136 MODEL AVIATION
RECORD: Bob Wilder has again taken
the lead in event 627: Indoor Electric
Duration (Radio Control). At the
UniDome in Cedar Rapids, Iowa, he had a
flight of 20:57—a substantial increase
over the previous record time in that
event.
West Coast Flying: Steve Brown reports
that there is essentially zero opportunity
to fly serious Indoor, such as F1D, on the
West Coast. He is building new models to
fly at the Kibbie Dome at the University
of Idaho. How sad! That area can be
considered the cradle of Indoor as we
know it today.
Fédération Aéronautique Internationale
(FAI) Record Process: The following are
excerpts from an E-mail message Jim
Richmond sent to me.
“I’m sending this in response to your
questions a while back. This is the routine
needed to establish FAI records:
“1. Get an individual world record
sanction ($2) and an FAI stamp. Do it
right away. Be sure to give AMA precise
info about the event and category (FAI #)
you want the sanction for. I’ve never
heard of any meet having an FAI sanction
except a world championship, so always
get an individual one.
“You can order by mail or call it in to
AMA (credit card). Amy Wilson in the
Competitions Dept. is your contact person
for this. This sanction is good for the
entire year for a specific model type &
ceiling category.
“2. AMA requires that you notify them
prior to each world record attempt, so Email
Steve Kaluf (skaluf@modelaircraft.
org) 2 weeks before the event (include the
FAI info on the sanction so he will know
what you are doing).
“3. Although FAI doesn’t require the
attempt to be made during an official
AMA event, I think AMA does, and they
want it to be able to qualify as an AMA
national record if it exceeds the current
one. Also, although FAI doesn’t require
your 2 timers to be AMA members, I
think AMA would require that, so don’t
fight it.
“4. Required participants: An AMA
contest director, 2 timers (AMA
members), 3 witnesses (minimum). Be
sure to get the names and AMA numbers
of these people if you wish to file a record
application. Also, you will need the
address of the contest director (for him to
sign the documents).
“5. Notification of a record
performance: AMA requires that you
notify them (Steve Kaluf preferably)
within 48 hours after the record flight(s).
FAI requires notification from either
AMA, NAA, or the Contest Director
within 7 days of the event. This is a
timing problem requiring your
participation. The sequence is: From you
to AMA to NAA [National Aeronautic
Association] to FAI.
“6. Documentation: You will need the
following in order to prepare your record
application ‘dossier’:
“A time card with your flight times
and the timers’ names signed in ink. You
Bud Tenny, Box 830545, Richardson TX 75083
FREE FLIGHT INDOOR
Fixture compares torsional strength of wood used for motorsticks of unbraced events such as Easy B (206). Fixture breaks down for
storage as shown on right.
Bill Gowen launches glider. Carbonfiber/
balsa framework, covered with grocery
produce-bag plastic. Dave Linstrum photo.
08sig5.QXD 5.23.03 12:37 pm Page 136
can prepare your own card for this.
“The names of the stop watches used.
You will also be required to testify that
they had been checked for accuracy prior
to the flight.
“You will need to be able to make a
sketch of the cross section of the building
showing the ceiling height.
“Record details of the flight(s) and
other conditions such as temperature and
outdoor weather and any unusual
difficulties or unusual happenings so a
descriptive story can be written for the
dossier.
“You will need a photograph and a 3
view drawing of your airplane.
“7. The dossier: This is an 11 page
document requiring a number of signatures
by the contest director. You need to get it
completed and signed off and delivered to
AMA (Steve Kaluf) within one month.
You can refer to the FAI rule book for
guidance, but it’s very helpful to have a
prior successful form on hand for
reference.
“Hope this helps. Let me know if you
have questions.”
Tan II Is No More: Rubber-model fliers
were dismayed by the announcement that
Tan II rubber will no longer be available
because of a change in golf-ball
construction. Balls with rubber thread
wound on a central core have been
replaced by balls using a different
construction technique. This removes the
only source for the Tan rubber.
Work had already begun on some
lower-energy rubber designated “Tan
Sport.” A follow-on product called “Tan
Super Sport” is also being made now. Fred
Tellier has been conducting some tests on
the new rubber as it becomes available. He
wrote:
“I did some revisited tests on Tan 5-99
after the WC and got energy readings
about 5100+ and turns/inch of 171-173.
