124 MODEL AVIATION
designer and maker Andreas Mergner.
The Thorn kit consists of solid-wood
parts, machined and sanded: fuselage,
wing halves, canopy, fin, horizontal
stabilizer, ailerons, and elevator, plus a
bag of hardware and printed instructions.
My model took 7.5 hours to build, 4.25
hours to finish, and 3.5 hours to install
the radio gear. It weighs 59 ounces, for a wing loading of 25
ounces per square foot.
Its first flight exceeded an hour in duration, flown by Joe
Chovan and myself over Lake Ontario near Syracuse, New
York, from a 115-foot escarpment in 15-20 mph wind blowing
into the hill approximately 10˚ from perpendicular. Many thanks
to Joe for flying for the camera.
The Thorn was in its element and was impressive in the air.
It penetrates extremely well in slightly cross and gusty
conditions. It displays smooth movements with no sign of
twitchiness or overcontrol.
My version is moderately quick in axial rolls, with more than
one per second. It does not love inverted flight. It does love the
Cuban Eight maneuver. It handles stall turns well, but an
intentional forward stall was dramatic; it fell 20-30 feet before
[[email protected]]
Radio Control Slope Soaring Dave Garwood
A flight report of the Thorn from Plane Insane Models
Plane Insane Models’ 60-inch-span Thorn over Lake Ontario in
upstate New York. Its parts are made entirely from solid wood.
Dave’s 60-inch Thorn over Lake Ontario on its initial flight. A 100-
inch-span version of this model has already been flown.
Plane Insane Models owner Andreas Mergner with another of his
kits: the large scale EPP-foam Hawker Hurricane.
Andreas turns and burns over Cape Cod Bay in Massachusetts
with a Hurricane. It flies well and looks realistic in the air.
THERE IS A new concept in highperformance
sailplane design and kit
production, brought to you by a maker
you may not have heard of: Plane Insane
Models in Albany, New York.
The Thorn is a 60-inch-span fast Slope
Soarer, made entirely from solid wood by
modern computer-controlled machining
processes. The model has been in production since January
2006 and, as of this writing, has flown in California, Colorado,
Massachusetts, Michigan, New York, and Australia.
I built an early production kit of the Thorn and flew it. This
column contains a brief flight report and an interview with
Also included in this column:
• An interview with Thorn
designer Andreas Mergner
08sig4.QXD 6/23/06 10:31 AM Page 124recovering. It is good to fly this speedster like the heavy-wingloading
sailplane it is and avoid stalls.
This is not a trainer, but if you fancy the fast, heavy stuff, the
Thorn will bring a smile to your face. A full kit review will follow in
a future issue of MA.
The following interview was conducted with Andreas Mergner:
proprietor of Plane Insane Models. Andreas designs and kits Slope
Soaring models, including the solid-wood-construction Thorn.
Andreas and I have flown slope together in Kansas, New York, and
Massachusetts.
DG: Response from Thorn early adopters as reported on RC Groupshas been phenomenal. Anyway one looks
at it, you have a cutting-edge sailplane
here. This must make you feel great as a
designer. Please tell us about your design
philosophy.
AM: I try to take into account
performance, durability, ease of building,
and value in the design. I also try to keep
things as simple as I can.
My goal was to get within 90-95% of
the performance of composites, and from
the feedback I have received, it looks like I
met and exceeded my goal. I also really
enjoy experimenting with materials and
construction techniques. I like to think of
126 MODEL AVIATION
design does use relatively light wood, a
thin airfoil, and high-aspect-ratio wings to
reduce the overall weight.
DG: Stiffness is a major advantage of
wood—an essential characteristic of
high-performance model sailplanes. What
less desirable characteristics of wood
have you had to deal with, and how have
you overcome the problems?
AM: Actually, wood is not as stiff as
most composites out there, but there just
happens to be a lot of it in the airplane in
the right places. So the wings are stiff
under flight loads, but flexible during
higher crash impacts.
One disadvantage to wood is warping
due to water-content changes. For this
reason and a few others, I use poplar
wood, which is very stable and not as
prone to warping.
Sealing the wood with paint, stain, or
covering will also reduce the risk of
warping. All that being said, I haven’t had
a problem with warping in my prototype
over the last couple years. High weight is
the other major disadvantage.
DG: Model parts have been made by diecutting,
machining, molding, and handshaping.
Your manufacturing process is
revolutionary for a model kit maker.
“Computer controlled machining” is
mentioned on your Web site. Please tell
us generally how computer-controlled
part-shaping in general works, and how it
is used to make the parts for Thorn kits.
