THIS SAILPLANE IS nothing
less than revolutionary. The Plane Insane
Models Thorn smashes through to claim new
ground in model-sailplane design, in materials
used, and in parts-production methods.
Machined from planks of wood by a
specially designed computer-controlled
cutting machine, the solid-wood wing and
solid-wood fuselage parts are far different
from those in 99% of the gliders we’ve built.
In addition to these design and production
advances, the model flies great.
One of the Thorn’s big benefits is the kit’s
low parts count, so construction proceeds
rapidly. Another advantage is that the
completed airframe is strong and heavy.
Strong is good because we like rugged
models; heavy is good because it is the key to
going fast.
This aircraft is designed to compete with
ballasted-up composite sailplanes at roughly
half the cost. The Thorn is heavy when it’s
built, so there is no need to have to purchase
or mount lead, steel, tungsten, or other ballast.
In addition to the design innovation and
kit coolness, this sailplane flies superbly. It is
not a trainer by any means; it is a slope
screamer. Many of us were taught to build
light for best glider performance, but once
you experience the adrenalin rush of flying
high-performance sailplanes, all you want to
do is fly heavier and faster gliders. The Thorn
delivers the thrills.
Kit Contents: As I mentioned, this model’s
Plane Talk: Plane Insane Models Thorn
DAVE GARWOOD
+
• High performance. If you have the lift,
the Thorn will deliver the speed.
• Quick to build because of good design
and advanced parts-production methods.
• A strong and rugged airframe; the
Thorn is able to land successfully in less
than perfect areas.
• Customization is available when
ordering the kit, such as custom-cut
servo bays in the wing and the ability to
specify light, medium, or heavy wood. -• Narrow fuselage (a good thing for
aerodynamics) allows little space for
the receiver and elevator servo.
Microsize components are required.
• A number of people don’t like sanding;
some is required with this all-wood
model.
• Although the sacrificial nylon wingmount
bolts break as intended on a
rough landing, they may break too
easily. Larger bolts should be
considered. (The kit has been upgraded
to include 1/4-inch bolts. Threaded inserts
and replacement bolts are free to early kit
buyers who request them.)
Pluses and Minuses
Dave holds his Thorn against the wind
before the initial flight. Lake Ontario is in
the background. Joe Chovan photo.
A model that expands the envelope of high-perfo rmance slope design
September 2006 91
parts are solid wood. The kit includes
machined wing halves, ailerons, fuselage,
elevator, and hatch. The vertical and
horizontal stabilizers and elevator are precut
from basswood sheet stock. The pushrods are
09sig3.QXD 7/25/06 10:46 AM Page 9192 MODEL AVIATION
Radio system: Airtronics VG6000
transmitter, JR 610M receiver, Hitec HS-
125 thin metal gear aileron wing servos,
JR NES-341 elevator servo, Airtronics
97020 Y cable, Electrodynamics 600
mAh 4.8-volt battery
Flight duration: As long as the wind
blows and until the onboard battery
capacity is exhausted. Two hours is a
practical limit.
Test-Model Details
Type: High-performance Slope Soaring
glider
Pilot skill level: Experienced Slope
Soaring pilots
Wingspan: 60 inches
Wing area: 336 square inches
Length: 37.5 inches
Ready-to-fly weight: 58.7 ounces
Wing loading: 25.2 ounces per square
foot
Airfoil: RG-15 (modified and thinned to
7% thickness)
Recommended radio: Two channels
minimum with exponential
Construction: Solid-wood parts—
different from most other kits but goes
together quickly
Covering/finish: Paint on review
model, but could be stain or iron-on
covering, depending on builder
preference
Price: $160 (shipping included)
Specifications
Right: The completed Thorn airframe
before sealing, painting, and applying Goop
hinges to mount the control surfaces.
Below: The Thorn, complete and ready to
fly. Real slope sailplanes are painted—not
covered. Krylon spray paint was used over
Minwax sealer.
The model’s parts are made entirely from solid wood via computer-controlled machining.
Vertical and horizontal stabilizers and elevator are precut from basswood sheet.
Pushrods are installed in the fuselage at the factory.
Dave’s removable tail parts are mounted with bolts coming up through the plywood
plate. This modification was made with encouragement from the Thorn’s manufacturer.
Photos by the author except as noted
09sig3.QXD 7/25/06 10:55 AM Page 92September 2006 93
Notice how accurately the pocket is cut for a Hitec HS-125 aileron
servo. Any of several servo pockets can be specified when a kit is
ordered.
The TE pieces are glued in place and clamped until cured. Notice
how the wing-joiner system works. Wing halves have been joined
and the center sanded.
The Thorn fuselage front end showing trial-fitting of JR NES-341 elevator servo, JR 610M
receiver, and Electrodynamics 4KR-600AE battery pack.
Dave applies Goop hinges for ailerons, as detailed in the
instructions. He found that Goop hinges for elevator and ailerons
worked well on this model.
The Thorn fuselage front end showing all gear and wiring installed.
It’s tight, but all specified gear does fit. Nose weight (pieces cut
from roofing lead sheeting) fits under battery pack.
Dave’s Thorn rips up the air over Lake Ontario, near Syracuse
New York, on its initial test flight. This is a fast Slope Soarer.
installed in the fuselage at the factory.
Also included is a bag of small wood
parts, all the necessary hardware, and an
instruction manual. The kit is complete,
containing everything except adhesives, radio
components, and finishing materials.
The 13-page instruction manual is
thorough and features six drawings and 10
photographs to amplify the text. It is detailed
and complete, and experienced modelers will
have no trouble building the kit using it. The
manual is downloadable from the Plane
Insane Models Web site.
Owing partially to the fact that software
runs the computer-controlled machine
processes and mostly because of Plane Insane
Models’ Andreas Mergner’s meticulous
09sig3.QXD 7/25/06 10:47 AM Page 93production planning, you can order wing
servo cutouts to accurately fit your choice of
servos, and you can specify light or heavy
wood parts to match the model you build to
your anticipated lift conditions.
Construction: My four building sessions,
each ranging from a half hour to two hours,
went as follows.
1) Sand the fuselage and wing halves, join
the wing halves, and set them aside for the
epoxy to cure. Glue the hatch hold-down
magnets into the hatch and the fuselage, and
attach the hatch rear wire with epoxy and
fiberglass cloth. I decided that removable tail
parts would make storage and transportation
easier, so I fitted a plywood plate to have a
place to mount the horizontal and vertical
stabilizers with bolts.
2) Sand the now-cured center-section of
the wing. Glue the wing TE pieces with
polyurethane glue.
3) Trim and sand the ailerons and the
elevator. Final-sand the tail parts.
4) I built a modified vertical-stabilizer
mounting mechanism to make transportation
and storage easier. I installed blind nuts (also
called T-nuts) on the top side of a plywood
plate at the bottom of the fin that receive a
pair of bolts inserted from the bottom. Skip
this step if you don’t need compact storage,
and glue the tail parts on as instructed.
You can stain, paint, or cover your Thorn
with heat-shrink film covering, but to my
mind real Slope Soarers are painted—not
covered. This is a real slope sailplane if ever
there was one.
To finish all airframe surfaces, I did my
final sanding and applied Minwax Water-
Based Polycrylic Protective Finish—a
material I have used for years and like
because it has nearly no odor. After one coat I
sanded again with 240-grit paper, applied
another coat of Minwax Polycrylic, and
sanded again in preparation for primer paint,
which I wet-sanded with 400-grit paper in
preparation for the color coats.
I used Krylon spray-can paints for the
color. They included the primer (number
1381), Gloss White (number 1501) for the
fuselage and upper sides, Regal Blue (number
1901) for the underside of the wing and
stabilizer, and Banner Red (number 2108) for
the wingtips. The “THORN” lettering is cut
vinyl from the local truck-lettering shop.
After painting I applied Goop hinges for
ailerons and elevator, as described in the kit
instructions. They outline a top-notch method
for installing the Goop hinges, which are
similar to, but tougher than, silicone hinges.
I have to admit that I never got the hang of
silicone hinges, but I know how to install
them now. My main problem in the past was
applying too much adhesive, rendering the
finished hinges too stiff.
That’s all behind me now, thanks to the
instructions in the manual. I like the look of
these hinges applied after painting the parts;
the paint can look uneven and flake off of the
Goop hinges.
Radio Installation and Balance: I used an
Airtronics VG6000 transmitter for this
project. Although a two-channel rig will
suffice for the 60-inch-span Thorn, I have
grown accustomed to having rates and
exponential on slope sailplanes.
The designer recommends exponential,
and the VG6000 delivers all this in a
computer transmitter without menus. All
functions show on the LCD screen all the
time.
I installed a diminutive JR 610M receiver:
the smallest I had in stock. I’m thrilled with
the installation of the thin Hitec HS-125
servos for ailerons, and I used a JR NES-341
servo for elevator; I’ve grown accustomed to
their toughness.
The precut pockets (into wings ordered
from the factory to fit your choice of servo)
for the Hitec 125 aileron servos fit snugly and
make installing these servos go quickly using
nothing but the screws provided by the servo
maker. There’s plenty of room in the fuselage
for my JR-341 elevator servo; the same goes
for the microreceiver and Electrodynamics
battery pack.
