152 MODEL AVIATION
DISCUS-LAUNCH Gliders look like oversized Hand-Launched
Gliders (HLGs). A 3-foot wingspan is typical.
Instead of the usual overhand, near-vertical javelin throw,
discus-launch Gliders are gripped by the wingtip and thrown with
a circular motion that is slightly above horizontal. The discus
action is not only much easier on the arm, but it also yields a
considerably higher launch altitude.
Early experiments (circa 2004) with discus-launch FF Gliders
were based on RC discus-launch designs. In England Phil Ball
and Andy Hewitt developed 5-foot-span models that used timeroperated
auto rudder and stabilizer to control launch trajectory,
transition, and glide. The aircraft were successful but
complicated by the built-up wing construction and auto surfaces.
Soon another British modeler, Mark Benns, came up with a
smaller model, spanning approximately 36 inches, that used a
conventional solid-balsa wing and required no auto surfaces.
Flight adjustments were built in. The wing was set at roughly 2°
positive incidence relative to the stabilizer. (Typical javelinlaunch
gliders are set close to zero.)
Instead of the usual flat stabilizer, Mark used a V-shaped
version that was slightly skewed on the tailboom (LE offset to the
left). The bottom-mounted rudder was set for a slight right turn.
The stabilizer and rudder offsets were carefully set to
counterbalance the
strong left turn of
the discus launch
and produce a right
circle in the glide.
Right-handed fliers
grip the model’s
left tip in the right
hand and launch
with a
counterclockwise
rotation.
Thanks to
several FF
publications, the
Internet, and a few
enterprising kit manufacturers, discus launch had become
mainstream by the time the 2007 Nats took place. Bruce Kimball
was one of a number of top American Glider fliers to make the
transition from javelin to discus launch. He experimented with
the larger auto-surface models but soon settled on the smaller
Glider. Nine of the top 10 places in HLG at the Nats went to
discus-launch models.
“The whole idea was to make it a simple model; when you
start adding gadgets a lot of people will complain,” said Bruce.
“These models are simple enough that everybody can build and
fly them.”
Compared to traditional javelin-launch aircraft, the new
discus-launch Gliders seem heavy. Bruce said:
“My first model was 62 grams, but I think that was too light.
The Glider I won with at the 2006 Nats was 72 grams; 75-90
grams is a good range, though models seem to tolerate being a
heavier weight with no problem. Len Surtees has one model at
120 grams and he says that it flies well. I know that Tim Batiuk
said that a couple of his Gliders were over 100 grams.”
If you want to give discus launch, also called tip launch, a try,
the best suggestion is to start with a kit. The two most popular are
Stan Buddenbohm’s Dynamo Hum II and Mark Benn’s Spin-Up
Discus-launch Gliders: history, kits, and building tips
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Razor planes
• Finding balsa
Bruce Kimball’s model is typical of the new discus-launch Gliders • 2007 Nats DVD
that are rapidly replacing conventional javelin-launch Gliders.
Jim Buxton (L) and Tim Batiuk are top Glider fliers who
transitioned to discus launch. The model on the ground is not
damaged; it’s in its “broken-back” DT mode.
02sig5.QXD 12/20/07 1:24 PM Page 152February 2008 153
36. (See sources for more info.) Even if you
decide to start from scratch, as I did, order
plans. It will save you a great deal of time
and aggravation.
I picked a short kit (plans and tailboom)
from Len Surtees at the 2007 Nats. Figuring
that my learning curve might include some
broken models, I decided to set up fixtures
and “mass produce” three identical models.
On Bruce Kimball’s recommendation I
ordered some tapered carbon-fiber kite spars
for booms. Everything else was the usual
hobby-shop balsa and plywood. I made a
few construction notes.
• The typical way to shape a Glider wing is
to taper the balsa sheet from root to tip and
then sand in the airfoil. Instead I cut the
wing to its planform shape, added basswood
edging at the LE and TE, did some rough
planing, and then sanded the airfoil from
high point to TE using a fixture. Typical
Glider airfoils feature a straight-line upper
surface from the high point back to the TE.
The fixture is a piece of 3/4 birch
plywood measuring roughly 7 x 20 inches
with a strip of 3/8 pine glued approximately
5 inches from one long edge. The exact
position of the 3/8 strip was chosen to give
the desired taper angle from high point to
the TE at the wing root.
A sanding block bridges from the edge of the plywood board to
the 3/8 strip. A stop on the underside of the sanding block keeps it
from sliding forward.
The block is moved in a spanwise direction. By keeping the
wing TE approximately 1/4 inch from the edge, sanding
automatically produces both a straight taper from high point to TE
and a taper in wing thickness from root to tip.
• The V-shaped stabilizer turned out to be easier to make than I
had anticipated.
After sanding the 3/32 balsa stabilizer to shape and giving it one
coat of finish, I ran a strip of masking tape along the centerline on
the flat underside. I made a straight cut along the top centerline
Simple fixture makes sanding wing fast,
accurate. Pine strip attached to plywood
base provides correct angle to create
straight line from wing high point to TE.
Aluminum screw posts from the hardware
store can be used to join two-piece
fuselage and provide pivot for “brokenback”
DT.
Most discus-launch models feature V-shaped stabilizer and subrudder mounted on a
tapered carbon-fiber kite-spar tailboom. V-tail is skewed slightly to counteract left roll of
launch.
A good razor plane makes rough shaping
of Gilder wings quick and reduces amount
of messy sanding needed. Blades are
expensive but long-lasting.
with a razor saw. Then I used a small triangular file to open the
cut to the correct angle. It took only a few seconds to file down
to the masking tape. Then I added glue and propped up one side
of the stabilizer to the correct angle.
• I probably spent too much time agonizing over what to use for
the hinge pin. Most discus-launch models use what’s called a
broken-back DT. The wing and front fuselage are a separate
assembly from the tailboom, stabilizer, and rudder. A removable
hinge pin holds the two components together and allows the
boom to pivot up for DT.
Some people use a nylon screw or even a pop rivet for the
hinge, but I was worried about long-term wear from taking the
02sig5.QXD 12/20/07 2:00 PM Page 153154 MODEL AVIATION
model apart for transport or storage. I ended
up using an aluminum screw post, also called
a binder post. Although it is an office-supply
item, it is easier to find at a local Ace
Hardware store than at a big-box officesupply
store.
I bored out a short length of thick-wall
aluminum tubing (i.e., rear peg material from
FAI Model Supply) with a 13/64 drill bit
(another Ace Hardware item) and epoxied the
tubing in the boom assembly to provide a
durable pivot. The female portion of the
screw post was trimmed to length so the
screw could be tightened all the way without
pinching in the fuselage sides and binding
movement of the boom for DT.
I hope you will give discus launch a try.
Your arm will thank you. To help, following
are some additional places to find more
information, kits, and materials.
• Free Flight Digest, June-July 2007: kit
review of Stan Buddenbohm’s Twirly Bird
discus-launch Glider, written by Larry Kruse
• Free Flight Digest, December 2006: kit
review of the Mark Benns-designed Spin-Up
36 kitted by Sting Aero Products, written by
Dohrman Crawford
• Aeromodeller, April 2007: kit review of
Spin-Up 36 written by Bob Bailey
(Aeromodeller is now published as the FF
section within Aviation Modeller
International magazine.)