AM: Computer-control machining has
been used for a long time and is generally
referred to as CNC, or Computer
Numerical Control. Only recently has it
become cheaper and easier to buy a
machine or make one yourself, which is
what I did.
The process of making a part using
CNC is done in a few steps. First you
design a model of the part you want to
make using CAD [Computer Aided
Design] software. This model is then put
into other software called CAM [Computer
Aided Machining]. The CAM software is
used to produce a path that the router will
take to cut out the part on the machine.
Finally, the cutting path is put into the
controller (software or hardware) for the
machine and moves the router along the
path using motors. There are typically three
motors in the machine that control
movement of the router: one for the X [left
to right], Y [front to back], and Z [up and
down] axes.
My general production process is to
secure a piece of stock wood in the
machine and start the cutting path. The
router first takes off the bulk of the wood
with faster, coarser movements. I then
change bits and the router makes smaller,
finer movements to get a final shape on the
part. Usually I will need to do this for both
sides of the part.
new ways to make something work and
then test them.
DG: I’ve seen others of your designs in the
air—your smooth-finish EPP wing, your
EPP One Design Racer, and your scale
Hurricane—but none of these has caught
on with fliers like the Thorn. Please say a
little about the origin and development of
the design for the Thorn in particular.
AM: I used to live and fly slope in
Tucson, Arizona. One flier built a solidbalsa
wing for a fuselage of an old model
called the Tempest by Scott Metze.
It flew like the business and was fast,
retained energy well, and was efficient. It
had a single taper wing and was sanded
and carved by hand using templates on the
root and tip. This was probably nine years
ago. I always had it in the back of my
mind that I would build my own but didn’t
get around to it until recently.
I thought that a solid-hardwood sloper
would be a good middle ground between
EPP and composites in terms of
performance, durability, reparability, and
value. I ended up making a proof-ofconcept
model out of cheap lumber.
I shaped it using an electric hand planer
and a belt sander along with some
templates. It was ugly and very rough, but
it flew okay enough to pursue the next step
to a machined design.
The machined design took a lot of
effort to get something that would actually
work. I made about 20 versions before
coming up with one that I would actually
make and fly. My first prototype flew
great right from the start, which was quite
a relief. I continue to refine the design
even today.
DG: Could you discuss the considerations
behind selection of solid wood as a
sailplane construction material? At first it
seems like it might be too heavy, then one
realizes we do add quite a bit of weight to
our sailplanes when we want them to go
fast.
AM: I am not the first one to say that
weight is good on a slope airplane. I think
since traditionally most slopers start out
learning to fly thermal duration, they get
used to construction that is very weightconscious.
This is great on the light lift
and wind days, but as the lift and wind
increase, things change.
More speed actually makes it safer for
you to fly in greater wind up to a point.
Instead of having to fly straight ahead into
the wind the majority of the time, you can
move to any point in the sky with ease.
I think there is also a feeling that an
airplane that is twice as heavy will need
twice as much lift/wind, which is not the
case. It will require less than 40% more
lift/wind since it is related to the square
root of the weight.
The Thorn does not require as much lift
to fly as you’d think. Saying all of this, theAfter the machining, I sand the parts
by hand using a random orbital sander to
get a nice, smooth part.
DG: What’s next for Thorn development?
What other new ideas might we see
coming from Plane Insane Models?AM: I have more ideas for cool products
down the road. Pretty much all of them will
be made from solid wood.
I recently made a 100-inch Thorn
prototype, which flies great but will be going
through more testing before release. It flies in
lighter lift than the 60-inch version but should
be just as fast. It has very effective camber
and crow due to the four-servo wing.
I have a prototype European-style flying
wing [very fast] that I am hoping will work
out. It’s tentatively named the Decapitator. I
also have an idea for a wingeron/pitcherontype
airplane that may be a bit more durable
than usual.
I have a mailing list on my Web site that
people can join if they are interested in
finding out about new products as they
become available.
Thanks, Andreas, for bringing these
unusual and high-performance airplanes to
market.
I have flown the Thorn 60-inch-span and
100-inch-span versions, and both are highly
impressive in design, in quality of parts
supplied, and in flight performance.
You can contact Andreas Mergner at
Plane Insane Models, Basement Apt., 366
Hamilton St., Albany NY 12210; Tel.: (518)
542-9527; E-mail: Andreas@planeinsane
models.com; Web site: www.planeinsanemodels.com
Edition: Model Aviation - 2006/08
Page Numbers: 124,125,126,128
Edition: Model Aviation - 2006/08
Page Numbers: 124,125,126,128
124 MODEL AVIATION
designer and maker Andreas Mergner.
