September 2004 133
JUNIOR TEAM: Eleven young FF fliers
will be representing the United States at the
2004 Junior World Championships in
Moncontour, France, August 8-14.
Normally only three team members fly in
each of three events (F1A Towline Glider,
F1B Wakefield Rubber, and F1J Power).
This time there are two extra team
members. Reigning Junior World
Champion Austin Gunder will be defending
his title.
Amanda Barr will be flying F1P as the
fourth Power flier. In this World Champs,
the new, simpler F1P models are being
phased in to replace the more
technologically advanced and higherperformance
F1J models. To encourage the
F1P event, each country is allowed to have
one flier in that category in addition to the
three F1J competitors. Only F1P will be
flown in the next Junior World Champs.
The other team members are Michael
Avallone, Brian Bauer, and Tyler Secor in
F1A; Taylor Gunder, Sara Radziunas, and
Phillip Scheiman in F1B; and John
Lorbiecki, Jon Schelp, and Cody Secor in
F1J/F1P. Brian Van Nest is the team
manager.
Although AMA pays for travel expenses and entry fees, there
are other costs involved. You can help with a donation. Please
send your check to Brian Van Nest, 2346 Cheyenne Dr., Bishop
CA 93514.
Louis Joyner, 6 Saturday Rd., Mt. Pleasant SC 29464
FREE FLIGHT DURATION
Austin Gunder—2002 Junior World Champ—helps fellow 2004
team member Amanda Barr at special Juniors-only contest.
Repeat team member John Lorbiecki will fly F1J Power at the 2004 Junior World
Champs. His model uses a 1cc Cyclone engine; note folding propeller blades.
F1B flier Taylor Gunder sets for launch. Model has carbon-fiber
D-box wing construction, carbon-tube stabilizer spar.
09sig5.QXD 6/23/04 12:39 pm Page 133
134 MODEL AVIATION
CG Part Two: The discussion of CG in the March 2004 Duration
column prompted letters from two noted model aerodynamicists:
Ron St. Jean and Bill Bogart.
Ron—who is best known for his 1950s Ramrod design—has
also had some experience with full-scale aircraft. He wrote:
“I used to own an old, tired Tri-Pacer that turned out to be
nose-heavy. Each time during landing flare-out, I’d have the stick
Andrew Hewitt’s discus-launch glider has timer-operated auto
stab and rudder. It’s held by left wingtip for launch.
Jon Schelp watches for signs of lift upwind before starting his F1J’s
engine. His father and grandfather have competed in World Champs.
First-time team member Phillip Scheiman checks turns on winder’s
electronic counter. Model is Andriukov-Kulakovsky design.
Sara Radziunas launches her F1B Wakefield model. This will be
her first time on the Junior Free Flight team.
full back and the nose well up. But just before touch-down, the
nose would fall and the airplane would bounce.”
Ron finally sat down and applied his modeling experience to
the problem.
“The up-elevator was holding the nose up to a point where the
slowing speed caused it [the elevator] to lose its effectiveness.
Then the forward CG overpowered the elevator and caused the
nose to drop just before touchdown. Here was a classic case of
high-speed vs. low-speed factors reaching the balance of power.”
The solution: add some ballast in the cargo box to move the
CG aft slightly.
In his letter, Ron also noted that too often we think of the CG
09sig5.QXD 6/23/04 12:40 pm Page 134
in terms of root chord. This works only
for a constant-chord wing or a wing with
equal taper front and back. Unequal taper
or a forward- or back-swept wing can
affect the CG location significantly.
Bill Bogart has written extensively
about CG location and its relationship to
tail moment arm and stabilizer area. An
article that he co-authored with Bud
Rhodes about tail volume and CG location
was published in the January 1959 Model
Airplane News. (Many public libraries
have back issues of MAN.) A condensed
version of the article ran in the 1959-1961
Model Aeronautic Year Book edited by
Frank Zaic. (The Zaic Year Books are
available from AMA.)
