TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]
Edition: Model Aviation - 2007/04
Page Numbers: 17,18,19,20,21,22,24
TO MOST OF you I am probably best known for my micro and
indoor projects. My modeling activities actually span a wide range
of sizes/types including quarter scale and FF.
I have owned and run a variety of nitromethane and gas
engines in my time, but somehow I managed to miss out on the
four-stroke power plant. I recently had the opportunity to purchase
a new O.S. .40 Surpass at an attractive price. A review of this
engine’s capabilities made it clear that it would be well suited to a
large, light model.
Meanwhile, I have had enough birthdays to slow my reflexes a
bit, and watching larger models can be a help. I have never been
content to just “fly around” with an RC model; I enjoy flying
Aerobatics (Pattern) maneuvers. These considerations framed the
reference for my new project.
The original Perky was an .010 two-channel model and did
well for its size. Later I enlarged it to the Perky Plus, which
spanned 33 inches and was powered with a Norvel .061 engine. Its
performance went well beyond my expectations. It had a broad
speed range and the ability to fly a wide variety of maneuvers on
limited power.
The basic Perky design has some useful features that may not
be immediately obvious. Although it is a high-wing model, the
wing is set fairly low on the fuselage. When this is coupled with
low dihedral, the roll performance is great. The deep fuselage
provides valuable side area for knife-edge flight, and the simple,
boxy shape lends itself to light construction.
With that background I decided to scale up the Perky Plus to a
wingspan of 63 inches, yielding a wing area of 775 square inches. I
changed the airfoil to a semisymmetrical section and added aileron
control. It was clear that a model this size could become too heavy
Dave checks out the
control functions
before beginning the
first takeoff run with
his Perky Grande.
The stabilizer is built over the plans. Note Warren truss ribbing for extra rigidity and the
massive center spar. The elevators are made from sheet balsa.
Fuselage construction is easy and durable. The fuselage sides have had the vertical-grain
nose doublers and the wing-saddle doublers attached.
The front end of the assembled fuselage reveals the engine mounts, firewall, and built-up
former at the front of the wing mount.
Photos courtesy the author
for the .40 Surpass without serious weight
control. Therefore, I used 6- to 7-pound-percubic-
foot balsa in the construction. An
excellent source is www.lonestar-models.com.
I used park flyer-size servos for the
ailerons and throttle and a 720 mAh, AAAcell
NiMH four-cell battery. Covered with
MonoKote, the Perky Grande’s total
weight came out at 3.5 pounds without
fuel. That seemed reasonable, especially
with a wing loading of only 10.5 ounces
per square foot.
I installed a seven-channel receiver and
set the model up to my Hitec RCD Optic 6
transmitter. This allowed the strip ailerons
to be drooped in a flap model and still
function as ailerons. It was time to take the
airplane outside.
With a satisfactory range check
completed, it was time to break in the new
engine. The furnished literature sheet
recommended a maximum of 10%-
nitromethane fuel, so that was what I
started with. Starting and basic running
went okay, but the needle valve seemed
overly sensitive and the idle was too fast
with a sloppy transition.
I have been fortunate to have access to
a master modeler—Forrest Mason—who
really knows his engines. He pointed out
that I should be using a minimum of 15%
Type: Sport aerobatic
Wingspan: 63 inches
Flying weight: 3.5 pounds
Wing area: 806 square inches
Engine: O.S. .40 Surpass four-stroke
Propeller: 12 x 6 Master Airscrew
Fuel-tank capacity: 6 ounces
Controls: Five channels (five servos)
Equipment: Seven-channel Futaba
receiver, two Futaba S148 servos, three
GWS Naro servos
Battery: 720 mAh, 4.8-volt NiMH
AAA cells
Control mixes: Flaperon, rudder with
aileron (15%)
Construction: Balsa and plywood
Covering/finish: MonoKote
The wing ribs are flat-bottomed, allowing accurate assembly on a flat bench. This is a
logical first built-up model.
Note the
turbulator strip
spar that runs
along the front
of the wing just
behind the LE
and in front of
the main spar.
No LE sheeting
is required!
This view of the entire fuselage crutch assembly shows just how few parts are needed to
achieve a strong, accurate structure.
nitro and a composite propeller such as a
Master Airscrew on a four-stroke engine.
With these changes my engine settled down
and ran like a charm.
With all the excuses used up it was time
to go flying. Even on the takeoff roll it was
becoming clear that the .40 Surpass would
be more than ample power for the Perky
Grande. As the flight progressed I worked
my way through the Pattern maneuvers,
delighting in the realistic speed and quiet
sound during the flight.
