FREE FLIGHT SPORT - 2003/06

132 MODEL AVIATION
TRIMMING A FREE Flight model is like working a jigsaw
puzzle. Well, it’s sort of like working a jigsaw puzzle if you stretch
the analogy almost as far as it can go and still maintain some
semblance of a cogent line of reasoning.
When is a low wing not a low wing? When it has lots of dihedral.
The Black Bullet (BB) has lots of dihedral. It can be trimmed just
like a high-wing cabin model. Before the first low-powered (30-50
hand winds) test glides, I made sure that the model balanced at the
wing spar. Then it was checked for warps.
Sometime between the last coat of nitrate and test-flying day, the
BB developed 1⁄8 inch of washin in the right wing. Everything else
looked straight. For grins I tried a low-powered test glide. As I
suspected, the model was pushed into a gentle left turn by the excess
right washin.
I misted the right wing with water and pinned it to the building
Gene Smith, 1401 N. Husband St., Stillwater OK 74075; E-mail: [email protected]
FREE FLIGHT SPORT
Yes, the Black Bullet really flies. Is this fun or what? The flight
pattern is to the right under power and in the glide.
Proud designer George Perryman with Mini-Maxer. Atlanta Thermal
Thumbers fly them in a one-design contest six times a year.
Pliers are specially made for bending loops in wire. Shims and
bubble level are to check incidence on small models.
Turn the model upside down. Support and shim the model until
the bubble is centered while on the bottom of the wing.
June 2003 133
board with a washout shim. When it was dry, I checked the right
wing and found that it had a trace of washin remaining. I could live
with that. The next low-powered test glide was essentially flat and
straight. It was time to head for the flying field.
The first powered flights were made with 200 winds, working up
to 500. I used P-30 motors (two loops of 3⁄16 rubber weighing 10
grams) as the power source. All flights were essentially safe, with
the model flying straight ahead. I placed a 1⁄16-inch balsa shim on the
left side of the nose block for right thrust and put 700 winds in the
motor. The result was a nice right-climbing circle. The glide
wandered hither and yon, sometimes a little right and sometimes a
little left.
I wanted to establish a right turn in the glide. The stabilizer could
have been tilted to the left, but that would have messed up the DT
(dethermalizer) key and would have compromised the airplane’s
“good looks.” Some clay on the right wingtip could induce a right
turn, but it adds weight and has always been a “trimming method of
last resort” for me.
Because of the large amount of dihedral, I figured the rudder
could be used for the right turn without causing a problem. Very
little rudder extends beyond the narrow slot in the elevator, but I
managed to put approximately 1⁄4 inch of right tab in the last 1⁄2 inch
of the rudder. This did the trick: right turn under power, nice right
turn in the glide.
Why did I decide to use old P-30 motors in the BB? Its weight
without the rubber motor was 44 grams. That’s what a somewhat
Place 3° shim, narrow end to the front, on the stabilizer. The
bubble should center or be slightly forward of center.
This was one of a series of 35¢ models, all with 25-inch
wingspans: Major, Bantam, Windsor, Hornet, Royal, and Ranger.
134 MODEL AVIATION
portly P-30 weighs, so I figured that if a 10-
gram motor was good enough for a P-30, it
was good enough for a BB.
I could have used a heavier motor, but
that would have required more nose weight,
which gets to be a vicious cycle. The added
weight of the heavier motor and nose weight
increase the wing loading. Therefore, the
model has to fly faster and at a more
positive angle of attack to generate more
lift. That creates more drag. Warps become
more effective at the higher airspeed,
causing more problems with trimming. I
shudder just thinking about it. The 10-gram
motor will have to do.
I have always wanted to build a Mini-
Maxer. The distinctive swept flying surfaces
and stabilizer dihedral set the Mini-Maxer
apart from your everyday sport Free Flight
model. The place to which it is set apart is
wherever you put all of the late George
Perryman’s designs.
All of George’s models have a variation
of this distinctive tailplane, and they all
seem to fly well. Perhaps it has something
to do with George’s success designing
models and full-scale aircraft. Perhaps it is
because George was such a true gentleman
that his designs don’t dare do anything but
behave politely.
