June 2004 97
THIS MONTH I’LL begin on a more
technical note. Included are a series of
excerpts from Dave Lockhart, who wrote an
interesting note about two-stroke and fourstroke
engines. Dave is a top-of-the-line FAI
pilot who has been flying competitively for
at least 15 years. His observations are
informative, and he presents several less
obvious angles that might not crop up unless
you are a serious competitor.
Dave wrote:
“When looking at different designs of
engines, there are a couple of initial items to
consider.
“Initial price vs. secondary costs: The
average two-stroke is running on lower nitro
than the average four-stroke (multiply that
by the number of times you fly in a year).
“Vibration: The average four-stroke
vibrates more than the average two-stroke.
(Make your own estimates for airplane
longevity, servo gears, servo pots, etc.—and
don’t forget to include your time for
completing the maintenance.)
“Maintenance cost of engine: Parts is
parts; they all wear, and all cost money to
replace/fix. Four-strokes have more parts.
Again, based on the number of flights you
fly in a year, add up the cost for parts and the
time to make the repairs. When I do the
math, the two-stroke wins.
“Throttle linearity and consistency: In
my opinion, throttle linearity is far
overrated; everyone has his or her own idea
on what a linear throttle is. Is 50% stick =
50% rpm and 90% stick = 90% rpm? Linear
to one person is not linear to another—
which is why you see many identical setups
using different throttle curves in the hands
of different pilots.
“Throttle consistency is what we really
care about. If the throttle is consistent and
predictable it is easy to fly, and if it doesn’t
feel linear, the ‘curve’ can be adjusted to
make it feel ‘more linear’—the curve can be
adjusted mechanically or with the radio.
“Influence of exhaust system on engines:
We all know the exhaust system is primarily
to quiet the engine and secondarily to not
detract from the power the engine makes (or
maybe increase the power the engine
makes).
“How the exhaust system affects a twostroke
is very different than a four-stroke,
primarily because a four-stroke has
dedicated intake and exhaust phases while a
two-stroke shares them. (This may be a gross
simplification.)
“In a four-stroke the best that the exhaust
system can do is scavenge the exhaust gases
from the combustion chamber and efficiently
exhaust them out the tailpipe. Depending on
the design of the exhaust system, the torque
curve might be enhanced in some rpm ranges
to a small extent.
“In a two-stroke, the exhaust system can
have a far greater influence on how the
engine runs; it can not only scavenge exhaust
gases, but it can increase the volume/density
of the intake charge, and it can affect the
pressure (or vacuum) at the carburetor itself.
“With the two-stroke, the specific design
of the exhaust system can have a huge effect
on the torque curve, peak power, and
‘linearity’ of the throttle. Two-strokes do not
suffer from lack of midrange torque and do
not suffer from poor throttle response. A
poorly set up two-stroke may lack midrange
torque and throttle response, but so will a
poorly set up four-stroke.
“If your engine has a linear throttle and
consistent throttle, and you aren’t using a
throttle curve, an EFI, or an MC carburetor
(or the O.S. equivalent carburetor), then you
don’t need a throttle curve, an EFI, or an MC
carburetor (or the O.S. equivalent
carburetor).
“Many of the two-strokes available today
and in recent years have been labeled as
poorly carbureted—because the carburetor
appeared to have rich/lean spots, flat spots,
hesitations, etc. The majority of the time, it is
not the carburetor that has the problem—it is
the fault of a poorly set up or designed
exhaust system (or one that is designed for
max power, not throttle response).
“Because it is possible for the exhaust
system to influence the pressure (vacuum) at
the carburetor inlet, it can also affect
mixture at the carburetor. So, if your twostroke’s
carburetor has rich/lean spots, there
are two ways to fix it: retune the exhaust
system or adjust the carburetor mixture at
that throttle setting.
Eric Henderson, 303 Shady Ln., Marlton NJ 08053; E-mail: [email protected]
RADIO CONTROL AEROBATICS
Are the days of the standard carburetor
numbered? Pumped and pipe engines
need special carburetors.
FAI pilot Dave Lockhart with his O.S. 1.40 FI-powered EMC. Dave shares his
experiences with two-stroke and four-stroke engines in this month’s column.
06sig4.QXD 3/24/04 12:25 pm Page 97
98 MODEL AVIATION
“Fixing the problems with the exhaust
system is where the whole art of two-stroke
tuning comes into play. Odds are, if you
copy the setup (propeller, plug, fuel, pipe,
tune length, header) recommended by the
manufacturer, you won’t have any carburetor
issues; the manufacturer has already done the
two-stroke’s tuning so you don’t have to.
