(Editor’s note: This is the second of a two-part series, the first of
which was published in last month’s issue.)
MOTOR-BOX CONSTRUCTION: The instructions mention some
longitudinal reinforcement pieces for the motor-box construction, but
the photographs look as if the covering is removed from the side of
the aircraft when they’re installed. The airplane was originally
designed with the front hatch removable so that those pieces would be
fine to fit into place, but with the present design it is impossible to fit
those pieces into the fuselage without some deconstruction. So even
though the parts are there and the instructions discuss it, the bracing is
left out.
The instructions advise to measure for the motor-box length and
cut them to fit, but I left the motor-box sides at full length. Right
thrust is already calculated, but you must mark the thrustline and
calculate the centerline offset on the firewall so that the engine will
still exit the cowl in the center. I did this and drilled the firewall for
blind nuts for the engine before it was glued into the model.
Once the motor-box sides are in place, the firewall is supposed to
be gusseted with spruce triangle stock, but the factory supplied only
balsa. If you go out and find some 1/2 spruce triangle stock and epoxy
it in place, you’ll be fine, but I had already glued the balsa into the
motor box. Rather than tear all that out, Aeroworks suggested that I
bolt some 3/4-inch angled aluminum to the outside of the motor box—
a perfect solution.
Landing Gear: The instructions for the
landing-gear installation were vague. The
gear is clearly swept, but there is no mention
of which orientation the sweep is intended
for! Then there is the matter of the bolt holes
that are predrilled in the gear. You are
supplied with 10-32 cap screws and blind nuts
to mount the gear, but the gear is drilled to 5/16
inch. The No. 10 cap screws’ heads pass right
through! Sweep the gear toward the rear of
the airplane. The axles should be almost even
with the LE of the bottom wing at the root.
Aeroworks indicated that the latest
production run was complete and all of the
kits were drilled like this. The company
suggested that I drill the holes a little larger
and use some wheel collars as a sleeve in the
oversized landing-gear holes and use a hefty
fender washer under the cap screw.
Instead of doing that, I found some 5/16 x
1/4-inch aluminum bushings at the hardware
store that fit perfectly, and I found the right
size of washer to work with the gear. Either
way will yield the same results.
Gas Tank: Putting together a proper gas tank
is one of those things you probably won’t see
June 2005 33
According to the author, this model is a dream to fly. It tracks like a competition aircraft,
yet it can be set up to fly 3-D with the best of them.
Although the Aeroworks 33% Ultimate biplane’s span just
exceeds 6 feet, it is still a fairly large airplane, making it perfect
for a 100cc engine.
Giant Scale Aerobatic
ARF Building Tips by Mike Hurley
Part 2
Photos by the author
use the fitting because it’s a solid mount and it’s neat. You can close off
the vent during transportation and moving the model in and out of the
shop. The vent is kept open during flight and storage so the tank doesn’t
deform or rupture.
The pickup line goes directly to the carburetor. I use a “T” fitting in
the pickup as a fill line. Just exit the side of the fuselage or the cowl and
plug it off with a fuel dot. You cannot flood the engine during fueling
with this method. Gasoline carburetors have a needle and seat that
won’t allow gas into the system while the engine is not running.
The Hatch: I was unhappy with the way the hatch fit out of the box.
The rear canopy former was too large, so the canopy didn’t match to the
turtledeck very well. The aft hold-down tabs are supposed to fit tight in
the fuselage but had quite a bit of play. Attempting to tighten those rear
bolts would surely have led to a broken tab, and one of the hold-down
bolts wouldn’t engage because of misaligned holes. So a little work was
in order to clear those things up.
I sanded the rear canopy former to fit the turtledeck. That took
approximately 10 minutes. For the tabs to fit I had to add 1/32 plywood
to the outside of the tabs, but before that I popped the blind nut out of
the tab that didn’t line up and plugged the hole with a dowel. Then I
added the plywood and sanded to get a nice, snug fit. After that, all that
was left was to redrill the plugged tab, using the fuselage as a fixture,
and reinstall the blind nut.
I want to pass along a building tip that makes a great deal of sense
when working with ARFs. Use a machine screw into a blind nut
whenever possible and try to avoid using wood screws, especially into
balsa. If you have many wood screws in your airplane and have access,
change them to bolts with blind nuts.
As a final step, use the appropriate thread locker on all machine
screws and cyanoacrylate on wood screws. The only exception I can
think of is propeller bolts; I don’t use thread locker there.
The Finished Product: I’ve discussed many things I had to fine-tune or
adjust with this model, but I haven’t touched on the things that worked
or fit exceptionally well. The vertical fin’s construction and the way it
integrates into the rear of the fuselage is outstanding, with a tight fit and
perfect alignment. Likewise for the horizontal stabilizers; the fit to the
fuselage sides is perfect, and there is no slop in the joiner tubes or
alignment pins. In general, the aircraft has excellent fit with tight joints
and no slop.
For a factory-built ARF, all of the incidences were amazingly close.
I doubt if my adjustments made much difference in flight. The quality
of the fiberglass parts, the wood, and the construction overall is firstrate.
