Saito’s Four-Stroke CL Engines - 2009/08

Saito’s
Four-
Stroke CL
Engines
by Joe Wagner
Flight comparisons included the author’s scratch-built red Shrike with a Brodak
.40 and the heavily reworked Brodak Cardinal ARF with a Saito .56.
The Saito’s installation in a typical profile CL airplane puts the
bottom of the carburetor intake to the fuselage side. An intake
extension through the body makes priming easy and improves
engine performance.
Weighing 171/4 ounces, this Saito .72 differs most noticeably
from its smaller-displacement siblings because its carburetor is
offset from the centerline.
I began by reading the instruction booklets (two come with each
engine) twice. I’ve been using model airplane power plants since
before World War II—I have decades of experience with them—and
one thing I’ve learned is to read the instructions.
The people at model engine factories want satisfied customers.
Their manuals are prepared with that purpose in mind. Yes, the
directions can contain errors (I’ll cover this in the following), but
they’re more helpful than not.
The smaller Saito booklet shows in detail how to change the airinlet
venturi size. Since these are CL engines, they don’t have
throttles.
They come with intake restrictors in their venturi bodies; after
WHEN I WAS offered the opportunity to test Saito’s newly issued
four-stroke engines—the FA-40CL AAC, FA-56CL, FA-62ACL,
and FA-72CL—made specifically for powering CL Precision
Aerobatics (Stunt) models, I couldn’t help feeling skeptical. After
all, two-strokers have been hauling CL models around effectively
since 1941. They’re lighter, simpler, and less costly than four-stroke
engines. So why would anyone want to change?
I found out why! I won’t dwell at length on the exquisite yet
almost bulletproof packaging that Saito uses or the company’s
thoughtfulness in providing the proper-size Allen wrenches and
even a tiny valve-adjustment wrench with each of these power
plants. Every Saito package serves as an effective “quality
statement.”
66 MODEL AVIATION
08sig3.QXD 6/22/09 2:35 PM Page 66
break-in, these can be removed to provide
extra power and rpm. The well-illustrated
manual shows exactly how to do that.
However, I stayed with the small-diameter
inlets throughout my tests.
I followed the break-in instructions in
the larger booklet. One of its paragraphs
recommends oiling the engine before its
first run. Besides injecting oil through the
crankcase breather, Saito advises putting a
few drops down the pushrod tubes, to
lubricate the camshaft area. That requires
removing the rocker-arm covers. While I
had the covers off to add oil, I admired the
valve mechanisms’ Swiss-watchlike
precision.
When considering switching to fourstroke
power, some two-stroke users worry
about the valves needing constant
readjustment. That was indeed a problem
with earlier four-strokers—but not with
Saitos.
I mounted the Saito .62 in my test stand
for its break-in. Saito’s instructions for its
CL engines advise using fuel with 10%-
15% nitro and 20%-22% oil—no more than
half of that castor. I used 15% nitro, 22%
oil, and proceeded. Then came a hiccup.
The instructions warn not to exceed
4,000 rpm for the first 10 minutes of breakin
time. But with the recommended 13 x 6
propeller and small venturi insert, the
slowest I could get the .62 to run was 6,200
rpm. That was with the needle set
“slobbering rich,” too.
Yet the .62 showed no sign of distress or
overheating, and its exhaust oil came out
undarkened. That’s an excellent indicator of
mild operating temperatures.
I had similar results with the .56 and .72.
Neither would run anywhere nearly as slow
as 4,000 rpm, but no problems resulted
from my exceeding the prescribed “top
limit” for break-in. The way I understand it,
the 4,000 rpm limit is for the RC line of
engines, which can easily adjust power
output with the throttle.
Flight-Test Vehicles: My helper and I
decided to try one of John Brodak’s biggest
ARF kits—the Cardinal—for our first
attempt with Saito power. But as soon as
the kit arrived, a few problems emerged
Photos by Yana Sarai
Surprise Performance
An interesting possibility occurred to me regarding models
for the Saito FA-72CL. It develops approximately the same
power as some of the best Class C spark-ignition two-stroke
engines of the late 1940s, such as the Anderson Spitfire .65, the
Atwood Champion .60, and the Orwick .64. With their ignition
components—coil, condenser, battery packs, and wiring—plus
propeller, they weighed close to the big Saito four-stroker’s
191/2 ounces.