“Why use an EFI? Why use an MC
(Mixture Carb)? Because it allows the
carburetion to be matched to a greater variety
of exhaust setups. It does increase the
linearity and consistency compared to the
majority of setups being used.
“The O.S. EFI system allows the mixture
to be set at three points—idle, midrange, and
high speed—and then itself regulates the
mixture (to an extent, only effectively within
a limited range). The MC (and O.S.-
equivalent carburetor) allows the setup to be
adjusted just about anywhere. (Eight points
is easy with a JR 10X; I can’t speak for other
transmitters but figure they are close to the
same). And as has been pointed out, both
systems have some advantages so far as no
needle valves.”
Thank you for this gold mine of
information, Dave. You definitely gave us a
lot to think about.
This month I am going to take a close look
at the products and services that Radio South
has available. You may have seen one of its
bright-orange Ni-starter boxes on the
flightline.
Steve Helms formed Radio South in the
summer of 1976. It was a Pattern-oriented
company from the start because of Steve’s
competition involvement and personal
enthusiasm. Current owner Tony Stillman
began working for Radio South in 1978. As
the sport of Pattern flying grew, they began
to include Pattern equipment in their
inventory, in addition to the top brands of
radio equipment.
Radio South carries most of the hard-tofind
Pattern and International Miniature
Aerobatic Club (IMAC) specialty items. The
company also has its own products, such as
the famous Pro-Driver, MonoKote/UltraCote
matching paints, and the recently introduced
ball-bearing Pro-Horns.
Tony Stillman attended his first of many
Nats in 1976. Since then he has CDed
several Nats, Team Selections, and even two
World Championships! He has also been the
team manager for the US F3A team four
times, including in 2003 when the US placed
first as a team and third individually at the
World Championships.
Radio South is not only a supplier, but a
large contributor and supporter of the US
Nats and Team Selection competitions. The
company proudly supports local Pattern
events every year. In addition to products
Radio South offers radio repair for all major
brands of equipment, such as Futaba, JR,
Airtronics, and Hitec. For more information,
go to www.radiosouthrc.com or call (800)
962-7802.
Radio South has a new model called the
Panacea. This design was started
approximately 18 months ago. It is similar to
a Smaragd, using the same wing and tail
airfoils. The fuselage can be built with a pipe
floor or a pipe tunnel.
The Panacea features carbon fiber (CF)
landing gear and wheel pants (Bolly), CF
wing and stabilizer tubes (PBG), and a
fiberglass/CF fuselage with removable
engine cowl and canopy areas. The canopy
area is fiberglass. (A clear-canopy version
may be available in the future.) Initial flighttesting
has been excellent; Todd Blose and
Steve Kessler have reported excellent rolling
and snap characteristics.
Many questions come to me via E-mail and
US mail. A common inquiry is, Why do my
fellow contestants keep pressing me to move
up?
When these “fellow contestants” are in
the same class, it is most likely because you
have gotten too good. When the contestants
are in the classes above you, it is a bit more
perplexing.
There is a thing in life that we call a
“leap of faith.” For some of us, it was that
move from sport flying to entering a funfly
or even a Pattern contest. Once that
leap has been taken, it seems far easier
than before the leap. The human mind is
great at minimizing. It softens the premoment
memory with the balm of
progress or success.
That means once someone has taken
these leaps and has had success, naturally
that person would like all of us to experience
the same joy. It is easy for those early
trepidations to be long forgotten and hard to
place yourself in your past and fully recall
how it felt.
For me, it takes a tremendous leap of
faith to try to compete in FAI. The class
always seems to be two years ahead of me; I
seem to be able to fly the defunct schedule
better than the new one.
Of all the classes, FAI is the most
demanding on equipment. It does require top
of-the-line gear. The P-05 schedule has a
vertical positive snap that requires the best
available power, or a 10-pound or less
model, to get it to keep going high enough
for the following midentry vertical 8.
FAI is really for those who do not fear
making that leap of faith and leap of
investment; more power to them and their
wallets. Meanwhile, there are four AMA
Aerobatics classes in which airplanes from
six years ago or more are still competitive.
Another question is, Why compete when
there is a dominant pilot in my class?
There is a fierce flame that burns in the
creature known as man; it is easily
recognized as our competitive spirit. It drives
us to compete without necessarily having to
win or even having a chance of winning.
This spirit makes us show up no matter how
well we know we will do.