Roughly 10 years ago I bought a Sig kit
of the Mini-Maxer. Since then I have
opened the box to start construction half a
dozen times, only to pick up the die-cut kit
wood, estimate its weight, and return the
contents to the box and the box to the shelf.
Deciding it was now or never, I made a
copy of the kit wood and cut my own parts
from light balsa. Any model airplane worth
building is worth building light. The time or
money you might save by using heavy kit
wood is not worth the frustration of trying
to get a pig to fly. No offense to the Air Hog
lovers in the crowd.
In two months: Adventures in trimming
the Mini-Maxer. Hint: The center of gravity
(CG) worked best for me 23⁄4 inches behind
the wing’s leading edge—not where it is
shown on the plans. Use an 8-inch-diameter
propeller for better performance.
When I was deciding what model I
wanted to build for this column, I checked
to make sure the kit was available to those
who might be inspired to try the airplane.
Penn Valley Hobby Center has not only the
Mini-Maxer, but most, if not all, of the
currently available kits for rubber-powered
and gas-engine-powered Free Flights.
Check out www.pennvalleyhobby
center.com or send $2 for a catalog to Penn
Valley Hobby Center, 837 W. Main St.,
Lansdale PA 19446.
You’ve Got to Have an Angle: If your
model is going to fly, there has to be an
angle between the bottom of the wing and
the stabilizer. As I understand it, the term
“decalage” refers to the angle between the
chord lines of a biplane’s wings. However,
many people use the term to refer to the
angular difference between the wing chord
and stabilizer, and that is how I will use it. If
you want to pursue the definition further,
look it up in a book about aerodynamics.
That angle is typically 3° or 4°. If you
think all of the plans you see in the
magazines and in kits have that angle drawn
correctly, there is a bridge in Brooklyn I
would like to sell to you.
When I resumed building rubberpowered
models, one of my first projects
was a cute little No-Cal built from plans in a
magazine. It was a low-winger in pre-World
War II Army Air Corps colors. I built it
according to the plans and did a nice job,
considering it was my first such effort since
the seventh grade.
When it was time for the first test flight,
doink—a nose dive! I gave it another try,
and doink! To make a long story shorter, I
finally realized that the poor little model had
no decalage. Few things are so sad as a Free
Flight model with no decalage. I was
unhappy because I had no Tan II rubber
until I met a model that had no decalage,
then I was really unhappy.
The stabilizer was on the bottom of the
fuselage, and it took roughly 1⁄4 inch of
shims between the fuselage and the leading
edge of the stabilizer to get the model to fly.
The model flew great with the proper
decalage. The plans showed no decalage.
So always check the decalage shown on
the plans and double-check the decalage on
the finished model before the first test flight.
June 2003 135
136 MODEL AVIATION
There are some neat commercial products
available for checking Radio Control (RC)
models’ decalage, but they are too heavy
for most rubber-powered aircraft.
I have seen plans for a slick, build-ityourself,
miniature decalage checker; I may
build one someday, but for now I use a
simple method that requires little in the
way of construction or materials. You will
need the following.
Ernst Products makes a set of plastic
wedges that RC modelers use to shim
motor mounts for downthrust or sidethrust.
Each pack contains three shims: one each
1°, 2°, and 3°. The shims come in three
sizes; mine are 21⁄2 inches square. Purchase
a bubble line level at a building center and
glue it to a small balsa base.
Assemble the model, turn it upside
down, and place the bubble level on the
wing. Support the tail, and shim it until the
bubble is level on the bottom of the wing.
Put the 3° wedge on the bottom of the
stabilizer with the thick end of the wedge to
the rear. Move the level to the wedge on
the stabilizer. The bubble should be near
level. If the decalage is off, shim the front
or rear of the stabilizer until you have it
close.
This is a good starting point for those
first test glides. If the model’s wing has no
upsweep to the leading edge and a small
stabilizer, it may require more negative in
the stabilizer. If your local hobby shop
can’t get the Ernst shims, try Sheldon’s
hobbies at www.sheldonshobbies.com.
I Think I’m in Love: What kind of pliers
do you use to bend loops in music wire?
Round-nose, of course. I have a relatively
inexpensive pair of round-nose pliers I
have been using in my shop for the last 10
or so years. After those years of use and
abuse they have lost some of their temper,
and it has become a contest between which
will bend first: the pliers or the wire.