The Thorn kit consists of solid-wood
parts, machined and sanded: fuselage,
wing halves, canopy, fin, horizontal
stabilizer, ailerons, and elevator, plus a
bag of hardware and printed instructions.
My model took 7.5 hours to build, 4.25
hours to finish, and 3.5 hours to install
the radio gear. It weighs 59 ounces, for a wing loading of 25
ounces per square foot.
Its first flight exceeded an hour in duration, flown by Joe
Chovan and myself over Lake Ontario near Syracuse, New
York, from a 115-foot escarpment in 15-20 mph wind blowing
into the hill approximately 10˚ from perpendicular. Many thanks
to Joe for flying for the camera.
The Thorn was in its element and was impressive in the air.
It penetrates extremely well in slightly cross and gusty
conditions. It displays smooth movements with no sign of
twitchiness or overcontrol.
My version is moderately quick in axial rolls, with more than
one per second. It does not love inverted flight. It does love the
Cuban Eight maneuver. It handles stall turns well, but an
intentional forward stall was dramatic; it fell 20-30 feet before
[[email protected]]
Radio Control Slope Soaring Dave Garwood
A flight report of the Thorn from Plane Insane Models
Plane Insane Models’ 60-inch-span Thorn over Lake Ontario in
upstate New York. Its parts are made entirely from solid wood.
Dave’s 60-inch Thorn over Lake Ontario on its initial flight. A 100-
inch-span version of this model has already been flown.
Plane Insane Models owner Andreas Mergner with another of his
kits: the large scale EPP-foam Hawker Hurricane.
Andreas turns and burns over Cape Cod Bay in Massachusetts
with a Hurricane. It flies well and looks realistic in the air.
THERE IS A new concept in highperformance
sailplane design and kit
production, brought to you by a maker
you may not have heard of: Plane Insane
Models in Albany, New York.
The Thorn is a 60-inch-span fast Slope
Soarer, made entirely from solid wood by
modern computer-controlled machining
processes. The model has been in production since January
2006 and, as of this writing, has flown in California, Colorado,
Massachusetts, Michigan, New York, and Australia.
I built an early production kit of the Thorn and flew it. This
column contains a brief flight report and an interview with
Also included in this column:
• An interview with Thorn
designer Andreas Mergner
08sig4.QXD 6/23/06 10:31 AM Page 124recovering. It is good to fly this speedster like the heavy-wingloading
sailplane it is and avoid stalls.
This is not a trainer, but if you fancy the fast, heavy stuff, the
Thorn will bring a smile to your face. A full kit review will follow in
a future issue of MA.
The following interview was conducted with Andreas Mergner:
proprietor of Plane Insane Models. Andreas designs and kits Slope
Soaring models, including the solid-wood-construction Thorn.
Andreas and I have flown slope together in Kansas, New York, and
Massachusetts.
DG: Response from Thorn early adopters as reported on RC Groupshas been phenomenal. Anyway one looks
at it, you have a cutting-edge sailplane
here. This must make you feel great as a
designer. Please tell us about your design
philosophy.
AM: I try to take into account
performance, durability, ease of building,
and value in the design. I also try to keep
things as simple as I can.
My goal was to get within 90-95% of
the performance of composites, and from
the feedback I have received, it looks like I
met and exceeded my goal. I also really
enjoy experimenting with materials and
construction techniques. I like to think of
126 MODEL AVIATION
design does use relatively light wood, a
thin airfoil, and high-aspect-ratio wings to
reduce the overall weight.
DG: Stiffness is a major advantage of
wood—an essential characteristic of
high-performance model sailplanes. What
less desirable characteristics of wood
have you had to deal with, and how have
you overcome the problems?
AM: Actually, wood is not as stiff as
most composites out there, but there just
happens to be a lot of it in the airplane in
the right places. So the wings are stiff
under flight loads, but flexible during
higher crash impacts.
One disadvantage to wood is warping
due to water-content changes. For this
reason and a few others, I use poplar
wood, which is very stable and not as
prone to warping.
Sealing the wood with paint, stain, or
covering will also reduce the risk of
warping. All that being said, I haven’t had
a problem with warping in my prototype
over the last couple years. High weight is
the other major disadvantage.
DG: Model parts have been made by diecutting,
machining, molding, and handshaping.
Your manufacturing process is
revolutionary for a model kit maker.