Sometimes we get a break, such as good
air versus a competitor’s bad air. Sometimes
our equipment is better maintained and we
get an unexpected win. Deep inside we know
that there will always be an element of
chance that might change the outcome, so we
show up! You really don’t need the latest
and greatest to win. Maybe you do in the top
class (classes), but you get more mileage
from practicing than from having the latest
and greatest.
A big question is, You spend a lot of
time encouraging us to give Pattern a try,
but what about pilots who stop
A prototype version of the new Radio
South Panacea by Todd Blose. Initial
flight-testing has been excellent.
Steve Kessler with his Radio South Panacea. He reports great rolls and snaps.
06sig4.QXD 3/24/04 12:26 pm Page 98
100 MODEL AVIATION
competing—why do they?
Based on my informal survey of pilots at
all levels (long-timers and relatively new
participants) during my times of NSRCA
service, I was told that there are many
reasons why some pilots stop competing;
some are unique and some are unavoidable.
Following is a list ranging from the most
uncommon (first) to the most common
(last) reasons.
1) Once in awhile, people compete who
are just not cut out for competition. It
affects them badly, degrades their
enjoyment, and gets to them in a way in
which they “go backward” and are
unsuccessful. Even when they are
successful, the stress of competition makes
them behave poorly. Sooner, rather than
later, they quit, usually for some other sport.
2) A big change in life, such as a new
partner, a new job, losing one or both, or
children getting older and getting involved
in T-ball, basketball, soccer.
3) Cost. Not that it is flat-out too
OWN A MACHINE SHOP
1-800-476-4849
O r V i s i t u s a t w w w.smithy.com
GUARANTEED To pay for itself! FREE!
Info Kit
FREE!
Info Kit
Call
Today!
“I can fix ‘most anything. I don’t know how I lived
without my Smithy. It paid for itself in no time.”
• Easy to use – No
experience
required.
• Versatile – Fix or
make almost anything.
• Affordalbe-- 6
models starting
at $995.
• CNC Compatible
Do It Yourself on a Smithy Lathe•Mill•Drill!
expensive, but that competitors begin
spending too much for little in return. They
feel that they won’t get the scores unless
they have the latest equipment, so they stop
right there.
4) Time. Not building time, but flying
time. These pilots could not dedicate the
practice time to handle new routines or do
well with existing ones. This made them
unhappy with their performances because of
lack of practice.
5) Age and eyesight. Inevitably, this will
get all of us.
6) Judging. Most of the pilots who quit
felt that they couldn’t get a fair shake. There
were two main reasons for their conclusion,
the first of which was that the standard of
judging did not meet their flying skills. They
knew from contest after contest and personal
contact that the people behind them did not
know the rules. They felt that no matter how
well they executed the geometry, it would
not be scored correctly against pilots who
did not execute as well.
The second reason was that they had
built too many prejudices with the people
who could be judging them—a result of old
feuds from previous classes, etc. Those they
used to “hammer” were getting even.
Whatever the reason that makes you
decide to move on or hang it up, you need to
try it first. It is amazing how hard that first
step can be. So, how is your competitive
spirit doing? MA
06sig4.QXD 3/24/04 12:26 pm Page 100
Edition: Model Aviation - 2004/06
Page Numbers: 97,98,100
Edition: Model Aviation - 2004/06
Page Numbers: 97,98,100
June 2004 97
THIS MONTH I’LL begin on a more
technical note. Included are a series of
excerpts from Dave Lockhart, who wrote an
interesting note about two-stroke and fourstroke
engines. Dave is a top-of-the-line FAI
pilot who has been flying competitively for
at least 15 years. His observations are
informative, and he presents several less
obvious angles that might not crop up unless
you are a serious competitor.
Dave wrote:
“When looking at different designs of
engines, there are a couple of initial items to
consider.
“Initial price vs. secondary costs: The
average two-stroke is running on lower nitro
than the average four-stroke (multiply that
by the number of times you fly in a year).
“Vibration: The average four-stroke
vibrates more than the average two-stroke.
(Make your own estimates for airplane
longevity, servo gears, servo pots, etc.—and
don’t forget to include your time for
completing the maintenance.)
“Maintenance cost of engine: Parts is
parts; they all wear, and all cost money to
replace/fix. Four-strokes have more parts.
Again, based on the number of flights you
fly in a year, add up the cost for parts and the
time to make the repairs. When I do the
math, the two-stroke wins.
“Throttle linearity and consistency: In
my opinion, throttle linearity is far
overrated; everyone has his or her own idea
on what a linear throttle is. Is 50% stick =
50% rpm and 90% stick = 90% rpm? Linear
to one person is not linear to another—
which is why you see many identical setups
using different throttle curves in the hands
of different pilots.