I added 3 ounces of nose weight in the
battery compartment to balance my Thorn at
the extreme rear of the recommended balancepoint
range. I set the control-surface throws as
instructed in the manual, including specs for
high and low rates and approximately 85%
exponential on ailerons and elevator.
My ready-to-fly model weighs 59 ounces,
for a wing loading of 25 ounces per square foot.My Thorn took 7.5 hours to build
(including a couple hours engineering and
building the removable tail parts), 4.25
hours to finish with paint, and 3.5 hours to
install and test the radio gear, for a total of
15.25 hours of workbench time, spread
over two weeks.
Flying: For test-flying we had an earlyspring
day with some fine slope-flying
conditions over Lake Ontario near
Syracuse, New York. We fly from a 115-
foot escarpment, and that day we had a 15-
20 mph wind blowing into the hill from
approximately 10° left of perpendicular.
After a final radio check we heaved the
Thorn off of the ridge toward the lake.
After letting it dive for a few long seconds
to gather speed, I leveled it out and began
the classic figure-eight slope pattern.
The first turn went smoothly, and, still
accelerating, it came on step by the time it
crossed in front of me. The Thorn climbed
quickly and easily, and controls were
smooth, with no sign of twitchiness.
Phrases from years ago when flighttesting
my first sleek, fast sailplane (a Sig
Samurai) came to mind: “Cuts through the
air like a knife” and “It doesn’t care which
way the wind is blowing.” The wind
direction did not switch around to straightin
as forecast, so we had windy, slightly
cross conditions for the entire flying day.
The heavy Thorn reveled in these
conditions. It seems like all other pilots put
down foam sailplanes after a minute or
two of flying; they would not penetrate.
The Thorn was in its element; Joe Chovan
and I logged a one-hour flight, passing the
transmitter twice. Control throws were set
up according to the instructions, and we
did not take it off high rates.
Our conclusions about the Thorn’s
flight performance are as follows.
• It penetrates extremely well in vigorous
wind, including crosswinds and gusty
conditions.
• It exhibits smooth control movements,
with no evidence of twitchiness or
overcontrol.
• It performs moderately fast axial rolls—
more than one per second.
• It hangs in with inverted flight adequately,
but it does not love that flight condition.
• It does love the Cuban Eight maneuver.
Hammerhead stall turns and half-pipe
maneuvers are competent for an aircraft
without a working rudder. Inside loops are
solid, with no aileron correction needed. (I
have not tried outside loops yet.)
The result on an intentional forward stall
was fairly dramatic; the Thorn fell 20-30 feet
before recovering. This is not a surprise for a
sailplane with a wing loading exceeding 20
ounces per square foot. This stood as a
reminder to fly this, and all heavy sailplanes,
smoothly and without stalling them.
Throughout the flying session we did not
worry about lift coming and going. Keep this
model moving, and it flies fine in momentary
varying lift conditions.
I landed it back on top, shiny-side up in
grass. The landing broke one nylon wingmount
bolt, and the sailplane incurred no
other damage. I’m fully pleased with the
Thorn’s flight performance.
Many thanks to Joe Chovan for flying for
the camera. He’s great at it.
Given the uncommon construction materials,
the unusual solid-wood wing design, and the
advanced computer-controlled machining
used in the production of the parts, just
owning a Thorn kit puts you in the forefront
of Slope Soaring glider technology.
Spend the rather pleasant (if you like
working with wood) 5.5 hours building and
the satisfying (if you like finishing a model
with paint) 4.25 hours final-sanding, sealing,
and painting the model, and you’ll have a
slope speedster that impresses you and your
friends. The kit is sold at a righteous price. If
you like fast and unusual sailplanes, it’s hard
to see how you can go wrong with a Thorn.
There is even better news in the future: I
have already flown a prototype of the 100-
inch-span, six-servo version, and that was a
real fun time; the 2.5-meter version covers a
great deal of sky in a short time.
Furthermore, customer requests for
four-servo wings to incorporate flaps in
addition to ailerons have been fulfilled,
and 60- and 80-inch-span wings have been
shipped. Plane Insane Models is one maker
to watch.
The Thorn is impressive in the air. It
penetrates the wind well. It carves a smooth
course with no sign of twitchiness or
overcontrol. My Thorn is quick in axial rolls
and solid when flown through loops.
Although it’s not optimized for inverted
flight, it performs excellent Cuban Eights. A
stall becomes a serious departure from
controlled flight, and the aircraft must fall 20
feet or more before regaining flying speed and
recovering.
This is not a trainer; it is a heavy-wingloaded,
high-performance sailplane. For those
who delight in flying a fast, heavy glider, the
Thorn is an exceptional candidate to meet
your need for speed. MA
Manufacturer:
Plane Insane Models, Andreas Mergner
366 Hamilton St.
Albany NY 12210
(518) 542-9527
[email protected]
www.planeinsanemodels.com
Products Used in Review:
Airtronics VG6000 transmitter
www.airtronics.net
JR 610M receiver
www.horizonhobby.com
Hitec HS-125 aileron servos
www.hitecrcd.com
JR NES-341 elevator servo
www.horizonhobby.com
Electrodynamics battery pack
www.electrodynam.com
Minwax Polycrylic sanding sealer
www.minwax.com
Krylon rattle-can spray paint
www.krylon.com
Edition: Model Aviation - 2006/09
Page Numbers: 91,92,93,94,96
Edition: Model Aviation - 2006/09
Page Numbers: 91,92,93,94,96
THIS SAILPLANE IS nothing
less than revolutionary. The Plane Insane
Models Thorn smashes through to claim new
ground in model-sailplane design, in materials
used, and in parts-production methods.
Machined from planks of wood by a
specially designed computer-controlled
cutting machine, the solid-wood wing and
solid-wood fuselage parts are far different
from those in 99% of the gliders we’ve built.
In addition to these design and production
advances, the model flies great.
One of the Thorn’s big benefits is the kit’s
low parts count, so construction proceeds
rapidly. Another advantage is that the
completed airframe is strong and heavy.
Strong is good because we like rugged
models; heavy is good because it is the key to
going fast.
This aircraft is designed to compete with
ballasted-up composite sailplanes at roughly
half the cost. The Thorn is heavy when it’s
built, so there is no need to have to purchase
or mount lead, steel, tungsten, or other ballast.
In addition to the design innovation and
kit coolness, this sailplane flies superbly. It is
not a trainer by any means; it is a slope
screamer. Many of us were taught to build
light for best glider performance, but once
you experience the adrenalin rush of flying
high-performance sailplanes, all you want to
do is fly heavier and faster gliders. The Thorn
delivers the thrills.
Kit Contents: As I mentioned, this model’s
Plane Talk: Plane Insane Models Thorn
DAVE GARWOOD
+
• High performance. If you have the lift,
the Thorn will deliver the speed.
• Quick to build because of good design
and advanced parts-production methods.
• A strong and rugged airframe; the
Thorn is able to land successfully in less
than perfect areas.
• Customization is available when
ordering the kit, such as custom-cut
servo bays in the wing and the ability to
specify light, medium, or heavy wood. -• Narrow fuselage (a good thing for
aerodynamics) allows little space for
the receiver and elevator servo.
Microsize components are required.
• A number of people don’t like sanding;
some is required with this all-wood
model.
• Although the sacrificial nylon wingmount
bolts break as intended on a
rough landing, they may break too
easily. Larger bolts should be
considered. (The kit has been upgraded
to include 1/4-inch bolts. Threaded inserts
and replacement bolts are free to early kit
buyers who request them.)
Pluses and Minuses
Dave holds his Thorn against the wind
before the initial flight. Lake Ontario is in
the background. Joe Chovan photo.
A model that expands the envelope of high-perfo rmance slope design
September 2006 91
parts are solid wood. The kit includes
machined wing halves, ailerons, fuselage,
elevator, and hatch. The vertical and
horizontal stabilizers and elevator are precut
from basswood sheet stock. The pushrods are
09sig3.QXD 7/25/06 10:46 AM Page 9192 MODEL AVIATION
Radio system: Airtronics VG6000
transmitter, JR 610M receiver, Hitec HS-
125 thin metal gear aileron wing servos,
JR NES-341 elevator servo, Airtronics
97020 Y cable, Electrodynamics 600
mAh 4.8-volt battery
Flight duration: As long as the wind
blows and until the onboard battery
capacity is exhausted. Two hours is a
practical limit.
Test-Model Details
Type: High-performance Slope Soaring
glider
Pilot skill level: Experienced Slope
Soaring pilots
Wingspan: 60 inches
Wing area: 336 square inches
Length: 37.5 inches
Ready-to-fly weight: 58.7 ounces
Wing loading: 25.2 ounces per square
foot
Airfoil: RG-15 (modified and thinned to
7% thickness)
Recommended radio: Two channels
minimum with exponential
Construction: Solid-wood parts—
different from most other kits but goes
together quickly
Covering/finish: Paint on review
model, but could be stain or iron-on
covering, depending on builder
preference
Price: $160 (shipping included)
Specifications
Right: The completed Thorn airframe
before sealing, painting, and applying Goop
hinges to mount the control surfaces.