• Free Flight Forum 2004: “Discus-Launched
Gliders” by Phil Ball and Andrew Hewitt is
an extensive discussion of design,
development, and construction of Phil and
Andy’s large (approximately 60-inch-span)
auto-surface discus-launch Gliders.
• Free Flight Forum 2005: “Further
Experiments with Discus Launched Gliders
and the Development of Big Bertha &
Slippery Sam” by Andrew Hewitt. In this
follow-on to the 2004 Forum piece, Andy
details the development of smaller (39-inchspan)
models with solid-balsa wings. They
still incorporate timer-actuated auto
surfaces.
• Free Flight Forum 2005: “Update on Last
Year’s Report on Free Flight Discus HLG—
The 60-inch All Singing and Dancing
Model” by Phil Ball. This features further
exploration of the large auto-surface Glider.
• Free Flight Forum 2006: “Gadget-Free
Discus-Launched Gliders” by Mark Benns.
The Spin-Up 36’s designer details his
design approach to discus launch without
the use of auto surfaces. If you don’t read
anything else, read this article. (Copies of
the Free Flight Forum are available from
Bob Stalick, NFFS Publications Service.
Check the National Free Flight Society
[NFFS] Web site for additional
information.)
• 36th Annual Report of the National Free
Flight Society: “2005 Models of the Year—
Discus Launched Gliders: ‘Stork’ &
‘Flingituicus’” by Andy Hewitt and Phil
Ball. This includes three-views and
information about the two large autosurface-
equipped models. (Check with
NFFS Publications at the previous address
for availability.)
• Discus Launched Gliders by Kurt
Krempetz. Contains information and threeviews
of Kurt’s Round-A-Bout design. It’s
available online at the AMA Glider Web
site, which also contains photos and videos
of a variety of discus-launch models, tips
for converting traditional javelin-launch
models to tip launch, and a variety of
plans and construction tips for all types of
HLGs and Catapult Gliders.
• Hand Launch Glider Airfoils by Curt
Stevens. Although written about
conventional HLGs, Curt details the
Glider airfoil he developed almost a half
century ago that is still the choice for
many discus-launch designs.
• Sting Aero Products sells Spin-Up 36
and Spin-Up 42 discus-launch kits and
short kits, tailbooms, Smoothie and
Cooltube viscous DTs, and other HLG and
Catapult Glider kits. Sting Aero founder,
noted Australian Glider flier Len Surtees,
recently sold the company to Tim
Goldstein. All sales are now through
Tim’s A2Z Corporation’s Peck-Polymers
division.
• Stan Buddenbohm’s discus-launch kits
include the Twirly Bird, Meerkat, Dynamo
Hum, and Dynamo Hum II. Five of the top
10 places in Open outdoor HLG at the
2007 Nats went to fliers using the Dynamo
Hum II. Stan also sells fuselage kits,
plans, and instructions for discus-launch
models. You can find more information on
the AMA Glider Web site.
• FAI Model Supply carries Sting Aero
Products kits and components, Ikara,
Button, and Badge viscous DT timers, and
many other FF kits, supplies, and
accessories.
• Stevens AeroModel sells pop-up
fuselage kits for discus-launch gliders,
available in two sizes and with or
without viscous timer. Kits feature lasercut
balsa-and-plywood front sections and
carbon-fiber tailbooms.
• Hang-em High Fabrics has tapered
02sig5.QXD 12/20/07 1:25 PM Page 154February 2008 155
carbon-fiber kite spars for use as
tailbooms. The G-Force Skinny (item
WIND-SK32) is 32.5 inches long and
weighs 7.5 grams.
Razor Planes: After 50 years my Little
Giant razor plane was starting to show
its age, and I used up my stash of
Gillette Super Blue blades long ago.
(The stainless-steel blades that replaced
the Super Blues in the 1970s were
worthless for planing balsa.) It was time
to find a replacement.
The German-made Balsa-Hobel plane
seemed like a reasonable replacement
and, allowing for inflation, the $14 price
tag was in line with what the Little Giant
cost a half century ago. The big surprise
was what razor blades cost now. The
Solingen steel blades are $1.35 each. I
figured 10 blades would get me through
the three discus-launch wings if I were
careful.
I placed an order with Tim Goldstein
(A2Z Corporation), and a few days later
the plane arrived. It even came with one
blade. This tool is a joy to use. It makes
nice, wide shavings and no chatter. Best
of all, I turned three 4 x 36 balsa sheets
into wings, and I’m still on the first
blade.
Finding Balsa: Longtime Free Flight
digest editor Walt Rozelle, who died last
October, once told me that he found the
best sheet of balsa he had ever seen in
the display rack at a craft store. The
sheet of 4-pound-per-cubic-foot C-grain
was mixed in with the usual rock-hard
sheets that could pass for basswood.
In a typical Walt gesture, he gave the
piece of balsa to an Indoor modeler who
could make better use of it.
Ever since I’ve been pawing through
the balsa bins at chain craft stores and
occasionally find a good sheet of light Cgrain.
But I hate to think how much time
and gas I’ve wasted.
Now Peck-Polymers offers an
alternative. Each sheet of its contest balsa
is individually weighed and sorted. Most
sizes are available in your choice of A/Bor
C-grain. Density ranges are 4-4.99, 5-
5.99, and 6-6.99 pounds per cubic foot.
“As you can imagine the supply is
limited, particularly in the real light 4-
pound stuff,” said Peck-Polymers owner
Tim Goldstein. “But many people are glad
to pay the price to get the density sheets
they really want instead of buying 20
sheets from others and hoping to get what
they need.”
For more information contact A2Z
Corp.
2007 Nats Video: Alan Abriss’s latest
Nats video is now available as a twohour
DVD. Coverage of the weeklong
Outdoor FF event includes Dawn
Unlimited, ROW (rise-off-water), and
the new electric categories.
The DVD is $20 plus $3 shipping
and is available from Homegrown
Television Productions. MA
Sources:
A2Z Corp
(720) 833-9300
www.peck-polymers.com/store
AMA Glider
www.amaglider.vze.com/
Aviation Modeller International
0044 (0)1494 433 453
www.modelactivitypress.com/amimonthly.
htm
Bob Stalick (NFFS Publications Service)
Box 1775
Albany OR 97321
FAI Model Supply
www.faimodelsupply.com
(570) 882-9873
Hand Launch Glider Airfoils
www.modelresearchlabs.com/hand_launch
_glider_airfoils.htm
Hang-em High Fabrics
http://ecom.citystar.com/hang-em-high/
(800) 233-6155
Homegrown Television Productions
www.homegrowntv.com/catalog.html
National Free Flight Society
www.freeflight.org
Stan Buddenbohm
5652 Meinhardt Rd.
Westminster CA 92683
Page 155
Edition: Model Aviation - 2008/02
Page Numbers: 152,153,154,155
Edition: Model Aviation - 2008/02
Page Numbers: 152,153,154,155
152 MODEL AVIATION
DISCUS-LAUNCH Gliders look like oversized Hand-Launched
Gliders (HLGs). A 3-foot wingspan is typical.