And as I mentioned, there’s no cheap or inappropriate hardware or
materials anywhere in this kit. The same cannot be said for all ARFs.
You can see where some experience with building and with large
aerobatic models may pay off when building an ARF. Much of this
model’s fit and finish work is left to the builder and without clear
Finished motor box augmented with aluminum angles for
strength. Because Mike prefers no air pressure inside fuselage,
he covered all lightening holes with clear MonoKote.
Since gasoline engines tend to vibrate, Mike recommends
replacing wood screws with blind nuts. Here, blind nuts are used
in tabs attaching cowl to fuselage.
Four servos were located in rear of fuselage. After length of
servo wiring extensions were calculated, all four leads were
taped to wire fed through provided fiberglass wiring tube and
fished through tube together.
34 MODEL AVIATION
in any instruction manual. Most modelers are supposed to know how
to do that, but every year I hear of another airplane going down
because of fuel tank-problems. I used a 32-ounce Du-Bro tank for this
model.
I like a tight-fitting stopper cap and really horse the screw that
holds it all together (without deforming the stopper). With the OEM
plastic caps, overtightening will cause the cap to collapse. So I use the
machined aluminum caps from SWB. Be sure you use the gascompatible
red rubber stopper that comes with the tank.
The first part in assembling the tank is to solder a barb to the
internal end of the pickup tube. This is important to keep the clunk
line from falling off inside the tank. You can get the barbs from Du-
Bro.
If you have to cut the copper tubes, be sure to chamfer all of the
edges to relieve any sharp corners that may cut into the Tygon tubing
during use. I use Tygon tubing from Du-Bro and Easy Flex from
Aerotrend; both are 1/8 inch in inside diameter.
Be sure to secure all of the hoses with a nylon wire tie. Bend the
copper portion of the pickup tube down inside the tank a bit; this will
put the flexible portion of the pickup in a central location so that the
clunk line will be the same length upright, inverted, or in any
orientation. Make sure the clunk moves freely inside the tank and
reaches the back corners as closely as possible without hindering any
movement.
The vent curves up to the top of the tank just behind the stopper.
Make sure it can’t be blocked off by the inside wall of the tank.
Outside the tank I loop the vent line back behind the rear edge of the
tank so that fuel cannot pour out while in flight. You’ll be surprised
by how much your fuel consumption will be improved with this
simple loop!
The vent simply exits the bottom of the cowl to a B&B fitting. I
instruction at times. But for me, those steps left up to the builder
ensure a better finished product.
I’ve done enough of the work on this airplane to know that all the
parts fit well, its alignment is spot on, and there’s nothing left to
question. This ARF is as solid as any of the aircraft I’ve built, and it’s
just as good as many of them.
The guys at Aeroworks were always there and happy to help with
my questions. I’m probably one of those perfectionists who really
shouldn’t build an ARF; but for a perfectionist, I’m pretty darn
pleased with the finished product. In fact, I’m downright stoked! I
don’t see this Ultimate as an ARF anymore; it feels like any airplane I
would have built, and I think the finished model’s quality is what
gives me such confidence.
Flying: As all biplanes do, the Aeroworks Ultimate takes a bit more
time and effort to field-assemble. At first it seemed as if the flyingwire
setup would make life easier, but so far I’ve had to readjust them
after every flight. I’m reasonably sure there will come a point when
they will settle in and stay taut.
I went with a three-blade propeller because the Ultimate’s
advertised flying weight was 24-25 pounds, but mine came in at 27
pounds, 10 ounces. At our mile-high altitude here in Denver, a 100cc
engine on a three-blade at that weight isn’t going to have all the power
I wanted, but I’ll give the three-blade a couple flights before I switch
to the two-blade. The three-blade Mejzlik 25 x 12 was noticeably
quieter than my other DA engines with two-blade propellers during
the first flight tests.
I had not prerun the engine or made any adjustments to it before
going out to the field. Once the DA-100 was primed, it fired and
started easily. After a few minutes to let it warm up, we did a range
check with the engine running and inspected the throttle response. The
engine was a tad on the lean side but responded well, so I made the
first flight without a single adjustment or tweak of the needle.
Precision Flight: The Aeroworks Ultimate is rock solid and grooves
like a Pattern airplane. The ailerons are extremely effective and rolls
are axial. I hadn’t even looked at the recommended throws; I set
everything to max for the first flight and adjusted from there according
to performance. I don’t recommend that you do this unless you have
considerable flying experience and feel comfortable with extreme
throws in flight. I dialed down the throw on the ailerons for the next
few flights, and I’ll be dialing up the exponential on the next outing.
The rudder is also effective but accurate, meaning that finessing
the yaw on this airplane was easier than on some other models I’ve
flown. The elevators are not overly powerful but adequate. There’s
little pitch coupling and even less roll. I’ll worry about mixing that out
when I get a little further along in the trimming process.