Although the stalls were completely
benign, I noted some yawing with aileron
when flying at low speeds. I ended up
mixing in 10% rudder with the aileron for a
complete solution. An alternative is to add
differential to the ailerons; that should
accomplish the same thing but with a
reduction in the maximum roll rate.
That deep fuselage really shone in
knife-edge flight. Only approximately 30%
rudder is needed to hold altitude. The stalls
are gentle with the rudder and ailerons
centered, and the generous controls provide
positive snap rolls and spins, both positive
and negative.
There was a mild surprise with the
flaperon deployment. Instead of adding
drag along with extra lift, it appears that in
this case there is only an additional
increment of lift without added drag. This
brought the minimum speed down,
allowing short landing rolls.
CONSTRUCTION
I benefit in my projects by rounding up
the amount of materials needed at the
beginning. I used a variety of glue products
during construction: Elmer’s Carpenter’s
Wood Glue, medium cyanoacrylate, thin
cyanoacrylate, and 3M Super 77 spray
contact cement.
In traditional fashion the landing gear is held into the mount slot with metal straps
and wood screws.
An O.S. .40 Surpass four-stroke was chosen for power on the original Perky. Many
other two- and four-stroke engine choices are available.
Also traditional is the elevator pushrod and horn arrangement. It’s easy to adjust at
the field. Notice the steerable tailwheel.
Fresh, sharp cutting blades are a big help,
as are a variety of sanding blocks. I have
found the “Sand Blaster” brand of sandpaper
to be especially useful on models. I found
mine in the paint department at Wal-Mart.
Some sort of power saw, either a small
band saw or a jigsaw, will be a big help. I
also enjoyed using my Dremel circular saw
for stripping wood.
As I mentioned, this model should be
built with light balsa. The .40 four-stroke
engine does not put excessive strain on the
airframe, and the material sizes are adequate
for the stresses. If you choose to go with
more power, you are on your own. A .40-.46
two-stroke should be fine as an alternative to
the .40 four-stroke.
Wing: Construction should begin with the
wing. I made a “kit” of parts before
assembly so I could keep moving once I
started pinning and clamping. The wing
panels may be assembled on a flat surface.
For the 1/2 x 1/2-inch LE strips I
laminated two 1/4 x 1/2-inch strips with
carpenter’s glue, which trims and sands well
and is plenty strong. Notice that one ribcutting
pattern is adequate for the various
ribs. Except for the center ribs that are
undercut for the sheeting, the only difference
in the rest is the depth of the notches and
holes for the servo cables.
This is also a good time to laminate the
four spars. Be sure to taper the outer ends to
avoid a stress concentration.
I started constructing my wing panels by
clamping down the lower spar and TE. I
added the center-section lower sheet
between the spar and the TE, and I added all
the ribs. Notice the webbing in the centersection;
this will be stronger with the grain
vertical. Be sure to add the filler blocks for
the center-section and hinges at this stage.
Glue in the LE, upper spars, upper TE,
and tip plate, and one panel is finished.
Repeat for the second panel. A minute
amount of sanding will be needed on the
root ribs to get a tight fit with the dihedral.
At this point you can join the panels and add
the center-section brace. Finish the sheeting
to complete assembly.
Trim and sand the LE to the shape
shown. A female template is a big help to
check that both sides match. After a general
sanding of the glue lumps, etc., set the wing
aside until later.
Fuselage: Begin the fuselage construction
by splicing the side sheets for adequate
depth. You need to make a decision here. If
you purchase 48-inch-long wood, no
additional splicing is necessary. Wood that
is 36 inches long will require some length to
be added at the tail.
When splicing the long pieces, fit the
edges carefully, trimming if necessary to get
a tight seam without warping the sheet. If
you splice length on the tail, use a scarf joint
for adequate strength.
My favorite technique for long splices is
to hold the two sheets together and add
patches of masking tape every few inches
along the seam. Turn the sheets over, open
the seam, and put a bead of carpenter’s glue
along one edge.
Press the assembly flat on the table with
the masking-tape-side down and wipe off the
excess glue with a paper towel. Little sanding
will be needed to obtain a smooth seam.
The nose doublers go on next. The 3M
Super 77 spray cement can make a real mess
of a floor, so lay down adequate newspaper at
the start. Mask off the part of the main side
that is not glued and spray on a light coat of
cement. Make a left and a right side.
You can join the doublers to the fuselage
sides when the glue becomes tacky to the
touch. Rub the area firmly for a permanent
bond. Add the rest of the edge stringers,
landing-gear brace, and vertical cabin strips
to complete two side assemblies. I chose this
point in construction to cut the stabilizer
opening in the two sides.
The two sides should be joined with the
cabin braces first, making sure things are
square. Pull the tail together and glue.