Tan Sport gave energy readings in the
August 2003 137
Who are they? The author took this photo
at a 1960s-era World Championships.
Dick Obarski contemplates a flight
strategy. Linstrum photo.
Larry Coslick tops off a steering balloon
at a US Indoor Championships.
Kansas City-area fliers Tem Johnson
(standing) and Emil Schutzel prepare for
another flight. Linstrum photo.
4600-4700 range with higher torque 0.67
in./oz. compared to 0.62 in./oz. for 5-99.
“I test all motors using strips 0.050
inch wide weighing 0.6 g. The 5-99 is less
dense as it gives motors slightly longer—9
to 9.5 inch for 5-99 and 8.75 to 9.25 inch
for Sport. The torque drops off faster in
the Sport; later in the unwind the samples
are close in value.
“I think that if Super Sport is higher in
energy it will be quite usable but not in the
same class as Tan 10-97, 5-99 or 3-02.
“I flew some of the Sport on a Limited
PP [Pennyplane] and found it usable but
not great. Again I hope the Super Sport
will be better. We have to use this rubber,
but I think it will be hard to get enough
turns so longer motors will be needed.
“My ft. lbs./lb. numbers on most rubber
have improved; I think my winding skills
have gotten better allowing more turns in
the test motors. In the formula turns are
equivalent to stretch so this greatly affects
the results.
“I test motors made up to F1D weight;
break-in consists of winding to 0.3 in./oz.
and holding for 2 minutes then increasing
to 0.4 for 2 minutes. I test the next day and
test each motor only once. I try to test 5
separate motors and average the results. I
find for flying I can only get one safe
flight from a motor, but if I test a second
time I get more turns due to the extra
length; this a higher ft. lbs./lb. value.
“I am curious how others break in
motors as I get good turns but usually
break on second flight. I feel that we are
not out of the woods on the rubber
situation yet, but I think there is hope.”
Flight Trim From the Brainbusters
Newsletter (Edited by Abram Vandover):
“Put this in your field box! This article
is from an old newsletter and is by Jack
McGillivray, but the information is still
current and will help deciding what size
and length motor to use. I’m serious about
putting it in your tool box or in that book
that you keep all your info in, you do write
08sig5.QXD 5.23.03 12:37 pm Page 137
increasing its overall length; Use another
motor with the original cross section, but
with increased length; Increase the
propeller pitch, and/or propeller diameter;
If motor is new, problem will diminish
somewhat as motor breaks in.
“Problem 2: Aircraft lands with unused
turns left in motor (underpowered).
“Solutions: Shorten up the existing
motor; Use another motor with a larger
cross section, maintaining or shortening
overall motor length; Decrease the
propeller pitch, and/or propeller diameter.
“When considering solutions to
Problem 1 or 2, keep these parameters in
mind. If possible, the rubber motor weight
should exceed the airframe weight, but
should not exceed twice the airframe
weight. On many aircraft, though, motors
this heavy can’t be utilized because of high
wing loading.
“When the motor length exceeds the
aircraft motor base by more than 21⁄2 times,
vibration or risk of rubber bunching can
occur, spoiling good flights due to center
of gravity shifts.
“With each successive wind on the
rubber motor, the power output will fall,
particularly when near-breaking turns are
applied, and an insufficient rest period
between windings is not provided.”
Limited Pennyplane is an example in
which the 10-inch motorstick length poses
a problem in handling motor weights
138 MODEL AVIATION
greater than 95% of the model weight.
The most pressing problem is preventing
motor bunching and the resulting loss of
usable turns. This problem is most
pressing in high-ceiling flying, where a
longer loop is needed for the required
turns.
Prime batches of Tan II can handle as
many as five or six hard winds in one day
and continue to be used until it incurs
physical damage. Some data I have
implies that the output of each successive
windup is greater, not less, as applied to
my Limited Pennyplane. This good rubber
can be identified by keeping detailed
records of stretch recovery.
The best 20-inch loop of 0.090-inch
width will typically have a permanent
stretch of 0.06-0.08 inch after the first
wind. On subsequent flights it will
typically return to almost that same length
within 30 minutes after the flight.