I saw a pair of pliers in a catalog with
fish-tackle-making supplies. They had one
jaw that was round, and the other was
concave. They cost $28.99, but I took the
plunge and am really happy. These pliers
make bending loops a breeze. Mine are
www.modelaircraft.org
June 2003 137
made from stainless steel and came from
Cabelas (item HN-31-4024); call (800)
237-4444.
Similar stainless-steel pliers are
available in two sizes at less expense from
Micro-Mark tools at (800) 225-1066. The
item numbers are 14483 and 14484; they
are $10.95 apiece, but both pairs are
available for $18.95.
The Scientific Major by Karl Gies was
one of a series of 35¢ models with 25-inch
wingspans. The Major, Bantam, and
Ranger kits are available from Penn
Valley Hobby Center (at 21st-century
prices); they are good-looking models.
Karl carved an 8-inch-diameter propeller
with a power-to-drag ratio of 1.5. He used
the Major as a guinea pig for applying
Japanese tissue over Mylar.
Karl used contact cement thinned with
Methyl Ethyl Ketone (MEK) to adhere the
Mylar to the framework. Al Brush told
Karl that Velcro cement thinned 2:1 with
MEK works even better.
Let the cement get pretty dry, then use
a trim iron to adhere and reposition the
Mylar. Wet the tissue, lay it on the Mylar
surface, position it, then brush thinned
nitrate dope over it. Karl learned that if he
used a UHU purple glue stick on the
edges of the Mylar and let it dry, he could
put the wet tissue over it, apply thinner,
and it would adhere the tissue to the
Mylar. Karl added:
“I have a building tip for other
modelers that probably is not original to
me. When it came to the windows I cut
out that area of tissue/Mylar, then went
around the outside with the UHU glue, let
it get fairly dry, and laid the Mylar on a
thin cardboard pattern to cut the Mylar to
shape.
After positioning the Mylar and
pulling out the wrinkles, go over it with
the trim iron to activate the glue stick.
Gently shrink the window areas with the
iron and the result is perfect windows that
are very light. Cut tissue trim to go over
the uprights in the cabin area and attach it
with glue stick.” MA
Visit the AMA Education Committee
Web site at www.buildandfly.com.

132 MODEL AVIATION
TRIMMING A FREE Flight model is like working a jigsaw
puzzle. Well, it’s sort of like working a jigsaw puzzle if you stretch
the analogy almost as far as it can go and still maintain some
semblance of a cogent line of reasoning.
When is a low wing not a low wing? When it has lots of dihedral.
The Black Bullet (BB) has lots of dihedral. It can be trimmed just
like a high-wing cabin model. Before the first low-powered (30-50
hand winds) test glides, I made sure that the model balanced at the
wing spar. Then it was checked for warps.
Sometime between the last coat of nitrate and test-flying day, the
BB developed 1⁄8 inch of washin in the right wing. Everything else
looked straight. For grins I tried a low-powered test glide. As I
suspected, the model was pushed into a gentle left turn by the excess
right washin.
I misted the right wing with water and pinned it to the building
Gene Smith, 1401 N. Husband St., Stillwater OK 74075; E-mail: [email protected]
FREE FLIGHT SPORT
Yes, the Black Bullet really flies. Is this fun or what? The flight
pattern is to the right under power and in the glide.
Proud designer George Perryman with Mini-Maxer. Atlanta Thermal
Thumbers fly them in a one-design contest six times a year.
Pliers are specially made for bending loops in wire. Shims and
bubble level are to check incidence on small models.
Turn the model upside down. Support and shim the model until
the bubble is centered while on the bottom of the wing.
June 2003 133
board with a washout shim. When it was dry, I checked the right
wing and found that it had a trace of washin remaining. I could live
with that. The next low-powered test glide was essentially flat and
straight. It was time to head for the flying field.
The first powered flights were made with 200 winds, working up
to 500. I used P-30 motors (two loops of 3⁄16 rubber weighing 10
grams) as the power source. All flights were essentially safe, with
the model flying straight ahead. I placed a 1⁄16-inch balsa shim on the
left side of the nose block for right thrust and put 700 winds in the
motor. The result was a nice right-climbing circle. The glide
wandered hither and yon, sometimes a little right and sometimes a
little left.