At the initial balance point, inverted flight is a thing of beauty. The
airplane doesn’t drop right away and gives me time to feel for exactly
the right amount of down-elevator pressure, delivering a seamless half
roll into a direct horizontal line. I felt that it required only slight
pressure on the stick to hold the line. Unless you are doing an
extremely slow roll, rudder input is just not needed to control the line
in a roll.
Up and down vertical lines had good tendencies in yaw, with no
left or right wandering, but did tend to pull to the canopy on downlines,
requiring some down-elevator pressure. Because of this, rolls
on the down-line are affected, giving the airplane a nasty wobble. I
may experiment with mixing or some upthrust to help fix the problem
later.
I had the balance set slightly aft of the recommended starting
position but well within flying specifications. Moving the balance
forward will help the pull on the vertical down-line if it doesn’t
completely eliminate the problem. The balance point will also affect
the feel in inverted flight, the need for rudder in rolling maneuvers,
and the amount of mix needed to adjust for coupling. I may
experiment with that later.
From my initial experiences, I think the Aeroworks Ultimate
would make a great platform for IMAC (International Miniature
Aerobatic Club)-style competition.
3-D Freestyle: 3-D on the Ultimate is not for beginners. Although
high-alpha flight is controllable with the strong ailerons, the model
rocks rapidly, needing quick responses and a keen eye. An
experienced 3-D pilot can get on the stick in short order with some
practice and the airplane will do almost any 3-D maneuver, but this is
probably not the best model for those who want to do 3-D for the first
time.
Holes in supplied landing gear were drilled too large from the
factory. Mike shows 5/16 x 1/4-inch bushings and washers used to
mount the gear.
The Ultimate’s fuel tank is mounted on separate platform, as a
module, then bolted in place using blind nuts. Mike wraps vent
line toward rear of tank to prevent overflow during flight.
DA-100 engine was mounted using polyurethane standoffs cut
from kitchen cutting board. Electrical components are protected
from vibration and wear with neoprene sleeves. Braided steel
spark-plug wires are protected with nylon automotive wire wrap.
Make sure all electrical connections are well secure.
Inverted high-alpha flight is doable
with the Ultimate, but, again, you have to
be on the ball with the ailerons and know
the rudder corrections; the model can roll
out quickly. Outside Waterfalls had a
tendency to roll out on the last quarter, and
inverted flat spins take a little finesse and
some modulation on the elevator and
throttle.
Because the roll rate is so fast on this
airplane, Blenders can be extremely
violent. Imagine the model rolling at a rate
you can’t even count, and then it explodes
into a blurry ball and just stops like it
reappeared from warp drive! Kind of
scary.
Torque rolls and hovering are a blast
and come easily with this 33% Ultimate,
but beware: once its thrust vector hits the
vertical balance point, the model will
rotate rapidly. A 5° tilt in any direction
will stop the torque roll.
Aeroworks indicated that it has had the
best success when the airplane is outfitted
for “3D mode”; that is, to move the CG
roughly an inch behind its center point and
increase the elevator throw to
approximately 65°. Setting the model up
like this could remove some of the rollout
problems I was having. But I found the 3-
D performance perfectly acceptable at a
“normal” 3-D setup of a neutral balance
point and only 45° of elevator throw.
The Ultimate biplane can get wild
doing ultrafast snaps and rolling in a blur.
Tumbles are crazy tight and knife-edge is
amazing with the ability to do
extraordinarily tight knife-edge loops and
Figure 8s. I’ll continue to experiment with
3-D flight, and in the meantime I’ll enjoy
what it does well right off the board.
It seems that the Ultimate can be set up
as either a good precision aircraft or a
good 3-D aircraft, but it may be difficult to
set up to do both well in the same flight. It
is not like a scale monoplane, but you
already knew that. It’s best to capitalize on
its strong points and enjoy the uniqueness
of a high-performance biplane. Whether
you want a competition model that stands
out in a crowd or an outrageous Freestyle
airplane, the Ultimate can be set up to
excel.
Although the 33% Aeroworks Ultimate
biplane was the subject for this article, it
was not meant to be a kit review, but
rather a collection of thoughts that could
be adapted to other Giant Scale aerobatic
ARF kits. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
Manufacturers:
JR radio equipment:
Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 352-1913
Toll-free: (800) 338-4639
Fax: (217) 355-1552
www.horizonhobby.com/
Engine, mufflers, propeller:
Desert Aircraft
1815 S. Research Loop
Tucson AZ 85710
(520) 722-0607
Fax: (520) 722-5622
www.desertaircraft.com/
4-inch Ultimate spinner:
Tru-Turn Precision Model Products
100 W. 1st St.
Deer Park TX 77536
(281) 479-9600
Fax: (281) 479-9090
www.tru-turn.com/
33% Ultimate biplane:
Aeroworks
401 Laredo St. Suite D
Aurora CO 80011
(303) 366-4205
Fax: (303) 366-4203
www.aero-works.net/
Edition: Model Aviation - 2005/06
Page Numbers: 33,34,35,37
Edition: Model Aviation - 2005/06
Page Numbers: 33,34,35,37
(Editor’s note: This is the second of a two-part series, the first of
which was published in last month’s issue.)