Many 60-powered Old Time Stunt models were fine
performers in their day. These included Jim Saftig’s big Zilch,
J.C. Yates’s Madman, Hal deBolt’s Stunt Wagon, Bob
Palmer’s Go-Devil Sr., and his scale model of Sammy Mason’s
orange-and-white-checkerboard aerobatic Stearman biplane.
Saito’s .72 would make an ideal modern power provider for
all those airplanes. They should require little or no nose
shortening. MA
The smallest of Saito’s first three CL power plants (a .40 is now —Joe Wagner
available), the .56 produces slightly more power than a typical
two-stroke .40 and runs as smoothly.
Both models use a
Uniflow fuel tank
design, unassisted by
muffler pressure. It
works fine. The
steeply downwardangled
muffler keeps
the airplane’s
underside clean but
could cause damage
in a fast nose-over
landing.
should be shortened by approximately 3 inches.
That’s too much! It could be done, but it wouldn’t leave room
for my fuel tank between the engine and the wing. I was forced to
compromise by shortening the nose only 11/2 inches. Doing so
would barely leave room for a 31/2-ounce Oval Profile Uniflow tank.
So to balance my Mauler at the proper place, I’ll need to leave
the aft end of the profile body untapered, extend the tail by close to
an inch, and probably install a heavy, brass-hub tail wheel on a 3/32-
inch-diameter wire strut.
I’ve gone into detail to show that substituting a four-stroke
engine for a two-stroke in a modern CL aircraft is more than a
matter of changing power plants. The Brodak Mauler, a typical
large profile Stunt design, is an excellent example of the conversion
problem.
However, the Brodak Cardinal was a different story. Since it had
a longer nose, it was readily possible to shorten it enough for proper
balance.
I did that by fully assembling the model except for the power
system. I tied the propped Saito .56 to a loop of string and hung it
beneath the Cardinal’s nose. I slid the string loop fore and aft until
the model balanced.
The string-loop location showed me precisely where the Saito’s
cylinder centerline belonged. The engine-mounting process was
straightforward from there.
Then another consideration emerged: propeller clearance.
Brodak’s Cardinal ARF comes with 13/4-inch wheels. Evidently it’s
supposed to be flown strictly from smoothly paved surfaces. But the
small wheels don’t provide enough propeller clearance for the 12-
inch propeller with which the Saito .56 performs best.
Installing a pair of 3-inch SkyLite wheels and rebending the
Cardinal’s aluminum landing gear struts inward a tad solved that
The model was designed to be powered with a Brodak .40 twostroke:
a lightweight, mostly aluminum engine. With its muffler and
11 x 5 Master Airscrew propeller, the .40 weighs 9.7 ounces. The
Saito .56 weighs 16.1 ounces with its muffler and propeller.
Following is one way to calculate how much to shorten a model’s
nose to accommodate a heavier engine.
Measure the distance (on plans if possible) from the design’s
balance point to the center of the cylinder of the engine that the
model was designed to use. Multiply that engine’s weight by its
distance from the balance point. Divide that number by the heavier
engine’s weight. That gives you the distance from the model’s
balance point to the heavy engine’s cylinder centerline.
Brodak’s warbird-series Martin Mauler profile Stunter was
designed for the lightweight Fox .35 power. It weighs 10 ounces
exactly with muffler and a 10 x 5 Graupner propeller.
However, I know from experience that a completed Mauler
usually comes out tail-heavy with a Fox .35 and needs roughly a 1-
ounce spinner to bring the CG to the right place. That puts the Fox
installation’s gross weight at 11 ounces. On the Mauler plans, the
Fox cylinder centerline is 81/4 inches ahead of the CG.
Therefore, 11 x 81/4 = 903/4 inch-ounces. Dividing that by the
Saito .62’s weight plus its propeller—171/2 ounces—gives us 53/16
inches. To maintain the same CG with the Saito, the Mauler’s nose
68 MODEL AVIATION
08sig3.QXD 6/22/09 2:55 PM Page 68
problem. It also eliminated takeoff and
landing difficulties at the grassy field I
typically use for CL flying.