Instead of the usual overhand, near-vertical javelin throw,
discus-launch Gliders are gripped by the wingtip and thrown with
a circular motion that is slightly above horizontal. The discus
action is not only much easier on the arm, but it also yields a
considerably higher launch altitude.
Early experiments (circa 2004) with discus-launch FF Gliders
were based on RC discus-launch designs. In England Phil Ball
and Andy Hewitt developed 5-foot-span models that used timeroperated
auto rudder and stabilizer to control launch trajectory,
transition, and glide. The aircraft were successful but
complicated by the built-up wing construction and auto surfaces.
Soon another British modeler, Mark Benns, came up with a
smaller model, spanning approximately 36 inches, that used a
conventional solid-balsa wing and required no auto surfaces.
Flight adjustments were built in. The wing was set at roughly 2°
positive incidence relative to the stabilizer. (Typical javelinlaunch
gliders are set close to zero.)
Instead of the usual flat stabilizer, Mark used a V-shaped
version that was slightly skewed on the tailboom (LE offset to the
left). The bottom-mounted rudder was set for a slight right turn.
The stabilizer and rudder offsets were carefully set to
counterbalance the
strong left turn of
the discus launch
and produce a right
circle in the glide.
Right-handed fliers
grip the model’s
left tip in the right
hand and launch
with a
counterclockwise
rotation.
Thanks to
several FF
publications, the
Internet, and a few
enterprising kit manufacturers, discus launch had become
mainstream by the time the 2007 Nats took place. Bruce Kimball
was one of a number of top American Glider fliers to make the
transition from javelin to discus launch. He experimented with
the larger auto-surface models but soon settled on the smaller
Glider. Nine of the top 10 places in HLG at the Nats went to
discus-launch models.
“The whole idea was to make it a simple model; when you
start adding gadgets a lot of people will complain,” said Bruce.
“These models are simple enough that everybody can build and
fly them.”
Compared to traditional javelin-launch aircraft, the new
discus-launch Gliders seem heavy. Bruce said:
“My first model was 62 grams, but I think that was too light.
The Glider I won with at the 2006 Nats was 72 grams; 75-90
grams is a good range, though models seem to tolerate being a
heavier weight with no problem. Len Surtees has one model at
120 grams and he says that it flies well. I know that Tim Batiuk
said that a couple of his Gliders were over 100 grams.”
If you want to give discus launch, also called tip launch, a try,
the best suggestion is to start with a kit. The two most popular are
Stan Buddenbohm’s Dynamo Hum II and Mark Benn’s Spin-Up
Discus-launch Gliders: history, kits, and building tips
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Razor planes
• Finding balsa
Bruce Kimball’s model is typical of the new discus-launch Gliders • 2007 Nats DVD
that are rapidly replacing conventional javelin-launch Gliders.
Jim Buxton (L) and Tim Batiuk are top Glider fliers who
transitioned to discus launch. The model on the ground is not
damaged; it’s in its “broken-back” DT mode.
02sig5.QXD 12/20/07 1:24 PM Page 152February 2008 153
36. (See sources for more info.) Even if you
decide to start from scratch, as I did, order
plans. It will save you a great deal of time
and aggravation.
I picked a short kit (plans and tailboom)
from Len Surtees at the 2007 Nats. Figuring
that my learning curve might include some
broken models, I decided to set up fixtures
and “mass produce” three identical models.
On Bruce Kimball’s recommendation I
ordered some tapered carbon-fiber kite spars
for booms. Everything else was the usual
hobby-shop balsa and plywood. I made a
few construction notes.
• The typical way to shape a Glider wing is
to taper the balsa sheet from root to tip and
then sand in the airfoil. Instead I cut the
wing to its planform shape, added basswood
edging at the LE and TE, did some rough
planing, and then sanded the airfoil from
high point to TE using a fixture. Typical
Glider airfoils feature a straight-line upper
surface from the high point back to the TE.
The fixture is a piece of 3/4 birch
plywood measuring roughly 7 x 20 inches
with a strip of 3/8 pine glued approximately
5 inches from one long edge. The exact
position of the 3/8 strip was chosen to give
the desired taper angle from high point to
the TE at the wing root.
A sanding block bridges from the edge of the plywood board to
the 3/8 strip. A stop on the underside of the sanding block keeps it
from sliding forward.
The block is moved in a spanwise direction. By keeping the
wing TE approximately 1/4 inch from the edge, sanding
automatically produces both a straight taper from high point to TE
and a taper in wing thickness from root to tip.
• The V-shaped stabilizer turned out to be easier to make than I
had anticipated.
After sanding the 3/32 balsa stabilizer to shape and giving it one
coat of finish, I ran a strip of masking tape along the centerline on
the flat underside. I made a straight cut along the top centerline
Simple fixture makes sanding wing fast,
accurate. Pine strip attached to plywood
base provides correct angle to create
straight line from wing high point to TE.
Aluminum screw posts from the hardware
store can be used to join two-piece
fuselage and provide pivot for “brokenback”
DT.
Most discus-launch models feature V-shaped stabilizer and subrudder mounted on a
tapered carbon-fiber kite-spar tailboom. V-tail is skewed slightly to counteract left roll of
launch.
A good razor plane makes rough shaping
of Gilder wings quick and reduces amount
of messy sanding needed. Blades are
expensive but long-lasting.
with a razor saw. Then I used a small triangular file to open the
cut to the correct angle. It took only a few seconds to file down
to the masking tape. Then I added glue and propped up one side
of the stabilizer to the correct angle.
• I probably spent too much time agonizing over what to use for
the hinge pin. Most discus-launch models use what’s called a
broken-back DT. The wing and front fuselage are a separate
assembly from the tailboom, stabilizer, and rudder. A removable
hinge pin holds the two components together and allows the
boom to pivot up for DT.
Some people use a nylon screw or even a pop rivet for the
hinge, but I was worried about long-term wear from taking the
02sig5.QXD 12/20/07 2:00 PM Page 153154 MODEL AVIATION
model apart for transport or storage. I ended
up using an aluminum screw post, also called
a binder post. Although it is an office-supply
item, it is easier to find at a local Ace
Hardware store than at a big-box officesupply
store.
I bored out a short length of thick-wall
aluminum tubing (i.e., rear peg material from
FAI Model Supply) with a 13/64 drill bit
(another Ace Hardware item) and epoxied the
tubing in the boom assembly to provide a
durable pivot. The female portion of the
screw post was trimmed to length so the
screw could be tightened all the way without
pinching in the fuselage sides and binding
movement of the boom for DT.
I hope you will give discus launch a try.
Your arm will thank you. To help, following
are some additional places to find more
information, kits, and materials.