Below: The Thorn, complete and ready to
fly. Real slope sailplanes are painted—not
covered. Krylon spray paint was used over
Minwax sealer.
The model’s parts are made entirely from solid wood via computer-controlled machining.
Vertical and horizontal stabilizers and elevator are precut from basswood sheet.
Pushrods are installed in the fuselage at the factory.
Dave’s removable tail parts are mounted with bolts coming up through the plywood
plate. This modification was made with encouragement from the Thorn’s manufacturer.
Photos by the author except as noted
09sig3.QXD 7/25/06 10:55 AM Page 92September 2006 93
Notice how accurately the pocket is cut for a Hitec HS-125 aileron
servo. Any of several servo pockets can be specified when a kit is
ordered.
The TE pieces are glued in place and clamped until cured. Notice
how the wing-joiner system works. Wing halves have been joined
and the center sanded.
The Thorn fuselage front end showing trial-fitting of JR NES-341 elevator servo, JR 610M
receiver, and Electrodynamics 4KR-600AE battery pack.
Dave applies Goop hinges for ailerons, as detailed in the
instructions. He found that Goop hinges for elevator and ailerons
worked well on this model.
The Thorn fuselage front end showing all gear and wiring installed.
It’s tight, but all specified gear does fit. Nose weight (pieces cut
from roofing lead sheeting) fits under battery pack.
Dave’s Thorn rips up the air over Lake Ontario, near Syracuse
New York, on its initial test flight. This is a fast Slope Soarer.
installed in the fuselage at the factory.
Also included is a bag of small wood
parts, all the necessary hardware, and an
instruction manual. The kit is complete,
containing everything except adhesives, radio
components, and finishing materials.
The 13-page instruction manual is
thorough and features six drawings and 10
photographs to amplify the text. It is detailed
and complete, and experienced modelers will
have no trouble building the kit using it. The
manual is downloadable from the Plane
Insane Models Web site.
Owing partially to the fact that software
runs the computer-controlled machine
processes and mostly because of Plane Insane
Models’ Andreas Mergner’s meticulous
09sig3.QXD 7/25/06 10:47 AM Page 93production planning, you can order wing
servo cutouts to accurately fit your choice of
servos, and you can specify light or heavy
wood parts to match the model you build to
your anticipated lift conditions.
Construction: My four building sessions,
each ranging from a half hour to two hours,
went as follows.
1) Sand the fuselage and wing halves, join
the wing halves, and set them aside for the
epoxy to cure. Glue the hatch hold-down
magnets into the hatch and the fuselage, and
attach the hatch rear wire with epoxy and
fiberglass cloth. I decided that removable tail
parts would make storage and transportation
easier, so I fitted a plywood plate to have a
place to mount the horizontal and vertical
stabilizers with bolts.
2) Sand the now-cured center-section of
the wing. Glue the wing TE pieces with
polyurethane glue.
3) Trim and sand the ailerons and the
elevator. Final-sand the tail parts.
4) I built a modified vertical-stabilizer
mounting mechanism to make transportation
and storage easier. I installed blind nuts (also
called T-nuts) on the top side of a plywood
plate at the bottom of the fin that receive a
pair of bolts inserted from the bottom. Skip
this step if you don’t need compact storage,
and glue the tail parts on as instructed.
You can stain, paint, or cover your Thorn
with heat-shrink film covering, but to my
mind real Slope Soarers are painted—not
covered. This is a real slope sailplane if ever
there was one.
To finish all airframe surfaces, I did my
final sanding and applied Minwax Water-
Based Polycrylic Protective Finish—a
material I have used for years and like
because it has nearly no odor. After one coat I
sanded again with 240-grit paper, applied
another coat of Minwax Polycrylic, and
sanded again in preparation for primer paint,
which I wet-sanded with 400-grit paper in
preparation for the color coats.
I used Krylon spray-can paints for the
color. They included the primer (number
1381), Gloss White (number 1501) for the
fuselage and upper sides, Regal Blue (number
1901) for the underside of the wing and
stabilizer, and Banner Red (number 2108) for
the wingtips. The “THORN” lettering is cut
vinyl from the local truck-lettering shop.
After painting I applied Goop hinges for
ailerons and elevator, as described in the kit
instructions. They outline a top-notch method
for installing the Goop hinges, which are
similar to, but tougher than, silicone hinges.
I have to admit that I never got the hang of
silicone hinges, but I know how to install
them now. My main problem in the past was
applying too much adhesive, rendering the
finished hinges too stiff.
That’s all behind me now, thanks to the
instructions in the manual. I like the look of
these hinges applied after painting the parts;
the paint can look uneven and flake off of the
Goop hinges.
Radio Installation and Balance: I used an
Airtronics VG6000 transmitter for this
project. Although a two-channel rig will
suffice for the 60-inch-span Thorn, I have
grown accustomed to having rates and
exponential on slope sailplanes.
The designer recommends exponential,
and the VG6000 delivers all this in a
computer transmitter without menus. All
functions show on the LCD screen all the
time.
I installed a diminutive JR 610M receiver:
the smallest I had in stock. I’m thrilled with
the installation of the thin Hitec HS-125
servos for ailerons, and I used a JR NES-341
servo for elevator; I’ve grown accustomed to
their toughness.
The precut pockets (into wings ordered
from the factory to fit your choice of servo)
for the Hitec 125 aileron servos fit snugly and
make installing these servos go quickly using
nothing but the screws provided by the servo
maker. There’s plenty of room in the fuselage
for my JR-341 elevator servo; the same goes
for the microreceiver and Electrodynamics
battery pack.
I added 3 ounces of nose weight in the
battery compartment to balance my Thorn at
the extreme rear of the recommended balancepoint
range. I set the control-surface throws as
instructed in the manual, including specs for
high and low rates and approximately 85%
exponential on ailerons and elevator.
My ready-to-fly model weighs 59 ounces,
for a wing loading of 25 ounces per square foot.My Thorn took 7.5 hours to build
(including a couple hours engineering and
building the removable tail parts), 4.25
hours to finish with paint, and 3.5 hours to
install and test the radio gear, for a total of
15.25 hours of workbench time, spread
over two weeks.
Flying: For test-flying we had an earlyspring
day with some fine slope-flying
conditions over Lake Ontario near
Syracuse, New York. We fly from a 115-
foot escarpment, and that day we had a 15-
20 mph wind blowing into the hill from
approximately 10° left of perpendicular.
After a final radio check we heaved the
Thorn off of the ridge toward the lake.
After letting it dive for a few long seconds
to gather speed, I leveled it out and began
the classic figure-eight slope pattern.
The first turn went smoothly, and, still
accelerating, it came on step by the time it
crossed in front of me. The Thorn climbed
quickly and easily, and controls were
smooth, with no sign of twitchiness.
Phrases from years ago when flighttesting
my first sleek, fast sailplane (a Sig
Samurai) came to mind: “Cuts through the
air like a knife” and “It doesn’t care which
way the wind is blowing.” The wind
direction did not switch around to straightin
as forecast, so we had windy, slightly
cross conditions for the entire flying day.
The heavy Thorn reveled in these
conditions. It seems like all other pilots put
down foam sailplanes after a minute or
two of flying; they would not penetrate.
The Thorn was in its element; Joe Chovan
and I logged a one-hour flight, passing the
transmitter twice. Control throws were set
up according to the instructions, and we
did not take it off high rates.
Our conclusions about the Thorn’s
flight performance are as follows.
• It penetrates extremely well in vigorous
wind, including crosswinds and gusty
conditions.
• It exhibits smooth control movements,
with no evidence of twitchiness or
overcontrol.
• It performs moderately fast axial rolls—
more than one per second.
• It hangs in with inverted flight adequately,
but it does not love that flight condition.
• It does love the Cuban Eight maneuver.
Hammerhead stall turns and half-pipe
maneuvers are competent for an aircraft
without a working rudder. Inside loops are
solid, with no aileron correction needed. (I
have not tried outside loops yet.)
The result on an intentional forward stall
was fairly dramatic; the Thorn fell 20-30 feet
before recovering. This is not a surprise for a
sailplane with a wing loading exceeding 20
ounces per square foot. This stood as a
reminder to fly this, and all heavy sailplanes,
smoothly and without stalling them.
Throughout the flying session we did not
worry about lift coming and going. Keep this
model moving, and it flies fine in momentary
varying lift conditions.
I landed it back on top, shiny-side up in
grass. The landing broke one nylon wingmount
bolt, and the sailplane incurred no
other damage. I’m fully pleased with the
Thorn’s flight performance.
Many thanks to Joe Chovan for flying for
the camera. He’s great at it.
Given the uncommon construction materials,
the unusual solid-wood wing design, and the
advanced computer-controlled machining
used in the production of the parts, just
owning a Thorn kit puts you in the forefront
of Slope Soaring glider technology.