When the Cardinal’s engine
installation was complete, I tried handstarting
the Saito in the model; I much
prefer this starting method.
For one thing, it gives me a feel for
what’s happening with the engine. For
another, hand-starting eliminates having
to lug heavy equipment out to the edge of
the flying circle for electric startups and
then toting it back after takeoff.
However, I couldn’t get the Saito to
perk. That was because of the narrow gap
between its intake and the side of the
Cardinal’s profile fuselage. Fingerchoking
was impossible, and so was
squirting fuel into the carburetor inlet.
I solved this problem by adding an
extension to the .56’s intake. A 2-inch
length of brass tubing through a hole in
the Cardinal’s side did the trick.
That not only made hand-starting easy,
but it also added a couple hundred rpm.
That was no doubt because of a tuned
intake effect. I’ve seen the same
improvement from extensions I’ve added
to many other two- and four-stroke
engines, and I recommend it for the Saito.
Later I found another way to add an
intake extender. This one was made from
a length of 3/8-inch-OD rigid plastic pipe.
(Lowe’s home-improvement store sells
it.)
The pipe’s wall is thick enough to
allow its end to be tapered to match the
Saito intake’s internal taper. You can do
this on a drill press, using file-to-fit
methods and checking for proper fit as the
pipe is shaped with a file and sanding
tools. The pipe’s other end’s entry should
be bell-mouthed, to eliminate inlet stall
and the power loss that it can cause.
Flight Performance: To make valid
performance comparisons between the
Saito .56 and a two-stroke engine with
similar power, I installed a well-broken-in
Brodak .40 in a faithful old Stunter of my
own design—the Vanga Shrike—that I’d
flown for years with a mild-mannered
McCoy .35 Redhead.
The Shrike and the Cardinal have an
almost identical aerodynamic setup. They
are especially alike since I altered the
Cardinal wing’s LE radius to the more
rounded contour that I’ve learned is best
for my preferred Stunt flying style.
The Shrike weighs 2 pounds, 15
ounces in ready-to-takeoff condition. The
Cardinal came out 5 ounces heavier. But
with 4 square feet of working wing area
(including the flaps) on each model, the
wing loading difference between the
Stunters seemed negligible, at a mere 1.25
ounces per square foot.
Saitos are heavier than the two-stroke engines that most large CL Stunters were
designed to use. For proper balance, the engine for this Brodak Martin Mauler must be
moved back.
Conditions were ideal for initial flight
tests. The temperature was near 70°,
humidity was near 60%, and there was just
enough wind to ensure that the lines stayed
taut in severe maneuvers.
I flew both models on 70-foot .015
braided steel lines. For sound-level
comparisons on the same lines that day, I
also flew my old faithful Flite Streak, which
is powered with an O.S. 25LA-S.
First up was the Shrike. I’d flown it many
times with its original McCoy .35—which
never needed an intake extension. And the
model performed similarly with the Brodak.
The .40 is a more advanced design, but it has
a muffler whereas the McCoy doesn’t.
Lap speed varied depending on how rich
the needle was set. With its Brodak .40 twostroking
steadily but not quite fully leaned
out, the Shrike flew shoulder-level laps at 4.8
seconds.
That works out to nearly 95 feet per
second, or 65 mph. At that speed, the Shrike
pulled the lines almost straight between
handle and wingtip, but not hard enough to
make me need to lean over backward as I
piloted.
My helper, Yana Sarai, measured the
Shrike’s sound level at 110 dBA on the
ground at takeoff, 90 dBA as it passed by on
her side of the circle, and 70 dBA on the far
side. We performed our flight tests at an
extremely quiet location, with an ambient
sound level close to 60 dBA. At no time
during any in-flight tests did Yana find the
sound quality annoying.
Now for the Cardinal. Its not-completelybroken-
in Saito .56 turned the 12 x 6 Master
Airscrew propeller at 9,450 rpm on the
ground. That’s 450 rpm faster than the
factory obtained with a 12 x 6 APC
propeller and the small venturi insert. The
improvement was probably owed to my
intake extension.
70 MODEL AVIATION
I ran the .56 with the same 15%
nitro/22% oil fuel I used to break in the other
three Saitos. I’d also flown the Brodak .40
and the O.S. 25LA-S with that fuel blend. I
like it.