• Free Flight Digest, June-July 2007: kit
review of Stan Buddenbohm’s Twirly Bird
discus-launch Glider, written by Larry Kruse
• Free Flight Digest, December 2006: kit
review of the Mark Benns-designed Spin-Up
36 kitted by Sting Aero Products, written by
Dohrman Crawford
• Aeromodeller, April 2007: kit review of
Spin-Up 36 written by Bob Bailey
(Aeromodeller is now published as the FF
section within Aviation Modeller
International magazine.)
• Free Flight Forum 2004: “Discus-Launched
Gliders” by Phil Ball and Andrew Hewitt is
an extensive discussion of design,
development, and construction of Phil and
Andy’s large (approximately 60-inch-span)
auto-surface discus-launch Gliders.
• Free Flight Forum 2005: “Further
Experiments with Discus Launched Gliders
and the Development of Big Bertha &
Slippery Sam” by Andrew Hewitt. In this
follow-on to the 2004 Forum piece, Andy
details the development of smaller (39-inchspan)
models with solid-balsa wings. They
still incorporate timer-actuated auto
surfaces.
• Free Flight Forum 2005: “Update on Last
Year’s Report on Free Flight Discus HLG—
The 60-inch All Singing and Dancing
Model” by Phil Ball. This features further
exploration of the large auto-surface Glider.
• Free Flight Forum 2006: “Gadget-Free
Discus-Launched Gliders” by Mark Benns.
The Spin-Up 36’s designer details his
design approach to discus launch without
the use of auto surfaces. If you don’t read
anything else, read this article. (Copies of
the Free Flight Forum are available from
Bob Stalick, NFFS Publications Service.
Check the National Free Flight Society
[NFFS] Web site for additional
information.)
• 36th Annual Report of the National Free
Flight Society: “2005 Models of the Year—
Discus Launched Gliders: ‘Stork’ &
‘Flingituicus’” by Andy Hewitt and Phil
Ball. This includes three-views and
information about the two large autosurface-
equipped models. (Check with
NFFS Publications at the previous address
for availability.)
• Discus Launched Gliders by Kurt
Krempetz. Contains information and threeviews
of Kurt’s Round-A-Bout design. It’s
available online at the AMA Glider Web
site, which also contains photos and videos
of a variety of discus-launch models, tips
for converting traditional javelin-launch
models to tip launch, and a variety of
plans and construction tips for all types of
HLGs and Catapult Gliders.
• Hand Launch Glider Airfoils by Curt
Stevens. Although written about
conventional HLGs, Curt details the
Glider airfoil he developed almost a half
century ago that is still the choice for
many discus-launch designs.
• Sting Aero Products sells Spin-Up 36
and Spin-Up 42 discus-launch kits and
short kits, tailbooms, Smoothie and
Cooltube viscous DTs, and other HLG and
Catapult Glider kits. Sting Aero founder,
noted Australian Glider flier Len Surtees,
recently sold the company to Tim
Goldstein. All sales are now through
Tim’s A2Z Corporation’s Peck-Polymers
division.
• Stan Buddenbohm’s discus-launch kits
include the Twirly Bird, Meerkat, Dynamo
Hum, and Dynamo Hum II. Five of the top
10 places in Open outdoor HLG at the
2007 Nats went to fliers using the Dynamo
Hum II. Stan also sells fuselage kits,
plans, and instructions for discus-launch
models. You can find more information on
the AMA Glider Web site.
• FAI Model Supply carries Sting Aero
Products kits and components, Ikara,
Button, and Badge viscous DT timers, and
many other FF kits, supplies, and
accessories.
• Stevens AeroModel sells pop-up
fuselage kits for discus-launch gliders,
available in two sizes and with or
without viscous timer. Kits feature lasercut
balsa-and-plywood front sections and
carbon-fiber tailbooms.
• Hang-em High Fabrics has tapered
02sig5.QXD 12/20/07 1:25 PM Page 154February 2008 155
carbon-fiber kite spars for use as
tailbooms. The G-Force Skinny (item
WIND-SK32) is 32.5 inches long and
weighs 7.5 grams.
Razor Planes: After 50 years my Little
Giant razor plane was starting to show
its age, and I used up my stash of
Gillette Super Blue blades long ago.
(The stainless-steel blades that replaced
the Super Blues in the 1970s were
worthless for planing balsa.) It was time
to find a replacement.
The German-made Balsa-Hobel plane
seemed like a reasonable replacement
and, allowing for inflation, the $14 price
tag was in line with what the Little Giant
cost a half century ago. The big surprise
was what razor blades cost now. The
Solingen steel blades are $1.35 each. I
figured 10 blades would get me through
the three discus-launch wings if I were
careful.
I placed an order with Tim Goldstein
(A2Z Corporation), and a few days later
the plane arrived. It even came with one
blade. This tool is a joy to use. It makes
nice, wide shavings and no chatter. Best
of all, I turned three 4 x 36 balsa sheets
into wings, and I’m still on the first
blade.
Finding Balsa: Longtime Free Flight
digest editor Walt Rozelle, who died last
October, once told me that he found the
best sheet of balsa he had ever seen in
the display rack at a craft store. The
sheet of 4-pound-per-cubic-foot C-grain
was mixed in with the usual rock-hard
sheets that could pass for basswood.
In a typical Walt gesture, he gave the
piece of balsa to an Indoor modeler who
could make better use of it.
Ever since I’ve been pawing through
the balsa bins at chain craft stores and
occasionally find a good sheet of light Cgrain.
But I hate to think how much time
and gas I’ve wasted.
Now Peck-Polymers offers an
alternative. Each sheet of its contest balsa
is individually weighed and sorted. Most
sizes are available in your choice of A/Bor
C-grain. Density ranges are 4-4.99, 5-
5.99, and 6-6.99 pounds per cubic foot.
“As you can imagine the supply is
limited, particularly in the real light 4-
pound stuff,” said Peck-Polymers owner
Tim Goldstein. “But many people are glad
to pay the price to get the density sheets
they really want instead of buying 20
sheets from others and hoping to get what
they need.”
For more information contact A2Z
Corp.
2007 Nats Video: Alan Abriss’s latest
Nats video is now available as a twohour
DVD. Coverage of the weeklong
Outdoor FF event includes Dawn
Unlimited, ROW (rise-off-water), and
the new electric categories.
The DVD is $20 plus $3 shipping
and is available from Homegrown
Television Productions. MA
Sources:
A2Z Corp
(720) 833-9300
www.peck-polymers.com/store
AMA Glider
www.amaglider.vze.com/
Aviation Modeller International
0044 (0)1494 433 453
www.modelactivitypress.com/amimonthly.
htm
Bob Stalick (NFFS Publications Service)
Box 1775
Albany OR 97321
FAI Model Supply
www.faimodelsupply.com
(570) 882-9873
Hand Launch Glider Airfoils
www.modelresearchlabs.com/hand_launch
_glider_airfoils.htm
Hang-em High Fabrics
http://ecom.citystar.com/hang-em-high/
(800) 233-6155
Homegrown Television Productions
www.homegrowntv.com/catalog.html
National Free Flight Society
www.freeflight.org
Stan Buddenbohm
5652 Meinhardt Rd.
Westminster CA 92683
Page 155
Edition: Model Aviation - 2008/02
Page Numbers: 152,153,154,155
152 MODEL AVIATION
DISCUS-LAUNCH Gliders look like oversized Hand-Launched
Gliders (HLGs). A 3-foot wingspan is typical.