MOTOR-BOX CONSTRUCTION: The instructions mention some
longitudinal reinforcement pieces for the motor-box construction, but
the photographs look as if the covering is removed from the side of
the aircraft when they’re installed. The airplane was originally
designed with the front hatch removable so that those pieces would be
fine to fit into place, but with the present design it is impossible to fit
those pieces into the fuselage without some deconstruction. So even
though the parts are there and the instructions discuss it, the bracing is
left out.
The instructions advise to measure for the motor-box length and
cut them to fit, but I left the motor-box sides at full length. Right
thrust is already calculated, but you must mark the thrustline and
calculate the centerline offset on the firewall so that the engine will
still exit the cowl in the center. I did this and drilled the firewall for
blind nuts for the engine before it was glued into the model.
Once the motor-box sides are in place, the firewall is supposed to
be gusseted with spruce triangle stock, but the factory supplied only
balsa. If you go out and find some 1/2 spruce triangle stock and epoxy
it in place, you’ll be fine, but I had already glued the balsa into the
motor box. Rather than tear all that out, Aeroworks suggested that I
bolt some 3/4-inch angled aluminum to the outside of the motor box—
a perfect solution.
Landing Gear: The instructions for the
landing-gear installation were vague. The
gear is clearly swept, but there is no mention
of which orientation the sweep is intended
for! Then there is the matter of the bolt holes
that are predrilled in the gear. You are
supplied with 10-32 cap screws and blind nuts
to mount the gear, but the gear is drilled to 5/16
inch. The No. 10 cap screws’ heads pass right
through! Sweep the gear toward the rear of
the airplane. The axles should be almost even
with the LE of the bottom wing at the root.
Aeroworks indicated that the latest
production run was complete and all of the
kits were drilled like this. The company
suggested that I drill the holes a little larger
and use some wheel collars as a sleeve in the
oversized landing-gear holes and use a hefty
fender washer under the cap screw.
Instead of doing that, I found some 5/16 x
1/4-inch aluminum bushings at the hardware
store that fit perfectly, and I found the right
size of washer to work with the gear. Either
way will yield the same results.
Gas Tank: Putting together a proper gas tank
is one of those things you probably won’t see
June 2005 33
According to the author, this model is a dream to fly. It tracks like a competition aircraft,
yet it can be set up to fly 3-D with the best of them.
Although the Aeroworks 33% Ultimate biplane’s span just
exceeds 6 feet, it is still a fairly large airplane, making it perfect
for a 100cc engine.
Giant Scale Aerobatic
ARF Building Tips by Mike Hurley
Part 2
Photos by the author
use the fitting because it’s a solid mount and it’s neat. You can close off
the vent during transportation and moving the model in and out of the
shop. The vent is kept open during flight and storage so the tank doesn’t
deform or rupture.
The pickup line goes directly to the carburetor. I use a “T” fitting in
the pickup as a fill line. Just exit the side of the fuselage or the cowl and
plug it off with a fuel dot. You cannot flood the engine during fueling
with this method. Gasoline carburetors have a needle and seat that
won’t allow gas into the system while the engine is not running.
The Hatch: I was unhappy with the way the hatch fit out of the box.
The rear canopy former was too large, so the canopy didn’t match to the
turtledeck very well. The aft hold-down tabs are supposed to fit tight in
the fuselage but had quite a bit of play. Attempting to tighten those rear
bolts would surely have led to a broken tab, and one of the hold-down
bolts wouldn’t engage because of misaligned holes. So a little work was
in order to clear those things up.
I sanded the rear canopy former to fit the turtledeck. That took
approximately 10 minutes. For the tabs to fit I had to add 1/32 plywood
to the outside of the tabs, but before that I popped the blind nut out of
the tab that didn’t line up and plugged the hole with a dowel. Then I
added the plywood and sanded to get a nice, snug fit. After that, all that
was left was to redrill the plugged tab, using the fuselage as a fixture,
and reinstall the blind nut.
I want to pass along a building tip that makes a great deal of sense
when working with ARFs. Use a machine screw into a blind nut
whenever possible and try to avoid using wood screws, especially into
balsa. If you have many wood screws in your airplane and have access,
change them to bolts with blind nuts.
As a final step, use the appropriate thread locker on all machine
screws and cyanoacrylate on wood screws. The only exception I can
think of is propeller bolts; I don’t use thread locker there.
The Finished Product: I’ve discussed many things I had to fine-tune or
adjust with this model, but I haven’t touched on the things that worked
or fit exceptionally well. The vertical fin’s construction and the way it
integrates into the rear of the fuselage is outstanding, with a tight fit and
perfect alignment. Likewise for the horizontal stabilizers; the fit to the
fuselage sides is perfect, and there is no slop in the joiner tubes or
alignment pins. In general, the aircraft has excellent fit with tight joints
and no slop.
For a factory-built ARF, all of the incidences were amazingly close.
I doubt if my adjustments made much difference in flight. The quality
of the fiberglass parts, the wood, and the construction overall is firstrate.