The .56 ran steadily throughout its flights.
I could expect no “two-four break” effect in
maneuvering; the Saito is a four-stroke, after
all. Still, its consistency impressed me,
especially since it was drawing its fuel from
a standard Uniflow tank setup. I’d decided to
try that and then switch to muffler pressure,
to see whether it made a difference. It didn’t.
The Saito .56-powered Cardinal
performed as well as any high-powered Stunt
model I’ve flown. Its extra weight compared
to the Shrike’s had no effect that I noticed.
The Cardinal’s flying speed was close to the
Shrike’s, too.
I did notice a small difference in control
response, but that could have been caused by
the way the Cardinal’s controls were set up.
This was the first CL model I’d ever flown
with its up-line ahead of the down-line; they
come out from the wingtip close, though.
Yana measured the Saito’s sound output
as 110 dBA at takeoff (same as the Brodak),
but only approximately 80 dBA as it passed
her in flight, and a mere 60 on the far side of
the circle. Considering that the background
noise was at roughly that dB level, the Saito
turned out to be amazingly quiet in flight. As
for the sound quality, Yana said that the only
real difference between the two-stroker and
the Saito was the latter’s lower tone.
A comparison flight with the .25-powered
Flite Streak confirmed our data. Yana got
almost identical sound-meter readings to
those she measured during the Saito’s
flights.
I almost forgot: the Shrike and Cardinal
have 31/2-ounce fuel tanks. From engine
startup to in-flight shutoff, the Shrike’s
Brodak .40 ran six-and-a-half minutes on
the average. The Saito .56 went almost a
minute longer.
In spite of requiring a different
installation, Saito’s CL four-stroke
engines are marvelous for round-the-circle
aerobatic flying—or for sport. Their
steady running, low sound output for the
size, and “businesslike attitude” seem well
worth the extra cost.
The only improvement I can suggest is
for Saito to supply a 2-inch-long intake
extension with each engine. That addition
makes a real difference. MA
Joe Wagner
[email protected]
Sources:
Saito Engines
(800) 338-4639
www.saitoengines.com
Brodak Manufacturing
(724) 966-2726
www.brodak.com

Saito’s
Four-
Stroke CL
Engines
by Joe Wagner
Flight comparisons included the author’s scratch-built red Shrike with a Brodak
.40 and the heavily reworked Brodak Cardinal ARF with a Saito .56.
The Saito’s installation in a typical profile CL airplane puts the
bottom of the carburetor intake to the fuselage side. An intake
extension through the body makes priming easy and improves
engine performance.
Weighing 171/4 ounces, this Saito .72 differs most noticeably
from its smaller-displacement siblings because its carburetor is
offset from the centerline.
I began by reading the instruction booklets (two come with each
engine) twice. I’ve been using model airplane power plants since
before World War II—I have decades of experience with them—and
one thing I’ve learned is to read the instructions.
The people at model engine factories want satisfied customers.
Their manuals are prepared with that purpose in mind. Yes, the
directions can contain errors (I’ll cover this in the following), but
they’re more helpful than not.
The smaller Saito booklet shows in detail how to change the airinlet
venturi size. Since these are CL engines, they don’t have
throttles.
They come with intake restrictors in their venturi bodies; after
WHEN I WAS offered the opportunity to test Saito’s newly issued
four-stroke engines—the FA-40CL AAC, FA-56CL, FA-62ACL,
and FA-72CL—made specifically for powering CL Precision
Aerobatics (Stunt) models, I couldn’t help feeling skeptical. After
all, two-strokers have been hauling CL models around effectively
since 1941. They’re lighter, simpler, and less costly than four-stroke
engines. So why would anyone want to change?
I found out why! I won’t dwell at length on the exquisite yet
almost bulletproof packaging that Saito uses or the company’s
thoughtfulness in providing the proper-size Allen wrenches and
even a tiny valve-adjustment wrench with each of these power
plants. Every Saito package serves as an effective “quality
statement.”
66 MODEL AVIATION
08sig3.QXD 6/22/09 2:35 PM Page 66
break-in, these can be removed to provide
extra power and rpm. The well-illustrated
manual shows exactly how to do that.
However, I stayed with the small-diameter
inlets throughout my tests.