To obtain this kind of performance
from any motor made from Tan (I or II),
it must be kept scrupulously clean. Tan
II’s surface is so smooth and slick that the
tiniest piece of grit will score the surface.
Consistent use of Armor All, before
winding and while stabilizing the knots
during the final phase of winding,
minimizes scuffing between strands.
Several fliers have reported scuffing with
most versions of Tan II, but I can’t
remember it happening under the hardest
use with Armor All and similar lubes. MA
3 AND 4 BLADE
SPINNERS
NO SPECIAL SLOTTING NECESSARY.
!"#$
#
%
&
'"#$
(
)
**)+
(281) 479-9600 www.tru-turn.com
,-
.),) %/)
"$$
0
%1%*2
334
5
PRECISION MODEL PRODUCTS
this stuff down, don’t you? Read and heed
guys—it can only help you and me. If you
don’t put it in your indoor kit, that’s OK,
just look in my tool box. Also thanks for
the help, Jack.”
“Optimization of Rubber Motor Size:
The object is to utilize the maximum
number of turns wound into the rubber
motor, during an efficient flight. It should
land on the floor, just as all of the turns
are used up. Following are methods of
achieving this.
“Problem 1: Aircraft runs out of turns
above the floor (overpowered).
“Solutions: Use another motor with a
smaller cross section, maintaining or
08sig5.QXD 5.23.03 12:37 pm Page 138
Edition: Model Aviation - 2003/08
Page Numbers: 136,137,138
Edition: Model Aviation - 2003/08
Page Numbers: 136,137,138
136 MODEL AVIATION
RECORD: Bob Wilder has again taken
the lead in event 627: Indoor Electric
Duration (Radio Control). At the
UniDome in Cedar Rapids, Iowa, he had a
flight of 20:57—a substantial increase
over the previous record time in that
event.
West Coast Flying: Steve Brown reports
that there is essentially zero opportunity
to fly serious Indoor, such as F1D, on the
West Coast. He is building new models to
fly at the Kibbie Dome at the University
of Idaho. How sad! That area can be
considered the cradle of Indoor as we
know it today.
Fédération Aéronautique Internationale
(FAI) Record Process: The following are
excerpts from an E-mail message Jim
Richmond sent to me.
“I’m sending this in response to your
questions a while back. This is the routine
needed to establish FAI records:
“1. Get an individual world record
sanction ($2) and an FAI stamp. Do it
right away. Be sure to give AMA precise
info about the event and category (FAI #)
you want the sanction for. I’ve never
heard of any meet having an FAI sanction
except a world championship, so always
get an individual one.
“You can order by mail or call it in to
AMA (credit card). Amy Wilson in the
Competitions Dept. is your contact person
for this. This sanction is good for the
entire year for a specific model type &
ceiling category.
“2. AMA requires that you notify them
prior to each world record attempt, so Email
Steve Kaluf (skaluf@modelaircraft.
org) 2 weeks before the event (include the
FAI info on the sanction so he will know
what you are doing).
“3. Although FAI doesn’t require the
attempt to be made during an official
AMA event, I think AMA does, and they
want it to be able to qualify as an AMA
national record if it exceeds the current
one. Also, although FAI doesn’t require
your 2 timers to be AMA members, I
think AMA would require that, so don’t
fight it.
“4. Required participants: An AMA
contest director, 2 timers (AMA
members), 3 witnesses (minimum). Be
sure to get the names and AMA numbers
of these people if you wish to file a record
application. Also, you will need the
address of the contest director (for him to
sign the documents).
“5. Notification of a record
performance: AMA requires that you
notify them (Steve Kaluf preferably)
within 48 hours after the record flight(s).
FAI requires notification from either
AMA, NAA, or the Contest Director
within 7 days of the event. This is a
timing problem requiring your
participation. The sequence is: From you
to AMA to NAA [National Aeronautic
Association] to FAI.
“6. Documentation: You will need the
following in order to prepare your record
application ‘dossier’:
“A time card with your flight times
and the timers’ names signed in ink. You
Bud Tenny, Box 830545, Richardson TX 75083
FREE FLIGHT INDOOR
Fixture compares torsional strength of wood used for motorsticks of unbraced events such as Easy B (206). Fixture breaks down for
storage as shown on right.
