September 2010 35
The author’s FlyBoy Models
Chipmunk sports a more
scale appearance because of
its Robart actuating struts—
and its landings are
smoother.
Straight stock wire landing gear offers minimal support and zero cushion
for rough fields. The Robart RoboStrut upgrade is easy.
very attractive scale appearance; here was a perfect excuse to improve
things functionally and make a major aesthetic boost in the process.
I considered making the gear longer to absorb some of the
landing jolt and hopefully make it more “springy,” to absorb the
initial jolt when aircraft and Mother Earth met.
Well-known Robart Manufacturing makes a set of springloaded
oleo struts for the similar-size Great Planes Chipmunk.
They seemed to be a perfect fit, so I ordered a set.
A week or so later they arrived on my front doorstep. The
struts were truly nice and would add much-needed scale looks to
the undercarriage of the Chipmunk, complementing the neat
Canadian Air Force livery.
The Robart oleo struts are remarkable. They consist of painted
tubular weldments that serve as the main body of the struts and
polished barrels that contain coil springs and a cast attachment for
the wire axles.
MY BIG DE HAVILLAND Chipmunk from FlyBoy Models
made a long, shallow approach and touched down on our grass
runway. It made a slight hop, as was usual because of its short,
stiff main landing gear, and settled into a long rollout. It had
almost come to a stop when the left wing dropped and the big
model slewed left and halted.
I uttered an epithet and then headed downfield to retrieve “Big
Bird,” as I had come to call the yellow airplane. I suspected that it
had encountered one of the many gopher holes at the far end of
the field.
The normal takeoff-and-landing area was devoid of such wheel
traps, but the Chipmunk, with its slight hop and long rollout, had
used much more runway than usual and ended up in the minefield.
The left side gear had folded back, almost touching
the wing.
The aircraft sorely needed a change in landing gear.
Its wire gear was the only departure from an otherwise
The right gear makes all the difference
Landings
Better
by Fred Randall
09sig2x_00MSTRPG.QXD 7/22/10 9:46 AM Page 35
36 MODEL AVIATION
Upgrades are typically part of a repair mission. The author’s
factory-installed gear block broke free. Glue and clamps left
on overnight assure the most secure bond possible.
A trick to disguise the repair is to lay in a patch of covering
over only the wood and then add a larger piece over the
whole area, to seal everything tight.
While landing my FlyBoy Models de Havilland
Chipmunk, the left gear collapsed back, almost touching
the wing. When I viewed the damage, I was baffled
because I didn’t know what could have caused the
collapse. The model had encountered no ruts or holes, as I
had originally feared.
Back at home, I removed the gear, cut away the
covering, and removed a rectangular section of balsa to
gain access to the structure. Then the reason for the break
became clear.
The part of the landing gear wire that extended into the
wing was too short. Underneath the 1/2-inch-thick external
mounting block, which had split, was another, drilled and
affixed to the wing structure and at least 1 inch deep.
It was clear that a new set of landing gear wires needed
to be fabricated. I made a set to eliminate the problem
with the originals and to accommodate the new struts.
Since the original gear mounting block was cleanly
split, I mixed some 30-minute epoxy and put the pieces
back together. I used ratchet clamps to hold the structure
together while the epoxy cured.
After examining the result for integrity, I replaced the
missing balsa planking and then filled and sanded it until
I could not feel the repair. Although it was not a perfect
match, AeroKote Cub Yellow was close. I applied similar
panels of the covering to both wings, to make it look as if
it were intended to be that way.
I used the original hardware to install new gear wires.
The inserted parts of these new wires extend deep into the
internal hardwood blocks and shouldn’t be as susceptible
to breakage as the original setup was. MA
—Fred Randall
Repair The
This shows the original and new landing gear systems. The
supplied gear was replaced with new wire that could be pinned
deeper into the torque block.
The Robart struts are supplied primed with a neutral gray
finish. They’re easy to disassemble and paint any color—Cub
Yellow, in this case.