I followed the break-in instructions in
the larger booklet. One of its paragraphs
recommends oiling the engine before its
first run. Besides injecting oil through the
crankcase breather, Saito advises putting a
few drops down the pushrod tubes, to
lubricate the camshaft area. That requires
removing the rocker-arm covers. While I
had the covers off to add oil, I admired the
valve mechanisms’ Swiss-watchlike
precision.
When considering switching to fourstroke
power, some two-stroke users worry
about the valves needing constant
readjustment. That was indeed a problem
with earlier four-strokers—but not with
Saitos.
I mounted the Saito .62 in my test stand
for its break-in. Saito’s instructions for its
CL engines advise using fuel with 10%-
15% nitro and 20%-22% oil—no more than
half of that castor. I used 15% nitro, 22%
oil, and proceeded. Then came a hiccup.
The instructions warn not to exceed
4,000 rpm for the first 10 minutes of breakin
time. But with the recommended 13 x 6
propeller and small venturi insert, the
slowest I could get the .62 to run was 6,200
rpm. That was with the needle set
“slobbering rich,” too.
Yet the .62 showed no sign of distress or
overheating, and its exhaust oil came out
undarkened. That’s an excellent indicator of
mild operating temperatures.
I had similar results with the .56 and .72.
Neither would run anywhere nearly as slow
as 4,000 rpm, but no problems resulted
from my exceeding the prescribed “top
limit” for break-in. The way I understand it,
the 4,000 rpm limit is for the RC line of
engines, which can easily adjust power
output with the throttle.
Flight-Test Vehicles: My helper and I
decided to try one of John Brodak’s biggest
ARF kits—the Cardinal—for our first
attempt with Saito power. But as soon as
the kit arrived, a few problems emerged
Photos by Yana Sarai
Surprise Performance
An interesting possibility occurred to me regarding models
for the Saito FA-72CL. It develops approximately the same
power as some of the best Class C spark-ignition two-stroke
engines of the late 1940s, such as the Anderson Spitfire .65, the
Atwood Champion .60, and the Orwick .64. With their ignition
components—coil, condenser, battery packs, and wiring—plus
propeller, they weighed close to the big Saito four-stroker’s
191/2 ounces.
Many 60-powered Old Time Stunt models were fine
performers in their day. These included Jim Saftig’s big Zilch,
J.C. Yates’s Madman, Hal deBolt’s Stunt Wagon, Bob
Palmer’s Go-Devil Sr., and his scale model of Sammy Mason’s
orange-and-white-checkerboard aerobatic Stearman biplane.
Saito’s .72 would make an ideal modern power provider for
all those airplanes. They should require little or no nose
shortening. MA
The smallest of Saito’s first three CL power plants (a .40 is now —Joe Wagner
available), the .56 produces slightly more power than a typical
two-stroke .40 and runs as smoothly.
Both models use a
Uniflow fuel tank
design, unassisted by
muffler pressure. It
works fine. The
steeply downwardangled
muffler keeps
the airplane’s
underside clean but
could cause damage
in a fast nose-over
landing.
should be shortened by approximately 3 inches.
That’s too much! It could be done, but it wouldn’t leave room
for my fuel tank between the engine and the wing. I was forced to
compromise by shortening the nose only 11/2 inches. Doing so
would barely leave room for a 31/2-ounce Oval Profile Uniflow tank.
So to balance my Mauler at the proper place, I’ll need to leave
the aft end of the profile body untapered, extend the tail by close to
an inch, and probably install a heavy, brass-hub tail wheel on a 3/32-
inch-diameter wire strut.
I’ve gone into detail to show that substituting a four-stroke
engine for a two-stroke in a modern CL aircraft is more than a
matter of changing power plants. The Brodak Mauler, a typical
large profile Stunt design, is an excellent example of the conversion
problem.
However, the Brodak Cardinal was a different story. Since it had
a longer nose, it was readily possible to shorten it enough for proper
balance.
I did that by fully assembling the model except for the power
system. I tied the propped Saito .56 to a loop of string and hung it
beneath the Cardinal’s nose. I slid the string loop fore and aft until
the model balanced.
The string-loop location showed me precisely where the Saito’s
cylinder centerline belonged. The engine-mounting process was
straightforward from there.