And as I mentioned, there’s no cheap or inappropriate hardware or
materials anywhere in this kit. The same cannot be said for all ARFs.
You can see where some experience with building and with large
aerobatic models may pay off when building an ARF. Much of this
model’s fit and finish work is left to the builder and without clear
Finished motor box augmented with aluminum angles for
strength. Because Mike prefers no air pressure inside fuselage,
he covered all lightening holes with clear MonoKote.
Since gasoline engines tend to vibrate, Mike recommends
replacing wood screws with blind nuts. Here, blind nuts are used
in tabs attaching cowl to fuselage.
Four servos were located in rear of fuselage. After length of
servo wiring extensions were calculated, all four leads were
taped to wire fed through provided fiberglass wiring tube and
fished through tube together.
34 MODEL AVIATION
in any instruction manual. Most modelers are supposed to know how
to do that, but every year I hear of another airplane going down
because of fuel tank-problems. I used a 32-ounce Du-Bro tank for this
model.
I like a tight-fitting stopper cap and really horse the screw that
holds it all together (without deforming the stopper). With the OEM
plastic caps, overtightening will cause the cap to collapse. So I use the
machined aluminum caps from SWB. Be sure you use the gascompatible
red rubber stopper that comes with the tank.
The first part in assembling the tank is to solder a barb to the
internal end of the pickup tube. This is important to keep the clunk
line from falling off inside the tank. You can get the barbs from Du-
Bro.
If you have to cut the copper tubes, be sure to chamfer all of the
edges to relieve any sharp corners that may cut into the Tygon tubing
during use. I use Tygon tubing from Du-Bro and Easy Flex from
Aerotrend; both are 1/8 inch in inside diameter.
Be sure to secure all of the hoses with a nylon wire tie. Bend the
copper portion of the pickup tube down inside the tank a bit; this will
put the flexible portion of the pickup in a central location so that the
clunk line will be the same length upright, inverted, or in any
orientation. Make sure the clunk moves freely inside the tank and
reaches the back corners as closely as possible without hindering any
movement.
The vent curves up to the top of the tank just behind the stopper.
Make sure it can’t be blocked off by the inside wall of the tank.
Outside the tank I loop the vent line back behind the rear edge of the
tank so that fuel cannot pour out while in flight. You’ll be surprised
by how much your fuel consumption will be improved with this
simple loop!
The vent simply exits the bottom of the cowl to a B&B fitting. I
instruction at times. But for me, those steps left up to the builder
ensure a better finished product.
I’ve done enough of the work on this airplane to know that all the
parts fit well, its alignment is spot on, and there’s nothing left to
question. This ARF is as solid as any of the aircraft I’ve built, and it’s
just as good as many of them.
The guys at Aeroworks were always there and happy to help with
my questions. I’m probably one of those perfectionists who really
shouldn’t build an ARF; but for a perfectionist, I’m pretty darn
pleased with the finished product. In fact, I’m downright stoked! I
don’t see this Ultimate as an ARF anymore; it feels like any airplane I
would have built, and I think the finished model’s quality is what
gives me such confidence.
Flying: As all biplanes do, the Aeroworks Ultimate takes a bit more
time and effort to field-assemble. At first it seemed as if the flyingwire
setup would make life easier, but so far I’ve had to readjust them
after every flight. I’m reasonably sure there will come a point when
they will settle in and stay taut.
I went with a three-blade propeller because the Ultimate’s
advertised flying weight was 24-25 pounds, but mine came in at 27
pounds, 10 ounces. At our mile-high altitude here in Denver, a 100cc
engine on a three-blade at that weight isn’t going to have all the power
I wanted, but I’ll give the three-blade a couple flights before I switch
to the two-blade. The three-blade Mejzlik 25 x 12 was noticeably
quieter than my other DA engines with two-blade propellers during
the first flight tests.
I had not prerun the engine or made any adjustments to it before
going out to the field. Once the DA-100 was primed, it fired and
started easily. After a few minutes to let it warm up, we did a range
check with the engine running and inspected the throttle response. The
engine was a tad on the lean side but responded well, so I made the
first flight without a single adjustment or tweak of the needle.
Precision Flight: The Aeroworks Ultimate is rock solid and grooves
like a Pattern airplane. The ailerons are extremely effective and rolls
are axial. I hadn’t even looked at the recommended throws; I set
everything to max for the first flight and adjusted from there according
to performance. I don’t recommend that you do this unless you have
considerable flying experience and feel comfortable with extreme
throws in flight. I dialed down the throw on the ailerons for the next
few flights, and I’ll be dialing up the exponential on the next outing.
The rudder is also effective but accurate, meaning that finessing
the yaw on this airplane was easier than on some other models I’ve
flown. The elevators are not overly powerful but adequate. There’s
little pitch coupling and even less roll. I’ll worry about mixing that out
when I get a little further along in the trimming process.
At the initial balance point, inverted flight is a thing of beauty. The
airplane doesn’t drop right away and gives me time to feel for exactly
the right amount of down-elevator pressure, delivering a seamless half
roll into a direct horizontal line. I felt that it required only slight
pressure on the stick to hold the line. Unless you are doing an
extremely slow roll, rudder input is just not needed to control the line
in a roll.