Spend the rather pleasant (if you like
working with wood) 5.5 hours building and
the satisfying (if you like finishing a model
with paint) 4.25 hours final-sanding, sealing,
and painting the model, and you’ll have a
slope speedster that impresses you and your
friends. The kit is sold at a righteous price. If
you like fast and unusual sailplanes, it’s hard
to see how you can go wrong with a Thorn.
There is even better news in the future: I
have already flown a prototype of the 100-
inch-span, six-servo version, and that was a
real fun time; the 2.5-meter version covers a
great deal of sky in a short time.
Furthermore, customer requests for
four-servo wings to incorporate flaps in
addition to ailerons have been fulfilled,
and 60- and 80-inch-span wings have been
shipped. Plane Insane Models is one maker
to watch.
The Thorn is impressive in the air. It
penetrates the wind well. It carves a smooth
course with no sign of twitchiness or
overcontrol. My Thorn is quick in axial rolls
and solid when flown through loops.
Although it’s not optimized for inverted
flight, it performs excellent Cuban Eights. A
stall becomes a serious departure from
controlled flight, and the aircraft must fall 20
feet or more before regaining flying speed and
recovering.
This is not a trainer; it is a heavy-wingloaded,
high-performance sailplane. For those
who delight in flying a fast, heavy glider, the
Thorn is an exceptional candidate to meet
your need for speed. MA
Manufacturer:
Plane Insane Models, Andreas Mergner
366 Hamilton St.
Albany NY 12210
(518) 542-9527
[email protected]
www.planeinsanemodels.com
Products Used in Review:
Airtronics VG6000 transmitter
www.airtronics.net
JR 610M receiver
www.horizonhobby.com
Hitec HS-125 aileron servos
www.hitecrcd.com
JR NES-341 elevator servo
www.horizonhobby.com
Electrodynamics battery pack
www.electrodynam.com
Minwax Polycrylic sanding sealer
www.minwax.com
Krylon rattle-can spray paint
www.krylon.com
Edition: Model Aviation - 2006/09
Page Numbers: 91,92,93,94,96
THIS SAILPLANE IS nothing
less than revolutionary. The Plane Insane
Models Thorn smashes through to claim new
ground in model-sailplane design, in materials
used, and in parts-production methods.
Machined from planks of wood by a
specially designed computer-controlled
cutting machine, the solid-wood wing and
solid-wood fuselage parts are far different
from those in 99% of the gliders we’ve built.
In addition to these design and production
advances, the model flies great.
One of the Thorn’s big benefits is the kit’s
low parts count, so construction proceeds
rapidly. Another advantage is that the
completed airframe is strong and heavy.
Strong is good because we like rugged
models; heavy is good because it is the key to
going fast.
This aircraft is designed to compete with
ballasted-up composite sailplanes at roughly
half the cost. The Thorn is heavy when it’s
built, so there is no need to have to purchase
or mount lead, steel, tungsten, or other ballast.
In addition to the design innovation and
kit coolness, this sailplane flies superbly. It is
not a trainer by any means; it is a slope
screamer. Many of us were taught to build
light for best glider performance, but once
you experience the adrenalin rush of flying
high-performance sailplanes, all you want to
do is fly heavier and faster gliders. The Thorn
delivers the thrills.
Kit Contents: As I mentioned, this model’s
Plane Talk: Plane Insane Models Thorn
DAVE GARWOOD
+
• High performance. If you have the lift,
the Thorn will deliver the speed.
• Quick to build because of good design
and advanced parts-production methods.
• A strong and rugged airframe; the
Thorn is able to land successfully in less
than perfect areas.
• Customization is available when
ordering the kit, such as custom-cut
servo bays in the wing and the ability to
specify light, medium, or heavy wood. -• Narrow fuselage (a good thing for
aerodynamics) allows little space for
the receiver and elevator servo.
Microsize components are required.
• A number of people don’t like sanding;
some is required with this all-wood
model.
• Although the sacrificial nylon wingmount
bolts break as intended on a
rough landing, they may break too
easily. Larger bolts should be
considered. (The kit has been upgraded
to include 1/4-inch bolts. Threaded inserts
and replacement bolts are free to early kit
buyers who request them.)
Pluses and Minuses
Dave holds his Thorn against the wind
before the initial flight. Lake Ontario is in
the background. Joe Chovan photo.
A model that expands the envelope of high-perfo rmance slope design
September 2006 91
parts are solid wood. The kit includes
machined wing halves, ailerons, fuselage,
elevator, and hatch. The vertical and
horizontal stabilizers and elevator are precut
from basswood sheet stock. The pushrods are
09sig3.QXD 7/25/06 10:46 AM Page 9192 MODEL AVIATION
Radio system: Airtronics VG6000
transmitter, JR 610M receiver, Hitec HS-
125 thin metal gear aileron wing servos,
JR NES-341 elevator servo, Airtronics
97020 Y cable, Electrodynamics 600
mAh 4.8-volt battery
Flight duration: As long as the wind
blows and until the onboard battery
capacity is exhausted. Two hours is a
practical limit.
Test-Model Details
Type: High-performance Slope Soaring
glider
Pilot skill level: Experienced Slope
Soaring pilots
Wingspan: 60 inches
Wing area: 336 square inches
Length: 37.5 inches
Ready-to-fly weight: 58.7 ounces
Wing loading: 25.2 ounces per square
foot
Airfoil: RG-15 (modified and thinned to
7% thickness)
Recommended radio: Two channels
minimum with exponential
Construction: Solid-wood parts—
different from most other kits but goes
together quickly
Covering/finish: Paint on review
model, but could be stain or iron-on
covering, depending on builder
preference
Price: $160 (shipping included)
Specifications
Right: The completed Thorn airframe
before sealing, painting, and applying Goop
hinges to mount the control surfaces.
Below: The Thorn, complete and ready to
fly. Real slope sailplanes are painted—not
covered. Krylon spray paint was used over
Minwax sealer.
The model’s parts are made entirely from solid wood via computer-controlled machining.
Vertical and horizontal stabilizers and elevator are precut from basswood sheet.
Pushrods are installed in the fuselage at the factory.
Dave’s removable tail parts are mounted with bolts coming up through the plywood
plate. This modification was made with encouragement from the Thorn’s manufacturer.
Photos by the author except as noted
09sig3.QXD 7/25/06 10:55 AM Page 92September 2006 93
Notice how accurately the pocket is cut for a Hitec HS-125 aileron
servo. Any of several servo pockets can be specified when a kit is
ordered.
The TE pieces are glued in place and clamped until cured. Notice
how the wing-joiner system works. Wing halves have been joined
and the center sanded.
The Thorn fuselage front end showing trial-fitting of JR NES-341 elevator servo, JR 610M
receiver, and Electrodynamics 4KR-600AE battery pack.
Dave applies Goop hinges for ailerons, as detailed in the
instructions. He found that Goop hinges for elevator and ailerons
worked well on this model.
The Thorn fuselage front end showing all gear and wiring installed.
It’s tight, but all specified gear does fit. Nose weight (pieces cut
from roofing lead sheeting) fits under battery pack.
Dave’s Thorn rips up the air over Lake Ontario, near Syracuse
New York, on its initial test flight. This is a fast Slope Soarer.
installed in the fuselage at the factory.
Also included is a bag of small wood
parts, all the necessary hardware, and an
instruction manual. The kit is complete,
containing everything except adhesives, radio
components, and finishing materials.
The 13-page instruction manual is
thorough and features six drawings and 10
photographs to amplify the text. It is detailed
and complete, and experienced modelers will
have no trouble building the kit using it. The
manual is downloadable from the Plane
Insane Models Web site.
Owing partially to the fact that software
runs the computer-controlled machine
processes and mostly because of Plane Insane
Models’ Andreas Mergner’s meticulous
09sig3.QXD 7/25/06 10:47 AM Page 93production planning, you can order wing
servo cutouts to accurately fit your choice of
servos, and you can specify light or heavy
wood parts to match the model you build to
your anticipated lift conditions.
Construction: My four building sessions,
each ranging from a half hour to two hours,
went as follows.
1) Sand the fuselage and wing halves, join
the wing halves, and set them aside for the
epoxy to cure. Glue the hatch hold-down
magnets into the hatch and the fuselage, and
attach the hatch rear wire with epoxy and
fiberglass cloth. I decided that removable tail
parts would make storage and transportation
easier, so I fitted a plywood plate to have a
place to mount the horizontal and vertical
stabilizers with bolts.
2) Sand the now-cured center-section of
the wing. Glue the wing TE pieces with
polyurethane glue.
3) Trim and sand the ailerons and the
elevator. Final-sand the tail parts.
4) I built a modified vertical-stabilizer
mounting mechanism to make transportation
and storage easier. I installed blind nuts (also
called T-nuts) on the top side of a plywood
plate at the bottom of the fin that receive a
pair of bolts inserted from the bottom. Skip
this step if you don’t need compact storage,
and glue the tail parts on as instructed.
You can stain, paint, or cover your Thorn
with heat-shrink film covering, but to my
mind real Slope Soarers are painted—not
covered. This is a real slope sailplane if ever
there was one.