Unlike the somewhat complicated
formula by Rene Jossien that I mentioned,
Bill boiled it down to a simple one-line
equation; aft CG/chord position is equal
to 0.25 + 0.4 x tail volume. (Tail volume
is [tail area multiplied by tail length]
divided by [wing area multiplied by wing
MAC].) MAC is mean aerodynamic
chord, which is determined by calculating
the wing area, and then dividing by the
wingspan. For a constant-chord wing, it
would, of course, be the chord.
In his recent letter, Bill pointed out
that the vertical position of the CG also
affects a model’s flight characteristics.
For a typical FF model with a pylonmounted
wing with dihedral, the CG can
be well above the fuselage centerline. As
the angle of attack increases, the CG will,
in effect, move slightly to the rear. The
higher above the fuselage centerline the
CG is, the more pronounced the effect.
Shifting the CG to the rear as the
model noses up will, of course, make the
model nose up even more; it makes the
stall worse. In a dive, the CG would shift
forward slightly, tending to increase the
nose-down forces on the model.
To find the vertical CG, Bill suggests
suspending the model by the rear of the
fuselage and lining up the hanging aircraft
with a known vertical line, such as the
edge of a door. The vertical CG will be on
a line passing vertically through the rear
suspension point. Note the position of the
line where it passes through the horizontal
CG position.
The best way to avoid problems with
CG shift at high or low angles of attack is
to keep the wing, especially the tips, as
light as possible. Since the bending loads
on a wing are highest in the center, there
is no reason to build a wing with a
constant-size spar.
Instead, taper the spar from the center
to the tip. This will not only reduce the tip
weight (thereby lowering the CG), but
will also reduce the overall wing weight.
If nothing else, try to pick lighter wood
for the tip panels.
Sympo 2004: By the time you read this,
the National Free Flight Society’s
(NFFS’s) 37th annual Symposium report
should be ready. This year’s Sympo,
edited by Walt Ghio, includes a wide
range of papers about the technical
aspects of FF.
Subjects include electric propulsion for
FF, software for airfoil plotting, wingtip
design, rubber testing, F1E (magnet
steering) design and construction, pin
turbulators at low Reynolds numbers,
vertical tail requirements for a steep
climb, composite molding at elevated
temperatures, growing your FF club, F1A
bunt computer simulation, and wing
design for F1A and F1B.
The Sympo will also feature the
Models of the Year winners and new
inductees into the Free Flight Hall of
Fame.
You can order your copy from NFFS
Publications, Box 1775, Albany OR
97321. The price is $25 for NFFS
members and $30 for nonmembers.
Postage is $4. For more information,
contact NFFS publications coordinator
Bob Stalick via E-mail at freefliter@aol.
com or visit the NFFS Web site at
http://freeflight.org.
Free Flight Forum 2004: For 20 years, a
dedicated group of British FF enthusiasts
have been staging a forum on the
technical and practical aspects of FF and
then publishing the report.
September 2004 135
Beep
Beep
Beep
Beep
Beep
Beep
Beep
Beep
WALSTON RETRIEVAL SYSTEMS
725 Cooper Lake Rd., S.E., Smyrna, GA 30082
770-434-4905 800-657-4672 Fax 770-431-0119
Visa • MC • AmEx • Disc
e-mail [email protected]
Call Now.
Edited by Martin Dilly and Mike
Evatt, Free Flight Forum 2004 offers
papers about such diverse topics as the
history of geared F1C engines,
constructing carbon-fiber power
propellers, thermal detection equipment,
a drum sander for smoothing sheet balsa,
blunt LE stabilizer airfoils, and testing P-
30 airfoils using a CO2 model flown
inside the giant Cargo Lifter hangar.
Glider fliers will find this issue
especially rich in material. In addition to
a piece about F1H Towline Gliders, there
are two papers on Catapult Gliders and
one on the new discus-launched handlaunched
gliders.
RC glider fliers have been using the
discus-launch technique for several years.
It offers a less-stressful launch (on the
model and modeler) and places less
emphasis on arm strength. However,
translating the discus technique to FF is
difficult.
Phil Ball and Andrew Hewitt came up
with a large model that spans almost 5
feet and weighs approximately 180
grams. A conventional Hand-Launched
Glider spans 18 inches and weighs
roughly 25 grams. To control the
transition from circular launch to glide,
they use a modified Tomy timer to allow
a three-position stabilizer and twoposition
rudder.