“Computer controlled machining” is
mentioned on your Web site. Please tell
us generally how computer-controlled
part-shaping in general works, and how it
is used to make the parts for Thorn kits.
AM: Computer-control machining has
been used for a long time and is generally
referred to as CNC, or Computer
Numerical Control. Only recently has it
become cheaper and easier to buy a
machine or make one yourself, which is
what I did.
The process of making a part using
CNC is done in a few steps. First you
design a model of the part you want to
make using CAD [Computer Aided
Design] software. This model is then put
into other software called CAM [Computer
Aided Machining]. The CAM software is
used to produce a path that the router will
take to cut out the part on the machine.
Finally, the cutting path is put into the
controller (software or hardware) for the
machine and moves the router along the
path using motors. There are typically three
motors in the machine that control
movement of the router: one for the X [left
to right], Y [front to back], and Z [up and
down] axes.
My general production process is to
secure a piece of stock wood in the
machine and start the cutting path. The
router first takes off the bulk of the wood
with faster, coarser movements. I then
change bits and the router makes smaller,
finer movements to get a final shape on the
part. Usually I will need to do this for both
sides of the part.
new ways to make something work and
then test them.
DG: I’ve seen others of your designs in the
air—your smooth-finish EPP wing, your
EPP One Design Racer, and your scale
Hurricane—but none of these has caught
on with fliers like the Thorn. Please say a
little about the origin and development of
the design for the Thorn in particular.
AM: I used to live and fly slope in
Tucson, Arizona. One flier built a solidbalsa
wing for a fuselage of an old model
called the Tempest by Scott Metze.
It flew like the business and was fast,
retained energy well, and was efficient. It
had a single taper wing and was sanded
and carved by hand using templates on the
root and tip. This was probably nine years
ago. I always had it in the back of my
mind that I would build my own but didn’t
get around to it until recently.
I thought that a solid-hardwood sloper
would be a good middle ground between
EPP and composites in terms of
performance, durability, reparability, and
value. I ended up making a proof-ofconcept
model out of cheap lumber.
I shaped it using an electric hand planer
and a belt sander along with some
templates. It was ugly and very rough, but
it flew okay enough to pursue the next step
to a machined design.
The machined design took a lot of
effort to get something that would actually
work. I made about 20 versions before
coming up with one that I would actually
make and fly. My first prototype flew
great right from the start, which was quite
a relief. I continue to refine the design
even today.
DG: Could you discuss the considerations
behind selection of solid wood as a
sailplane construction material? At first it
seems like it might be too heavy, then one
realizes we do add quite a bit of weight to
our sailplanes when we want them to go
fast.
AM: I am not the first one to say that
weight is good on a slope airplane. I think
since traditionally most slopers start out
learning to fly thermal duration, they get
used to construction that is very weightconscious.
This is great on the light lift
and wind days, but as the lift and wind
increase, things change.
More speed actually makes it safer for
you to fly in greater wind up to a point.
Instead of having to fly straight ahead into
the wind the majority of the time, you can
move to any point in the sky with ease.
I think there is also a feeling that an
airplane that is twice as heavy will need
twice as much lift/wind, which is not the
case. It will require less than 40% more
lift/wind since it is related to the square
root of the weight.
The Thorn does not require as much lift
to fly as you’d think. Saying all of this, theAfter the machining, I sand the parts
by hand using a random orbital sander to
get a nice, smooth part.
DG: What’s next for Thorn development?
What other new ideas might we see
coming from Plane Insane Models?AM: I have more ideas for cool products
down the road. Pretty much all of them will
be made from solid wood.
I recently made a 100-inch Thorn
prototype, which flies great but will be going
through more testing before release. It flies in
lighter lift than the 60-inch version but should
be just as fast. It has very effective camber
and crow due to the four-servo wing.
I have a prototype European-style flying
wing [very fast] that I am hoping will work
out. It’s tentatively named the Decapitator. I
also have an idea for a wingeron/pitcherontype
airplane that may be a bit more durable
than usual.
I have a mailing list on my Web site that
people can join if they are interested in
finding out about new products as they
become available.
Thanks, Andreas, for bringing these
unusual and high-performance airplanes to
market.
I have flown the Thorn 60-inch-span and
100-inch-span versions, and both are highly
impressive in design, in quality of parts
supplied, and in flight performance.
You can contact Andreas Mergner at
Plane Insane Models, Basement Apt., 366
Hamilton St., Albany NY 12210; Tel.: (518)
542-9527; E-mail: Andreas@planeinsane
models.com; Web site: www.planeinsanemodels.com
Edition: Model Aviation - 2006/08
Page Numbers: 124,125,126,128
124 MODEL AVIATION
designer and maker Andreas Mergner.