To finish all airframe surfaces, I did my
final sanding and applied Minwax Water-
Based Polycrylic Protective Finish—a
material I have used for years and like
because it has nearly no odor. After one coat I
sanded again with 240-grit paper, applied
another coat of Minwax Polycrylic, and
sanded again in preparation for primer paint,
which I wet-sanded with 400-grit paper in
preparation for the color coats.
I used Krylon spray-can paints for the
color. They included the primer (number
1381), Gloss White (number 1501) for the
fuselage and upper sides, Regal Blue (number
1901) for the underside of the wing and
stabilizer, and Banner Red (number 2108) for
the wingtips. The “THORN” lettering is cut
vinyl from the local truck-lettering shop.
After painting I applied Goop hinges for
ailerons and elevator, as described in the kit
instructions. They outline a top-notch method
for installing the Goop hinges, which are
similar to, but tougher than, silicone hinges.
I have to admit that I never got the hang of
silicone hinges, but I know how to install
them now. My main problem in the past was
applying too much adhesive, rendering the
finished hinges too stiff.
That’s all behind me now, thanks to the
instructions in the manual. I like the look of
these hinges applied after painting the parts;
the paint can look uneven and flake off of the
Goop hinges.
Radio Installation and Balance: I used an
Airtronics VG6000 transmitter for this
project. Although a two-channel rig will
suffice for the 60-inch-span Thorn, I have
grown accustomed to having rates and
exponential on slope sailplanes.
The designer recommends exponential,
and the VG6000 delivers all this in a
computer transmitter without menus. All
functions show on the LCD screen all the
time.
I installed a diminutive JR 610M receiver:
the smallest I had in stock. I’m thrilled with
the installation of the thin Hitec HS-125
servos for ailerons, and I used a JR NES-341
servo for elevator; I’ve grown accustomed to
their toughness.
The precut pockets (into wings ordered
from the factory to fit your choice of servo)
for the Hitec 125 aileron servos fit snugly and
make installing these servos go quickly using
nothing but the screws provided by the servo
maker. There’s plenty of room in the fuselage
for my JR-341 elevator servo; the same goes
for the microreceiver and Electrodynamics
battery pack.
I added 3 ounces of nose weight in the
battery compartment to balance my Thorn at
the extreme rear of the recommended balancepoint
range. I set the control-surface throws as
instructed in the manual, including specs for
high and low rates and approximately 85%
exponential on ailerons and elevator.
My ready-to-fly model weighs 59 ounces,
for a wing loading of 25 ounces per square foot.My Thorn took 7.5 hours to build
(including a couple hours engineering and
building the removable tail parts), 4.25
hours to finish with paint, and 3.5 hours to
install and test the radio gear, for a total of
15.25 hours of workbench time, spread
over two weeks.
Flying: For test-flying we had an earlyspring
day with some fine slope-flying
conditions over Lake Ontario near
Syracuse, New York. We fly from a 115-
foot escarpment, and that day we had a 15-
20 mph wind blowing into the hill from
approximately 10° left of perpendicular.
After a final radio check we heaved the
Thorn off of the ridge toward the lake.
After letting it dive for a few long seconds
to gather speed, I leveled it out and began
the classic figure-eight slope pattern.
The first turn went smoothly, and, still
accelerating, it came on step by the time it
crossed in front of me. The Thorn climbed
quickly and easily, and controls were
smooth, with no sign of twitchiness.
Phrases from years ago when flighttesting
my first sleek, fast sailplane (a Sig
Samurai) came to mind: “Cuts through the
air like a knife” and “It doesn’t care which
way the wind is blowing.” The wind
direction did not switch around to straightin
as forecast, so we had windy, slightly
cross conditions for the entire flying day.
The heavy Thorn reveled in these
conditions. It seems like all other pilots put
down foam sailplanes after a minute or
two of flying; they would not penetrate.
The Thorn was in its element; Joe Chovan
and I logged a one-hour flight, passing the
transmitter twice. Control throws were set
up according to the instructions, and we
did not take it off high rates.
Our conclusions about the Thorn’s
flight performance are as follows.
• It penetrates extremely well in vigorous
wind, including crosswinds and gusty
conditions.
• It exhibits smooth control movements,
with no evidence of twitchiness or
overcontrol.
• It performs moderately fast axial rolls—
more than one per second.
• It hangs in with inverted flight adequately,
but it does not love that flight condition.
• It does love the Cuban Eight maneuver.
Hammerhead stall turns and half-pipe
maneuvers are competent for an aircraft
without a working rudder. Inside loops are
solid, with no aileron correction needed. (I
have not tried outside loops yet.)
The result on an intentional forward stall
was fairly dramatic; the Thorn fell 20-30 feet
before recovering. This is not a surprise for a
sailplane with a wing loading exceeding 20
ounces per square foot. This stood as a
reminder to fly this, and all heavy sailplanes,
smoothly and without stalling them.
Throughout the flying session we did not
worry about lift coming and going. Keep this
model moving, and it flies fine in momentary
varying lift conditions.
I landed it back on top, shiny-side up in
grass. The landing broke one nylon wingmount
bolt, and the sailplane incurred no
other damage. I’m fully pleased with the
Thorn’s flight performance.
Many thanks to Joe Chovan for flying for
the camera. He’s great at it.
Given the uncommon construction materials,
the unusual solid-wood wing design, and the
advanced computer-controlled machining
used in the production of the parts, just
owning a Thorn kit puts you in the forefront
of Slope Soaring glider technology.
Spend the rather pleasant (if you like
working with wood) 5.5 hours building and
the satisfying (if you like finishing a model
with paint) 4.25 hours final-sanding, sealing,
and painting the model, and you’ll have a
slope speedster that impresses you and your
friends. The kit is sold at a righteous price. If
you like fast and unusual sailplanes, it’s hard
to see how you can go wrong with a Thorn.
There is even better news in the future: I
have already flown a prototype of the 100-
inch-span, six-servo version, and that was a
real fun time; the 2.5-meter version covers a
great deal of sky in a short time.
Furthermore, customer requests for
four-servo wings to incorporate flaps in
addition to ailerons have been fulfilled,
and 60- and 80-inch-span wings have been
shipped. Plane Insane Models is one maker
to watch.
The Thorn is impressive in the air. It
penetrates the wind well. It carves a smooth
course with no sign of twitchiness or
overcontrol. My Thorn is quick in axial rolls
and solid when flown through loops.
Although it’s not optimized for inverted
flight, it performs excellent Cuban Eights. A
stall becomes a serious departure from
controlled flight, and the aircraft must fall 20
feet or more before regaining flying speed and
recovering.
This is not a trainer; it is a heavy-wingloaded,
high-performance sailplane. For those
who delight in flying a fast, heavy glider, the
Thorn is an exceptional candidate to meet
your need for speed. MA
Manufacturer:
Plane Insane Models, Andreas Mergner
366 Hamilton St.
Albany NY 12210
(518) 542-9527
[email protected]
www.planeinsanemodels.com
Products Used in Review:
Airtronics VG6000 transmitter
www.airtronics.net
JR 610M receiver
www.horizonhobby.com
Hitec HS-125 aileron servos
www.hitecrcd.com
JR NES-341 elevator servo
www.horizonhobby.com
Electrodynamics battery pack
www.electrodynam.com
Minwax Polycrylic sanding sealer
www.minwax.com
Krylon rattle-can spray paint
www.krylon.com
Edition: Model Aviation - 2006/09
Page Numbers: 91,92,93,94,96
THIS SAILPLANE IS nothing
less than revolutionary. The Plane Insane
Models Thorn smashes through to claim new
ground in model-sailplane design, in materials
used, and in parts-production methods.
Machined from planks of wood by a
specially designed computer-controlled
cutting machine, the solid-wood wing and
solid-wood fuselage parts are far different
from those in 99% of the gliders we’ve built.
In addition to these design and production
advances, the model flies great.
One of the Thorn’s big benefits is the kit’s
low parts count, so construction proceeds
rapidly. Another advantage is that the
completed airframe is strong and heavy.
Strong is good because we like rugged
models; heavy is good because it is the key to
going fast.
This aircraft is designed to compete with
ballasted-up composite sailplanes at roughly
half the cost. The Thorn is heavy when it’s
built, so there is no need to have to purchase
or mount lead, steel, tungsten, or other ballast.
In addition to the design innovation and
kit coolness, this sailplane flies superbly. It is
not a trainer by any means; it is a slope
screamer. Many of us were taught to build
light for best glider performance, but once
you experience the adrenalin rush of flying
high-performance sailplanes, all you want to
do is fly heavier and faster gliders. The Thorn
delivers the thrills.
Kit Contents: As I mentioned, this model’s
Plane Talk: Plane Insane Models Thorn
DAVE GARWOOD
+
• High performance. If you have the lift,
the Thorn will deliver the speed.
• Quick to build because of good design
and advanced parts-production methods.
• A strong and rugged airframe; the
Thorn is able to land successfully in less
than perfect areas.
• Customization is available when
ordering the kit, such as custom-cut
servo bays in the wing and the ability to
specify light, medium, or heavy wood. -• Narrow fuselage (a good thing for
aerodynamics) allows little space for
the receiver and elevator servo.