The stabilizer is up slightly at launch,
then pulls down briefly at the end of the
climb for a bunt transition; then the
stabilizer and rudder go to glide setting.
Timer start is handled via a monofilament
line running from the wingtip launch peg
to the timer.
The 2004 Forum is available from
Martin Dilly, 20, Links Rd., West
Wickham, Kent BR4 OQW, UK. The
price, including airmail postage to the
United States, is 14.00 pounds sterling.
Make checks out to “BMFA F/F Team
Support Fund.” Since checks must be in
pounds sterling only and drawn on a bank
with a branch in the UK, it’s easier to pay
by credit card. You can contact Martin by
fax at (44)+(0)20-8777-5533 or by Email
at [email protected]. MA
Service & Repairs For Most Radio Control Systems,
Utilizing Calibrated Test Equipment & Spectrum Analyzers.
Futaba, Airtronics, JR, Ace, HiTec, Tower, Cirrus, World Engines & More
D&M ELECTRONICS • 1236 Marigold St. NW, Hartville, OH 44632 • 330-877-1445
Shipping & Insurance Extra – – UPS • U.S. Mail • C.O.D.’s
Visit our home page at http://www.dnmelectronics.com • Email: [email protected]
AMA # 256123-Dave ARRL WB8YSQ
D & M E L E C T R O N I C S
• WE USE GENUINE FACTORY REPLACEMENT PARTS
• Endorsed by AMA/RCMA as Sticker Station #105
• 1991/1998 Narrow Banding & Certification
• FCC Licensed
• Speed Control Repairs
• Quality Service
• Fast Turn Around
• RCD / HITEC R/C Dealer
• Miniature Aircraft Dealer
X-CELL Helicopters
09sig5.QXD 6/23/04 12:40 pm Page 135
Edition: Model Aviation - 2004/09
Page Numbers: 133,134,135
Edition: Model Aviation - 2004/09
Page Numbers: 133,134,135
September 2004 133
JUNIOR TEAM: Eleven young FF fliers
will be representing the United States at the
2004 Junior World Championships in
Moncontour, France, August 8-14.
Normally only three team members fly in
each of three events (F1A Towline Glider,
F1B Wakefield Rubber, and F1J Power).
This time there are two extra team
members. Reigning Junior World
Champion Austin Gunder will be defending
his title.
Amanda Barr will be flying F1P as the
fourth Power flier. In this World Champs,
the new, simpler F1P models are being
phased in to replace the more
technologically advanced and higherperformance
F1J models. To encourage the
F1P event, each country is allowed to have
one flier in that category in addition to the
three F1J competitors. Only F1P will be
flown in the next Junior World Champs.
The other team members are Michael
Avallone, Brian Bauer, and Tyler Secor in
F1A; Taylor Gunder, Sara Radziunas, and
Phillip Scheiman in F1B; and John
Lorbiecki, Jon Schelp, and Cody Secor in
F1J/F1P. Brian Van Nest is the team
manager.
Although AMA pays for travel expenses and entry fees, there
are other costs involved. You can help with a donation. Please
send your check to Brian Van Nest, 2346 Cheyenne Dr., Bishop
CA 93514.
Louis Joyner, 6 Saturday Rd., Mt. Pleasant SC 29464
FREE FLIGHT DURATION
Austin Gunder—2002 Junior World Champ—helps fellow 2004
team member Amanda Barr at special Juniors-only contest.
Repeat team member John Lorbiecki will fly F1J Power at the 2004 Junior World
Champs. His model uses a 1cc Cyclone engine; note folding propeller blades.
F1B flier Taylor Gunder sets for launch. Model has carbon-fiber
D-box wing construction, carbon-tube stabilizer spar.
09sig5.QXD 6/23/04 12:39 pm Page 133
134 MODEL AVIATION
CG Part Two: The discussion of CG in the March 2004 Duration
column prompted letters from two noted model aerodynamicists:
Ron St. Jean and Bill Bogart.
Ron—who is best known for his 1950s Ramrod design—has
also had some experience with full-scale aircraft. He wrote:
“I used to own an old, tired Tri-Pacer that turned out to be
nose-heavy. Each time during landing flare-out, I’d have the stick
Andrew Hewitt’s discus-launch glider has timer-operated auto
stab and rudder. It’s held by left wingtip for launch.