I wanted to establish a right turn in the glide. The stabilizer could
have been tilted to the left, but that would have messed up the DT
(dethermalizer) key and would have compromised the airplane’s
“good looks.” Some clay on the right wingtip could induce a right
turn, but it adds weight and has always been a “trimming method of
last resort” for me.
Because of the large amount of dihedral, I figured the rudder
could be used for the right turn without causing a problem. Very
little rudder extends beyond the narrow slot in the elevator, but I
managed to put approximately 1⁄4 inch of right tab in the last 1⁄2 inch
of the rudder. This did the trick: right turn under power, nice right
turn in the glide.
Why did I decide to use old P-30 motors in the BB? Its weight
without the rubber motor was 44 grams. That’s what a somewhat
Place 3° shim, narrow end to the front, on the stabilizer. The
bubble should center or be slightly forward of center.
This was one of a series of 35¢ models, all with 25-inch
wingspans: Major, Bantam, Windsor, Hornet, Royal, and Ranger.
134 MODEL AVIATION
portly P-30 weighs, so I figured that if a 10-
gram motor was good enough for a P-30, it
was good enough for a BB.
I could have used a heavier motor, but
that would have required more nose weight,
which gets to be a vicious cycle. The added
weight of the heavier motor and nose weight
increase the wing loading. Therefore, the
model has to fly faster and at a more
positive angle of attack to generate more
lift. That creates more drag. Warps become
more effective at the higher airspeed,
causing more problems with trimming. I
shudder just thinking about it. The 10-gram
motor will have to do.
I have always wanted to build a Mini-
Maxer. The distinctive swept flying surfaces
and stabilizer dihedral set the Mini-Maxer
apart from your everyday sport Free Flight
model. The place to which it is set apart is
wherever you put all of the late George
Perryman’s designs.
All of George’s models have a variation
of this distinctive tailplane, and they all
seem to fly well. Perhaps it has something
to do with George’s success designing
models and full-scale aircraft. Perhaps it is
because George was such a true gentleman
that his designs don’t dare do anything but
behave politely.
Roughly 10 years ago I bought a Sig kit
of the Mini-Maxer. Since then I have
opened the box to start construction half a
dozen times, only to pick up the die-cut kit
wood, estimate its weight, and return the
contents to the box and the box to the shelf.
Deciding it was now or never, I made a
copy of the kit wood and cut my own parts
from light balsa. Any model airplane worth
building is worth building light. The time or
money you might save by using heavy kit
wood is not worth the frustration of trying
to get a pig to fly. No offense to the Air Hog
lovers in the crowd.
In two months: Adventures in trimming
the Mini-Maxer. Hint: The center of gravity
(CG) worked best for me 23⁄4 inches behind
the wing’s leading edge—not where it is
shown on the plans. Use an 8-inch-diameter
propeller for better performance.
When I was deciding what model I
wanted to build for this column, I checked
to make sure the kit was available to those
who might be inspired to try the airplane.
Penn Valley Hobby Center has not only the
Mini-Maxer, but most, if not all, of the
currently available kits for rubber-powered
and gas-engine-powered Free Flights.
Check out www.pennvalleyhobby
center.com or send $2 for a catalog to Penn
Valley Hobby Center, 837 W. Main St.,
Lansdale PA 19446.
You’ve Got to Have an Angle: If your
model is going to fly, there has to be an
angle between the bottom of the wing and
the stabilizer. As I understand it, the term
“decalage” refers to the angle between the
chord lines of a biplane’s wings. However,
many people use the term to refer to the
angular difference between the wing chord
and stabilizer, and that is how I will use it. If
you want to pursue the definition further,
look it up in a book about aerodynamics.
That angle is typically 3° or 4°. If you
think all of the plans you see in the
magazines and in kits have that angle drawn
correctly, there is a bridge in Brooklyn I
would like to sell to you.
When I resumed building rubberpowered
models, one of my first projects
was a cute little No-Cal built from plans in a
magazine. It was a low-winger in pre-World
War II Army Air Corps colors. I built it
according to the plans and did a nice job,
considering it was my first such effort since
the seventh grade.
When it was time for the first test flight,
doink—a nose dive! I gave it another try,
and doink! To make a long story shorter, I
finally realized that the poor little model had
no decalage. Few things are so sad as a Free
Flight model with no decalage. I was
unhappy because I had no Tan II rubber
until I met a model that had no decalage,
then I was really unhappy.