Instead of the usual overhand, near-vertical javelin throw,
discus-launch Gliders are gripped by the wingtip and thrown with
a circular motion that is slightly above horizontal. The discus
action is not only much easier on the arm, but it also yields a
considerably higher launch altitude.
Early experiments (circa 2004) with discus-launch FF Gliders
were based on RC discus-launch designs. In England Phil Ball
and Andy Hewitt developed 5-foot-span models that used timeroperated
auto rudder and stabilizer to control launch trajectory,
transition, and glide. The aircraft were successful but
complicated by the built-up wing construction and auto surfaces.
Soon another British modeler, Mark Benns, came up with a
smaller model, spanning approximately 36 inches, that used a
conventional solid-balsa wing and required no auto surfaces.
Flight adjustments were built in. The wing was set at roughly 2°
positive incidence relative to the stabilizer. (Typical javelinlaunch
gliders are set close to zero.)
Instead of the usual flat stabilizer, Mark used a V-shaped
version that was slightly skewed on the tailboom (LE offset to the
left). The bottom-mounted rudder was set for a slight right turn.
The stabilizer and rudder offsets were carefully set to
counterbalance the
strong left turn of
the discus launch
and produce a right
circle in the glide.
Right-handed fliers
grip the model’s
left tip in the right
hand and launch
with a
counterclockwise
rotation.
Thanks to
several FF
publications, the
Internet, and a few
enterprising kit manufacturers, discus launch had become
mainstream by the time the 2007 Nats took place. Bruce Kimball
was one of a number of top American Glider fliers to make the
transition from javelin to discus launch. He experimented with
the larger auto-surface models but soon settled on the smaller
Glider. Nine of the top 10 places in HLG at the Nats went to
discus-launch models.
“The whole idea was to make it a simple model; when you
start adding gadgets a lot of people will complain,” said Bruce.
“These models are simple enough that everybody can build and
fly them.”
Compared to traditional javelin-launch aircraft, the new
discus-launch Gliders seem heavy. Bruce said:
“My first model was 62 grams, but I think that was too light.
The Glider I won with at the 2006 Nats was 72 grams; 75-90
grams is a good range, though models seem to tolerate being a
heavier weight with no problem. Len Surtees has one model at
120 grams and he says that it flies well. I know that Tim Batiuk
said that a couple of his Gliders were over 100 grams.”
If you want to give discus launch, also called tip launch, a try,
the best suggestion is to start with a kit. The two most popular are
Stan Buddenbohm’s Dynamo Hum II and Mark Benn’s Spin-Up
Discus-launch Gliders: history, kits, and building tips
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Razor planes
• Finding balsa
Bruce Kimball’s model is typical of the new discus-launch Gliders • 2007 Nats DVD
that are rapidly replacing conventional javelin-launch Gliders.
Jim Buxton (L) and Tim Batiuk are top Glider fliers who
transitioned to discus launch. The model on the ground is not
damaged; it’s in its “broken-back” DT mode.
02sig5.QXD 12/20/07 1:24 PM Page 152February 2008 153
36. (See sources for more info.) Even if you
decide to start from scratch, as I did, order
plans. It will save you a great deal of time
and aggravation.
I picked a short kit (plans and tailboom)
from Len Surtees at the 2007 Nats. Figuring
that my learning curve might include some
broken models, I decided to set up fixtures
and “mass produce” three identical models.
On Bruce Kimball’s recommendation I
ordered some tapered carbon-fiber kite spars
for booms. Everything else was the usual
hobby-shop balsa and plywood. I made a
few construction notes.
• The typical way to shape a Glider wing is
to taper the balsa sheet from root to tip and
then sand in the airfoil. Instead I cut the
wing to its planform shape, added basswood
edging at the LE and TE, did some rough
planing, and then sanded the airfoil from
high point to TE using a fixture. Typical
Glider airfoils feature a straight-line upper
surface from the high point back to the TE.
The fixture is a piece of 3/4 birch
plywood measuring roughly 7 x 20 inches
with a strip of 3/8 pine glued approximately
5 inches from one long edge. The exact
position of the 3/8 strip was chosen to give
the desired taper angle from high point to
the TE at the wing root.
A sanding block bridges from the edge of the plywood board to
the 3/8 strip. A stop on the underside of the sanding block keeps it
from sliding forward.
The block is moved in a spanwise direction. By keeping the
wing TE approximately 1/4 inch from the edge, sanding
automatically produces both a straight taper from high point to TE
and a taper in wing thickness from root to tip.
• The V-shaped stabilizer turned out to be easier to make than I
had anticipated.
After sanding the 3/32 balsa stabilizer to shape and giving it one
coat of finish, I ran a strip of masking tape along the centerline on
the flat underside. I made a straight cut along the top centerline
Simple fixture makes sanding wing fast,
accurate. Pine strip attached to plywood
base provides correct angle to create
straight line from wing high point to TE.
Aluminum screw posts from the hardware
store can be used to join two-piece
fuselage and provide pivot for “brokenback”
DT.
Most discus-launch models feature V-shaped stabilizer and subrudder mounted on a
tapered carbon-fiber kite-spar tailboom. V-tail is skewed slightly to counteract left roll of
launch.
A good razor plane makes rough shaping
of Gilder wings quick and reduces amount
of messy sanding needed. Blades are
expensive but long-lasting.
with a razor saw. Then I used a small triangular file to open the
cut to the correct angle. It took only a few seconds to file down
to the masking tape. Then I added glue and propped up one side
of the stabilizer to the correct angle.
• I probably spent too much time agonizing over what to use for
the hinge pin. Most discus-launch models use what’s called a
broken-back DT. The wing and front fuselage are a separate
assembly from the tailboom, stabilizer, and rudder. A removable
hinge pin holds the two components together and allows the
boom to pivot up for DT.
Some people use a nylon screw or even a pop rivet for the
hinge, but I was worried about long-term wear from taking the
02sig5.QXD 12/20/07 2:00 PM Page 153154 MODEL AVIATION
model apart for transport or storage. I ended
up using an aluminum screw post, also called
a binder post. Although it is an office-supply
item, it is easier to find at a local Ace
Hardware store than at a big-box officesupply
store.
I bored out a short length of thick-wall
aluminum tubing (i.e., rear peg material from
FAI Model Supply) with a 13/64 drill bit
(another Ace Hardware item) and epoxied the
tubing in the boom assembly to provide a
durable pivot. The female portion of the
screw post was trimmed to length so the
screw could be tightened all the way without
pinching in the fuselage sides and binding
movement of the boom for DT.
I hope you will give discus launch a try.
Your arm will thank you. To help, following
are some additional places to find more
information, kits, and materials.