The Thorn kit consists of solid-wood
parts, machined and sanded: fuselage,
wing halves, canopy, fin, horizontal
stabilizer, ailerons, and elevator, plus a
bag of hardware and printed instructions.
My model took 7.5 hours to build, 4.25
hours to finish, and 3.5 hours to install
the radio gear. It weighs 59 ounces, for a wing loading of 25
ounces per square foot.
Its first flight exceeded an hour in duration, flown by Joe
Chovan and myself over Lake Ontario near Syracuse, New
York, from a 115-foot escarpment in 15-20 mph wind blowing
into the hill approximately 10˚ from perpendicular. Many thanks
to Joe for flying for the camera.
The Thorn was in its element and was impressive in the air.
It penetrates extremely well in slightly cross and gusty
conditions. It displays smooth movements with no sign of
twitchiness or overcontrol.
My version is moderately quick in axial rolls, with more than
one per second. It does not love inverted flight. It does love the
Cuban Eight maneuver. It handles stall turns well, but an
intentional forward stall was dramatic; it fell 20-30 feet before
[[email protected]]
Radio Control Slope Soaring Dave Garwood
A flight report of the Thorn from Plane Insane Models
Plane Insane Models’ 60-inch-span Thorn over Lake Ontario in
upstate New York. Its parts are made entirely from solid wood.
Dave’s 60-inch Thorn over Lake Ontario on its initial flight. A 100-
inch-span version of this model has already been flown.
Plane Insane Models owner Andreas Mergner with another of his
kits: the large scale EPP-foam Hawker Hurricane.
Andreas turns and burns over Cape Cod Bay in Massachusetts
with a Hurricane. It flies well and looks realistic in the air.
THERE IS A new concept in highperformance
sailplane design and kit
production, brought to you by a maker
you may not have heard of: Plane Insane
Models in Albany, New York.
The Thorn is a 60-inch-span fast Slope
Soarer, made entirely from solid wood by
modern computer-controlled machining
processes. The model has been in production since January
2006 and, as of this writing, has flown in California, Colorado,
Massachusetts, Michigan, New York, and Australia.
I built an early production kit of the Thorn and flew it. This
column contains a brief flight report and an interview with
Also included in this column:
• An interview with Thorn
designer Andreas Mergner
08sig4.QXD 6/23/06 10:31 AM Page 124recovering. It is good to fly this speedster like the heavy-wingloading
sailplane it is and avoid stalls.
This is not a trainer, but if you fancy the fast, heavy stuff, the
Thorn will bring a smile to your face. A full kit review will follow in
a future issue of MA.
The following interview was conducted with Andreas Mergner:
proprietor of Plane Insane Models. Andreas designs and kits Slope
Soaring models, including the solid-wood-construction Thorn.
Andreas and I have flown slope together in Kansas, New York, and
Massachusetts.
DG: Response from Thorn early adopters as reported on RC Groupshas been phenomenal. Anyway one looks
at it, you have a cutting-edge sailplane
here. This must make you feel great as a
designer. Please tell us about your design
philosophy.
AM: I try to take into account
performance, durability, ease of building,
and value in the design. I also try to keep
things as simple as I can.
My goal was to get within 90-95% of
the performance of composites, and from
the feedback I have received, it looks like I
met and exceeded my goal. I also really
enjoy experimenting with materials and
construction techniques. I like to think of
126 MODEL AVIATION
design does use relatively light wood, a
thin airfoil, and high-aspect-ratio wings to
reduce the overall weight.
DG: Stiffness is a major advantage of
wood—an essential characteristic of
high-performance model sailplanes. What
less desirable characteristics of wood
have you had to deal with, and how have
you overcome the problems?
AM: Actually, wood is not as stiff as
most composites out there, but there just
happens to be a lot of it in the airplane in
the right places. So the wings are stiff
under flight loads, but flexible during
higher crash impacts.
One disadvantage to wood is warping
due to water-content changes. For this
reason and a few others, I use poplar
wood, which is very stable and not as
prone to warping.
Sealing the wood with paint, stain, or
covering will also reduce the risk of
warping. All that being said, I haven’t had
a problem with warping in my prototype
over the last couple years. High weight is
the other major disadvantage.
DG: Model parts have been made by diecutting,
machining, molding, and handshaping.
Your manufacturing process is
revolutionary for a model kit maker.