Microsize components are required.
• A number of people don’t like sanding;
some is required with this all-wood
model.
• Although the sacrificial nylon wingmount
bolts break as intended on a
rough landing, they may break too
easily. Larger bolts should be
considered. (The kit has been upgraded
to include 1/4-inch bolts. Threaded inserts
and replacement bolts are free to early kit
buyers who request them.)
Pluses and Minuses
Dave holds his Thorn against the wind
before the initial flight. Lake Ontario is in
the background. Joe Chovan photo.
A model that expands the envelope of high-perfo rmance slope design
September 2006 91
parts are solid wood. The kit includes
machined wing halves, ailerons, fuselage,
elevator, and hatch. The vertical and
horizontal stabilizers and elevator are precut
from basswood sheet stock. The pushrods are
09sig3.QXD 7/25/06 10:46 AM Page 9192 MODEL AVIATION
Radio system: Airtronics VG6000
transmitter, JR 610M receiver, Hitec HS-
125 thin metal gear aileron wing servos,
JR NES-341 elevator servo, Airtronics
97020 Y cable, Electrodynamics 600
mAh 4.8-volt battery
Flight duration: As long as the wind
blows and until the onboard battery
capacity is exhausted. Two hours is a
practical limit.
Test-Model Details
Type: High-performance Slope Soaring
glider
Pilot skill level: Experienced Slope
Soaring pilots
Wingspan: 60 inches
Wing area: 336 square inches
Length: 37.5 inches
Ready-to-fly weight: 58.7 ounces
Wing loading: 25.2 ounces per square
foot
Airfoil: RG-15 (modified and thinned to
7% thickness)
Recommended radio: Two channels
minimum with exponential
Construction: Solid-wood parts—
different from most other kits but goes
together quickly
Covering/finish: Paint on review
model, but could be stain or iron-on
covering, depending on builder
preference
Price: $160 (shipping included)
Specifications
Right: The completed Thorn airframe
before sealing, painting, and applying Goop
hinges to mount the control surfaces.
Below: The Thorn, complete and ready to
fly. Real slope sailplanes are painted—not
covered. Krylon spray paint was used over
Minwax sealer.
The model’s parts are made entirely from solid wood via computer-controlled machining.
Vertical and horizontal stabilizers and elevator are precut from basswood sheet.
Pushrods are installed in the fuselage at the factory.
Dave’s removable tail parts are mounted with bolts coming up through the plywood
plate. This modification was made with encouragement from the Thorn’s manufacturer.
Photos by the author except as noted
09sig3.QXD 7/25/06 10:55 AM Page 92September 2006 93
Notice how accurately the pocket is cut for a Hitec HS-125 aileron
servo. Any of several servo pockets can be specified when a kit is
ordered.
The TE pieces are glued in place and clamped until cured. Notice
how the wing-joiner system works. Wing halves have been joined
and the center sanded.
The Thorn fuselage front end showing trial-fitting of JR NES-341 elevator servo, JR 610M
receiver, and Electrodynamics 4KR-600AE battery pack.
Dave applies Goop hinges for ailerons, as detailed in the
instructions. He found that Goop hinges for elevator and ailerons
worked well on this model.
The Thorn fuselage front end showing all gear and wiring installed.
It’s tight, but all specified gear does fit. Nose weight (pieces cut
from roofing lead sheeting) fits under battery pack.
Dave’s Thorn rips up the air over Lake Ontario, near Syracuse
New York, on its initial test flight. This is a fast Slope Soarer.
installed in the fuselage at the factory.
Also included is a bag of small wood
parts, all the necessary hardware, and an
instruction manual. The kit is complete,
containing everything except adhesives, radio
components, and finishing materials.
The 13-page instruction manual is
thorough and features six drawings and 10
photographs to amplify the text. It is detailed
and complete, and experienced modelers will
have no trouble building the kit using it. The
manual is downloadable from the Plane
Insane Models Web site.
Owing partially to the fact that software
runs the computer-controlled machine
processes and mostly because of Plane Insane
Models’ Andreas Mergner’s meticulous
09sig3.QXD 7/25/06 10:47 AM Page 93production planning, you can order wing
servo cutouts to accurately fit your choice of
servos, and you can specify light or heavy
wood parts to match the model you build to
your anticipated lift conditions.
Construction: My four building sessions,
each ranging from a half hour to two hours,
went as follows.
1) Sand the fuselage and wing halves, join
the wing halves, and set them aside for the
epoxy to cure. Glue the hatch hold-down
magnets into the hatch and the fuselage, and
attach the hatch rear wire with epoxy and
fiberglass cloth. I decided that removable tail
parts would make storage and transportation
easier, so I fitted a plywood plate to have a
place to mount the horizontal and vertical
stabilizers with bolts.
2) Sand the now-cured center-section of
the wing. Glue the wing TE pieces with
polyurethane glue.
3) Trim and sand the ailerons and the
elevator. Final-sand the tail parts.
4) I built a modified vertical-stabilizer
mounting mechanism to make transportation
and storage easier. I installed blind nuts (also
called T-nuts) on the top side of a plywood
plate at the bottom of the fin that receive a
pair of bolts inserted from the bottom. Skip
this step if you don’t need compact storage,
and glue the tail parts on as instructed.
You can stain, paint, or cover your Thorn
with heat-shrink film covering, but to my
mind real Slope Soarers are painted—not
covered. This is a real slope sailplane if ever
there was one.
To finish all airframe surfaces, I did my
final sanding and applied Minwax Water-
Based Polycrylic Protective Finish—a
material I have used for years and like
because it has nearly no odor. After one coat I
sanded again with 240-grit paper, applied
another coat of Minwax Polycrylic, and
sanded again in preparation for primer paint,
which I wet-sanded with 400-grit paper in
preparation for the color coats.
I used Krylon spray-can paints for the
color. They included the primer (number
1381), Gloss White (number 1501) for the
fuselage and upper sides, Regal Blue (number
1901) for the underside of the wing and
stabilizer, and Banner Red (number 2108) for
the wingtips. The “THORN” lettering is cut
vinyl from the local truck-lettering shop.
After painting I applied Goop hinges for
ailerons and elevator, as described in the kit
instructions. They outline a top-notch method
for installing the Goop hinges, which are
similar to, but tougher than, silicone hinges.
I have to admit that I never got the hang of
silicone hinges, but I know how to install
them now. My main problem in the past was
applying too much adhesive, rendering the
finished hinges too stiff.
That’s all behind me now, thanks to the
instructions in the manual. I like the look of
these hinges applied after painting the parts;
the paint can look uneven and flake off of the
Goop hinges.
Radio Installation and Balance: I used an
Airtronics VG6000 transmitter for this
project. Although a two-channel rig will
suffice for the 60-inch-span Thorn, I have
grown accustomed to having rates and
exponential on slope sailplanes.
The designer recommends exponential,
and the VG6000 delivers all this in a
computer transmitter without menus. All
functions show on the LCD screen all the
time.
I installed a diminutive JR 610M receiver:
the smallest I had in stock. I’m thrilled with
the installation of the thin Hitec HS-125
servos for ailerons, and I used a JR NES-341
servo for elevator; I’ve grown accustomed to
their toughness.
The precut pockets (into wings ordered
from the factory to fit your choice of servo)
for the Hitec 125 aileron servos fit snugly and
make installing these servos go quickly using
nothing but the screws provided by the servo
maker. There’s plenty of room in the fuselage
for my JR-341 elevator servo; the same goes
for the microreceiver and Electrodynamics
battery pack.
I added 3 ounces of nose weight in the
battery compartment to balance my Thorn at
the extreme rear of the recommended balancepoint
range. I set the control-surface throws as
instructed in the manual, including specs for
high and low rates and approximately 85%
exponential on ailerons and elevator.
My ready-to-fly model weighs 59 ounces,
for a wing loading of 25 ounces per square foot.My Thorn took 7.5 hours to build
(including a couple hours engineering and
building the removable tail parts), 4.25
hours to finish with paint, and 3.5 hours to
install and test the radio gear, for a total of
15.25 hours of workbench time, spread
over two weeks.
Flying: For test-flying we had an earlyspring
day with some fine slope-flying
conditions over Lake Ontario near
Syracuse, New York. We fly from a 115-
foot escarpment, and that day we had a 15-
20 mph wind blowing into the hill from
approximately 10° left of perpendicular.
After a final radio check we heaved the
Thorn off of the ridge toward the lake.
After letting it dive for a few long seconds
to gather speed, I leveled it out and began
the classic figure-eight slope pattern.
The first turn went smoothly, and, still
accelerating, it came on step by the time it
crossed in front of me. The Thorn climbed
quickly and easily, and controls were
smooth, with no sign of twitchiness.
Phrases from years ago when flighttesting
my first sleek, fast sailplane (a Sig
Samurai) came to mind: “Cuts through the
air like a knife” and “It doesn’t care which
way the wind is blowing.” The wind
direction did not switch around to straightin
as forecast, so we had windy, slightly
cross conditions for the entire flying day.
The heavy Thorn reveled in these
conditions. It seems like all other pilots put
down foam sailplanes after a minute or
two of flying; they would not penetrate.
