Little Fast - 2010/06

26 MODEL AVIATION
A generous wing area and thick airfoil make
this model easy-flying and aerobatically
capable. The tail-dragger landing gear setup
with 3-inch wheels makes grass-flying-field
handling simple.
AGAIN, I FOUND a reason/excuse to
build a new model. A Magnum .70 fourstroke
that I had bought for another
project didn’t work out, so it was
available.
The engine was broken in and had
been flown a few times, with good
performance. I figured that a .46 twostroke-
size airframe for aerobatics,
sport, and fun would be a good project.
I know; a bunch of ARFs on the
market would work fine for this project.
But regardless of the time, work, and
money involved, I like to build my
aircraft from scratch. I like to spend
time in the workshop, making sawdust
and wood chips.
If you don’t like to build, ARFs are
great. However, I consider the workshop
time a good part of this hobby.
I laid out a barn-door wing, which
had a 52-inch span and 14-inch chord,
for approximately 700 square inches of
area. I like a nice, thick 18% fully
symmetrical airfoil.
For easy, fast building, it’s tough to
beat a foam-core wing. To make it even
simpler, I employed no balsa sheeting
on this foam core. Good top and bottom
spars, which provide plenty of strength;
fiberglass cloth and epoxy around the
center; and a low-temperature, iron-on
covering are all that are needed.
Hey, CL Combat modelers have been
doing wings this way for years. I’ve
done it before on similar RC airplanes
and it works fine.
If you don’t like the thought of an
unsheeted foam wing, make the foamcutting
templates slightly smaller and
sheet the wing with balsa. Or cut a
bunch of balsa ribs and fashion a builtup
wing. When you’re building from
scratch, you can make it any way you
like.
I used foam blocks on the wingtips,
sanding the material to shape rather than
just capping the end of the core with
light plywood. It would be less work to
merely cut the cores a few inches longer
and cap the ends, if you like that
appearance.
The fuselage is 49 inches long
overall, featuring typical construction:
balsa sides and plywood doublers.
Rather than look for a suitable plastic
canopy, I laid out a side view I liked,
slanted the top fuselage sheeting, and
built in the canopy area. This method is
easy and strong.
I prefer a tail-dragger gear setup for
use on the grass fields from which I fly.
Tricycle gear can be troublesome when
the grass is a bit high.
I didn’t try for extremely light
weight. If you want to, you can cut holes
in the plywood doublers and fuselage
sides.
After a quick iron-on finishing job, I
had a new model to fly. This design is
not way different; there are no new
aerodynamics or claims of fantastic
performance. But it is easy to build and
fly, performs decently, is rugged, and I
like the appearance.
Are you interested? I’ll zip through
the construction procedure.
CONSTRUCTION
There are two ways you can go;
either cut all the parts at once to make a
kit or cut the parts you need as you
progress in building the airplane. Both
techniques work fine. On this version, I
completed the wing before I even started
the fuselage.
Cut the plans, or a copy of the plans,
for the parts templates. I drew around
the paper templates with a ballpoint pen
on the balsa or plywood and cut the
pieces with a band saw.
Wing: With my crude-but-it-works hot-
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:13 AM Page 26
June 2010 27
59
79
The author looks pleased with this design. He likes its
four-stroke engine, small size, and, best of all, flying
characteristics. It’s a cinch to build too; turn the page.
by Dick Sarpolus
Fun with
a 40-size
airframe
and foam
parts
06sig1.QXD_00MSTRPG.QXD 4/22/10 1:43 PM Page 27
Root ends of the two wing panels, showing the center plywood rib
and holes through the foam cores for aileron servo cables. The
plywood dihedral brace is used to support the wing joint.
The wingtip has its foam blocks glued in place on the balsa parts and
has been shaped with a sanding block. The bare foam wing cores are
covered with a low-temperature iron-on film.
The basic fuselage structure begins with balsa sides and plywood
doublers, joined by the first four plywood bulkheads. The next job is
to pull the tail together straight.