• Free Flight Digest, June-July 2007: kit
review of Stan Buddenbohm’s Twirly Bird
discus-launch Glider, written by Larry Kruse
• Free Flight Digest, December 2006: kit
review of the Mark Benns-designed Spin-Up
36 kitted by Sting Aero Products, written by
Dohrman Crawford
• Aeromodeller, April 2007: kit review of
Spin-Up 36 written by Bob Bailey
(Aeromodeller is now published as the FF
section within Aviation Modeller
International magazine.)
• Free Flight Forum 2004: “Discus-Launched
Gliders” by Phil Ball and Andrew Hewitt is
an extensive discussion of design,
development, and construction of Phil and
Andy’s large (approximately 60-inch-span)
auto-surface discus-launch Gliders.
• Free Flight Forum 2005: “Further
Experiments with Discus Launched Gliders
and the Development of Big Bertha &
Slippery Sam” by Andrew Hewitt. In this
follow-on to the 2004 Forum piece, Andy
details the development of smaller (39-inchspan)
models with solid-balsa wings. They
still incorporate timer-actuated auto
surfaces.
• Free Flight Forum 2005: “Update on Last
Year’s Report on Free Flight Discus HLG—
The 60-inch All Singing and Dancing
Model” by Phil Ball. This features further
exploration of the large auto-surface Glider.
• Free Flight Forum 2006: “Gadget-Free
Discus-Launched Gliders” by Mark Benns.
The Spin-Up 36’s designer details his
design approach to discus launch without
the use of auto surfaces. If you don’t read
anything else, read this article. (Copies of
the Free Flight Forum are available from
Bob Stalick, NFFS Publications Service.
Check the National Free Flight Society
[NFFS] Web site for additional
information.)
• 36th Annual Report of the National Free
Flight Society: “2005 Models of the Year—
Discus Launched Gliders: ‘Stork’ &
‘Flingituicus’” by Andy Hewitt and Phil
Ball. This includes three-views and
information about the two large autosurface-
equipped models. (Check with
NFFS Publications at the previous address
for availability.)
• Discus Launched Gliders by Kurt
Krempetz. Contains information and threeviews
of Kurt’s Round-A-Bout design. It’s
available online at the AMA Glider Web
site, which also contains photos and videos
of a variety of discus-launch models, tips
for converting traditional javelin-launch
models to tip launch, and a variety of
plans and construction tips for all types of
HLGs and Catapult Gliders.
• Hand Launch Glider Airfoils by Curt
Stevens. Although written about
conventional HLGs, Curt details the
Glider airfoil he developed almost a half
century ago that is still the choice for
many discus-launch designs.
• Sting Aero Products sells Spin-Up 36
and Spin-Up 42 discus-launch kits and
short kits, tailbooms, Smoothie and
Cooltube viscous DTs, and other HLG and
Catapult Glider kits. Sting Aero founder,
noted Australian Glider flier Len Surtees,
recently sold the company to Tim
Goldstein. All sales are now through
Tim’s A2Z Corporation’s Peck-Polymers
division.
• Stan Buddenbohm’s discus-launch kits
include the Twirly Bird, Meerkat, Dynamo
Hum, and Dynamo Hum II. Five of the top
10 places in Open outdoor HLG at the
2007 Nats went to fliers using the Dynamo
Hum II. Stan also sells fuselage kits,
plans, and instructions for discus-launch
models. You can find more information on
the AMA Glider Web site.
• FAI Model Supply carries Sting Aero
Products kits and components, Ikara,
Button, and Badge viscous DT timers, and
many other FF kits, supplies, and
accessories.
• Stevens AeroModel sells pop-up
fuselage kits for discus-launch gliders,
available in two sizes and with or
without viscous timer. Kits feature lasercut
balsa-and-plywood front sections and
carbon-fiber tailbooms.
• Hang-em High Fabrics has tapered
02sig5.QXD 12/20/07 1:25 PM Page 154February 2008 155
carbon-fiber kite spars for use as
tailbooms. The G-Force Skinny (item
WIND-SK32) is 32.5 inches long and
weighs 7.5 grams.
Razor Planes: After 50 years my Little
Giant razor plane was starting to show
its age, and I used up my stash of
Gillette Super Blue blades long ago.
(The stainless-steel blades that replaced
the Super Blues in the 1970s were
worthless for planing balsa.) It was time
to find a replacement.
The German-made Balsa-Hobel plane
seemed like a reasonable replacement
and, allowing for inflation, the $14 price
tag was in line with what the Little Giant
cost a half century ago. The big surprise
was what razor blades cost now. The
Solingen steel blades are $1.35 each. I
figured 10 blades would get me through
the three discus-launch wings if I were
careful.
I placed an order with Tim Goldstein
(A2Z Corporation), and a few days later
the plane arrived. It even came with one
blade. This tool is a joy to use. It makes
nice, wide shavings and no chatter. Best
of all, I turned three 4 x 36 balsa sheets
into wings, and I’m still on the first
blade.
Finding Balsa: Longtime Free Flight
digest editor Walt Rozelle, who died last
October, once told me that he found the
best sheet of balsa he had ever seen in
the display rack at a craft store. The
sheet of 4-pound-per-cubic-foot C-grain
was mixed in with the usual rock-hard
sheets that could pass for basswood.
In a typical Walt gesture, he gave the
piece of balsa to an Indoor modeler who
could make better use of it.
Ever since I’ve been pawing through
the balsa bins at chain craft stores and
occasionally find a good sheet of light Cgrain.
But I hate to think how much time
and gas I’ve wasted.
Now Peck-Polymers offers an
alternative. Each sheet of its contest balsa
is individually weighed and sorted. Most
sizes are available in your choice of A/Bor
C-grain. Density ranges are 4-4.99, 5-
5.99, and 6-6.99 pounds per cubic foot.
“As you can imagine the supply is
limited, particularly in the real light 4-
pound stuff,” said Peck-Polymers owner
Tim Goldstein. “But many people are glad
to pay the price to get the density sheets
they really want instead of buying 20
sheets from others and hoping to get what
they need.”
For more information contact A2Z
Corp.
2007 Nats Video: Alan Abriss’s latest
Nats video is now available as a twohour
DVD. Coverage of the weeklong
Outdoor FF event includes Dawn
Unlimited, ROW (rise-off-water), and
the new electric categories.
The DVD is $20 plus $3 shipping
and is available from Homegrown
Television Productions. MA
Sources:
A2Z Corp
(720) 833-9300
www.peck-polymers.com/store
AMA Glider
www.amaglider.vze.com/
Aviation Modeller International
0044 (0)1494 433 453
www.modelactivitypress.com/amimonthly.
htm
Bob Stalick (NFFS Publications Service)
Box 1775
Albany OR 97321
FAI Model Supply
www.faimodelsupply.com
(570) 882-9873
Hand Launch Glider Airfoils
www.modelresearchlabs.com/hand_launch
_glider_airfoils.htm
Hang-em High Fabrics
http://ecom.citystar.com/hang-em-high/
(800) 233-6155
Homegrown Television Productions
www.homegrowntv.com/catalog.html
National Free Flight Society
www.freeflight.org
Stan Buddenbohm
5652 Meinhardt Rd.
Westminster CA 92683
Page 155
Edition: Model Aviation - 2008/02
Page Numbers: 152,153,154,155
152 MODEL AVIATION
DISCUS-LAUNCH Gliders look like oversized Hand-Launched
Gliders (HLGs). A 3-foot wingspan is typical.