Bill Gowen launches glider. Carbonfiber/
balsa framework, covered with grocery
produce-bag plastic. Dave Linstrum photo.
08sig5.QXD 5.23.03 12:37 pm Page 136
can prepare your own card for this.
“The names of the stop watches used.
You will also be required to testify that
they had been checked for accuracy prior
to the flight.
“You will need to be able to make a
sketch of the cross section of the building
showing the ceiling height.
“Record details of the flight(s) and
other conditions such as temperature and
outdoor weather and any unusual
difficulties or unusual happenings so a
descriptive story can be written for the
dossier.
“You will need a photograph and a 3
view drawing of your airplane.
“7. The dossier: This is an 11 page
document requiring a number of signatures
by the contest director. You need to get it
completed and signed off and delivered to
AMA (Steve Kaluf) within one month.
You can refer to the FAI rule book for
guidance, but it’s very helpful to have a
prior successful form on hand for
reference.
“Hope this helps. Let me know if you
have questions.”
Tan II Is No More: Rubber-model fliers
were dismayed by the announcement that
Tan II rubber will no longer be available
because of a change in golf-ball
construction. Balls with rubber thread
wound on a central core have been
replaced by balls using a different
construction technique. This removes the
only source for the Tan rubber.
Work had already begun on some
lower-energy rubber designated “Tan
Sport.” A follow-on product called “Tan
Super Sport” is also being made now. Fred
Tellier has been conducting some tests on
the new rubber as it becomes available. He
wrote:
“I did some revisited tests on Tan 5-99
after the WC and got energy readings
about 5100+ and turns/inch of 171-173.
Tan Sport gave energy readings in the
August 2003 137
Who are they? The author took this photo
at a 1960s-era World Championships.
Dick Obarski contemplates a flight
strategy. Linstrum photo.
Larry Coslick tops off a steering balloon
at a US Indoor Championships.
Kansas City-area fliers Tem Johnson
(standing) and Emil Schutzel prepare for
another flight. Linstrum photo.
4600-4700 range with higher torque 0.67
in./oz. compared to 0.62 in./oz. for 5-99.
“I test all motors using strips 0.050
inch wide weighing 0.6 g. The 5-99 is less
dense as it gives motors slightly longer—9
to 9.5 inch for 5-99 and 8.75 to 9.25 inch
for Sport. The torque drops off faster in
the Sport; later in the unwind the samples
are close in value.
“I think that if Super Sport is higher in
energy it will be quite usable but not in the
same class as Tan 10-97, 5-99 or 3-02.
“I flew some of the Sport on a Limited
PP [Pennyplane] and found it usable but
not great. Again I hope the Super Sport
will be better. We have to use this rubber,
but I think it will be hard to get enough
turns so longer motors will be needed.
“My ft. lbs./lb. numbers on most rubber
have improved; I think my winding skills
have gotten better allowing more turns in
the test motors. In the formula turns are
equivalent to stretch so this greatly affects
the results.
“I test motors made up to F1D weight;
break-in consists of winding to 0.3 in./oz.
and holding for 2 minutes then increasing
to 0.4 for 2 minutes. I test the next day and
test each motor only once. I try to test 5
separate motors and average the results. I
find for flying I can only get one safe
flight from a motor, but if I test a second
time I get more turns due to the extra
length; this a higher ft. lbs./lb. value.
“I am curious how others break in
motors as I get good turns but usually
break on second flight. I feel that we are
not out of the woods on the rubber
situation yet, but I think there is hope.”
Flight Trim From the Brainbusters
Newsletter (Edited by Abram Vandover):
“Put this in your field box! This article
is from an old newsletter and is by Jack
McGillivray, but the information is still
current and will help deciding what size
and length motor to use. I’m serious about
putting it in your tool box or in that book
that you keep all your info in, you do write
08sig5.QXD 5.23.03 12:37 pm Page 137
increasing its overall length; Use another
motor with the original cross section, but
with increased length; Increase the
propeller pitch, and/or propeller diameter;
If motor is new, problem will diminish
somewhat as motor breaks in.
“Problem 2: Aircraft lands with unused
turns left in motor (underpowered).
“Solutions: Shorten up the existing
motor; Use another motor with a larger
cross section, maintaining or shortening
overall motor length; Decrease the
propeller pitch, and/or propeller diameter.