Photos by the author
09sig2x_00MSTRPG.QXD 7/22/10 9:47 AM Page 36
T he pol ishe d bar rels slide within the
u pper c ylinders and pr ovide effecti ve
shock absorption. The two parts are
co nnected w ith knee- action lin ks th at
pr ovi de directi onal stabilit y, keep ing the
wheels poin ted st rai ght ah ead.
Pu ttin g It To geth er: The ori gina l landing
ge ar wir es are normally c ut do wn to al low
the Robart ol eo struts to be mou nted . B ut
since th is modificati on was part iall y
caused by the o rigi nals b eing too sh ort, a
ne w set of wires was in order.
I us ed a digital caliper to measure th e
diameter of the landing g ear wi re, and then
I called J osep h Can dela’s Cre ative
Hob bies in Men don, Ma ssachusetts, to
order a length . Th is ou tsta nding hobby
sho p has f acilities for laser c utting, she etmet
al fab ric atin g, and other servic es.
The new lan din g gear w ires were b ent
on a purpose-built fixtu re th at Joe had in a
bac k room. Bending thi s tou gh wir e would
have been a s truggle witho ut it .
As wi th the o riginal set, the wires w ere
bent to extend the wheels fo rward to th e
wing LE. If tha t was not don e, the wh eel
center would have been dir ectly on the
balance point —not a good idea.
The new wir es wer e made longer than
the originals, to e xtend farther i nto t he
lowe r rein for cing b lock w ith in the w ing .
The ends of t he wire that exte nded t o the
whe els were cut a t an inch down from the
wing, providing a moun ting point for th e
new o leo st ruts .
As suppli ed, the p aint ed portions of the
struts are fini shed with a gray-green
prim er. I decided to pai nt the b arrels of t he
struts Top Flite Cub Yellow, a s was used
to paint the plas tic parts o f the Ch ipmunk.
The pr imed f ini sh didn’t s eem to b e a
good b ase fo r the y ello w paint, so I
disassem bled the struts a nd so aked the
p rim ed par ts in aceto ne, which eff ectively
removed the fact ory primer. T hen I
mask ed and spray ed the stru ts wi th sev eral
coats of Top Flite white primer. Whe n it
h ad dried su ffic ient ly, I app lied the fi nish
coats a nd re assemble d the struts.
Repai ring the la nding gear moun t was
relat ivel y simple. (Se e sidebar.) I a ppl ied a
s mall a mount of ep oxy to the hardwood
mount , to p rev ent fore-a nd-aft movement,
and mounted the landin g gear wire s using
t he original hardwar e. Then I inser ted th e
ex pos ed ends of th e gear wires in the
ba rrels of the new oleo struts and re tain ed
them with setscrews pr ovided in t he
Ro bart kit.
The provided axle s hafts are q uite l ong ,
to a ccom modate various-w idth wheel s. I
cu t them to the p roper length us ing a
ro tary-tool cut off wheel, an d then I
installed an d ret ained the s hafts usin g
mo re of th e rob ust se tscrews . Finally I
in stalled the origin al wheels u sing spacers
and whe el collars .
Th e finishe d inst all atio n is at trac tive and
much more sca leli ke than the o rigi nal.
Shock- absorbing oleo str uts al so preven t
th e hop on touchdow n, allowing t he mo del
to remain pla nted . Th at shorte ns the
landin g run to less than h alf of w hat it
was—a wi n-wi n sit uati on.
Th e Roba rt oleo str uts ha ve be en a
wor thw hile addit ion t o my de H avil land
Chi pmunk. MA
Fred Randall
aeromode [email protected]
Sources:
Fly Boy M odel s
(62 6) 922 -4181
www.f lyboymo dels .com
Rob art Manufa cturing
(63 0) 584 -761 6
www.r obart.com
Crea tiv e Hobb ies
(508) 473 -825 9
www.cr eativeh obbies.net
Top Flite
(800) 637- 766 0
www.to p-flite .com
38 MODEL AVIATION
09sig2x_00MSTRPG.QXD 7/22/10 9:47 AM Page 38
Edition: Model Aviation - 2010/09
Page Numbers: 35,36,38
Edition: Model Aviation - 2010/09
Page Numbers: 35,36,38
September 2010 35
The author’s FlyBoy Models
Chipmunk sports a more
scale appearance because of
its Robart actuating struts—
and its landings are
smoother.