“Throttle consistency is what we really
care about. If the throttle is consistent and
predictable it is easy to fly, and if it doesn’t
feel linear, the ‘curve’ can be adjusted to
make it feel ‘more linear’—the curve can be
adjusted mechanically or with the radio.
“Influence of exhaust system on engines:
We all know the exhaust system is primarily
to quiet the engine and secondarily to not
detract from the power the engine makes (or
maybe increase the power the engine
makes).
“How the exhaust system affects a twostroke
is very different than a four-stroke,
primarily because a four-stroke has
dedicated intake and exhaust phases while a
two-stroke shares them. (This may be a gross
simplification.)
“In a four-stroke the best that the exhaust
system can do is scavenge the exhaust gases
from the combustion chamber and efficiently
exhaust them out the tailpipe. Depending on
the design of the exhaust system, the torque
curve might be enhanced in some rpm ranges
to a small extent.
“In a two-stroke, the exhaust system can
have a far greater influence on how the
engine runs; it can not only scavenge exhaust
gases, but it can increase the volume/density
of the intake charge, and it can affect the
pressure (or vacuum) at the carburetor itself.
“With the two-stroke, the specific design
of the exhaust system can have a huge effect
on the torque curve, peak power, and
‘linearity’ of the throttle. Two-strokes do not
suffer from lack of midrange torque and do
not suffer from poor throttle response. A
poorly set up two-stroke may lack midrange
torque and throttle response, but so will a
poorly set up four-stroke.
“If your engine has a linear throttle and
consistent throttle, and you aren’t using a
throttle curve, an EFI, or an MC carburetor
(or the O.S. equivalent carburetor), then you
don’t need a throttle curve, an EFI, or an MC
carburetor (or the O.S. equivalent
carburetor).
“Many of the two-strokes available today
and in recent years have been labeled as
poorly carbureted—because the carburetor
appeared to have rich/lean spots, flat spots,
hesitations, etc. The majority of the time, it is
not the carburetor that has the problem—it is
the fault of a poorly set up or designed
exhaust system (or one that is designed for
max power, not throttle response).
“Because it is possible for the exhaust
system to influence the pressure (vacuum) at
the carburetor inlet, it can also affect
mixture at the carburetor. So, if your twostroke’s
carburetor has rich/lean spots, there
are two ways to fix it: retune the exhaust
system or adjust the carburetor mixture at
that throttle setting.
Eric Henderson, 303 Shady Ln., Marlton NJ 08053; E-mail: [email protected]
RADIO CONTROL AEROBATICS
Are the days of the standard carburetor
numbered? Pumped and pipe engines
need special carburetors.
FAI pilot Dave Lockhart with his O.S. 1.40 FI-powered EMC. Dave shares his
experiences with two-stroke and four-stroke engines in this month’s column.
06sig4.QXD 3/24/04 12:25 pm Page 97
98 MODEL AVIATION
“Fixing the problems with the exhaust
system is where the whole art of two-stroke
tuning comes into play. Odds are, if you
copy the setup (propeller, plug, fuel, pipe,
tune length, header) recommended by the
manufacturer, you won’t have any carburetor
issues; the manufacturer has already done the
two-stroke’s tuning so you don’t have to.
“Why use an EFI? Why use an MC
(Mixture Carb)? Because it allows the
carburetion to be matched to a greater variety
of exhaust setups. It does increase the
linearity and consistency compared to the
majority of setups being used.
“The O.S. EFI system allows the mixture
to be set at three points—idle, midrange, and
high speed—and then itself regulates the
mixture (to an extent, only effectively within
a limited range). The MC (and O.S.-
equivalent carburetor) allows the setup to be
adjusted just about anywhere. (Eight points
is easy with a JR 10X; I can’t speak for other
transmitters but figure they are close to the
same). And as has been pointed out, both
systems have some advantages so far as no
needle valves.”
Thank you for this gold mine of
information, Dave. You definitely gave us a
lot to think about.
This month I am going to take a close look
at the products and services that Radio South
has available. You may have seen one of its
bright-orange Ni-starter boxes on the
flightline.
Steve Helms formed Radio South in the
summer of 1976. It was a Pattern-oriented
company from the start because of Steve’s
competition involvement and personal
enthusiasm. Current owner Tony Stillman
began working for Radio South in 1978. As
the sport of Pattern flying grew, they began
to include Pattern equipment in their
inventory, in addition to the top brands of
radio equipment.