“When considering solutions to
Problem 1 or 2, keep these parameters in
mind. If possible, the rubber motor weight
should exceed the airframe weight, but
should not exceed twice the airframe
weight. On many aircraft, though, motors
this heavy can’t be utilized because of high
wing loading.
“When the motor length exceeds the
aircraft motor base by more than 21⁄2 times,
vibration or risk of rubber bunching can
occur, spoiling good flights due to center
of gravity shifts.
“With each successive wind on the
rubber motor, the power output will fall,
particularly when near-breaking turns are
applied, and an insufficient rest period
between windings is not provided.”
Limited Pennyplane is an example in
which the 10-inch motorstick length poses
a problem in handling motor weights
138 MODEL AVIATION
greater than 95% of the model weight.
The most pressing problem is preventing
motor bunching and the resulting loss of
usable turns. This problem is most
pressing in high-ceiling flying, where a
longer loop is needed for the required
turns.
Prime batches of Tan II can handle as
many as five or six hard winds in one day
and continue to be used until it incurs
physical damage. Some data I have
implies that the output of each successive
windup is greater, not less, as applied to
my Limited Pennyplane. This good rubber
can be identified by keeping detailed
records of stretch recovery.
The best 20-inch loop of 0.090-inch
width will typically have a permanent
stretch of 0.06-0.08 inch after the first
wind. On subsequent flights it will
typically return to almost that same length
within 30 minutes after the flight.
To obtain this kind of performance
from any motor made from Tan (I or II),
it must be kept scrupulously clean. Tan
II’s surface is so smooth and slick that the
tiniest piece of grit will score the surface.
Consistent use of Armor All, before
winding and while stabilizing the knots
during the final phase of winding,
minimizes scuffing between strands.
Several fliers have reported scuffing with
most versions of Tan II, but I can’t
remember it happening under the hardest
use with Armor All and similar lubes. MA
3 AND 4 BLADE
SPINNERS
NO SPECIAL SLOTTING NECESSARY.
!"#$
#
%
&
'"#$
(
)
**)+
(281) 479-9600 www.tru-turn.com
,-
.),) %/)
"$$
0
%1%*2
334
5
PRECISION MODEL PRODUCTS
this stuff down, don’t you? Read and heed
guys—it can only help you and me. If you
don’t put it in your indoor kit, that’s OK,
just look in my tool box. Also thanks for
the help, Jack.”
“Optimization of Rubber Motor Size:
The object is to utilize the maximum
number of turns wound into the rubber
motor, during an efficient flight. It should
land on the floor, just as all of the turns
are used up. Following are methods of
achieving this.
“Problem 1: Aircraft runs out of turns
above the floor (overpowered).
“Solutions: Use another motor with a
smaller cross section, maintaining or
08sig5.QXD 5.23.03 12:37 pm Page 138
Edition: Model Aviation - 2003/08
Page Numbers: 136,137,138
136 MODEL AVIATION
RECORD: Bob Wilder has again taken
the lead in event 627: Indoor Electric
Duration (Radio Control). At the
UniDome in Cedar Rapids, Iowa, he had a
flight of 20:57—a substantial increase
over the previous record time in that
event.
West Coast Flying: Steve Brown reports
that there is essentially zero opportunity
to fly serious Indoor, such as F1D, on the
West Coast. He is building new models to
fly at the Kibbie Dome at the University
of Idaho. How sad! That area can be
considered the cradle of Indoor as we
know it today.
Fédération Aéronautique Internationale
(FAI) Record Process: The following are
excerpts from an E-mail message Jim
Richmond sent to me.
“I’m sending this in response to your
questions a while back. This is the routine
needed to establish FAI records:
“1. Get an individual world record
sanction ($2) and an FAI stamp. Do it
right away. Be sure to give AMA precise
info about the event and category (FAI #)
you want the sanction for. I’ve never
heard of any meet having an FAI sanction
except a world championship, so always
get an individual one.
“You can order by mail or call it in to
AMA (credit card). Amy Wilson in the
Competitions Dept. is your contact person
for this. This sanction is good for the
entire year for a specific model type &
ceiling category.