“Computer controlled machining” is
mentioned on your Web site. Please tell
us generally how computer-controlled
part-shaping in general works, and how it
is used to make the parts for Thorn kits.
AM: Computer-control machining has
been used for a long time and is generally
referred to as CNC, or Computer
Numerical Control. Only recently has it
become cheaper and easier to buy a
machine or make one yourself, which is
what I did.
The process of making a part using
CNC is done in a few steps. First you
design a model of the part you want to
make using CAD [Computer Aided
Design] software. This model is then put
into other software called CAM [Computer
Aided Machining]. The CAM software is
used to produce a path that the router will
take to cut out the part on the machine.
Finally, the cutting path is put into the
controller (software or hardware) for the
machine and moves the router along the
path using motors. There are typically three
motors in the machine that control
movement of the router: one for the X [left
to right], Y [front to back], and Z [up and
down] axes.
My general production process is to
secure a piece of stock wood in the
machine and start the cutting path. The
router first takes off the bulk of the wood
with faster, coarser movements. I then
change bits and the router makes smaller,
finer movements to get a final shape on the
part. Usually I will need to do this for both
sides of the part.
new ways to make something work and
then test them.
DG: I’ve seen others of your designs in the
air—your smooth-finish EPP wing, your
EPP One Design Racer, and your scale
Hurricane—but none of these has caught
on with fliers like the Thorn. Please say a
little about the origin and development of
the design for the Thorn in particular.
AM: I used to live and fly slope in
Tucson, Arizona. One flier built a solidbalsa
wing for a fuselage of an old model
called the Tempest by Scott Metze.
It flew like the business and was fast,
retained energy well, and was efficient. It
had a single taper wing and was sanded
and carved by hand using templates on the
root and tip. This was probably nine years
ago. I always had it in the back of my
mind that I would build my own but didn’t
get around to it until recently.
I thought that a solid-hardwood sloper
would be a good middle ground between
EPP and composites in terms of
performance, durability, reparability, and
value. I ended up making a proof-ofconcept
model out of cheap lumber.
I shaped it using an electric hand planer
and a belt sander along with some
templates. It was ugly and very rough, but
it flew okay enough to pursue the next step
to a machined design.
The machined design took a lot of
effort to get something that would actually
work. I made about 20 versions before
coming up with one that I would actually
make and fly. My first prototype flew
great right from the start, which was quite
a relief. I continue to refine the design
even today.
DG: Could you discuss the considerations
behind selection of solid wood as a
sailplane construction material? At first it
seems like it might be too heavy, then one
realizes we do add quite a bit of weight to
our sailplanes when we want them to go
fast.
AM: I am not the first one to say that
weight is good on a slope airplane. I think
since traditionally most slopers start out
learning to fly thermal duration, they get
used to construction that is very weightconscious.
This is great on the light lift
and wind days, but as the lift and wind
increase, things change.
More speed actually makes it safer for
you to fly in greater wind up to a point.
Instead of having to fly straight ahead into
the wind the majority of the time, you can
move to any point in the sky with ease.
I think there is also a feeling that an
airplane that is twice as heavy will need
twice as much lift/wind, which is not the
case. It will require less than 40% more
lift/wind since it is related to the square
root of the weight.
The Thorn does not require as much lift
to fly as you’d think. Saying all of this, theAfter the machining, I sand the parts
by hand using a random orbital sander to
get a nice, smooth part.
DG: What’s next for Thorn development?
What other new ideas might we see
coming from Plane Insane Models?AM: I have more ideas for cool products
down the road. Pretty much all of them will
be made from solid wood.
I recently made a 100-inch Thorn
prototype, which flies great but will be going
through more testing before release. It flies in
lighter lift than the 60-inch version but should
be just as fast. It has very effective camber
and crow due to the four-servo wing.
I have a prototype European-style flying
wing [very fast] that I am hoping will work
out. It’s tentatively named the Decapitator. I
also have an idea for a wingeron/pitcherontype
airplane that may be a bit more durable
than usual.
I have a mailing list on my Web site that
people can join if they are interested in
finding out about new products as they
become available.
Thanks, Andreas, for bringing these
unusual and high-performance airplanes to
market.
I have flown the Thorn 60-inch-span and
100-inch-span versions, and both are highly
impressive in design, in quality of parts
supplied, and in flight performance.
You can contact Andreas Mergner at
Plane Insane Models, Basement Apt., 366
Hamilton St., Albany NY 12210; Tel.: (518)
542-9527; E-mail: Andreas@planeinsane
models.com; Web site: www.planeinsanemodels.com
Edition: Model Aviation - 2006/08
Page Numbers: 124,125,126,128
124 MODEL AVIATION
designer and maker Andreas Mergner.