Radio South carries most of the hard-tofind
Pattern and International Miniature
Aerobatic Club (IMAC) specialty items. The
company also has its own products, such as
the famous Pro-Driver, MonoKote/UltraCote
matching paints, and the recently introduced
ball-bearing Pro-Horns.
Tony Stillman attended his first of many
Nats in 1976. Since then he has CDed
several Nats, Team Selections, and even two
World Championships! He has also been the
team manager for the US F3A team four
times, including in 2003 when the US placed
first as a team and third individually at the
World Championships.
Radio South is not only a supplier, but a
large contributor and supporter of the US
Nats and Team Selection competitions. The
company proudly supports local Pattern
events every year. In addition to products
Radio South offers radio repair for all major
brands of equipment, such as Futaba, JR,
Airtronics, and Hitec. For more information,
go to www.radiosouthrc.com or call (800)
962-7802.
Radio South has a new model called the
Panacea. This design was started
approximately 18 months ago. It is similar to
a Smaragd, using the same wing and tail
airfoils. The fuselage can be built with a pipe
floor or a pipe tunnel.
The Panacea features carbon fiber (CF)
landing gear and wheel pants (Bolly), CF
wing and stabilizer tubes (PBG), and a
fiberglass/CF fuselage with removable
engine cowl and canopy areas. The canopy
area is fiberglass. (A clear-canopy version
may be available in the future.) Initial flighttesting
has been excellent; Todd Blose and
Steve Kessler have reported excellent rolling
and snap characteristics.
Many questions come to me via E-mail and
US mail. A common inquiry is, Why do my
fellow contestants keep pressing me to move
up?
When these “fellow contestants” are in
the same class, it is most likely because you
have gotten too good. When the contestants
are in the classes above you, it is a bit more
perplexing.
There is a thing in life that we call a
“leap of faith.” For some of us, it was that
move from sport flying to entering a funfly
or even a Pattern contest. Once that
leap has been taken, it seems far easier
than before the leap. The human mind is
great at minimizing. It softens the premoment
memory with the balm of
progress or success.
That means once someone has taken
these leaps and has had success, naturally
that person would like all of us to experience
the same joy. It is easy for those early
trepidations to be long forgotten and hard to
place yourself in your past and fully recall
how it felt.
For me, it takes a tremendous leap of
faith to try to compete in FAI. The class
always seems to be two years ahead of me; I
seem to be able to fly the defunct schedule
better than the new one.
Of all the classes, FAI is the most
demanding on equipment. It does require top
of-the-line gear. The P-05 schedule has a
vertical positive snap that requires the best
available power, or a 10-pound or less
model, to get it to keep going high enough
for the following midentry vertical 8.
FAI is really for those who do not fear
making that leap of faith and leap of
investment; more power to them and their
wallets. Meanwhile, there are four AMA
Aerobatics classes in which airplanes from
six years ago or more are still competitive.
Another question is, Why compete when
there is a dominant pilot in my class?
There is a fierce flame that burns in the
creature known as man; it is easily
recognized as our competitive spirit. It drives
us to compete without necessarily having to
win or even having a chance of winning.
This spirit makes us show up no matter how
well we know we will do.
Sometimes we get a break, such as good
air versus a competitor’s bad air. Sometimes
our equipment is better maintained and we
get an unexpected win. Deep inside we know
that there will always be an element of
chance that might change the outcome, so we
show up! You really don’t need the latest
and greatest to win. Maybe you do in the top
class (classes), but you get more mileage
from practicing than from having the latest
and greatest.
A big question is, You spend a lot of
time encouraging us to give Pattern a try,
but what about pilots who stop
A prototype version of the new Radio
South Panacea by Todd Blose. Initial
flight-testing has been excellent.
Steve Kessler with his Radio South Panacea. He reports great rolls and snaps.
06sig4.QXD 3/24/04 12:26 pm Page 98
100 MODEL AVIATION
competing—why do they?
Based on my informal survey of pilots at
all levels (long-timers and relatively new
participants) during my times of NSRCA
service, I was told that there are many
reasons why some pilots stop competing;
some are unique and some are unavoidable.
Following is a list ranging from the most
uncommon (first) to the most common
(last) reasons.
1) Once in awhile, people compete who
are just not cut out for competition. It
affects them badly, degrades their
enjoyment, and gets to them in a way in
which they “go backward” and are
unsuccessful. Even when they are
successful, the stress of competition makes
them behave poorly. Sooner, rather than
later, they quit, usually for some other sport.