Jon Schelp watches for signs of lift upwind before starting his F1J’s
engine. His father and grandfather have competed in World Champs.
First-time team member Phillip Scheiman checks turns on winder’s
electronic counter. Model is Andriukov-Kulakovsky design.
Sara Radziunas launches her F1B Wakefield model. This will be
her first time on the Junior Free Flight team.
full back and the nose well up. But just before touch-down, the
nose would fall and the airplane would bounce.”
Ron finally sat down and applied his modeling experience to
the problem.
“The up-elevator was holding the nose up to a point where the
slowing speed caused it [the elevator] to lose its effectiveness.
Then the forward CG overpowered the elevator and caused the
nose to drop just before touchdown. Here was a classic case of
high-speed vs. low-speed factors reaching the balance of power.”
The solution: add some ballast in the cargo box to move the
CG aft slightly.
In his letter, Ron also noted that too often we think of the CG
09sig5.QXD 6/23/04 12:40 pm Page 134
in terms of root chord. This works only
for a constant-chord wing or a wing with
equal taper front and back. Unequal taper
or a forward- or back-swept wing can
affect the CG location significantly.
Bill Bogart has written extensively
about CG location and its relationship to
tail moment arm and stabilizer area. An
article that he co-authored with Bud
Rhodes about tail volume and CG location
was published in the January 1959 Model
Airplane News. (Many public libraries
have back issues of MAN.) A condensed
version of the article ran in the 1959-1961
Model Aeronautic Year Book edited by
Frank Zaic. (The Zaic Year Books are
available from AMA.)
Unlike the somewhat complicated
formula by Rene Jossien that I mentioned,
Bill boiled it down to a simple one-line
equation; aft CG/chord position is equal
to 0.25 + 0.4 x tail volume. (Tail volume
is [tail area multiplied by tail length]
divided by [wing area multiplied by wing
MAC].) MAC is mean aerodynamic
chord, which is determined by calculating
the wing area, and then dividing by the
wingspan. For a constant-chord wing, it
would, of course, be the chord.
In his recent letter, Bill pointed out
that the vertical position of the CG also
affects a model’s flight characteristics.
For a typical FF model with a pylonmounted
wing with dihedral, the CG can
be well above the fuselage centerline. As
the angle of attack increases, the CG will,
in effect, move slightly to the rear. The
higher above the fuselage centerline the
CG is, the more pronounced the effect.
Shifting the CG to the rear as the
model noses up will, of course, make the
model nose up even more; it makes the
stall worse. In a dive, the CG would shift
forward slightly, tending to increase the
nose-down forces on the model.
To find the vertical CG, Bill suggests
suspending the model by the rear of the
fuselage and lining up the hanging aircraft
with a known vertical line, such as the
edge of a door. The vertical CG will be on
a line passing vertically through the rear
suspension point. Note the position of the
line where it passes through the horizontal
CG position.
The best way to avoid problems with
CG shift at high or low angles of attack is
to keep the wing, especially the tips, as
light as possible. Since the bending loads
on a wing are highest in the center, there
is no reason to build a wing with a
constant-size spar.
Instead, taper the spar from the center
to the tip. This will not only reduce the tip
weight (thereby lowering the CG), but
will also reduce the overall wing weight.
If nothing else, try to pick lighter wood
for the tip panels.
Sympo 2004: By the time you read this,
the National Free Flight Society’s
(NFFS’s) 37th annual Symposium report
should be ready. This year’s Sympo,
edited by Walt Ghio, includes a wide
range of papers about the technical
aspects of FF.
Subjects include electric propulsion for
FF, software for airfoil plotting, wingtip
design, rubber testing, F1E (magnet
steering) design and construction, pin
turbulators at low Reynolds numbers,
vertical tail requirements for a steep
climb, composite molding at elevated
temperatures, growing your FF club, F1A
bunt computer simulation, and wing
design for F1A and F1B.
The Sympo will also feature the
Models of the Year winners and new
inductees into the Free Flight Hall of
Fame.