The Thorn was in its element; Joe Chovan
and I logged a one-hour flight, passing the
transmitter twice. Control throws were set
up according to the instructions, and we
did not take it off high rates.
Our conclusions about the Thorn’s
flight performance are as follows.
• It penetrates extremely well in vigorous
wind, including crosswinds and gusty
conditions.
• It exhibits smooth control movements,
with no evidence of twitchiness or
overcontrol.
• It performs moderately fast axial rolls—
more than one per second.
• It hangs in with inverted flight adequately,
but it does not love that flight condition.
• It does love the Cuban Eight maneuver.
Hammerhead stall turns and half-pipe
maneuvers are competent for an aircraft
without a working rudder. Inside loops are
solid, with no aileron correction needed. (I
have not tried outside loops yet.)
The result on an intentional forward stall
was fairly dramatic; the Thorn fell 20-30 feet
before recovering. This is not a surprise for a
sailplane with a wing loading exceeding 20
ounces per square foot. This stood as a
reminder to fly this, and all heavy sailplanes,
smoothly and without stalling them.
Throughout the flying session we did not
worry about lift coming and going. Keep this
model moving, and it flies fine in momentary
varying lift conditions.
I landed it back on top, shiny-side up in
grass. The landing broke one nylon wingmount
bolt, and the sailplane incurred no
other damage. I’m fully pleased with the
Thorn’s flight performance.
Many thanks to Joe Chovan for flying for
the camera. He’s great at it.
Given the uncommon construction materials,
the unusual solid-wood wing design, and the
advanced computer-controlled machining
used in the production of the parts, just
owning a Thorn kit puts you in the forefront
of Slope Soaring glider technology.
Spend the rather pleasant (if you like
working with wood) 5.5 hours building and
the satisfying (if you like finishing a model
with paint) 4.25 hours final-sanding, sealing,
and painting the model, and you’ll have a
slope speedster that impresses you and your
friends. The kit is sold at a righteous price. If
you like fast and unusual sailplanes, it’s hard
to see how you can go wrong with a Thorn.
There is even better news in the future: I
have already flown a prototype of the 100-
inch-span, six-servo version, and that was a
real fun time; the 2.5-meter version covers a
great deal of sky in a short time.
Furthermore, customer requests for
four-servo wings to incorporate flaps in
addition to ailerons have been fulfilled,
and 60- and 80-inch-span wings have been
shipped. Plane Insane Models is one maker
to watch.
The Thorn is impressive in the air. It
penetrates the wind well. It carves a smooth
course with no sign of twitchiness or
overcontrol. My Thorn is quick in axial rolls
and solid when flown through loops.
Although it’s not optimized for inverted
flight, it performs excellent Cuban Eights. A
stall becomes a serious departure from
controlled flight, and the aircraft must fall 20
feet or more before regaining flying speed and
recovering.
This is not a trainer; it is a heavy-wingloaded,
high-performance sailplane. For those
who delight in flying a fast, heavy glider, the
Thorn is an exceptional candidate to meet
your need for speed. MA
Manufacturer:
Plane Insane Models, Andreas Mergner
366 Hamilton St.
Albany NY 12210
(518) 542-9527
[email protected]
www.planeinsanemodels.com
Products Used in Review:
Airtronics VG6000 transmitter
www.airtronics.net
JR 610M receiver
www.horizonhobby.com
Hitec HS-125 aileron servos
www.hitecrcd.com
JR NES-341 elevator servo
www.horizonhobby.com
Electrodynamics battery pack
www.electrodynam.com
Minwax Polycrylic sanding sealer
www.minwax.com
Krylon rattle-can spray paint
www.krylon.com
Edition: Model Aviation - 2006/09
Page Numbers: 91,92,93,94,96
THIS SAILPLANE IS nothing
less than revolutionary. The Plane Insane
Models Thorn smashes through to claim new
ground in model-sailplane design, in materials
used, and in parts-production methods.
Machined from planks of wood by a
specially designed computer-controlled
cutting machine, the solid-wood wing and
solid-wood fuselage parts are far different
from those in 99% of the gliders we’ve built.
In addition to these design and production
advances, the model flies great.
One of the Thorn’s big benefits is the kit’s
low parts count, so construction proceeds
rapidly. Another advantage is that the
completed airframe is strong and heavy.
Strong is good because we like rugged
models; heavy is good because it is the key to
going fast.
This aircraft is designed to compete with
ballasted-up composite sailplanes at roughly
half the cost. The Thorn is heavy when it’s
built, so there is no need to have to purchase
or mount lead, steel, tungsten, or other ballast.
In addition to the design innovation and
kit coolness, this sailplane flies superbly. It is
not a trainer by any means; it is a slope
screamer. Many of us were taught to build
light for best glider performance, but once
you experience the adrenalin rush of flying
high-performance sailplanes, all you want to
do is fly heavier and faster gliders. The Thorn
delivers the thrills.
Kit Contents: As I mentioned, this model’s
Plane Talk: Plane Insane Models Thorn
DAVE GARWOOD
+
• High performance. If you have the lift,
the Thorn will deliver the speed.
• Quick to build because of good design
and advanced parts-production methods.
• A strong and rugged airframe; the
Thorn is able to land successfully in less
than perfect areas.
• Customization is available when
ordering the kit, such as custom-cut
servo bays in the wing and the ability to
specify light, medium, or heavy wood. -• Narrow fuselage (a good thing for
aerodynamics) allows little space for
the receiver and elevator servo.
Microsize components are required.
• A number of people don’t like sanding;
some is required with this all-wood
model.
• Although the sacrificial nylon wingmount
bolts break as intended on a
rough landing, they may break too
easily. Larger bolts should be
considered. (The kit has been upgraded
to include 1/4-inch bolts. Threaded inserts
and replacement bolts are free to early kit
buyers who request them.)
Pluses and Minuses
Dave holds his Thorn against the wind
before the initial flight. Lake Ontario is in
the background. Joe Chovan photo.
A model that expands the envelope of high-perfo rmance slope design
September 2006 91
parts are solid wood. The kit includes
machined wing halves, ailerons, fuselage,
elevator, and hatch. The vertical and
horizontal stabilizers and elevator are precut
from basswood sheet stock. The pushrods are
09sig3.QXD 7/25/06 10:46 AM Page 9192 MODEL AVIATION
Radio system: Airtronics VG6000
transmitter, JR 610M receiver, Hitec HS-
125 thin metal gear aileron wing servos,
JR NES-341 elevator servo, Airtronics
97020 Y cable, Electrodynamics 600
mAh 4.8-volt battery
Flight duration: As long as the wind
blows and until the onboard battery
capacity is exhausted. Two hours is a
practical limit.
Test-Model Details
Type: High-performance Slope Soaring
glider
Pilot skill level: Experienced Slope
Soaring pilots
Wingspan: 60 inches
Wing area: 336 square inches
Length: 37.5 inches
Ready-to-fly weight: 58.7 ounces
Wing loading: 25.2 ounces per square
foot
Airfoil: RG-15 (modified and thinned to
7% thickness)
Recommended radio: Two channels
minimum with exponential
Construction: Solid-wood parts—
different from most other kits but goes
together quickly
Covering/finish: Paint on review
model, but could be stain or iron-on
covering, depending on builder
preference
Price: $160 (shipping included)
Specifications
Right: The completed Thorn airframe
before sealing, painting, and applying Goop
hinges to mount the control surfaces.
Below: The Thorn, complete and ready to
fly. Real slope sailplanes are painted—not
covered. Krylon spray paint was used over
Minwax sealer.
The model’s parts are made entirely from solid wood via computer-controlled machining.
Vertical and horizontal stabilizers and elevator are precut from basswood sheet.
Pushrods are installed in the fuselage at the factory.
Dave’s removable tail parts are mounted with bolts coming up through the plywood
plate. This modification was made with encouragement from the Thorn’s manufacturer.
Photos by the author except as noted
09sig3.QXD 7/25/06 10:55 AM Page 92September 2006 93
Notice how accurately the pocket is cut for a Hitec HS-125 aileron
servo. Any of several servo pockets can be specified when a kit is
ordered.
The TE pieces are glued in place and clamped until cured. Notice
how the wing-joiner system works. Wing halves have been joined
and the center sanded.
The Thorn fuselage front end showing trial-fitting of JR NES-341 elevator servo, JR 610M
receiver, and Electrodynamics 4KR-600AE battery pack.
Dave applies Goop hinges for ailerons, as detailed in the
instructions. He found that Goop hinges for elevator and ailerons
worked well on this model.
The Thorn fuselage front end showing all gear and wiring installed.
It’s tight, but all specified gear does fit. Nose weight (pieces cut
from roofing lead sheeting) fits under battery pack.
Dave’s Thorn rips up the air over Lake Ontario, near Syracuse
New York, on its initial test flight. This is a fast Slope Soarer.
installed in the fuselage at the factory.
Also included is a bag of small wood
parts, all the necessary hardware, and an
instruction manual. The kit is complete,
containing everything except adhesives, radio
components, and finishing materials.