2) A big change in life, such as a new
partner, a new job, losing one or both, or
children getting older and getting involved
in T-ball, basketball, soccer.
3) Cost. Not that it is flat-out too
OWN A MACHINE SHOP
1-800-476-4849
O r V i s i t u s a t w w w.smithy.com
GUARANTEED To pay for itself! FREE!
Info Kit
FREE!
Info Kit
Call
Today!
“I can fix ‘most anything. I don’t know how I lived
without my Smithy. It paid for itself in no time.”
• Easy to use – No
experience
required.
• Versatile – Fix or
make almost anything.
• Affordalbe-- 6
models starting
at $995.
• CNC Compatible
Do It Yourself on a Smithy Lathe•Mill•Drill!
expensive, but that competitors begin
spending too much for little in return. They
feel that they won’t get the scores unless
they have the latest equipment, so they stop
right there.
4) Time. Not building time, but flying
time. These pilots could not dedicate the
practice time to handle new routines or do
well with existing ones. This made them
unhappy with their performances because of
lack of practice.
5) Age and eyesight. Inevitably, this will
get all of us.
6) Judging. Most of the pilots who quit
felt that they couldn’t get a fair shake. There
were two main reasons for their conclusion,
the first of which was that the standard of
judging did not meet their flying skills. They
knew from contest after contest and personal
contact that the people behind them did not
know the rules. They felt that no matter how
well they executed the geometry, it would
not be scored correctly against pilots who
did not execute as well.
The second reason was that they had
built too many prejudices with the people
who could be judging them—a result of old
feuds from previous classes, etc. Those they
used to “hammer” were getting even.
Whatever the reason that makes you
decide to move on or hang it up, you need to
try it first. It is amazing how hard that first
step can be. So, how is your competitive
spirit doing? MA
06sig4.QXD 3/24/04 12:26 pm Page 100
Edition: Model Aviation - 2004/06
Page Numbers: 97,98,100
June 2004 97
THIS MONTH I’LL begin on a more
technical note. Included are a series of
excerpts from Dave Lockhart, who wrote an
interesting note about two-stroke and fourstroke
engines. Dave is a top-of-the-line FAI
pilot who has been flying competitively for
at least 15 years. His observations are
informative, and he presents several less
obvious angles that might not crop up unless
you are a serious competitor.
Dave wrote:
“When looking at different designs of
engines, there are a couple of initial items to
consider.
“Initial price vs. secondary costs: The
average two-stroke is running on lower nitro
than the average four-stroke (multiply that
by the number of times you fly in a year).
“Vibration: The average four-stroke
vibrates more than the average two-stroke.
(Make your own estimates for airplane
longevity, servo gears, servo pots, etc.—and
don’t forget to include your time for
completing the maintenance.)
“Maintenance cost of engine: Parts is
parts; they all wear, and all cost money to
replace/fix. Four-strokes have more parts.
Again, based on the number of flights you
fly in a year, add up the cost for parts and the
time to make the repairs. When I do the
math, the two-stroke wins.
“Throttle linearity and consistency: In
my opinion, throttle linearity is far
overrated; everyone has his or her own idea
on what a linear throttle is. Is 50% stick =
50% rpm and 90% stick = 90% rpm? Linear
to one person is not linear to another—
which is why you see many identical setups
using different throttle curves in the hands
of different pilots.
“Throttle consistency is what we really
care about. If the throttle is consistent and
predictable it is easy to fly, and if it doesn’t
feel linear, the ‘curve’ can be adjusted to
make it feel ‘more linear’—the curve can be
adjusted mechanically or with the radio.
“Influence of exhaust system on engines:
We all know the exhaust system is primarily
to quiet the engine and secondarily to not
detract from the power the engine makes (or
maybe increase the power the engine
makes).
“How the exhaust system affects a twostroke
is very different than a four-stroke,
primarily because a four-stroke has
dedicated intake and exhaust phases while a
two-stroke shares them. (This may be a gross
simplification.)
“In a four-stroke the best that the exhaust
system can do is scavenge the exhaust gases
from the combustion chamber and efficiently
exhaust them out the tailpipe. Depending on
the design of the exhaust system, the torque
curve might be enhanced in some rpm ranges
to a small extent.
“In a two-stroke, the exhaust system can
have a far greater influence on how the
engine runs; it can not only scavenge exhaust
gases, but it can increase the volume/density
of the intake charge, and it can affect the
pressure (or vacuum) at the carburetor itself.