Up and down vertical lines had good tendencies in yaw, with no
left or right wandering, but did tend to pull to the canopy on downlines,
requiring some down-elevator pressure. Because of this, rolls
on the down-line are affected, giving the airplane a nasty wobble. I
may experiment with mixing or some upthrust to help fix the problem
later.
I had the balance set slightly aft of the recommended starting
position but well within flying specifications. Moving the balance
forward will help the pull on the vertical down-line if it doesn’t
completely eliminate the problem. The balance point will also affect
the feel in inverted flight, the need for rudder in rolling maneuvers,
and the amount of mix needed to adjust for coupling. I may
experiment with that later.
From my initial experiences, I think the Aeroworks Ultimate
would make a great platform for IMAC (International Miniature
Aerobatic Club)-style competition.
3-D Freestyle: 3-D on the Ultimate is not for beginners. Although
high-alpha flight is controllable with the strong ailerons, the model
rocks rapidly, needing quick responses and a keen eye. An
experienced 3-D pilot can get on the stick in short order with some
practice and the airplane will do almost any 3-D maneuver, but this is
probably not the best model for those who want to do 3-D for the first
time.
Holes in supplied landing gear were drilled too large from the
factory. Mike shows 5/16 x 1/4-inch bushings and washers used to
mount the gear.
The Ultimate’s fuel tank is mounted on separate platform, as a
module, then bolted in place using blind nuts. Mike wraps vent
line toward rear of tank to prevent overflow during flight.
DA-100 engine was mounted using polyurethane standoffs cut
from kitchen cutting board. Electrical components are protected
from vibration and wear with neoprene sleeves. Braided steel
spark-plug wires are protected with nylon automotive wire wrap.
Make sure all electrical connections are well secure.
Inverted high-alpha flight is doable
with the Ultimate, but, again, you have to
be on the ball with the ailerons and know
the rudder corrections; the model can roll
out quickly. Outside Waterfalls had a
tendency to roll out on the last quarter, and
inverted flat spins take a little finesse and
some modulation on the elevator and
throttle.
Because the roll rate is so fast on this
airplane, Blenders can be extremely
violent. Imagine the model rolling at a rate
you can’t even count, and then it explodes
into a blurry ball and just stops like it
reappeared from warp drive! Kind of
scary.
Torque rolls and hovering are a blast
and come easily with this 33% Ultimate,
but beware: once its thrust vector hits the
vertical balance point, the model will
rotate rapidly. A 5° tilt in any direction
will stop the torque roll.
Aeroworks indicated that it has had the
best success when the airplane is outfitted
for “3D mode”; that is, to move the CG
roughly an inch behind its center point and
increase the elevator throw to
approximately 65°. Setting the model up
like this could remove some of the rollout
problems I was having. But I found the 3-
D performance perfectly acceptable at a
“normal” 3-D setup of a neutral balance
point and only 45° of elevator throw.
The Ultimate biplane can get wild
doing ultrafast snaps and rolling in a blur.
Tumbles are crazy tight and knife-edge is
amazing with the ability to do
extraordinarily tight knife-edge loops and
Figure 8s. I’ll continue to experiment with
3-D flight, and in the meantime I’ll enjoy
what it does well right off the board.
It seems that the Ultimate can be set up
as either a good precision aircraft or a
good 3-D aircraft, but it may be difficult to
set up to do both well in the same flight. It
is not like a scale monoplane, but you
already knew that. It’s best to capitalize on
its strong points and enjoy the uniqueness
of a high-performance biplane. Whether
you want a competition model that stands
out in a crowd or an outrageous Freestyle
airplane, the Ultimate can be set up to
excel.
Although the 33% Aeroworks Ultimate
biplane was the subject for this article, it
was not meant to be a kit review, but
rather a collection of thoughts that could
be adapted to other Giant Scale aerobatic
ARF kits. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
Manufacturers:
JR radio equipment:
Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 352-1913
Toll-free: (800) 338-4639
Fax: (217) 355-1552
www.horizonhobby.com/
Engine, mufflers, propeller:
Desert Aircraft
1815 S. Research Loop
Tucson AZ 85710
(520) 722-0607
Fax: (520) 722-5622
www.desertaircraft.com/
4-inch Ultimate spinner:
Tru-Turn Precision Model Products
100 W. 1st St.
Deer Park TX 77536
(281) 479-9600
Fax: (281) 479-9090
www.tru-turn.com/
33% Ultimate biplane:
Aeroworks
401 Laredo St. Suite D
Aurora CO 80011
(303) 366-4205
Fax: (303) 366-4203
www.aero-works.net/
Edition: Model Aviation - 2005/06
Page Numbers: 33,34,35,37
(Editor’s note: This is the second of a two-part series, the first of
which was published in last month’s issue.)