After I glued the F1 former in, I installed
the engine mounts. I clamped a flat plate
across the top of these in the engine area to
ensure a flat mounting zone. I have found that
medium cyanoacrylate glue gives me a
stronger bond in this area than epoxy and is
less messy.
Add the landing-gear block and wing
hold-down plate, and plank the top and
bottom with 3/32 balsa. Running the grain
crosswise will result in more glue seams but
is stronger and easier to install around the
curves.
The one part of planking to leave off at
this point is the windshield piece. You will
need access to this area to drill for the wing
hold-down tube.
Speaking of this, once the fuselage has
been smoothed up, fit the wing and trim as
necessary for a tight fit. I used a rather long
drill to reach through from the front to the
wing center brace. Slide a piece of tubing in
place and carefully square up the wing. Once
satisfied, drill and tap for the 1/4-20 rear holddown
screws.
Remove the wing and pull the tube out. I
waited until I had covered my model before I
finally glued the tube in. Now you can install
the windshield sheet.
The stabilizer construction is basic.
Assemble the 3/16 balsa frame and add the 1/8
balsa capstrips and sheeting on the top and
bottom. Refer to the side view for shaping the
center-section. Round the tips and LE, and
leave the TE square.
The ailerons may be sliced from 1/4 balsa
stock. Round the tips and TE, and put a
generous bevel on the LE. The elevators and
vertical tail are cut from 3/16 stock. I left the
elevators joined until I had installed the 3/32-
inch-diameter piano-wire connector.
The landing gear is bent from 5/32-inchdiameter
piano wire. I used a husky bench
vise and hammer for this task.
(Editor’s note: A better method might be
to use a heavy-duty K&S wire bender for this.
It will ensure smooth bends with no chance of
cracking the wire. If you do choose to use the
vise-and-hammer method, be sure to grind a
radius into one of the vise jaws and then bend
the gear around that radius.)
The tail-wheel assembly uses a Goldberg
bearing with a 1/16-inch-diameter wire strut
and 3/4-inch wheel. Install the landing gear
after covering.
Covering: I would offer some words of
wisdom for the task of covering, but my work
bears witness to my lack of skill in this area.
There are several good choices of material; I
selected MonoKote for a combination of light
weight, stiffness, and gloss.
Final Assembly: Once I glued the wing
hold-down tube in place, I mounted the wing
to use as a reference for aligning the tail.
Measure carefully here and get the stabilizer
parallel and square to the wing. The fin
should be on the centerline and square to the
stabilizer.
I used the “fuzzy” plastic cyanoacrylate
hinges on all the control surfaces. This is
where the thin cyanoacrylate was put to use.
Once I had the control surface pressed into
place and could move it freely through ample
throw, I flowed a small amount of
cyanoacrylate into the hinge slots. Give the
glue time to dry and pull on the hinges to
ensure that they really are secure.
You can mount the landing gear now,
drilling for the vertical leg into the mounting
blocks. I used a pair of aluminum straps to
secure the legs.
Mount the tailwheel using a hand grinder
fitted with a parting wheel to cut a slot for the
tab on the bearing. The assembly was glued
in place with medium cyanoacrylate. I ironed
four layers of MonoKote over the tiller arm
to secure it to the rudder.
Mount the servos and control horns. I
used a pair of Futaba S148 servos on the
rudder and elevator and GWS Naro servos on
the ailerons and throttle. My pushrods are
made from stiff 1/4 square balsa with wire
ends for the tail controls. The ailerons are
connected with the threaded end wire rods
and snap links.
When it came time to mount the engine, I
ran into a conflict with the carburetor linkage
fitting and the F1 former. My mentor Forrest
Mason suggested fitting a cap from a Sharpie
pen in the firewall to provide clearance for
the ball link I had chosen, and this worked to
perfection.
I coated all the exposed wood in the
engine area with five-minute epoxy before
mounting the engine. I chose clear
polyurethane soaked into the fuel-tank
compartment for protection there.
Locate the receiver and battery so that the
CG is on the mark. (Do not attempt to fly the
model tail-heavy.) Wrap these delicate parts
in soft foam for vibration protection.
At the Field: Run the engine as necessary
before leaving home to ensure that it is well
broken in and that the radio system has
adequate range. A good starting point for
control throws would be 1/2 inch up and down
on the ailerons, 3/4 inch up and down on the
elevator, and at least 1 inch right and left for
the rudder. These may be “seasoned to taste”
after the initial flights.
If your Perky Grande is as light as mine, it
will lift off easily with a rapid rate of climb.
There is no reason to use full power except
for those maneuvers requiring vertical pull.
I wish you every pleasure with your
project. I would love to see pictures from
anyone who builds one of these models. MA
Dave Robelen
[email protected]