Straight stock wire landing gear offers minimal support and zero cushion
for rough fields. The Robart RoboStrut upgrade is easy.
very attractive scale appearance; here was a perfect excuse to improve
things functionally and make a major aesthetic boost in the process.
I considered making the gear longer to absorb some of the
landing jolt and hopefully make it more “springy,” to absorb the
initial jolt when aircraft and Mother Earth met.
Well-known Robart Manufacturing makes a set of springloaded
oleo struts for the similar-size Great Planes Chipmunk.
They seemed to be a perfect fit, so I ordered a set.
A week or so later they arrived on my front doorstep. The
struts were truly nice and would add much-needed scale looks to
the undercarriage of the Chipmunk, complementing the neat
Canadian Air Force livery.
The Robart oleo struts are remarkable. They consist of painted
tubular weldments that serve as the main body of the struts and
polished barrels that contain coil springs and a cast attachment for
the wire axles.
MY BIG DE HAVILLAND Chipmunk from FlyBoy Models
made a long, shallow approach and touched down on our grass
runway. It made a slight hop, as was usual because of its short,
stiff main landing gear, and settled into a long rollout. It had
almost come to a stop when the left wing dropped and the big
model slewed left and halted.
I uttered an epithet and then headed downfield to retrieve “Big
Bird,” as I had come to call the yellow airplane. I suspected that it
had encountered one of the many gopher holes at the far end of
the field.
The normal takeoff-and-landing area was devoid of such wheel
traps, but the Chipmunk, with its slight hop and long rollout, had
used much more runway than usual and ended up in the minefield.
The left side gear had folded back, almost touching
the wing.
The aircraft sorely needed a change in landing gear.
Its wire gear was the only departure from an otherwise
The right gear makes all the difference
Landings
Better
by Fred Randall
09sig2x_00MSTRPG.QXD 7/22/10 9:46 AM Page 35
36 MODEL AVIATION
Upgrades are typically part of a repair mission. The author’s
factory-installed gear block broke free. Glue and clamps left
on overnight assure the most secure bond possible.
A trick to disguise the repair is to lay in a patch of covering
over only the wood and then add a larger piece over the
whole area, to seal everything tight.
While landing my FlyBoy Models de Havilland
Chipmunk, the left gear collapsed back, almost touching
the wing. When I viewed the damage, I was baffled
because I didn’t know what could have caused the
collapse. The model had encountered no ruts or holes, as I
had originally feared.
Back at home, I removed the gear, cut away the
covering, and removed a rectangular section of balsa to
gain access to the structure. Then the reason for the break
became clear.
The part of the landing gear wire that extended into the
wing was too short. Underneath the 1/2-inch-thick external
mounting block, which had split, was another, drilled and
affixed to the wing structure and at least 1 inch deep.
It was clear that a new set of landing gear wires needed
to be fabricated. I made a set to eliminate the problem
with the originals and to accommodate the new struts.
Since the original gear mounting block was cleanly
split, I mixed some 30-minute epoxy and put the pieces
back together. I used ratchet clamps to hold the structure
together while the epoxy cured.
After examining the result for integrity, I replaced the
missing balsa planking and then filled and sanded it until
I could not feel the repair. Although it was not a perfect
match, AeroKote Cub Yellow was close. I applied similar
panels of the covering to both wings, to make it look as if
it were intended to be that way.
I used the original hardware to install new gear wires.
The inserted parts of these new wires extend deep into the
internal hardwood blocks and shouldn’t be as susceptible
to breakage as the original setup was. MA
—Fred Randall
Repair The
This shows the original and new landing gear systems. The
supplied gear was replaced with new wire that could be pinned
deeper into the torque block.
The Robart struts are supplied primed with a neutral gray
finish. They’re easy to disassemble and paint any color—Cub
Yellow, in this case.