You can order your copy from NFFS
Publications, Box 1775, Albany OR
97321. The price is $25 for NFFS
members and $30 for nonmembers.
Postage is $4. For more information,
contact NFFS publications coordinator
Bob Stalick via E-mail at freefliter@aol.
com or visit the NFFS Web site at
http://freeflight.org.
Free Flight Forum 2004: For 20 years, a
dedicated group of British FF enthusiasts
have been staging a forum on the
technical and practical aspects of FF and
then publishing the report.
September 2004 135
Beep
Beep
Beep
Beep
Beep
Beep
Beep
Beep
WALSTON RETRIEVAL SYSTEMS
725 Cooper Lake Rd., S.E., Smyrna, GA 30082
770-434-4905 800-657-4672 Fax 770-431-0119
Visa • MC • AmEx • Disc
e-mail [email protected]
Call Now.
Edited by Martin Dilly and Mike
Evatt, Free Flight Forum 2004 offers
papers about such diverse topics as the
history of geared F1C engines,
constructing carbon-fiber power
propellers, thermal detection equipment,
a drum sander for smoothing sheet balsa,
blunt LE stabilizer airfoils, and testing P-
30 airfoils using a CO2 model flown
inside the giant Cargo Lifter hangar.
Glider fliers will find this issue
especially rich in material. In addition to
a piece about F1H Towline Gliders, there
are two papers on Catapult Gliders and
one on the new discus-launched handlaunched
gliders.
RC glider fliers have been using the
discus-launch technique for several years.
It offers a less-stressful launch (on the
model and modeler) and places less
emphasis on arm strength. However,
translating the discus technique to FF is
difficult.
Phil Ball and Andrew Hewitt came up
with a large model that spans almost 5
feet and weighs approximately 180
grams. A conventional Hand-Launched
Glider spans 18 inches and weighs
roughly 25 grams. To control the
transition from circular launch to glide,
they use a modified Tomy timer to allow
a three-position stabilizer and twoposition
rudder.
The stabilizer is up slightly at launch,
then pulls down briefly at the end of the
climb for a bunt transition; then the
stabilizer and rudder go to glide setting.
Timer start is handled via a monofilament
line running from the wingtip launch peg
to the timer.
The 2004 Forum is available from
Martin Dilly, 20, Links Rd., West
Wickham, Kent BR4 OQW, UK. The
price, including airmail postage to the
United States, is 14.00 pounds sterling.
Make checks out to “BMFA F/F Team
Support Fund.” Since checks must be in
pounds sterling only and drawn on a bank
with a branch in the UK, it’s easier to pay
by credit card. You can contact Martin by
fax at (44)+(0)20-8777-5533 or by Email
at [email protected]. MA
Service & Repairs For Most Radio Control Systems,
Utilizing Calibrated Test Equipment & Spectrum Analyzers.
Futaba, Airtronics, JR, Ace, HiTec, Tower, Cirrus, World Engines & More
D&M ELECTRONICS • 1236 Marigold St. NW, Hartville, OH 44632 • 330-877-1445
Shipping & Insurance Extra – – UPS • U.S. Mail • C.O.D.’s
Visit our home page at http://www.dnmelectronics.com • Email: [email protected]
AMA # 256123-Dave ARRL WB8YSQ
D & M E L E C T R O N I C S
• WE USE GENUINE FACTORY REPLACEMENT PARTS
• Endorsed by AMA/RCMA as Sticker Station #105
• 1991/1998 Narrow Banding & Certification
• FCC Licensed
• Speed Control Repairs
• Quality Service
• Fast Turn Around
• RCD / HITEC R/C Dealer
• Miniature Aircraft Dealer
X-CELL Helicopters
09sig5.QXD 6/23/04 12:40 pm Page 135
Edition: Model Aviation - 2004/09
Page Numbers: 133,134,135
September 2004 133
JUNIOR TEAM: Eleven young FF fliers
will be representing the United States at the
2004 Junior World Championships in
Moncontour, France, August 8-14.
Normally only three team members fly in
each of three events (F1A Towline Glider,
F1B Wakefield Rubber, and F1J Power).
This time there are two extra team
members. Reigning Junior World
Champion Austin Gunder will be defending
his title.
