut piece of
balsa and trim to the exact size and shape
on the router. It’s great for cutting Rubber
model propeller blanks and solid-balsa
glider wings.
• Build with a buddy. Constructing a
model doesn’t have to be a solitary
activity. Consider working with another
modeler to “kit” parts for several aircraft.
This works best if you are building the
same design. Or use the opportunity to
teach or learn a new technique, such as
vacuum-bagging carbon components. And
it doesn’t have to be another FFer.
• Find the time. Try to spend at least a
few minutes in the workshop every day.
Use the time to select a sheet of balsa, cut
a few ribs, or glue in one or two uprights.
Omit one sitcom a night, and you’ll gain
more than 180 hours of building time a
year. It helps if your shop is set up so that
you can leave things out.
If you travel, take something to work
on at the motel. I’ve cut ribs, carved
propellers, and made rubber motors on
business trips. MA
Sources:
NFFS
www.freeflight.org
FFQ
www.freeflightquarterly.com