A Magnum .70 four-stroke engine is located on a molded composite
radial mount. The hole in the cowl side provides access for the
needle valve and choke lever.
Photos by the author
16
June 2010 29
Type: 40-size RC sport aerobatic
Skill level: Novice builder, intermediate pilot
Wingspan: 52 inches
Wing area: 725
square inches
Airfoil: Fully symmetrical, 18% thick
Length: 49 inches
Weight: 5.75 pounds
Engine: .40-.52 two-stroke, .70-.82 four-stroke glow
Construction: Conventional built-up balsa and plywood, foam-core wing
Covering/finish: Hangar 9 UltraCote used
Radio: Four channels minimum, five standard servos
Other: 10-ounce fuel tank, aluminum landing gear, 3-inch wheels, 21/4-inch spinner
With a wing area of approximately 700
square inches, a .40-.45 two-stroke glow
engine or equivalent does well.
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:24 AM Page 29
Foam wing cores have top and bottom spars for strength and are not covered with
balsa; it’s unnecessary. Low-temperature iron-on film does the job.
The wing is held on with two 1/4-20 nylon bolts. The aluminum landing gear is secured
with three 1/4-20 nylon bolts. Cream and red UltraCote provide good contrast.
wire foam-cutting setup for such a wing, I
cut the core and trimmed off the TE. Then,
with a separate template, I cut the spar
notches and the LE notch.
If you don’t cut your own foam, Phil
Cartier at The Corehouse has a computercontrolled
setup to do this wing section.
And Bob Hunt at Robin’s View
Productions does a great job on any foamcutting
requirement. You can also ask the
AMA Plans Service if it will sell you a set
of cores when you order the plans. There
are many options when you build.
With your cut foam cores, add the slot
between the top and bottom spars at the
middle for the plywood joiner. Join the
wings flat or at a dihedral angle you prefer.
Many builders like a flat wing; on a lowwing
airframe such as this, I prefer a few
degrees of dihedral.
Oh, and make the hole for aileron servo
cables in the foam cores before you join
them. I use a piece of 1/4-inch music wire
with a collar on the end. I heat it with a
torch and then push it through the foam
from the root to the aileron servo cutout.
Epoxy the top and bottom spars into the
cores, and epoxy the plywood joiner into
one of the wing panels. Epoxy the center
plywood rib in place—it holds the wing
mounting tab—and epoxy the two wing
panels together.
I use a light-plywood tip rib to tie the
upper and lower spars together at the tips. I
epoxy heavy fiberglass cloth around the
wing center-section and use wood filler
blocks to support the two wing bolt
mounting holes.
On the top and bottom of the balsa
wingtips, I glued foam blocks in place and
cut and sanded them to shape for covering.
If those wingtips seem like too much
work, get the cores a couple inches longer
and use light-plywood caps on the tips of
the foam cores.
I hinged in place the balsa-strip
ailerons as usual. I made aileron servo
mounting plates from 1/4 plywood,
epoxying them into the foam, flush with
the surface.
Fuselage: This begins with epoxying the
plywood doublers to the balsa sides and
the wing-saddle pieces and the stabilizerarea
doublers. I’m careful to make a right
and a left side, because I once fabricated
two left sides.
With one fuselage side flat on the
building bench, add the first four
bulkheads, perpendicular to the side. Then
install the other side. This is fairly easy to
keep aligned, because the two sides are
parallel from the nose to the TE position.
With that completed, pull in the tail
ends of the sides and add the rear-section
bulkheads. Now add the upper fuselage
sides; there’s a front section and a rear
section. Sand their lower edges to a slight
bevel so that they sit flush on the top edge
of the fuselage sides. Sand their top edges
flush with the tops of the bulkheads, and
then add and round the top pieces.