Photos by the author
09sig2x_00MSTRPG.QXD 7/22/10 9:47 AM Page 36
T he pol ishe d bar rels slide within the
u pper c ylinders and pr ovide effecti ve
shock absorption. The two parts are
co nnected w ith knee- action lin ks th at
pr ovi de directi onal stabilit y, keep ing the
wheels poin ted st rai ght ah ead.
Pu ttin g It To geth er: The ori gina l landing
ge ar wir es are normally c ut do wn to al low
the Robart ol eo struts to be mou nted . B ut
since th is modificati on was part iall y
caused by the o rigi nals b eing too sh ort, a
ne w set of wires was in order.
I us ed a digital caliper to measure th e
diameter of the landing g ear wi re, and then
I called J osep h Can dela’s Cre ative
Hob bies in Men don, Ma ssachusetts, to
order a length . Th is ou tsta nding hobby
sho p has f acilities for laser c utting, she etmet
al fab ric atin g, and other servic es.
The new lan din g gear w ires were b ent
on a purpose-built fixtu re th at Joe had in a
bac k room. Bending thi s tou gh wir e would
have been a s truggle witho ut it .
As wi th the o riginal set, the wires w ere
bent to extend the wheels fo rward to th e
wing LE. If tha t was not don e, the wh eel
center would have been dir ectly on the
balance point —not a good idea.
The new wir es wer e made longer than
the originals, to e xtend farther i nto t he
lowe r rein for cing b lock w ith in the w ing .
The ends of t he wire that exte nded t o the
whe els were cut a t an inch down from the
wing, providing a moun ting point for th e
new o leo st ruts .
As suppli ed, the p aint ed portions of the
struts are fini shed with a gray-green
prim er. I decided to pai nt the b arrels of t he
struts Top Flite Cub Yellow, a s was used
to paint the plas tic parts o f the Ch ipmunk.
The pr imed f ini sh didn’t s eem to b e a
good b ase fo r the y ello w paint, so I
disassem bled the struts a nd so aked the
p rim ed par ts in aceto ne, which eff ectively
removed the fact ory primer. T hen I
mask ed and spray ed the stru ts wi th sev eral
coats of Top Flite white primer. Whe n it
h ad dried su ffic ient ly, I app lied the fi nish
coats a nd re assemble d the struts.
Repai ring the la nding gear moun t was
relat ivel y simple. (Se e sidebar.) I a ppl ied a
s mall a mount of ep oxy to the hardwood
mount , to p rev ent fore-a nd-aft movement,
and mounted the landin g gear wire s using
t he original hardwar e. Then I inser ted th e
ex pos ed ends of th e gear wires in the
ba rrels of the new oleo struts and re tain ed
them with setscrews pr ovided in t he
Ro bart kit.
The provided axle s hafts are q uite l ong ,
to a ccom modate various-w idth wheel s. I
cu t them to the p roper length us ing a
ro tary-tool cut off wheel, an d then I
installed an d ret ained the s hafts usin g
mo re of th e rob ust se tscrews . Finally I
in stalled the origin al wheels u sing spacers
and whe el collars .
Th e finishe d inst all atio n is at trac tive and
much more sca leli ke than the o rigi nal.
Shock- absorbing oleo str uts al so preven t
th e hop on touchdow n, allowing t he mo del
to remain pla nted . Th at shorte ns the
landin g run to less than h alf of w hat it
was—a wi n-wi n sit uati on.
Th e Roba rt oleo str uts ha ve be en a
wor thw hile addit ion t o my de H avil land
Chi pmunk. MA
Fred Randall
aeromode [email protected]
Sources:
Fly Boy M odel s
(62 6) 922 -4181
www.f lyboymo dels .com
Rob art Manufa cturing
(63 0) 584 -761 6
www.r obart.com
Crea tiv e Hobb ies
(508) 473 -825 9
www.cr eativeh obbies.net
Top Flite
(800) 637- 766 0
www.to p-flite .com
38 MODEL AVIATION
09sig2x_00MSTRPG.QXD 7/22/10 9:47 AM Page 38
Edition: Model Aviation - 2010/09
Page Numbers: 35,36,38
September 2010 35
The author’s FlyBoy Models
Chipmunk sports a more
scale appearance because of
its Robart actuating struts—
and its landings are
smoother.