The stabilizer was on the bottom of the
fuselage, and it took roughly 1⁄4 inch of
shims between the fuselage and the leading
edge of the stabilizer to get the model to fly.
The model flew great with the proper
decalage. The plans showed no decalage.
So always check the decalage shown on
the plans and double-check the decalage on
the finished model before the first test flight.
June 2003 135
136 MODEL AVIATION
There are some neat commercial products
available for checking Radio Control (RC)
models’ decalage, but they are too heavy
for most rubber-powered aircraft.
I have seen plans for a slick, build-ityourself,
miniature decalage checker; I may
build one someday, but for now I use a
simple method that requires little in the
way of construction or materials. You will
need the following.
Ernst Products makes a set of plastic
wedges that RC modelers use to shim
motor mounts for downthrust or sidethrust.
Each pack contains three shims: one each
1°, 2°, and 3°. The shims come in three
sizes; mine are 21⁄2 inches square. Purchase
a bubble line level at a building center and
glue it to a small balsa base.
Assemble the model, turn it upside
down, and place the bubble level on the
wing. Support the tail, and shim it until the
bubble is level on the bottom of the wing.
Put the 3° wedge on the bottom of the
stabilizer with the thick end of the wedge to
the rear. Move the level to the wedge on
the stabilizer. The bubble should be near
level. If the decalage is off, shim the front
or rear of the stabilizer until you have it
close.
This is a good starting point for those
first test glides. If the model’s wing has no
upsweep to the leading edge and a small
stabilizer, it may require more negative in
the stabilizer. If your local hobby shop
can’t get the Ernst shims, try Sheldon’s
hobbies at www.sheldonshobbies.com.
I Think I’m in Love: What kind of pliers
do you use to bend loops in music wire?
Round-nose, of course. I have a relatively
inexpensive pair of round-nose pliers I
have been using in my shop for the last 10
or so years. After those years of use and
abuse they have lost some of their temper,
and it has become a contest between which
will bend first: the pliers or the wire.
I saw a pair of pliers in a catalog with
fish-tackle-making supplies. They had one
jaw that was round, and the other was
concave. They cost $28.99, but I took the
plunge and am really happy. These pliers
make bending loops a breeze. Mine are
www.modelaircraft.org
June 2003 137
made from stainless steel and came from
Cabelas (item HN-31-4024); call (800)
237-4444.
Similar stainless-steel pliers are
available in two sizes at less expense from
Micro-Mark tools at (800) 225-1066. The
item numbers are 14483 and 14484; they
are $10.95 apiece, but both pairs are
available for $18.95.
The Scientific Major by Karl Gies was
one of a series of 35¢ models with 25-inch
wingspans. The Major, Bantam, and
Ranger kits are available from Penn
Valley Hobby Center (at 21st-century
prices); they are good-looking models.
Karl carved an 8-inch-diameter propeller
with a power-to-drag ratio of 1.5. He used
the Major as a guinea pig for applying
Japanese tissue over Mylar.
Karl used contact cement thinned with
Methyl Ethyl Ketone (MEK) to adhere the
Mylar to the framework. Al Brush told
Karl that Velcro cement thinned 2:1 with
MEK works even better.
Let the cement get pretty dry, then use
a trim iron to adhere and reposition the
Mylar. Wet the tissue, lay it on the Mylar
surface, position it, then brush thinned
nitrate dope over it. Karl learned that if he
used a UHU purple glue stick on the
edges of the Mylar and let it dry, he could
put the wet tissue over it, apply thinner,
and it would adhere the tissue to the
Mylar. Karl added:
“I have a building tip for other
modelers that probably is not original to
me. When it came to the windows I cut
out that area of tissue/Mylar, then went
around the outside with the UHU glue, let
it get fairly dry, and laid the Mylar on a
thin cardboard pattern to cut the Mylar to
shape.
After positioning the Mylar and
pulling out the wrinkles, go over it with
the trim iron to activate the glue stick.
Gently shrink the window areas with the
iron and the result is perfect windows that
are very light. Cut tissue trim to go over
the uprights in the cabin area and attach it
with glue stick.” MA
Visit the AMA Education Committee
Web site at www.buildandfly.com.