The Thorn kit consists of solid-wood
parts, machined and sanded: fuselage,
wing halves, canopy, fin, horizontal
stabilizer, ailerons, and elevator, plus a
bag of hardware and printed instructions.
My model took 7.5 hours to build, 4.25
hours to finish, and 3.5 hours to install
the radio gear. It weighs 59 ounces, for a wing loading of 25
ounces per square foot.
Its first flight exceeded an hour in duration, flown by Joe
Chovan and myself over Lake Ontario near Syracuse, New
York, from a 115-foot escarpment in 15-20 mph wind blowing
into the hill approximately 10˚ from perpendicular. Many thanks
to Joe for flying for the camera.
The Thorn was in its element and was impressive in the air.
It penetrates extremely well in slightly cross and gusty
conditions. It displays smooth movements with no sign of
twitchiness or overcontrol.
My version is moderately quick in axial rolls, with more than
one per second. It does not love inverted flight. It does love the
Cuban Eight maneuver. It handles stall turns well, but an
intentional forward stall was dramatic; it fell 20-30 feet before
[[email protected]]
Radio Control Slope Soaring Dave Garwood
A flight report of the Thorn from Plane Insane Models
Plane Insane Models’ 60-inch-span Thorn over Lake Ontario in
upstate New York. Its parts are made entirely from solid wood.
Dave’s 60-inch Thorn over Lake Ontario on its initial flight. A 100-
inch-span version of this model has already been flown.
Plane Insane Models owner Andreas Mergner with another of his
kits: the large scale EPP-foam Hawker Hurricane.
Andreas turns and burns over Cape Cod Bay in Massachusetts
with a Hurricane. It flies well and looks realistic in the air.
THERE IS A new concept in highperformance
sailplane design and kit
production, brought to you by a maker
you may not have heard of: Plane Insane
Models in Albany, New York.
The Thorn is a 60-inch-span fast Slope
Soarer, made entirely from solid wood by
modern computer-controlled machining
processes. The model has been in production since January
2006 and, as of this writing, has flown in California, Colorado,
Massachusetts, Michigan, New York, and Australia.
I built an early production kit of the Thorn and flew it. This
column contains a brief flight report and an interview with
Also included in this column:
• An interview with Thorn
designer Andreas Mergner
08sig4.QXD 6/23/06 10:31 AM Page 124recovering. It is good to fly this speedster like the heavy-wingloading
sailplane it is and avoid stalls.
This is not a trainer, but if you fancy the fast, heavy stuff, the
Thorn will bring a smile to your face. A full kit review will follow in
a future issue of MA.
The following interview was conducted with Andreas Mergner:
proprietor of Plane Insane Models. Andreas designs and kits Slope
Soaring models, including the solid-wood-construction Thorn.
Andreas and I have flown slope together in Kansas, New York, and
Massachusetts.
DG: Response from Thorn early adopters as reported on RC Groupshas been phenomenal. Anyway one looks
at it, you have a cutting-edge sailplane
here. This must make you feel great as a
designer. Please tell us about your design
philosophy.
AM: I try to take into account
performance, durability, ease of building,
and value in the design. I also try to keep
things as simple as I can.
My goal was to get within 90-95% of
the performance of composites, and from
the feedback I have received, it looks like I
met and exceeded my goal. I also really
enjoy experimenting with materials and
construction techniques. I like to think of
126 MODEL AVIATION
design does use relatively light wood, a
thin airfoil, and high-aspect-ratio wings to
reduce the overall weight.
DG: Stiffness is a major advantage of
wood—an essential characteristic of
high-performance model sailplanes. What
less desirable characteristics of wood
have you had to deal with, and how have
you overcome the problems?
AM: Actually, wood is not as stiff as
most composites out there, but there just
happens to be a lot of it in the airplane in
the right places. So the wings are stiff
under flight loads, but flexible during
higher crash impacts.
One disadvantage to wood is warping
due to water-content changes. For this
reason and a few others, I use poplar
wood, which is very stable and not as
prone to warping.
Sealing the wood with paint, stain, or
covering will also reduce the risk of
warping. All that being said, I haven’t had
a problem with warping in my prototype
over the last couple years. High weight is
the other major disadvantage.
DG: Model parts have been made by diecutting,
machining, molding, and handshaping.
Your manufacturing process is
revolutionary for a model kit maker.