Straight stock wire landing gear offers minimal support and zero cushion
for rough fields. The Robart RoboStrut upgrade is easy.
very attractive scale appearance; here was a perfect excuse to improve
things functionally and make a major aesthetic boost in the process.
I considered making the gear longer to absorb some of the
landing jolt and hopefully make it more “springy,” to absorb the
initial jolt when aircraft and Mother Earth met.
Well-known Robart Manufacturing makes a set of springloaded
oleo struts for the similar-size Great Planes Chipmunk.
They seemed to be a perfect fit, so I ordered a set.
A week or so later they arrived on my front doorstep. The
struts were truly nice and would add much-needed scale looks to
the undercarriage of the Chipmunk, complementing the neat
Canadian Air Force livery.
The Robart oleo struts are remarkable. They consist of painted
tubular weldments that serve as the main body of the struts and
polished barrels that contain coil springs and a cast attachment for
the wire axles.
MY BIG DE HAVILLAND Chipmunk from FlyBoy Models
made a long, shallow approach and touched down on our grass
runway. It made a slight hop, as was usual because of its short,
stiff main landing gear, and settled into a long rollout. It had
almost come to a stop when the left wing dropped and the big
model slewed left and halted.
I uttered an epithet and then headed downfield to retrieve “Big
Bird,” as I had come to call the yellow airplane. I suspected that it
had encountered one of the many gopher holes at the far end of
the field.
The normal takeoff-and-landing area was devoid of such wheel
traps, but the Chipmunk, with its slight hop and long rollout, had
used much more runway than usual and ended up in the minefield.
The left side gear had folded back, almost touching
the wing.
The aircraft sorely needed a change in landing gear.
Its wire gear was the only departure from an otherwise
The right gear makes all the difference
Landings
Better
by Fred Randall
09sig2x_00MSTRPG.QXD 7/22/10 9:46 AM Page 35
36 MODEL AVIATION
Upgrades are typically part of a repair mission. The author’s
factory-installed gear block broke free. Glue and clamps left
on overnight assure the most secure bond possible.
A trick to disguise the repair is to lay in a patch of covering
over only the wood and then add a larger piece over the
whole area, to seal everything tight.
While landing my FlyBoy Models de Havilland
Chipmunk, the left gear collapsed back, almost touching
the wing. When I viewed the damage, I was baffled
because I didn’t know what could have caused the
collapse. The model had encountered no ruts or holes, as I
had originally feared.
Back at home, I removed the gear, cut away the
covering, and removed a rectangular section of balsa to
gain access to the structure. Then the reason for the break
became clear.
The part of the landing gear wire that extended into the
wing was too short. Underneath the 1/2-inch-thick external
mounting block, which had split, was another, drilled and
affixed to the wing structure and at least 1 inch deep.
It was clear that a new set of landing gear wires needed
to be fabricated. I made a set to eliminate the problem
with the originals and to accommodate the new struts.
Since the original gear mounting block was cleanly
split, I mixed some 30-minute epoxy and put the pieces
back together. I used ratchet clamps to hold the structure
together while the epoxy cured.
After examining the result for integrity, I replaced the
missing balsa planking and then filled and sanded it until
I could not feel the repair. Although it was not a perfect
match, AeroKote Cub Yellow was close. I applied similar
panels of the covering to both wings, to make it look as if
it were intended to be that way.
I used the original hardware to install new gear wires.
The inserted parts of these new wires extend deep into the
internal hardwood blocks and shouldn’t be as susceptible
to breakage as the original setup was. MA
—Fred Randall
Repair The
This shows the original and new landing gear systems. The
supplied gear was replaced with new wire that could be pinned
deeper into the torque block.
The Robart struts are supplied primed with a neutral gray
finish. They’re easy to disassemble and paint any color—Cub
Yellow, in this case.