Then another consideration emerged: propeller clearance.
Brodak’s Cardinal ARF comes with 13/4-inch wheels. Evidently it’s
supposed to be flown strictly from smoothly paved surfaces. But the
small wheels don’t provide enough propeller clearance for the 12-
inch propeller with which the Saito .56 performs best.
Installing a pair of 3-inch SkyLite wheels and rebending the
Cardinal’s aluminum landing gear struts inward a tad solved that
The model was designed to be powered with a Brodak .40 twostroke:
a lightweight, mostly aluminum engine. With its muffler and
11 x 5 Master Airscrew propeller, the .40 weighs 9.7 ounces. The
Saito .56 weighs 16.1 ounces with its muffler and propeller.
Following is one way to calculate how much to shorten a model’s
nose to accommodate a heavier engine.
Measure the distance (on plans if possible) from the design’s
balance point to the center of the cylinder of the engine that the
model was designed to use. Multiply that engine’s weight by its
distance from the balance point. Divide that number by the heavier
engine’s weight. That gives you the distance from the model’s
balance point to the heavy engine’s cylinder centerline.
Brodak’s warbird-series Martin Mauler profile Stunter was
designed for the lightweight Fox .35 power. It weighs 10 ounces
exactly with muffler and a 10 x 5 Graupner propeller.
However, I know from experience that a completed Mauler
usually comes out tail-heavy with a Fox .35 and needs roughly a 1-
ounce spinner to bring the CG to the right place. That puts the Fox
installation’s gross weight at 11 ounces. On the Mauler plans, the
Fox cylinder centerline is 81/4 inches ahead of the CG.
Therefore, 11 x 81/4 = 903/4 inch-ounces. Dividing that by the
Saito .62’s weight plus its propeller—171/2 ounces—gives us 53/16
inches. To maintain the same CG with the Saito, the Mauler’s nose
68 MODEL AVIATION
08sig3.QXD 6/22/09 2:55 PM Page 68
problem. It also eliminated takeoff and
landing difficulties at the grassy field I
typically use for CL flying.
When the Cardinal’s engine
installation was complete, I tried handstarting
the Saito in the model; I much
prefer this starting method.
For one thing, it gives me a feel for
what’s happening with the engine. For
another, hand-starting eliminates having
to lug heavy equipment out to the edge of
the flying circle for electric startups and
then toting it back after takeoff.
However, I couldn’t get the Saito to
perk. That was because of the narrow gap
between its intake and the side of the
Cardinal’s profile fuselage. Fingerchoking
was impossible, and so was
squirting fuel into the carburetor inlet.
I solved this problem by adding an
extension to the .56’s intake. A 2-inch
length of brass tubing through a hole in
the Cardinal’s side did the trick.
That not only made hand-starting easy,
but it also added a couple hundred rpm.
That was no doubt because of a tuned
intake effect. I’ve seen the same
improvement from extensions I’ve added
to many other two- and four-stroke
engines, and I recommend it for the Saito.
Later I found another way to add an
intake extender. This one was made from
a length of 3/8-inch-OD rigid plastic pipe.
(Lowe’s home-improvement store sells
it.)
The pipe’s wall is thick enough to
allow its end to be tapered to match the
Saito intake’s internal taper. You can do
this on a drill press, using file-to-fit
methods and checking for proper fit as the
pipe is shaped with a file and sanding
tools. The pipe’s other end’s entry should
be bell-mouthed, to eliminate inlet stall
and the power loss that it can cause.
Flight Performance: To make valid
performance comparisons between the
Saito .56 and a two-stroke engine with
similar power, I installed a well-broken-in
Brodak .40 in a faithful old Stunter of my
own design—the Vanga Shrike—that I’d
flown for years with a mild-mannered
McCoy .35 Redhead.
The Shrike and the Cardinal have an
almost identical aerodynamic setup. They
are especially alike since I altered the
Cardinal wing’s LE radius to the more
rounded contour that I’ve learned is best
for my preferred Stunt flying style.
The Shrike weighs 2 pounds, 15
ounces in ready-to-takeoff condition. The
Cardinal came out 5 ounces heavier. But
with 4 square feet of working wing area
(including the flaps) on each model, the
wing loading difference between the
Stunters seemed negligible, at a mere 1.25
ounces per square foot.