To be sure that the firewall is secure, I
install two small screws on each side,
through the plywood doublers into the
edges of the firewall. The plywood wing
bolt mount plate is added to the fuselage,
along with the plywood landing gear
mounting plate and its reinforcements.
At this point, fit the fuselage to the
wing. Where the front plywood wing
mounting tab goes through the second
bulkhead, the lower edge of the opening in
that bulkhead can be sanded or shimmed
so that the wing fits tightly in place.
With the wing in place on the fuselage,
drill the two wing bolt mounting holes
through the wing TE area and into the
fuselage plate, and tap the plywood for the
1/4-20 nylon bolts.
Use a nylon engine mount bolted to the
firewall, and add the balsa sides and
bottom pieces to the front end of the
fuselage. If you want to do more work,
you could use balsa blocks faired to blend
smoothly with a spinner mounted on the
engine. I didn’t think that was necessary.
Tail Surfaces: The vertical fin and the
stabilizer are 1/4 balsa, and I use firm to
hard stock to prevent vibration. The
control surfaces, rudder, and elevators are
built from 1/4 x 1/2 and 1/4 square stock.
The elevator halves are joined by a piece
of 5/32-inch-diameter music wire epoxied
in place.
30 MODEL AVIATION
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:29 AM Page 30
With the fuselage bolted onto the wing,
I insert the stabilizer and epoxy it in place,
lining it up level with the wing. I insert
the vertical fin and glue it in place, lining
it up perpendicular with the stabilizer.
I like either fiberglass-tube pushrods or
Sullivan’s nylon-tube setup with the
carbon-fiber inner rods, and I use all 4-40
hardware. Cut holes in the rear bulkheads,
as required. When the rudder and elevator
linkages are installed, you can install the
bottom planking.
Finishing: I used UltraCote for the
covering; it’s one of the easier films to
apply. With the equipment located as
shown on the plans, the Little Fast
balanced as shown and it works for me.
I’ve always thought that the balance
point and control-surface movements
should suit the pilot. There’s a gigantic
variation in the way individuals like their
aircraft to “feel,” but today’s radios make
it easy to set up a model to suit you.
I’m happy with the way the Magnum .70
four-stroke engine performs and am
pleased with this latest building project.
Hey! Make some sawdust and wood
chips! MA
Dick Sarpolus
[email protected]
Sources:
Magnum engines
(714) 963-0329
http://magnum.globalhobby.com
The Corehouse
(717) 566-3810
http://home.earthlink.net/~philcartier/
Robin’s View Productions
(610) 746-0106
Sullivan Products
(410) 732-3500
www.sullivanproducts.com
Hangar 9 UltraCote
(800) 338-4639
www.hangar-9.com

26 MODEL AVIATION
A generous wing area and thick airfoil make
this model easy-flying and aerobatically
capable. The tail-dragger landing gear setup
with 3-inch wheels makes grass-flying-field
handling simple.
AGAIN, I FOUND a reason/excuse to
build a new model. A Magnum .70 fourstroke
that I had bought for another
project didn’t work out, so it was
available.
The engine was broken in and had
been flown a few times, with good
performance. I figured that a .46 twostroke-
size airframe for aerobatics,
sport, and fun would be a good project.
I know; a bunch of ARFs on the
market would work fine for this project.
But regardless of the time, work, and
money involved, I like to build my
aircraft from scratch. I like to spend
time in the workshop, making sawdust
and wood chips.
If you don’t like to build, ARFs are
great. However, I consider the workshop
time a good part of this hobby.
I laid out a barn-door wing, which
had a 52-inch span and 14-inch chord,
for approximately 700 square inches of
area. I like a nice, thick 18% fully
symmetrical airfoil.
For easy, fast building, it’s tough to
beat a foam-core wing. To make it even
simpler, I employed no balsa sheeting
on this foam core. Good top and bottom
spars, which provide plenty of strength;
fiberglass cloth and epoxy around the
center; and a low-temperature, iron-on
covering are all that are needed.