“2. AMA requires that you notify them
prior to each world record attempt, so Email
Steve Kaluf (skaluf@modelaircraft.
org) 2 weeks before the event (include the
FAI info on the sanction so he will know
what you are doing).
“3. Although FAI doesn’t require the
attempt to be made during an official
AMA event, I think AMA does, and they
want it to be able to qualify as an AMA
national record if it exceeds the current
one. Also, although FAI doesn’t require
your 2 timers to be AMA members, I
think AMA would require that, so don’t
fight it.
“4. Required participants: An AMA
contest director, 2 timers (AMA
members), 3 witnesses (minimum). Be
sure to get the names and AMA numbers
of these people if you wish to file a record
application. Also, you will need the
address of the contest director (for him to
sign the documents).
“5. Notification of a record
performance: AMA requires that you
notify them (Steve Kaluf preferably)
within 48 hours after the record flight(s).
FAI requires notification from either
AMA, NAA, or the Contest Director
within 7 days of the event. This is a
timing problem requiring your
participation. The sequence is: From you
to AMA to NAA [National Aeronautic
Association] to FAI.
“6. Documentation: You will need the
following in order to prepare your record
application ‘dossier’:
“A time card with your flight times
and the timers’ names signed in ink. You
Bud Tenny, Box 830545, Richardson TX 75083
FREE FLIGHT INDOOR
Fixture compares torsional strength of wood used for motorsticks of unbraced events such as Easy B (206). Fixture breaks down for
storage as shown on right.
Bill Gowen launches glider. Carbonfiber/
balsa framework, covered with grocery
produce-bag plastic. Dave Linstrum photo.
08sig5.QXD 5.23.03 12:37 pm Page 136
can prepare your own card for this.
“The names of the stop watches used.
You will also be required to testify that
they had been checked for accuracy prior
to the flight.
“You will need to be able to make a
sketch of the cross section of the building
showing the ceiling height.
“Record details of the flight(s) and
other conditions such as temperature and
outdoor weather and any unusual
difficulties or unusual happenings so a
descriptive story can be written for the
dossier.
“You will need a photograph and a 3
view drawing of your airplane.
“7. The dossier: This is an 11 page
document requiring a number of signatures
by the contest director. You need to get it
completed and signed off and delivered to
AMA (Steve Kaluf) within one month.
You can refer to the FAI rule book for
guidance, but it’s very helpful to have a
prior successful form on hand for
reference.
“Hope this helps. Let me know if you
have questions.”
Tan II Is No More: Rubber-model fliers
were dismayed by the announcement that
Tan II rubber will no longer be available
because of a change in golf-ball
construction. Balls with rubber thread
wound on a central core have been
replaced by balls using a different
construction technique. This removes the
only source for the Tan rubber.
Work had already begun on some
lower-energy rubber designated “Tan
Sport.” A follow-on product called “Tan
Super Sport” is also being made now. Fred
Tellier has been conducting some tests on
the new rubber as it becomes available. He
wrote:
“I did some revisited tests on Tan 5-99
after the WC and got energy readings
about 5100+ and turns/inch of 171-173.
Tan Sport gave energy readings in the
August 2003 137
Who are they? The author took this photo
at a 1960s-era World Championships.
Dick Obarski contemplates a flight
strategy. Linstrum photo.
Larry Coslick tops off a steering balloon
at a US Indoor Championships.
Kansas City-area fliers Tem Johnson
(standing) and Emil Schutzel prepare for
another flight. Linstrum photo.
4600-4700 range with higher torque 0.67
in./oz. compared to 0.62 in./oz. for 5-99.
“I test all motors using strips 0.050
inch wide weighing 0.6 g. The 5-99 is less
dense as it gives motors slightly longer—9
to 9.5 inch for 5-99 and 8.75 to 9.25 inch
for Sport. The torque drops off faster in
the Sport; later in the unwind the samples
are close in value.
“I think that if Super Sport is higher in
energy it will be quite usable but not in the
same class as Tan 10-97, 5-99 or 3-02.
“I flew some of the Sport on a Limited
PP [Pennyplane] and found it usable but
not great. Again I hope the Super Sport
will be better. We have to use this rubber,
but I think it will be hard to get enough
turns so longer motors will be needed.