Saitos are heavier than the two-stroke engines that most large CL Stunters were
designed to use. For proper balance, the engine for this Brodak Martin Mauler must be
moved back.
Conditions were ideal for initial flight
tests. The temperature was near 70°,
humidity was near 60%, and there was just
enough wind to ensure that the lines stayed
taut in severe maneuvers.
I flew both models on 70-foot .015
braided steel lines. For sound-level
comparisons on the same lines that day, I
also flew my old faithful Flite Streak, which
is powered with an O.S. 25LA-S.
First up was the Shrike. I’d flown it many
times with its original McCoy .35—which
never needed an intake extension. And the
model performed similarly with the Brodak.
The .40 is a more advanced design, but it has
a muffler whereas the McCoy doesn’t.
Lap speed varied depending on how rich
the needle was set. With its Brodak .40 twostroking
steadily but not quite fully leaned
out, the Shrike flew shoulder-level laps at 4.8
seconds.
That works out to nearly 95 feet per
second, or 65 mph. At that speed, the Shrike
pulled the lines almost straight between
handle and wingtip, but not hard enough to
make me need to lean over backward as I
piloted.
My helper, Yana Sarai, measured the
Shrike’s sound level at 110 dBA on the
ground at takeoff, 90 dBA as it passed by on
her side of the circle, and 70 dBA on the far
side. We performed our flight tests at an
extremely quiet location, with an ambient
sound level close to 60 dBA. At no time
during any in-flight tests did Yana find the
sound quality annoying.
Now for the Cardinal. Its not-completelybroken-
in Saito .56 turned the 12 x 6 Master
Airscrew propeller at 9,450 rpm on the
ground. That’s 450 rpm faster than the
factory obtained with a 12 x 6 APC
propeller and the small venturi insert. The
improvement was probably owed to my
intake extension.
70 MODEL AVIATION
I ran the .56 with the same 15%
nitro/22% oil fuel I used to break in the other
three Saitos. I’d also flown the Brodak .40
and the O.S. 25LA-S with that fuel blend. I
like it.
The .56 ran steadily throughout its flights.
I could expect no “two-four break” effect in
maneuvering; the Saito is a four-stroke, after
all. Still, its consistency impressed me,
especially since it was drawing its fuel from
a standard Uniflow tank setup. I’d decided to
try that and then switch to muffler pressure,
to see whether it made a difference. It didn’t.
The Saito .56-powered Cardinal
performed as well as any high-powered Stunt
model I’ve flown. Its extra weight compared
to the Shrike’s had no effect that I noticed.
The Cardinal’s flying speed was close to the
Shrike’s, too.
I did notice a small difference in control
response, but that could have been caused by
the way the Cardinal’s controls were set up.
This was the first CL model I’d ever flown
with its up-line ahead of the down-line; they
come out from the wingtip close, though.
Yana measured the Saito’s sound output
as 110 dBA at takeoff (same as the Brodak),
but only approximately 80 dBA as it passed
her in flight, and a mere 60 on the far side of
the circle. Considering that the background
noise was at roughly that dB level, the Saito
turned out to be amazingly quiet in flight. As
for the sound quality, Yana said that the only
real difference between the two-stroker and
the Saito was the latter’s lower tone.
A comparison flight with the .25-powered
Flite Streak confirmed our data. Yana got
almost identical sound-meter readings to
those she measured during the Saito’s
flights.
I almost forgot: the Shrike and Cardinal
have 31/2-ounce fuel tanks. From engine
startup to in-flight shutoff, the Shrike’s
Brodak .40 ran six-and-a-half minutes on
the average. The Saito .56 went almost a
minute longer.
In spite of requiring a different
installation, Saito’s CL four-stroke
engines are marvelous for round-the-circle
aerobatic flying—or for sport. Their
steady running, low sound output for the
size, and “businesslike attitude” seem well
worth the extra cost.
The only improvement I can suggest is
for Saito to supply a 2-inch-long intake
extension with each engine. That addition
makes a real difference. MA
Joe Wagner
[email protected]
Sources:
Saito Engines
(800) 338-4639
www.saitoengines.com
Brodak Manufacturing
(724) 966-2726
www.brodak.com