Hey, CL Combat modelers have been
doing wings this way for years. I’ve
done it before on similar RC airplanes
and it works fine.
If you don’t like the thought of an
unsheeted foam wing, make the foamcutting
templates slightly smaller and
sheet the wing with balsa. Or cut a
bunch of balsa ribs and fashion a builtup
wing. When you’re building from
scratch, you can make it any way you
like.
I used foam blocks on the wingtips,
sanding the material to shape rather than
just capping the end of the core with
light plywood. It would be less work to
merely cut the cores a few inches longer
and cap the ends, if you like that
appearance.
The fuselage is 49 inches long
overall, featuring typical construction:
balsa sides and plywood doublers.
Rather than look for a suitable plastic
canopy, I laid out a side view I liked,
slanted the top fuselage sheeting, and
built in the canopy area. This method is
easy and strong.
I prefer a tail-dragger gear setup for
use on the grass fields from which I fly.
Tricycle gear can be troublesome when
the grass is a bit high.
I didn’t try for extremely light
weight. If you want to, you can cut holes
in the plywood doublers and fuselage
sides.
After a quick iron-on finishing job, I
had a new model to fly. This design is
not way different; there are no new
aerodynamics or claims of fantastic
performance. But it is easy to build and
fly, performs decently, is rugged, and I
like the appearance.
Are you interested? I’ll zip through
the construction procedure.
CONSTRUCTION
There are two ways you can go;
either cut all the parts at once to make a
kit or cut the parts you need as you
progress in building the airplane. Both
techniques work fine. On this version, I
completed the wing before I even started
the fuselage.
Cut the plans, or a copy of the plans,
for the parts templates. I drew around
the paper templates with a ballpoint pen
on the balsa or plywood and cut the
pieces with a band saw.
Wing: With my crude-but-it-works hot-
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:13 AM Page 26
June 2010 27
59
79
The author looks pleased with this design. He likes its
four-stroke engine, small size, and, best of all, flying
characteristics. It’s a cinch to build too; turn the page.
by Dick Sarpolus
Fun with
a 40-size
airframe
and foam
parts
06sig1.QXD_00MSTRPG.QXD 4/22/10 1:43 PM Page 27
Root ends of the two wing panels, showing the center plywood rib
and holes through the foam cores for aileron servo cables. The
plywood dihedral brace is used to support the wing joint.
The wingtip has its foam blocks glued in place on the balsa parts and
has been shaped with a sanding block. The bare foam wing cores are
covered with a low-temperature iron-on film.
The basic fuselage structure begins with balsa sides and plywood
doublers, joined by the first four plywood bulkheads. The next job is
to pull the tail together straight.
A Magnum .70 four-stroke engine is located on a molded composite
radial mount. The hole in the cowl side provides access for the
needle valve and choke lever.
Photos by the author
16
June 2010 29
Type: 40-size RC sport aerobatic
Skill level: Novice builder, intermediate pilot
Wingspan: 52 inches
Wing area: 725
square inches
Airfoil: Fully symmetrical, 18% thick
Length: 49 inches
Weight: 5.75 pounds
Engine: .40-.52 two-stroke, .70-.82 four-stroke glow
Construction: Conventional built-up balsa and plywood, foam-core wing
Covering/finish: Hangar 9 UltraCote used
Radio: Four channels minimum, five standard servos
Other: 10-ounce fuel tank, aluminum landing gear, 3-inch wheels, 21/4-inch spinner
With a wing area of approximately 700
square inches, a .40-.45 two-stroke glow
engine or equivalent does well.
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:24 AM Page 29
Foam wing cores have top and bottom spars for strength and are not covered with
balsa; it’s unnecessary. Low-temperature iron-on film does the job.
The wing is held on with two 1/4-20 nylon bolts. The aluminum landing gear is secured
with three 1/4-20 nylon bolts. Cream and red UltraCote provide good contrast.
wire foam-cutting setup for such a wing, I
cut the core and trimmed off the TE. Then,
with a separate template, I cut the spar
notches and the LE notch.