Instead of the usual overhand, near-vertical javelin throw,
discus-launch Gliders are gripped by the wingtip and thrown with
a circular motion that is slightly above horizontal. The discus
action is not only much easier on the arm, but it also yields a
considerably higher launch altitude.
Early experiments (circa 2004) with discus-launch FF Gliders
were based on RC discus-launch designs. In England Phil Ball
and Andy Hewitt developed 5-foot-span models that used timeroperated
auto rudder and stabilizer to control launch trajectory,
transition, and glide. The aircraft were successful but
complicated by the built-up wing construction and auto surfaces.
Soon another British modeler, Mark Benns, came up with a
smaller model, spanning approximately 36 inches, that used a
conventional solid-balsa wing and required no auto surfaces.
Flight adjustments were built in. The wing was set at roughly 2°
positive incidence relative to the stabilizer. (Typical javelinlaunch
gliders are set close to zero.)
Instead of the usual flat stabilizer, Mark used a V-shaped
version that was slightly skewed on the tailboom (LE offset to the
left). The bottom-mounted rudder was set for a slight right turn.
The stabilizer and rudder offsets were carefully set to
counterbalance the
strong left turn of
the discus launch
and produce a right
circle in the glide.
Right-handed fliers
grip the model’s
left tip in the right
hand and launch
with a
counterclockwise
rotation.
Thanks to
several FF
publications, the
Internet, and a few
enterprising kit manufacturers, discus launch had become
mainstream by the time the 2007 Nats took place. Bruce Kimball
was one of a number of top American Glider fliers to make the
transition from javelin to discus launch. He experimented with
the larger auto-surface models but soon settled on the smaller
Glider. Nine of the top 10 places in HLG at the Nats went to
discus-launch models.
“The whole idea was to make it a simple model; when you
start adding gadgets a lot of people will complain,” said Bruce.
“These models are simple enough that everybody can build and
fly them.”
Compared to traditional javelin-launch aircraft, the new
discus-launch Gliders seem heavy. Bruce said:
“My first model was 62 grams, but I think that was too light.
The Glider I won with at the 2006 Nats was 72 grams; 75-90
grams is a good range, though models seem to tolerate being a
heavier weight with no problem. Len Surtees has one model at
120 grams and he says that it flies well. I know that Tim Batiuk
said that a couple of his Gliders were over 100 grams.”
If you want to give discus launch, also called tip launch, a try,
the best suggestion is to start with a kit. The two most popular are
Stan Buddenbohm’s Dynamo Hum II and Mark Benn’s Spin-Up
Discus-launch Gliders: history, kits, and building tips
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Razor planes
• Finding balsa
Bruce Kimball’s model is typical of the new discus-launch Gliders • 2007 Nats DVD
that are rapidly replacing conventional javelin-launch Gliders.
Jim Buxton (L) and Tim Batiuk are top Glider fliers who
transitioned to discus launch. The model on the ground is not
damaged; it’s in its “broken-back” DT mode.
02sig5.QXD 12/20/07 1:24 PM Page 152February 2008 153
36. (See sources for more info.) Even if you
decide to start from scratch, as I did, order
plans. It will save you a great deal of time
and aggravation.
I picked a short kit (plans and tailboom)
from Len Surtees at the 2007 Nats. Figuring
that my learning curve might include some
broken models, I decided to set up fixtures
and “mass produce” three identical models.
On Bruce Kimball’s recommendation I
ordered some tapered carbon-fiber kite spars
for booms. Everything else was the usual
hobby-shop balsa and plywood. I made a
few construction notes.
• The typical way to shape a Glider wing is
to taper the balsa sheet from root to tip and
then sand in the airfoil. Instead I cut the
wing to its planform shape, added basswood
edging at the LE and TE, did some rough
planing, and then sanded the airfoil from
high point to TE using a fixture. Typical
Glider airfoils feature a straight-line upper
surface from the high point back to the TE.
The fixture is a piece of 3/4 birch
plywood measuring roughly 7 x 20 inches
with a strip of 3/8 pine glued approximately
5 inches from one long edge. The exact
position of the 3/8 strip was chosen to give
the desired taper angle from high point to
the TE at the wing root.
A sanding block bridges from the edge of the plywood board to
the 3/8 strip. A stop on the underside of the sanding block keeps it
from sliding forward.
The block is moved in a spanwise direction. By keeping the
wing TE approximately 1/4 inch from the edge, sanding
automatically produces both a straight taper from high point to TE
and a taper in wing thickness from root to tip.
• The V-shaped stabilizer turned out to be easier to make than I
had anticipated.
After sanding the 3/32 balsa stabilizer to shape and giving it one
coat of finish, I ran a strip of masking tape along the centerline on
the flat underside. I made a straight cut along the top centerline
Simple fixture makes sanding wing fast,
accurate. Pine strip attached to plywood
base provides correct angle to create
straight line from wing high point to TE.
Aluminum screw posts from the hardware
store can be used to join two-piece
fuselage and provide pivot for “brokenback”
DT.
Most discus-launch models feature V-shaped stabilizer and subrudder mounted on a
tapered carbon-fiber kite-spar tailboom. V-tail is skewed slightly to counteract left roll of
launch.
A good razor plane makes rough shaping
of Gilder wings quick and reduces amount
of messy sanding needed. Blades are
expensive but long-lasting.
with a razor saw. Then I used a small triangular file to open the
cut to the correct angle. It took only a few seconds to file down
to the masking tape. Then I added glue and propped up one side
of the stabilizer to the correct angle.
• I probably spent too much time agonizing over what to use for
the hinge pin. Most discus-launch models use what’s called a
broken-back DT. The wing and front fuselage are a separate
assembly from the tailboom, stabilizer, and rudder. A removable
hinge pin holds the two components together and allows the
boom to pivot up for DT.
Some people use a nylon screw or even a pop rivet for the
hinge, but I was worried about long-term wear from taking the
02sig5.QXD 12/20/07 2:00 PM Page 153154 MODEL AVIATION
model apart for transport or storage. I ended
up using an aluminum screw post, also called
a binder post. Although it is an office-supply
item, it is easier to find at a local Ace
Hardware store than at a big-box officesupply
store.
I bored out a short length of thick-wall
aluminum tubing (i.e., rear peg material from
FAI Model Supply) with a 13/64 drill bit
(another Ace Hardware item) and epoxied the
tubing in the boom assembly to provide a
durable pivot. The female portion of the
screw post was trimmed to length so the
screw could be tightened all the way without
pinching in the fuselage sides and binding
movement of the boom for DT.
I hope you will give discus launch a try.
Your arm will thank you. To help, following
are some additional places to find more
information, kits, and materials.