Amanda Barr will be flying F1P as the
fourth Power flier. In this World Champs,
the new, simpler F1P models are being
phased in to replace the more
technologically advanced and higherperformance
F1J models. To encourage the
F1P event, each country is allowed to have
one flier in that category in addition to the
three F1J competitors. Only F1P will be
flown in the next Junior World Champs.
The other team members are Michael
Avallone, Brian Bauer, and Tyler Secor in
F1A; Taylor Gunder, Sara Radziunas, and
Phillip Scheiman in F1B; and John
Lorbiecki, Jon Schelp, and Cody Secor in
F1J/F1P. Brian Van Nest is the team
manager.
Although AMA pays for travel expenses and entry fees, there
are other costs involved. You can help with a donation. Please
send your check to Brian Van Nest, 2346 Cheyenne Dr., Bishop
CA 93514.
Louis Joyner, 6 Saturday Rd., Mt. Pleasant SC 29464
FREE FLIGHT DURATION
Austin Gunder—2002 Junior World Champ—helps fellow 2004
team member Amanda Barr at special Juniors-only contest.
Repeat team member John Lorbiecki will fly F1J Power at the 2004 Junior World
Champs. His model uses a 1cc Cyclone engine; note folding propeller blades.
F1B flier Taylor Gunder sets for launch. Model has carbon-fiber
D-box wing construction, carbon-tube stabilizer spar.
09sig5.QXD 6/23/04 12:39 pm Page 133
134 MODEL AVIATION
CG Part Two: The discussion of CG in the March 2004 Duration
column prompted letters from two noted model aerodynamicists:
Ron St. Jean and Bill Bogart.
Ron—who is best known for his 1950s Ramrod design—has
also had some experience with full-scale aircraft. He wrote:
“I used to own an old, tired Tri-Pacer that turned out to be
nose-heavy. Each time during landing flare-out, I’d have the stick
Andrew Hewitt’s discus-launch glider has timer-operated auto
stab and rudder. It’s held by left wingtip for launch.
Jon Schelp watches for signs of lift upwind before starting his F1J’s
engine. His father and grandfather have competed in World Champs.
First-time team member Phillip Scheiman checks turns on winder’s
electronic counter. Model is Andriukov-Kulakovsky design.
Sara Radziunas launches her F1B Wakefield model. This will be
her first time on the Junior Free Flight team.
full back and the nose well up. But just before touch-down, the
nose would fall and the airplane would bounce.”
Ron finally sat down and applied his modeling experience to
the problem.
“The up-elevator was holding the nose up to a point where the
slowing speed caused it [the elevator] to lose its effectiveness.
Then the forward CG overpowered the elevator and caused the
nose to drop just before touchdown. Here was a classic case of
high-speed vs. low-speed factors reaching the balance of power.”
The solution: add some ballast in the cargo box to move the
CG aft slightly.
In his letter, Ron also noted that too often we think of the CG
09sig5.QXD 6/23/04 12:40 pm Page 134
in terms of root chord. This works only
for a constant-chord wing or a wing with
equal taper front and back. Unequal taper
or a forward- or back-swept wing can
affect the CG location significantly.
Bill Bogart has written extensively
about CG location and its relationship to
tail moment arm and stabilizer area. An
article that he co-authored with Bud
Rhodes about tail volume and CG location
was published in the January 1959 Model
Airplane News. (Many public libraries
have back issues of MAN.) A condensed
version of the article ran in the 1959-1961
Model Aeronautic Year Book edited by
Frank Zaic. (The Zaic Year Books are
available from AMA.)
Unlike the somewhat complicated
formula by Rene Jossien that I mentioned,
Bill boiled it down to a simple one-line
equation; aft CG/chord position is equal
to 0.25 + 0.4 x tail volume. (Tail volume
is [tail area multiplied by tail length]
divided by [wing area multiplied by wing
MAC].) MAC is mean aerodynamic
chord, which is determined by calculating
the wing area, and then dividing by the
wingspan. For a constant-chord wing, it
would, of course, be the chord.
In his recent letter, Bill pointed out
that the vertical position of the CG also
affects a model’s flight characteristics.