Photos by the author
09sig2x_00MSTRPG.QXD 7/22/10 9:47 AM Page 36
T he pol ishe d bar rels slide within the
u pper c ylinders and pr ovide effecti ve
shock absorption. The two parts are
co nnected w ith knee- action lin ks th at
pr ovi de directi onal stabilit y, keep ing the
wheels poin ted st rai ght ah ead.
Pu ttin g It To geth er: The ori gina l landing
ge ar wir es are normally c ut do wn to al low
the Robart ol eo struts to be mou nted . B ut
since th is modificati on was part iall y
caused by the o rigi nals b eing too sh ort, a
ne w set of wires was in order.
I us ed a digital caliper to measure th e
diameter of the landing g ear wi re, and then
I called J osep h Can dela’s Cre ative
Hob bies in Men don, Ma ssachusetts, to
order a length . Th is ou tsta nding hobby
sho p has f acilities for laser c utting, she etmet
al fab ric atin g, and other servic es.
The new lan din g gear w ires were b ent
on a purpose-built fixtu re th at Joe had in a
bac k room. Bending thi s tou gh wir e would
have been a s truggle witho ut it .
As wi th the o riginal set, the wires w ere
bent to extend the wheels fo rward to th e
wing LE. If tha t was not don e, the wh eel
center would have been dir ectly on the
balance point —not a good idea.
The new wir es wer e made longer than
the originals, to e xtend farther i nto t he
lowe r rein for cing b lock w ith in the w ing .
The ends of t he wire that exte nded t o the
whe els were cut a t an inch down from the
wing, providing a moun ting point for th e
new o leo st ruts .
As suppli ed, the p aint ed portions of the
struts are fini shed with a gray-green
prim er. I decided to pai nt the b arrels of t he
struts Top Flite Cub Yellow, a s was used
to paint the plas tic parts o f the Ch ipmunk.
The pr imed f ini sh didn’t s eem to b e a
good b ase fo r the y ello w paint, so I
disassem bled the struts a nd so aked the
p rim ed par ts in aceto ne, which eff ectively
removed the fact ory primer. T hen I
mask ed and spray ed the stru ts wi th sev eral
coats of Top Flite white primer. Whe n it
h ad dried su ffic ient ly, I app lied the fi nish
coats a nd re assemble d the struts.
Repai ring the la nding gear moun t was
relat ivel y simple. (Se e sidebar.) I a ppl ied a
s mall a mount of ep oxy to the hardwood
mount , to p rev ent fore-a nd-aft movement,
and mounted the landin g gear wire s using
t he original hardwar e. Then I inser ted th e
ex pos ed ends of th e gear wires in the
ba rrels of the new oleo struts and re tain ed
them with setscrews pr ovided in t he
Ro bart kit.
The provided axle s hafts are q uite l ong ,
to a ccom modate various-w idth wheel s. I
cu t them to the p roper length us ing a
ro tary-tool cut off wheel, an d then I
installed an d ret ained the s hafts usin g
mo re of th e rob ust se tscrews . Finally I
in stalled the origin al wheels u sing spacers
and whe el collars .
Th e finishe d inst all atio n is at trac tive and
much more sca leli ke than the o rigi nal.
Shock- absorbing oleo str uts al so preven t
th e hop on touchdow n, allowing t he mo del
to remain pla nted . Th at shorte ns the
landin g run to less than h alf of w hat it
was—a wi n-wi n sit uati on.
Th e Roba rt oleo str uts ha ve be en a
wor thw hile addit ion t o my de H avil land
Chi pmunk. MA
Fred Randall
aeromode [email protected]
Sources:
Fly Boy M odel s
(62 6) 922 -4181
www.f lyboymo dels .com
Rob art Manufa cturing
(63 0) 584 -761 6
www.r obart.com
Crea tiv e Hobb ies
(508) 473 -825 9
www.cr eativeh obbies.net
Top Flite
(800) 637- 766 0
www.to p-flite .com
38 MODEL AVIATION
09sig2x_00MSTRPG.QXD 7/22/10 9:47 AM Page 38