“My ft. lbs./lb. numbers on most rubber
have improved; I think my winding skills
have gotten better allowing more turns in
the test motors. In the formula turns are
equivalent to stretch so this greatly affects
the results.
“I test motors made up to F1D weight;
break-in consists of winding to 0.3 in./oz.
and holding for 2 minutes then increasing
to 0.4 for 2 minutes. I test the next day and
test each motor only once. I try to test 5
separate motors and average the results. I
find for flying I can only get one safe
flight from a motor, but if I test a second
time I get more turns due to the extra
length; this a higher ft. lbs./lb. value.
“I am curious how others break in
motors as I get good turns but usually
break on second flight. I feel that we are
not out of the woods on the rubber
situation yet, but I think there is hope.”
Flight Trim From the Brainbusters
Newsletter (Edited by Abram Vandover):
“Put this in your field box! This article
is from an old newsletter and is by Jack
McGillivray, but the information is still
current and will help deciding what size
and length motor to use. I’m serious about
putting it in your tool box or in that book
that you keep all your info in, you do write
08sig5.QXD 5.23.03 12:37 pm Page 137
increasing its overall length; Use another
motor with the original cross section, but
with increased length; Increase the
propeller pitch, and/or propeller diameter;
If motor is new, problem will diminish
somewhat as motor breaks in.
“Problem 2: Aircraft lands with unused
turns left in motor (underpowered).
“Solutions: Shorten up the existing
motor; Use another motor with a larger
cross section, maintaining or shortening
overall motor length; Decrease the
propeller pitch, and/or propeller diameter.
“When considering solutions to
Problem 1 or 2, keep these parameters in
mind. If possible, the rubber motor weight
should exceed the airframe weight, but
should not exceed twice the airframe
weight. On many aircraft, though, motors
this heavy can’t be utilized because of high
wing loading.
“When the motor length exceeds the
aircraft motor base by more than 21⁄2 times,
vibration or risk of rubber bunching can
occur, spoiling good flights due to center
of gravity shifts.
“With each successive wind on the
rubber motor, the power output will fall,
particularly when near-breaking turns are
applied, and an insufficient rest period
between windings is not provided.”
Limited Pennyplane is an example in
which the 10-inch motorstick length poses
a problem in handling motor weights
138 MODEL AVIATION
greater than 95% of the model weight.
The most pressing problem is preventing
motor bunching and the resulting loss of
usable turns. This problem is most
pressing in high-ceiling flying, where a
longer loop is needed for the required
turns.
Prime batches of Tan II can handle as
many as five or six hard winds in one day
and continue to be used until it incurs
physical damage. Some data I have
implies that the output of each successive
windup is greater, not less, as applied to
my Limited Pennyplane. This good rubber
can be identified by keeping detailed
records of stretch recovery.
The best 20-inch loop of 0.090-inch
width will typically have a permanent
stretch of 0.06-0.08 inch after the first
wind. On subsequent flights it will
typically return to almost that same length
within 30 minutes after the flight.
To obtain this kind of performance
from any motor made from Tan (I or II),
it must be kept scrupulously clean. Tan
II’s surface is so smooth and slick that the
tiniest piece of grit will score the surface.
Consistent use of Armor All, before
winding and while stabilizing the knots
during the final phase of winding,
minimizes scuffing between strands.
Several fliers have reported scuffing with
most versions of Tan II, but I can’t
remember it happening under the hardest
use with Armor All and similar lubes. MA
3 AND 4 BLADE
SPINNERS
NO SPECIAL SLOTTING NECESSARY.
!"#$
#
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'"#$
(
)
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(281) 479-9600 www.tru-turn.com
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334
5
PRECISION MODEL PRODUCTS
this stuff down, don’t you? Read and heed
guys—it can only help you and me. If you
don’t put it in your indoor kit, that’s OK,
just look in my tool box. Also thanks for
the help, Jack.”
“Optimization of Rubber Motor Size:
The object is to utilize the maximum
number of turns wound into the rubber
motor, during an efficient flight. It should
land on the floor, just as all of the turns
are used up. Following are methods of
achieving this.
“Problem 1: Aircraft runs out of turns
above the floor (overpowered).
“Solutions: Use another motor with a
smaller cross section, maintaining or
08sig5.QXD 5.23.03 12:37 pm Page 138