If you don’t cut your own foam, Phil
Cartier at The Corehouse has a computercontrolled
setup to do this wing section.
And Bob Hunt at Robin’s View
Productions does a great job on any foamcutting
requirement. You can also ask the
AMA Plans Service if it will sell you a set
of cores when you order the plans. There
are many options when you build.
With your cut foam cores, add the slot
between the top and bottom spars at the
middle for the plywood joiner. Join the
wings flat or at a dihedral angle you prefer.
Many builders like a flat wing; on a lowwing
airframe such as this, I prefer a few
degrees of dihedral.
Oh, and make the hole for aileron servo
cables in the foam cores before you join
them. I use a piece of 1/4-inch music wire
with a collar on the end. I heat it with a
torch and then push it through the foam
from the root to the aileron servo cutout.
Epoxy the top and bottom spars into the
cores, and epoxy the plywood joiner into
one of the wing panels. Epoxy the center
plywood rib in place—it holds the wing
mounting tab—and epoxy the two wing
panels together.
I use a light-plywood tip rib to tie the
upper and lower spars together at the tips. I
epoxy heavy fiberglass cloth around the
wing center-section and use wood filler
blocks to support the two wing bolt
mounting holes.
On the top and bottom of the balsa
wingtips, I glued foam blocks in place and
cut and sanded them to shape for covering.
If those wingtips seem like too much
work, get the cores a couple inches longer
and use light-plywood caps on the tips of
the foam cores.
I hinged in place the balsa-strip
ailerons as usual. I made aileron servo
mounting plates from 1/4 plywood,
epoxying them into the foam, flush with
the surface.
Fuselage: This begins with epoxying the
plywood doublers to the balsa sides and
the wing-saddle pieces and the stabilizerarea
doublers. I’m careful to make a right
and a left side, because I once fabricated
two left sides.
With one fuselage side flat on the
building bench, add the first four
bulkheads, perpendicular to the side. Then
install the other side. This is fairly easy to
keep aligned, because the two sides are
parallel from the nose to the TE position.
With that completed, pull in the tail
ends of the sides and add the rear-section
bulkheads. Now add the upper fuselage
sides; there’s a front section and a rear
section. Sand their lower edges to a slight
bevel so that they sit flush on the top edge
of the fuselage sides. Sand their top edges
flush with the tops of the bulkheads, and
then add and round the top pieces.
To be sure that the firewall is secure, I
install two small screws on each side,
through the plywood doublers into the
edges of the firewall. The plywood wing
bolt mount plate is added to the fuselage,
along with the plywood landing gear
mounting plate and its reinforcements.
At this point, fit the fuselage to the
wing. Where the front plywood wing
mounting tab goes through the second
bulkhead, the lower edge of the opening in
that bulkhead can be sanded or shimmed
so that the wing fits tightly in place.
With the wing in place on the fuselage,
drill the two wing bolt mounting holes
through the wing TE area and into the
fuselage plate, and tap the plywood for the
1/4-20 nylon bolts.
Use a nylon engine mount bolted to the
firewall, and add the balsa sides and
bottom pieces to the front end of the
fuselage. If you want to do more work,
you could use balsa blocks faired to blend
smoothly with a spinner mounted on the
engine. I didn’t think that was necessary.
Tail Surfaces: The vertical fin and the
stabilizer are 1/4 balsa, and I use firm to
hard stock to prevent vibration. The
control surfaces, rudder, and elevators are
built from 1/4 x 1/2 and 1/4 square stock.
The elevator halves are joined by a piece
of 5/32-inch-diameter music wire epoxied
in place.
30 MODEL AVIATION
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:29 AM Page 30
With the fuselage bolted onto the wing,
I insert the stabilizer and epoxy it in place,
lining it up level with the wing. I insert
the vertical fin and glue it in place, lining
it up perpendicular with the stabilizer.