The 13-page instruction manual is
thorough and features six drawings and 10
photographs to amplify the text. It is detailed
and complete, and experienced modelers will
have no trouble building the kit using it. The
manual is downloadable from the Plane
Insane Models Web site.
Owing partially to the fact that software
runs the computer-controlled machine
processes and mostly because of Plane Insane
Models’ Andreas Mergner’s meticulous
09sig3.QXD 7/25/06 10:47 AM Page 93production planning, you can order wing
servo cutouts to accurately fit your choice of
servos, and you can specify light or heavy
wood parts to match the model you build to
your anticipated lift conditions.
Construction: My four building sessions,
each ranging from a half hour to two hours,
went as follows.
1) Sand the fuselage and wing halves, join
the wing halves, and set them aside for the
epoxy to cure. Glue the hatch hold-down
magnets into the hatch and the fuselage, and
attach the hatch rear wire with epoxy and
fiberglass cloth. I decided that removable tail
parts would make storage and transportation
easier, so I fitted a plywood plate to have a
place to mount the horizontal and vertical
stabilizers with bolts.
2) Sand the now-cured center-section of
the wing. Glue the wing TE pieces with
polyurethane glue.
3) Trim and sand the ailerons and the
elevator. Final-sand the tail parts.
4) I built a modified vertical-stabilizer
mounting mechanism to make transportation
and storage easier. I installed blind nuts (also
called T-nuts) on the top side of a plywood
plate at the bottom of the fin that receive a
pair of bolts inserted from the bottom. Skip
this step if you don’t need compact storage,
and glue the tail parts on as instructed.
You can stain, paint, or cover your Thorn
with heat-shrink film covering, but to my
mind real Slope Soarers are painted—not
covered. This is a real slope sailplane if ever
there was one.
To finish all airframe surfaces, I did my
final sanding and applied Minwax Water-
Based Polycrylic Protective Finish—a
material I have used for years and like
because it has nearly no odor. After one coat I
sanded again with 240-grit paper, applied
another coat of Minwax Polycrylic, and
sanded again in preparation for primer paint,
which I wet-sanded with 400-grit paper in
preparation for the color coats.
I used Krylon spray-can paints for the
color. They included the primer (number
1381), Gloss White (number 1501) for the
fuselage and upper sides, Regal Blue (number
1901) for the underside of the wing and
stabilizer, and Banner Red (number 2108) for
the wingtips. The “THORN” lettering is cut
vinyl from the local truck-lettering shop.
After painting I applied Goop hinges for
ailerons and elevator, as described in the kit
instructions. They outline a top-notch method
for installing the Goop hinges, which are
similar to, but tougher than, silicone hinges.
I have to admit that I never got the hang of
silicone hinges, but I know how to install
them now. My main problem in the past was
applying too much adhesive, rendering the
finished hinges too stiff.
That’s all behind me now, thanks to the
instructions in the manual. I like the look of
these hinges applied after painting the parts;
the paint can look uneven and flake off of the
Goop hinges.
Radio Installation and Balance: I used an
Airtronics VG6000 transmitter for this
project. Although a two-channel rig will
suffice for the 60-inch-span Thorn, I have
grown accustomed to having rates and
exponential on slope sailplanes.
The designer recommends exponential,
and the VG6000 delivers all this in a
computer transmitter without menus. All
functions show on the LCD screen all the
time.
I installed a diminutive JR 610M receiver:
the smallest I had in stock. I’m thrilled with
the installation of the thin Hitec HS-125
servos for ailerons, and I used a JR NES-341
servo for elevator; I’ve grown accustomed to
their toughness.
The precut pockets (into wings ordered
from the factory to fit your choice of servo)
for the Hitec 125 aileron servos fit snugly and
make installing these servos go quickly using
nothing but the screws provided by the servo
maker. There’s plenty of room in the fuselage
for my JR-341 elevator servo; the same goes
for the microreceiver and Electrodynamics
battery pack.
I added 3 ounces of nose weight in the
battery compartment to balance my Thorn at
the extreme rear of the recommended balancepoint
range. I set the control-surface throws as
instructed in the manual, including specs for
high and low rates and approximately 85%
exponential on ailerons and elevator.
My ready-to-fly model weighs 59 ounces,
for a wing loading of 25 ounces per square foot.My Thorn took 7.5 hours to build
(including a couple hours engineering and
building the removable tail parts), 4.25
hours to finish with paint, and 3.5 hours to
install and test the radio gear, for a total of
15.25 hours of workbench time, spread
over two weeks.
Flying: For test-flying we had an earlyspring
day with some fine slope-flying
conditions over Lake Ontario near
Syracuse, New York. We fly from a 115-
foot escarpment, and that day we had a 15-
20 mph wind blowing into the hill from
approximately 10° left of perpendicular.
After a final radio check we heaved the
Thorn off of the ridge toward the lake.
After letting it dive for a few long seconds
to gather speed, I leveled it out and began
the classic figure-eight slope pattern.
The first turn went smoothly, and, still
accelerating, it came on step by the time it
crossed in front of me. The Thorn climbed
quickly and easily, and controls were
smooth, with no sign of twitchiness.
Phrases from years ago when flighttesting
my first sleek, fast sailplane (a Sig
Samurai) came to mind: “Cuts through the
air like a knife” and “It doesn’t care which
way the wind is blowing.” The wind
direction did not switch around to straightin
as forecast, so we had windy, slightly
cross conditions for the entire flying day.
The heavy Thorn reveled in these
conditions. It seems like all other pilots put
down foam sailplanes after a minute or
two of flying; they would not penetrate.
The Thorn was in its element; Joe Chovan
and I logged a one-hour flight, passing the
transmitter twice. Control throws were set
up according to the instructions, and we
did not take it off high rates.
Our conclusions about the Thorn’s
flight performance are as follows.
• It penetrates extremely well in vigorous
wind, including crosswinds and gusty
conditions.
• It exhibits smooth control movements,
with no evidence of twitchiness or
overcontrol.
• It performs moderately fast axial rolls—
more than one per second.
• It hangs in with inverted flight adequately,
but it does not love that flight condition.
• It does love the Cuban Eight maneuver.
Hammerhead stall turns and half-pipe
maneuvers are competent for an aircraft
without a working rudder. Inside loops are
solid, with no aileron correction needed. (I
have not tried outside loops yet.)
The result on an intentional forward stall
was fairly dramatic; the Thorn fell 20-30 feet
before recovering. This is not a surprise for a
sailplane with a wing loading exceeding 20
ounces per square foot. This stood as a
reminder to fly this, and all heavy sailplanes,
smoothly and without stalling them.
Throughout the flying session we did not
worry about lift coming and going. Keep this
model moving, and it flies fine in momentary
varying lift conditions.
I landed it back on top, shiny-side up in
grass. The landing broke one nylon wingmount
bolt, and the sailplane incurred no
other damage. I’m fully pleased with the
Thorn’s flight performance.
Many thanks to Joe Chovan for flying for
the camera. He’s great at it.
Given the uncommon construction materials,
the unusual solid-wood wing design, and the
advanced computer-controlled machining
used in the production of the parts, just
owning a Thorn kit puts you in the forefront
of Slope Soaring glider technology.
Spend the rather pleasant (if you like
working with wood) 5.5 hours building and
the satisfying (if you like finishing a model
with paint) 4.25 hours final-sanding, sealing,
and painting the model, and you’ll have a
slope speedster that impresses you and your
friends. The kit is sold at a righteous price. If
you like fast and unusual sailplanes, it’s hard
to see how you can go wrong with a Thorn.
There is even better news in the future: I
have already flown a prototype of the 100-
inch-span, six-servo version, and that was a
real fun time; the 2.5-meter version covers a
great deal of sky in a short time.
Furthermore, customer requests for
four-servo wings to incorporate flaps in
addition to ailerons have been fulfilled,
and 60- and 80-inch-span wings have been
shipped. Plane Insane Models is one maker
to watch.
The Thorn is impressive in the air. It
penetrates the wind well. It carves a smooth
course with no sign of twitchiness or
overcontrol. My Thorn is quick in axial rolls
and solid when flown through loops.
Although it’s not optimized for inverted
flight, it performs excellent Cuban Eights. A
stall becomes a serious departure from
controlled flight, and the aircraft must fall 20
feet or more before regaining flying speed and
recovering.
This is not a trainer; it is a heavy-wingloaded,
high-performance sailplane. For those
who delight in flying a fast, heavy glider, the
Thorn is an exceptional candidate to meet
your need for speed. MA
Manufacturer:
Plane Insane Models, Andreas Mergner
366 Hamilton St.
Albany NY 12210
(518) 542-9527
[email protected]
www.planeinsanemodels.com
Products Used in Review:
Airtronics VG6000 transmitter
www.airtronics.net
JR 610M receiver
www.horizonhobby.com
Hitec HS-125 aileron servos
www.hitecrcd.com
JR NES-341 elevator servo
www.horizonhobby.com
Electrodynamics battery pack
www.electrodynam.com
Minwax Polycrylic sanding sealer
www.minwax.com
Krylon rattle-can spray paint
www.krylon.com