“With the two-stroke, the specific design
of the exhaust system can have a huge effect
on the torque curve, peak power, and
‘linearity’ of the throttle. Two-strokes do not
suffer from lack of midrange torque and do
not suffer from poor throttle response. A
poorly set up two-stroke may lack midrange
torque and throttle response, but so will a
poorly set up four-stroke.
“If your engine has a linear throttle and
consistent throttle, and you aren’t using a
throttle curve, an EFI, or an MC carburetor
(or the O.S. equivalent carburetor), then you
don’t need a throttle curve, an EFI, or an MC
carburetor (or the O.S. equivalent
carburetor).
“Many of the two-strokes available today
and in recent years have been labeled as
poorly carbureted—because the carburetor
appeared to have rich/lean spots, flat spots,
hesitations, etc. The majority of the time, it is
not the carburetor that has the problem—it is
the fault of a poorly set up or designed
exhaust system (or one that is designed for
max power, not throttle response).
“Because it is possible for the exhaust
system to influence the pressure (vacuum) at
the carburetor inlet, it can also affect
mixture at the carburetor. So, if your twostroke’s
carburetor has rich/lean spots, there
are two ways to fix it: retune the exhaust
system or adjust the carburetor mixture at
that throttle setting.
Eric Henderson, 303 Shady Ln., Marlton NJ 08053; E-mail: [email protected]
RADIO CONTROL AEROBATICS
Are the days of the standard carburetor
numbered? Pumped and pipe engines
need special carburetors.
FAI pilot Dave Lockhart with his O.S. 1.40 FI-powered EMC. Dave shares his
experiences with two-stroke and four-stroke engines in this month’s column.
06sig4.QXD 3/24/04 12:25 pm Page 97
98 MODEL AVIATION
“Fixing the problems with the exhaust
system is where the whole art of two-stroke
tuning comes into play. Odds are, if you
copy the setup (propeller, plug, fuel, pipe,
tune length, header) recommended by the
manufacturer, you won’t have any carburetor
issues; the manufacturer has already done the
two-stroke’s tuning so you don’t have to.
“Why use an EFI? Why use an MC
(Mixture Carb)? Because it allows the
carburetion to be matched to a greater variety
of exhaust setups. It does increase the
linearity and consistency compared to the
majority of setups being used.
“The O.S. EFI system allows the mixture
to be set at three points—idle, midrange, and
high speed—and then itself regulates the
mixture (to an extent, only effectively within
a limited range). The MC (and O.S.-
equivalent carburetor) allows the setup to be
adjusted just about anywhere. (Eight points
is easy with a JR 10X; I can’t speak for other
transmitters but figure they are close to the
same). And as has been pointed out, both
systems have some advantages so far as no
needle valves.”
Thank you for this gold mine of
information, Dave. You definitely gave us a
lot to think about.
This month I am going to take a close look
at the products and services that Radio South
has available. You may have seen one of its
bright-orange Ni-starter boxes on the
flightline.
Steve Helms formed Radio South in the
summer of 1976. It was a Pattern-oriented
company from the start because of Steve’s
competition involvement and personal
enthusiasm. Current owner Tony Stillman
began working for Radio South in 1978. As
the sport of Pattern flying grew, they began
to include Pattern equipment in their
inventory, in addition to the top brands of
radio equipment.
Radio South carries most of the hard-tofind
Pattern and International Miniature
Aerobatic Club (IMAC) specialty items. The
company also has its own products, such as
the famous Pro-Driver, MonoKote/UltraCote
matching paints, and the recently introduced
ball-bearing Pro-Horns.
Tony Stillman attended his first of many
Nats in 1976. Since then he has CDed
several Nats, Team Selections, and even two
World Championships! He has also been the
team manager for the US F3A team four
times, including in 2003 when the US placed
first as a team and third individually at the
World Championships.
Radio South is not only a supplier, but a
large contributor and supporter of the US
Nats and Team Selection competitions. The
company proudly supports local Pattern
events every year. In addition to products
Radio South offers radio repair for all major
brands of equipment, such as Futaba, JR,
Airtronics, and Hitec. For more information,
go to www.radiosouthrc.com or call (800)
962-7802.
Radio South has a new model called the
Panacea. This design was started
approximately 18 months ago. It is similar to
a Smaragd, using the same wing and tail
airfoils. The fuselage can be built with a pipe
floor or a pipe tunnel.