“Computer controlled machining” is
mentioned on your Web site. Please tell
us generally how computer-controlled
part-shaping in general works, and how it
is used to make the parts for Thorn kits.
AM: Computer-control machining has
been used for a long time and is generally
referred to as CNC, or Computer
Numerical Control. Only recently has it
become cheaper and easier to buy a
machine or make one yourself, which is
what I did.
The process of making a part using
CNC is done in a few steps. First you
design a model of the part you want to
make using CAD [Computer Aided
Design] software. This model is then put
into other software called CAM [Computer
Aided Machining]. The CAM software is
used to produce a path that the router will
take to cut out the part on the machine.
Finally, the cutting path is put into the
controller (software or hardware) for the
machine and moves the router along the
path using motors. There are typically three
motors in the machine that control
movement of the router: one for the X [left
to right], Y [front to back], and Z [up and
down] axes.
My general production process is to
secure a piece of stock wood in the
machine and start the cutting path. The
router first takes off the bulk of the wood
with faster, coarser movements. I then
change bits and the router makes smaller,
finer movements to get a final shape on the
part. Usually I will need to do this for both
sides of the part.
new ways to make something work and
then test them.
DG: I’ve seen others of your designs in the
air—your smooth-finish EPP wing, your
EPP One Design Racer, and your scale
Hurricane—but none of these has caught
on with fliers like the Thorn. Please say a
little about the origin and development of
the design for the Thorn in particular.
AM: I used to live and fly slope in
Tucson, Arizona. One flier built a solidbalsa
wing for a fuselage of an old model
called the Tempest by Scott Metze.
It flew like the business and was fast,
retained energy well, and was efficient. It
had a single taper wing and was sanded
and carved by hand using templates on the
root and tip. This was probably nine years
ago. I always had it in the back of my
mind that I would build my own but didn’t
get around to it until recently.
I thought that a solid-hardwood sloper
would be a good middle ground between
EPP and composites in terms of
performance, durability, reparability, and
value. I ended up making a proof-ofconcept
model out of cheap lumber.
I shaped it using an electric hand planer
and a belt sander along with some
templates. It was ugly and very rough, but
it flew okay enough to pursue the next step
to a machined design.
The machined design took a lot of
effort to get something that would actually
work. I made about 20 versions before
coming up with one that I would actually
make and fly. My first prototype flew
great right from the start, which was quite
a relief. I continue to refine the design
even today.
DG: Could you discuss the considerations
behind selection of solid wood as a
sailplane construction material? At first it
seems like it might be too heavy, then one
realizes we do add quite a bit of weight to
our sailplanes when we want them to go
fast.
AM: I am not the first one to say that
weight is good on a slope airplane. I think
since traditionally most slopers start out
learning to fly thermal duration, they get
used to construction that is very weightconscious.
This is great on the light lift
and wind days, but as the lift and wind
increase, things change.
More speed actually makes it safer for
you to fly in greater wind up to a point.
Instead of having to fly straight ahead into
the wind the majority of the time, you can
move to any point in the sky with ease.
I think there is also a feeling that an
airplane that is twice as heavy will need
twice as much lift/wind, which is not the
case. It will require less than 40% more
lift/wind since it is related to the square
root of the weight.
The Thorn does not require as much lift
to fly as you’d think. Saying all of this, theAfter the machining, I sand the parts
by hand using a random orbital sander to
get a nice, smooth part.
DG: What’s next for Thorn development?
What other new ideas might we see
coming from Plane Insane Models?AM: I have more ideas for cool products
down the road. Pretty much all of them will
be made from solid wood.
I recently made a 100-inch Thorn
prototype, which flies great but will be going
through more testing before release. It flies in
lighter lift than the 60-inch version but should
be just as fast. It has very effective camber
and crow due to the four-servo wing.
I have a prototype European-style flying
wing [very fast] that I am hoping will work
out. It’s tentatively named the Decapitator. I
also have an idea for a wingeron/pitcherontype
airplane that may be a bit more durable
than usual.
I have a mailing list on my Web site that
people can join if they are interested in
finding out about new products as they
become available.
Thanks, Andreas, for bringing these
unusual and high-performance airplanes to
market.
I have flown the Thorn 60-inch-span and
100-inch-span versions, and both are highly
impressive in design, in quality of parts
supplied, and in flight performance.
You can contact Andreas Mergner at
Plane Insane Models, Basement Apt., 366
Hamilton St., Albany NY 12210; Tel.: (518)
542-9527; E-mail: Andreas@planeinsane
models.com; Web site: www.planeinsanemodels.com