MOTOR-BOX CONSTRUCTION: The instructions mention some
longitudinal reinforcement pieces for the motor-box construction, but
the photographs look as if the covering is removed from the side of
the aircraft when they’re installed. The airplane was originally
designed with the front hatch removable so that those pieces would be
fine to fit into place, but with the present design it is impossible to fit
those pieces into the fuselage without some deconstruction. So even
though the parts are there and the instructions discuss it, the bracing is
left out.
The instructions advise to measure for the motor-box length and
cut them to fit, but I left the motor-box sides at full length. Right
thrust is already calculated, but you must mark the thrustline and
calculate the centerline offset on the firewall so that the engine will
still exit the cowl in the center. I did this and drilled the firewall for
blind nuts for the engine before it was glued into the model.
Once the motor-box sides are in place, the firewall is supposed to
be gusseted with spruce triangle stock, but the factory supplied only
balsa. If you go out and find some 1/2 spruce triangle stock and epoxy
it in place, you’ll be fine, but I had already glued the balsa into the
motor box. Rather than tear all that out, Aeroworks suggested that I
bolt some 3/4-inch angled aluminum to the outside of the motor box—
a perfect solution.
Landing Gear: The instructions for the
landing-gear installation were vague. The
gear is clearly swept, but there is no mention
of which orientation the sweep is intended
for! Then there is the matter of the bolt holes
that are predrilled in the gear. You are
supplied with 10-32 cap screws and blind nuts
to mount the gear, but the gear is drilled to 5/16
inch. The No. 10 cap screws’ heads pass right
through! Sweep the gear toward the rear of
the airplane. The axles should be almost even
with the LE of the bottom wing at the root.
Aeroworks indicated that the latest
production run was complete and all of the
kits were drilled like this. The company
suggested that I drill the holes a little larger
and use some wheel collars as a sleeve in the
oversized landing-gear holes and use a hefty
fender washer under the cap screw.
Instead of doing that, I found some 5/16 x
1/4-inch aluminum bushings at the hardware
store that fit perfectly, and I found the right
size of washer to work with the gear. Either
way will yield the same results.
Gas Tank: Putting together a proper gas tank
is one of those things you probably won’t see
June 2005 33
According to the author, this model is a dream to fly. It tracks like a competition aircraft,
yet it can be set up to fly 3-D with the best of them.
Although the Aeroworks 33% Ultimate biplane’s span just
exceeds 6 feet, it is still a fairly large airplane, making it perfect
for a 100cc engine.
Giant Scale Aerobatic
ARF Building Tips by Mike Hurley
Part 2
Photos by the author
use the fitting because it’s a solid mount and it’s neat. You can close off
the vent during transportation and moving the model in and out of the
shop. The vent is kept open during flight and storage so the tank doesn’t
deform or rupture.
The pickup line goes directly to the carburetor. I use a “T” fitting in
the pickup as a fill line. Just exit the side of the fuselage or the cowl and
plug it off with a fuel dot. You cannot flood the engine during fueling
with this method. Gasoline carburetors have a needle and seat that
won’t allow gas into the system while the engine is not running.
The Hatch: I was unhappy with the way the hatch fit out of the box.
The rear canopy former was too large, so the canopy didn’t match to the
turtledeck very well. The aft hold-down tabs are supposed to fit tight in
the fuselage but had quite a bit of play. Attempting to tighten those rear
bolts would surely have led to a broken tab, and one of the hold-down
bolts wouldn’t engage because of misaligned holes. So a little work was
in order to clear those things up.
I sanded the rear canopy former to fit the turtledeck. That took
approximately 10 minutes. For the tabs to fit I had to add 1/32 plywood
to the outside of the tabs, but before that I popped the blind nut out of
the tab that didn’t line up and plugged the hole with a dowel. Then I
added the plywood and sanded to get a nice, snug fit. After that, all that
was left was to redrill the plugged tab, using the fuselage as a fixture,
and reinstall the blind nut.
I want to pass along a building tip that makes a great deal of sense
when working with ARFs. Use a machine screw into a blind nut
whenever possible and try to avoid using wood screws, especially into
balsa. If you have many wood screws in your airplane and have access,
change them to bolts with blind nuts.
As a final step, use the appropriate thread locker on all machine
screws and cyanoacrylate on wood screws. The only exception I can
think of is propeller bolts; I don’t use thread locker there.
The Finished Product: I’ve discussed many things I had to fine-tune or
adjust with this model, but I haven’t touched on the things that worked
or fit exceptionally well. The vertical fin’s construction and the way it
integrates into the rear of the fuselage is outstanding, with a tight fit and
perfect alignment. Likewise for the horizontal stabilizers; the fit to the
fuselage sides is perfect, and there is no slop in the joiner tubes or
alignment pins. In general, the aircraft has excellent fit with tight joints
and no slop.
For a factory-built ARF, all of the incidences were amazingly close.
I doubt if my adjustments made much difference in flight. The quality
of the fiberglass parts, the wood, and the construction overall is firstrate.
And as I mentioned, there’s no cheap or inappropriate hardware or
materials anywhere in this kit. The same cannot be said for all ARFs.