I like either fiberglass-tube pushrods or
Sullivan’s nylon-tube setup with the
carbon-fiber inner rods, and I use all 4-40
hardware. Cut holes in the rear bulkheads,
as required. When the rudder and elevator
linkages are installed, you can install the
bottom planking.
Finishing: I used UltraCote for the
covering; it’s one of the easier films to
apply. With the equipment located as
shown on the plans, the Little Fast
balanced as shown and it works for me.
I’ve always thought that the balance
point and control-surface movements
should suit the pilot. There’s a gigantic
variation in the way individuals like their
aircraft to “feel,” but today’s radios make
it easy to set up a model to suit you.
I’m happy with the way the Magnum .70
four-stroke engine performs and am
pleased with this latest building project.
Hey! Make some sawdust and wood
chips! MA
Dick Sarpolus
[email protected]
Sources:
Magnum engines
(714) 963-0329
http://magnum.globalhobby.com
The Corehouse
(717) 566-3810
http://home.earthlink.net/~philcartier/
Robin’s View Productions
(610) 746-0106
Sullivan Products
(410) 732-3500
www.sullivanproducts.com
Hangar 9 UltraCote
(800) 338-4639
www.hangar-9.com

26 MODEL AVIATION
A generous wing area and thick airfoil make
this model easy-flying and aerobatically
capable. The tail-dragger landing gear setup
with 3-inch wheels makes grass-flying-field
handling simple.
AGAIN, I FOUND a reason/excuse to
build a new model. A Magnum .70 fourstroke
that I had bought for another
project didn’t work out, so it was
available.
The engine was broken in and had
been flown a few times, with good
performance. I figured that a .46 twostroke-
size airframe for aerobatics,
sport, and fun would be a good project.
I know; a bunch of ARFs on the
market would work fine for this project.
But regardless of the time, work, and
money involved, I like to build my
aircraft from scratch. I like to spend
time in the workshop, making sawdust
and wood chips.
If you don’t like to build, ARFs are
great. However, I consider the workshop
time a good part of this hobby.
I laid out a barn-door wing, which
had a 52-inch span and 14-inch chord,
for approximately 700 square inches of
area. I like a nice, thick 18% fully
symmetrical airfoil.
For easy, fast building, it’s tough to
beat a foam-core wing. To make it even
simpler, I employed no balsa sheeting
on this foam core. Good top and bottom
spars, which provide plenty of strength;
fiberglass cloth and epoxy around the
center; and a low-temperature, iron-on
covering are all that are needed.
Hey, CL Combat modelers have been
doing wings this way for years. I’ve
done it before on similar RC airplanes
and it works fine.
If you don’t like the thought of an
unsheeted foam wing, make the foamcutting
templates slightly smaller and
sheet the wing with balsa. Or cut a
bunch of balsa ribs and fashion a builtup
wing. When you’re building from
scratch, you can make it any way you
like.
I used foam blocks on the wingtips,
sanding the material to shape rather than
just capping the end of the core with
light plywood. It would be less work to
merely cut the cores a few inches longer
and cap the ends, if you like that
appearance.
The fuselage is 49 inches long
overall, featuring typical construction:
balsa sides and plywood doublers.
Rather than look for a suitable plastic
canopy, I laid out a side view I liked,
slanted the top fuselage sheeting, and
built in the canopy area. This method is
easy and strong.
I prefer a tail-dragger gear setup for
use on the grass fields from which I fly.
Tricycle gear can be troublesome when
the grass is a bit high.
I didn’t try for extremely light
weight. If you want to, you can cut holes
in the plywood doublers and fuselage
sides.
After a quick iron-on finishing job, I
had a new model to fly. This design is
not way different; there are no new
aerodynamics or claims of fantastic
performance. But it is easy to build and
fly, performs decently, is rugged, and I
like the appearance.
Are you interested? I’ll zip through
the construction procedure.