• Free Flight Digest, June-July 2007: kit
review of Stan Buddenbohm’s Twirly Bird
discus-launch Glider, written by Larry Kruse
• Free Flight Digest, December 2006: kit
review of the Mark Benns-designed Spin-Up
36 kitted by Sting Aero Products, written by
Dohrman Crawford
• Aeromodeller, April 2007: kit review of
Spin-Up 36 written by Bob Bailey
(Aeromodeller is now published as the FF
section within Aviation Modeller
International magazine.)
• Free Flight Forum 2004: “Discus-Launched
Gliders” by Phil Ball and Andrew Hewitt is
an extensive discussion of design,
development, and construction of Phil and
Andy’s large (approximately 60-inch-span)
auto-surface discus-launch Gliders.
• Free Flight Forum 2005: “Further
Experiments with Discus Launched Gliders
and the Development of Big Bertha &
Slippery Sam” by Andrew Hewitt. In this
follow-on to the 2004 Forum piece, Andy
details the development of smaller (39-inchspan)
models with solid-balsa wings. They
still incorporate timer-actuated auto
surfaces.
• Free Flight Forum 2005: “Update on Last
Year’s Report on Free Flight Discus HLG—
The 60-inch All Singing and Dancing
Model” by Phil Ball. This features further
exploration of the large auto-surface Glider.
• Free Flight Forum 2006: “Gadget-Free
Discus-Launched Gliders” by Mark Benns.
The Spin-Up 36’s designer details his
design approach to discus launch without
the use of auto surfaces. If you don’t read
anything else, read this article. (Copies of
the Free Flight Forum are available from
Bob Stalick, NFFS Publications Service.
Check the National Free Flight Society
[NFFS] Web site for additional
information.)
• 36th Annual Report of the National Free
Flight Society: “2005 Models of the Year—
Discus Launched Gliders: ‘Stork’ &
‘Flingituicus’” by Andy Hewitt and Phil
Ball. This includes three-views and
information about the two large autosurface-
equipped models. (Check with
NFFS Publications at the previous address
for availability.)
• Discus Launched Gliders by Kurt
Krempetz. Contains information and threeviews
of Kurt’s Round-A-Bout design. It’s
available online at the AMA Glider Web
site, which also contains photos and videos
of a variety of discus-launch models, tips
for converting traditional javelin-launch
models to tip launch, and a variety of
plans and construction tips for all types of
HLGs and Catapult Gliders.
• Hand Launch Glider Airfoils by Curt
Stevens. Although written about
conventional HLGs, Curt details the
Glider airfoil he developed almost a half
century ago that is still the choice for
many discus-launch designs.
• Sting Aero Products sells Spin-Up 36
and Spin-Up 42 discus-launch kits and
short kits, tailbooms, Smoothie and
Cooltube viscous DTs, and other HLG and
Catapult Glider kits. Sting Aero founder,
noted Australian Glider flier Len Surtees,
recently sold the company to Tim
Goldstein. All sales are now through
Tim’s A2Z Corporation’s Peck-Polymers
division.
• Stan Buddenbohm’s discus-launch kits
include the Twirly Bird, Meerkat, Dynamo
Hum, and Dynamo Hum II. Five of the top
10 places in Open outdoor HLG at the
2007 Nats went to fliers using the Dynamo
Hum II. Stan also sells fuselage kits,
plans, and instructions for discus-launch
models. You can find more information on
the AMA Glider Web site.
• FAI Model Supply carries Sting Aero
Products kits and components, Ikara,
Button, and Badge viscous DT timers, and
many other FF kits, supplies, and
accessories.
• Stevens AeroModel sells pop-up
fuselage kits for discus-launch gliders,
available in two sizes and with or
without viscous timer. Kits feature lasercut
balsa-and-plywood front sections and
carbon-fiber tailbooms.
• Hang-em High Fabrics has tapered
02sig5.QXD 12/20/07 1:25 PM Page 154February 2008 155
carbon-fiber kite spars for use as
tailbooms. The G-Force Skinny (item
WIND-SK32) is 32.5 inches long and
weighs 7.5 grams.
Razor Planes: After 50 years my Little
Giant razor plane was starting to show
its age, and I used up my stash of
Gillette Super Blue blades long ago.
(The stainless-steel blades that replaced
the Super Blues in the 1970s were
worthless for planing balsa.) It was time
to find a replacement.
The German-made Balsa-Hobel plane
seemed like a reasonable replacement
and, allowing for inflation, the $14 price
tag was in line with what the Little Giant
cost a half century ago. The big surprise
was what razor blades cost now. The
Solingen steel blades are $1.35 each. I
figured 10 blades would get me through
the three discus-launch wings if I were
careful.
I placed an order with Tim Goldstein
(A2Z Corporation), and a few days later
the plane arrived. It even came with one
blade. This tool is a joy to use. It makes
nice, wide shavings and no chatter. Best
of all, I turned three 4 x 36 balsa sheets
into wings, and I’m still on the first
blade.
Finding Balsa: Longtime Free Flight
digest editor Walt Rozelle, who died last
October, once told me that he found the
best sheet of balsa he had ever seen in
the display rack at a craft store. The
sheet of 4-pound-per-cubic-foot C-grain
was mixed in with the usual rock-hard
sheets that could pass for basswood.
In a typical Walt gesture, he gave the
piece of balsa to an Indoor modeler who
could make better use of it.
Ever since I’ve been pawing through
the balsa bins at chain craft stores and
occasionally find a good sheet of light Cgrain.
But I hate to think how much time
and gas I’ve wasted.
Now Peck-Polymers offers an
alternative. Each sheet of its contest balsa
is individually weighed and sorted. Most
sizes are available in your choice of A/Bor
C-grain. Density ranges are 4-4.99, 5-
5.99, and 6-6.99 pounds per cubic foot.
“As you can imagine the supply is
limited, particularly in the real light 4-
pound stuff,” said Peck-Polymers owner
Tim Goldstein. “But many people are glad
to pay the price to get the density sheets
they really want instead of buying 20
sheets from others and hoping to get what
they need.”
For more information contact A2Z
Corp.
2007 Nats Video: Alan Abriss’s latest
Nats video is now available as a twohour
DVD. Coverage of the weeklong
Outdoor FF event includes Dawn
Unlimited, ROW (rise-off-water), and
the new electric categories.
The DVD is $20 plus $3 shipping
and is available from Homegrown
Television Productions. MA
Sources:
A2Z Corp
(720) 833-9300
www.peck-polymers.com/store
AMA Glider
www.amaglider.vze.com/
Aviation Modeller International
0044 (0)1494 433 453
www.modelactivitypress.com/amimonthly.
htm
Bob Stalick (NFFS Publications Service)
Box 1775
Albany OR 97321
FAI Model Supply
www.faimodelsupply.com
(570) 882-9873
Hand Launch Glider Airfoils
www.modelresearchlabs.com/hand_launch
_glider_airfoils.htm
Hang-em High Fabrics
http://ecom.citystar.com/hang-em-high/
(800) 233-6155
Homegrown Television Productions
www.homegrowntv.com/catalog.html
National Free Flight Society
www.freeflight.org
Stan Buddenbohm
5652 Meinhardt Rd.
Westminster CA 92683
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