For a typical FF model with a pylonmounted
wing with dihedral, the CG can
be well above the fuselage centerline. As
the angle of attack increases, the CG will,
in effect, move slightly to the rear. The
higher above the fuselage centerline the
CG is, the more pronounced the effect.
Shifting the CG to the rear as the
model noses up will, of course, make the
model nose up even more; it makes the
stall worse. In a dive, the CG would shift
forward slightly, tending to increase the
nose-down forces on the model.
To find the vertical CG, Bill suggests
suspending the model by the rear of the
fuselage and lining up the hanging aircraft
with a known vertical line, such as the
edge of a door. The vertical CG will be on
a line passing vertically through the rear
suspension point. Note the position of the
line where it passes through the horizontal
CG position.
The best way to avoid problems with
CG shift at high or low angles of attack is
to keep the wing, especially the tips, as
light as possible. Since the bending loads
on a wing are highest in the center, there
is no reason to build a wing with a
constant-size spar.
Instead, taper the spar from the center
to the tip. This will not only reduce the tip
weight (thereby lowering the CG), but
will also reduce the overall wing weight.
If nothing else, try to pick lighter wood
for the tip panels.
Sympo 2004: By the time you read this,
the National Free Flight Society’s
(NFFS’s) 37th annual Symposium report
should be ready. This year’s Sympo,
edited by Walt Ghio, includes a wide
range of papers about the technical
aspects of FF.
Subjects include electric propulsion for
FF, software for airfoil plotting, wingtip
design, rubber testing, F1E (magnet
steering) design and construction, pin
turbulators at low Reynolds numbers,
vertical tail requirements for a steep
climb, composite molding at elevated
temperatures, growing your FF club, F1A
bunt computer simulation, and wing
design for F1A and F1B.
The Sympo will also feature the
Models of the Year winners and new
inductees into the Free Flight Hall of
Fame.
You can order your copy from NFFS
Publications, Box 1775, Albany OR
97321. The price is $25 for NFFS
members and $30 for nonmembers.
Postage is $4. For more information,
contact NFFS publications coordinator
Bob Stalick via E-mail at freefliter@aol.
com or visit the NFFS Web site at
http://freeflight.org.
Free Flight Forum 2004: For 20 years, a
dedicated group of British FF enthusiasts
have been staging a forum on the
technical and practical aspects of FF and
then publishing the report.
September 2004 135
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Edited by Martin Dilly and Mike
Evatt, Free Flight Forum 2004 offers
papers about such diverse topics as the
history of geared F1C engines,
constructing carbon-fiber power
propellers, thermal detection equipment,
a drum sander for smoothing sheet balsa,
blunt LE stabilizer airfoils, and testing P-
30 airfoils using a CO2 model flown
inside the giant Cargo Lifter hangar.
Glider fliers will find this issue
especially rich in material. In addition to
a piece about F1H Towline Gliders, there
are two papers on Catapult Gliders and
one on the new discus-launched handlaunched
gliders.
RC glider fliers have been using the
discus-launch technique for several years.
It offers a less-stressful launch (on the
model and modeler) and places less
emphasis on arm strength. However,
translating the discus technique to FF is
difficult.
Phil Ball and Andrew Hewitt came up
with a large model that spans almost 5
feet and weighs approximately 180
grams. A conventional Hand-Launched
Glider spans 18 inches and weighs
roughly 25 grams. To control the
transition from circular launch to glide,
they use a modified Tomy timer to allow
a three-position stabilizer and twoposition
rudder.
The stabilizer is up slightly at launch,
then pulls down briefly at the end of the
climb for a bunt transition; then the
stabilizer and rudder go to glide setting.
Timer start is handled via a monofilament
line running from the wingtip launch peg
to the timer.
The 2004 Forum is available from
Martin Dilly, 20, Links Rd., West
Wickham, Kent BR4 OQW, UK. The
price, including airmail postage to the
United States, is 14.00 pounds sterling.
Make checks out to “BMFA F/F Team
Support Fund.” Since checks must be in
pounds sterling only and drawn on a bank
with a branch in the UK, it’s easier to pay
by credit card. You can contact Martin by
fax at (44)+(0)20-8777-5533 or by Email
at [email protected]. MA
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