The Panacea features carbon fiber (CF)
landing gear and wheel pants (Bolly), CF
wing and stabilizer tubes (PBG), and a
fiberglass/CF fuselage with removable
engine cowl and canopy areas. The canopy
area is fiberglass. (A clear-canopy version
may be available in the future.) Initial flighttesting
has been excellent; Todd Blose and
Steve Kessler have reported excellent rolling
and snap characteristics.
Many questions come to me via E-mail and
US mail. A common inquiry is, Why do my
fellow contestants keep pressing me to move
up?
When these “fellow contestants” are in
the same class, it is most likely because you
have gotten too good. When the contestants
are in the classes above you, it is a bit more
perplexing.
There is a thing in life that we call a
“leap of faith.” For some of us, it was that
move from sport flying to entering a funfly
or even a Pattern contest. Once that
leap has been taken, it seems far easier
than before the leap. The human mind is
great at minimizing. It softens the premoment
memory with the balm of
progress or success.
That means once someone has taken
these leaps and has had success, naturally
that person would like all of us to experience
the same joy. It is easy for those early
trepidations to be long forgotten and hard to
place yourself in your past and fully recall
how it felt.
For me, it takes a tremendous leap of
faith to try to compete in FAI. The class
always seems to be two years ahead of me; I
seem to be able to fly the defunct schedule
better than the new one.
Of all the classes, FAI is the most
demanding on equipment. It does require top
of-the-line gear. The P-05 schedule has a
vertical positive snap that requires the best
available power, or a 10-pound or less
model, to get it to keep going high enough
for the following midentry vertical 8.
FAI is really for those who do not fear
making that leap of faith and leap of
investment; more power to them and their
wallets. Meanwhile, there are four AMA
Aerobatics classes in which airplanes from
six years ago or more are still competitive.
Another question is, Why compete when
there is a dominant pilot in my class?
There is a fierce flame that burns in the
creature known as man; it is easily
recognized as our competitive spirit. It drives
us to compete without necessarily having to
win or even having a chance of winning.
This spirit makes us show up no matter how
well we know we will do.
Sometimes we get a break, such as good
air versus a competitor’s bad air. Sometimes
our equipment is better maintained and we
get an unexpected win. Deep inside we know
that there will always be an element of
chance that might change the outcome, so we
show up! You really don’t need the latest
and greatest to win. Maybe you do in the top
class (classes), but you get more mileage
from practicing than from having the latest
and greatest.
A big question is, You spend a lot of
time encouraging us to give Pattern a try,
but what about pilots who stop
A prototype version of the new Radio
South Panacea by Todd Blose. Initial
flight-testing has been excellent.
Steve Kessler with his Radio South Panacea. He reports great rolls and snaps.
06sig4.QXD 3/24/04 12:26 pm Page 98
100 MODEL AVIATION
competing—why do they?
Based on my informal survey of pilots at
all levels (long-timers and relatively new
participants) during my times of NSRCA
service, I was told that there are many
reasons why some pilots stop competing;
some are unique and some are unavoidable.
Following is a list ranging from the most
uncommon (first) to the most common
(last) reasons.
1) Once in awhile, people compete who
are just not cut out for competition. It
affects them badly, degrades their
enjoyment, and gets to them in a way in
which they “go backward” and are
unsuccessful. Even when they are
successful, the stress of competition makes
them behave poorly. Sooner, rather than
later, they quit, usually for some other sport.
2) A big change in life, such as a new
partner, a new job, losing one or both, or
children getting older and getting involved
in T-ball, basketball, soccer.
3) Cost. Not that it is flat-out too
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expensive, but that competitors begin
spending too much for little in return. They
feel that they won’t get the scores unless
they have the latest equipment, so they stop
right there.
4) Time. Not building time, but flying
time. These pilots could not dedicate the
practice time to handle new routines or do
well with existing ones. This made them
unhappy with their performances because of
lack of practice.
5) Age and eyesight. Inevitably, this will
get all of us.
6) Judging. Most of the pilots who quit
felt that they couldn’t get a fair shake. There
were two main reasons for their conclusion,
the first of which was that the standard of
judging did not meet their flying skills. They
knew from contest after contest and personal
contact that the people behind them did not
know the rules. They felt that no matter how
well they executed the geometry, it would
not be scored correctly against pilots who
did not execute as well.
The second reason was that they had
built too many prejudices with the people
who could be judging them—a result of old
feuds from previous classes, etc. Those they
used to “hammer” were getting even.
Whatever the reason that makes you
decide to move on or hang it up, you need to
try it first. It is amazing how hard that first
step can be. So, how is your competitive
spirit doing? MA
06sig4.QXD 3/24/04 12:26 pm Page 100