CONSTRUCTION
There are two ways you can go;
either cut all the parts at once to make a
kit or cut the parts you need as you
progress in building the airplane. Both
techniques work fine. On this version, I
completed the wing before I even started
the fuselage.
Cut the plans, or a copy of the plans,
for the parts templates. I drew around
the paper templates with a ballpoint pen
on the balsa or plywood and cut the
pieces with a band saw.
Wing: With my crude-but-it-works hot-
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:13 AM Page 26
June 2010 27
59
79
The author looks pleased with this design. He likes its
four-stroke engine, small size, and, best of all, flying
characteristics. It’s a cinch to build too; turn the page.
by Dick Sarpolus
Fun with
a 40-size
airframe
and foam
parts
06sig1.QXD_00MSTRPG.QXD 4/22/10 1:43 PM Page 27
Root ends of the two wing panels, showing the center plywood rib
and holes through the foam cores for aileron servo cables. The
plywood dihedral brace is used to support the wing joint.
The wingtip has its foam blocks glued in place on the balsa parts and
has been shaped with a sanding block. The bare foam wing cores are
covered with a low-temperature iron-on film.
The basic fuselage structure begins with balsa sides and plywood
doublers, joined by the first four plywood bulkheads. The next job is
to pull the tail together straight.
A Magnum .70 four-stroke engine is located on a molded composite
radial mount. The hole in the cowl side provides access for the
needle valve and choke lever.
Photos by the author
16
June 2010 29
Type: 40-size RC sport aerobatic
Skill level: Novice builder, intermediate pilot
Wingspan: 52 inches
Wing area: 725
square inches
Airfoil: Fully symmetrical, 18% thick
Length: 49 inches
Weight: 5.75 pounds
Engine: .40-.52 two-stroke, .70-.82 four-stroke glow
Construction: Conventional built-up balsa and plywood, foam-core wing
Covering/finish: Hangar 9 UltraCote used
Radio: Four channels minimum, five standard servos
Other: 10-ounce fuel tank, aluminum landing gear, 3-inch wheels, 21/4-inch spinner
With a wing area of approximately 700
square inches, a .40-.45 two-stroke glow
engine or equivalent does well.
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:24 AM Page 29
Foam wing cores have top and bottom spars for strength and are not covered with
balsa; it’s unnecessary. Low-temperature iron-on film does the job.
The wing is held on with two 1/4-20 nylon bolts. The aluminum landing gear is secured
with three 1/4-20 nylon bolts. Cream and red UltraCote provide good contrast.
wire foam-cutting setup for such a wing, I
cut the core and trimmed off the TE. Then,
with a separate template, I cut the spar
notches and the LE notch.
If you don’t cut your own foam, Phil
Cartier at The Corehouse has a computercontrolled
setup to do this wing section.
And Bob Hunt at Robin’s View
Productions does a great job on any foamcutting
requirement. You can also ask the
AMA Plans Service if it will sell you a set
of cores when you order the plans. There
are many options when you build.
With your cut foam cores, add the slot
between the top and bottom spars at the
middle for the plywood joiner. Join the
wings flat or at a dihedral angle you prefer.
Many builders like a flat wing; on a lowwing
airframe such as this, I prefer a few
degrees of dihedral.
Oh, and make the hole for aileron servo
cables in the foam cores before you join
them. I use a piece of 1/4-inch music wire
with a collar on the end. I heat it with a
torch and then push it through the foam
from the root to the aileron servo cutout.
Epoxy the top and bottom spars into the
cores, and epoxy the plywood joiner into
one of the wing panels. Epoxy the center
plywood rib in place—it holds the wing
mounting tab—and epoxy the two wing
panels together.
I use a light-plywood tip rib to tie the
upper and lower spars together at the tips. I
epoxy heavy fiberglass cloth around the
wing center-section and use wood filler
blocks to support the two wing bolt
mounting holes.
On the top and bottom of the balsa
wingtips, I glued foam blocks in place and
cut and sanded them to shape for covering.
If those wingtips seem like too much
work, get the cores a couple inches longer
and use light-plywood caps on the tips of
the foam cores.
I hinged in place the balsa-strip
ailerons as usual. I made aileron servo
mounting plates from 1/4 plywood,
epoxying them into the foam, flush with
the surface.
Fuselage: This begins with epoxying the
plywood doublers to the balsa sides and
the wing-saddle pieces and the stabilizerarea
doublers. I’m careful to make a right
and a left side, because I once fabricated
two left sides.
With one fuselage side flat on the
building bench, add the first four
bulkheads, perpendicular to the side. Then
install the other side. This is fairly easy to
keep aligned, because the two sides are
parallel from the nose to the TE position.
With that completed, pull in the tail
ends of the sides and add the rear-section
bulkheads. Now add the upper fuselage
sides; there’s a front section and a rear
section. Sand their lower edges to a slight
bevel so that they sit flush on the top edge
of the fuselage sides. Sand their top edges
flush with the tops of the bulkheads, and
then add and round the top pieces.
To be sure that the firewall is secure, I
install two small screws on each side,
through the plywood doublers into the
edges of the firewall. The plywood wing
bolt mount plate is added to the fuselage,
along with the plywood landing gear
mounting plate and its reinforcements.
At this point, fit the fuselage to the
wing. Where the front plywood wing
mounting tab goes through the second
bulkhead, the lower edge of the opening in
that bulkhead can be sanded or shimmed
so that the wing fits tightly in place.
With the wing in place on the fuselage,
drill the two wing bolt mounting holes
through the wing TE area and into the
fuselage plate, and tap the plywood for the
1/4-20 nylon bolts.
Use a nylon engine mount bolted to the
firewall, and add the balsa sides and
bottom pieces to the front end of the
fuselage. If you want to do more work,
you could use balsa blocks faired to blend
smoothly with a spinner mounted on the
engine. I didn’t think that was necessary.
Tail Surfaces: The vertical fin and the
stabilizer are 1/4 balsa, and I use firm to
hard stock to prevent vibration. The
control surfaces, rudder, and elevators are
built from 1/4 x 1/2 and 1/4 square stock.
The elevator halves are joined by a piece
of 5/32-inch-diameter music wire epoxied
in place.
30 MODEL AVIATION
06sig1.QXD_00MSTRPG.QXD 4/22/10 11:29 AM Page 30
With the fuselage bolted onto the wing,
I insert the stabilizer and epoxy it in place,
lining it up level with the wing. I insert
the vertical fin and glue it in place, lining
it up perpendicular with the stabilizer.
I like either fiberglass-tube pushrods or
Sullivan’s nylon-tube setup with the
carbon-fiber inner rods, and I use all 4-40
hardware. Cut holes in the rear bulkheads,
as required. When the rudder and elevator
linkages are installed, you can install the
bottom planking.
Finishing: I used UltraCote for the
covering; it’s one of the easier films to
apply. With the equipment located as
shown on the plans, the Little Fast
balanced as shown and it works for me.
I’ve always thought that the balance
point and control-surface movements
should suit the pilot. There’s a gigantic
variation in the way individuals like their
aircraft to “feel,” but today’s radios make
it easy to set up a model to suit you.
I’m happy with the way the Magnum .70
four-stroke engine performs and am
pleased with this latest building project.
Hey! Make some sawdust and wood
chips! MA
Dick Sarpolus
[email protected]
Sources:
Magnum engines
(714) 963-0329
http://magnum.globalhobby.com
The Corehouse
(717) 566-3810
http://home.earthlink.net/~philcartier/
Robin’s View Productions
(610) 746-0106
Sullivan Products
(410) 732-3500
www.sullivanproducts.com
Hangar 9 UltraCote
(800) 338-4639
www.hangar-9.com