You can see where some experience with building and with large
aerobatic models may pay off when building an ARF. Much of this
model’s fit and finish work is left to the builder and without clear
Finished motor box augmented with aluminum angles for
strength. Because Mike prefers no air pressure inside fuselage,
he covered all lightening holes with clear MonoKote.
Since gasoline engines tend to vibrate, Mike recommends
replacing wood screws with blind nuts. Here, blind nuts are used
in tabs attaching cowl to fuselage.
Four servos were located in rear of fuselage. After length of
servo wiring extensions were calculated, all four leads were
taped to wire fed through provided fiberglass wiring tube and
fished through tube together.
34 MODEL AVIATION
in any instruction manual. Most modelers are supposed to know how
to do that, but every year I hear of another airplane going down
because of fuel tank-problems. I used a 32-ounce Du-Bro tank for this
model.
I like a tight-fitting stopper cap and really horse the screw that
holds it all together (without deforming the stopper). With the OEM
plastic caps, overtightening will cause the cap to collapse. So I use the
machined aluminum caps from SWB. Be sure you use the gascompatible
red rubber stopper that comes with the tank.
The first part in assembling the tank is to solder a barb to the
internal end of the pickup tube. This is important to keep the clunk
line from falling off inside the tank. You can get the barbs from Du-
Bro.
If you have to cut the copper tubes, be sure to chamfer all of the
edges to relieve any sharp corners that may cut into the Tygon tubing
during use. I use Tygon tubing from Du-Bro and Easy Flex from
Aerotrend; both are 1/8 inch in inside diameter.
Be sure to secure all of the hoses with a nylon wire tie. Bend the
copper portion of the pickup tube down inside the tank a bit; this will
put the flexible portion of the pickup in a central location so that the
clunk line will be the same length upright, inverted, or in any
orientation. Make sure the clunk moves freely inside the tank and
reaches the back corners as closely as possible without hindering any
movement.
The vent curves up to the top of the tank just behind the stopper.
Make sure it can’t be blocked off by the inside wall of the tank.
Outside the tank I loop the vent line back behind the rear edge of the
tank so that fuel cannot pour out while in flight. You’ll be surprised
by how much your fuel consumption will be improved with this
simple loop!
The vent simply exits the bottom of the cowl to a B&B fitting. I
instruction at times. But for me, those steps left up to the builder
ensure a better finished product.
I’ve done enough of the work on this airplane to know that all the
parts fit well, its alignment is spot on, and there’s nothing left to
question. This ARF is as solid as any of the aircraft I’ve built, and it’s
just as good as many of them.
The guys at Aeroworks were always there and happy to help with
my questions. I’m probably one of those perfectionists who really
shouldn’t build an ARF; but for a perfectionist, I’m pretty darn
pleased with the finished product. In fact, I’m downright stoked! I
don’t see this Ultimate as an ARF anymore; it feels like any airplane I
would have built, and I think the finished model’s quality is what
gives me such confidence.
Flying: As all biplanes do, the Aeroworks Ultimate takes a bit more
time and effort to field-assemble. At first it seemed as if the flyingwire
setup would make life easier, but so far I’ve had to readjust them
after every flight. I’m reasonably sure there will come a point when
they will settle in and stay taut.
I went with a three-blade propeller because the Ultimate’s
advertised flying weight was 24-25 pounds, but mine came in at 27
pounds, 10 ounces. At our mile-high altitude here in Denver, a 100cc
engine on a three-blade at that weight isn’t going to have all the power
I wanted, but I’ll give the three-blade a couple flights before I switch
to the two-blade. The three-blade Mejzlik 25 x 12 was noticeably
quieter than my other DA engines with two-blade propellers during
the first flight tests.
I had not prerun the engine or made any adjustments to it before
going out to the field. Once the DA-100 was primed, it fired and
started easily. After a few minutes to let it warm up, we did a range
check with the engine running and inspected the throttle response. The
engine was a tad on the lean side but responded well, so I made the
first flight without a single adjustment or tweak of the needle.
Precision Flight: The Aeroworks Ultimate is rock solid and grooves
like a Pattern airplane. The ailerons are extremely effective and rolls
are axial. I hadn’t even looked at the recommended throws; I set
everything to max for the first flight and adjusted from there according
to performance. I don’t recommend that you do this unless you have
considerable flying experience and feel comfortable with extreme
throws in flight. I dialed down the throw on the ailerons for the next
few flights, and I’ll be dialing up the exponential on the next outing.
The rudder is also effective but accurate, meaning that finessing
the yaw on this airplane was easier than on some other models I’ve
flown. The elevators are not overly powerful but adequate. There’s
little pitch coupling and even less roll. I’ll worry about mixing that out
when I get a little further along in the trimming process.
At the initial balance point, inverted flight is a thing of beauty. The
airplane doesn’t drop right away and gives me time to feel for exactly
the right amount of down-elevator pressure, delivering a seamless half
roll into a direct horizontal line. I felt that it required only slight
pressure on the stick to hold the line. Unless you are doing an
extremely slow roll, rudder input is just not needed to control the line
in a roll.
Up and down vertical lines had good tendencies in yaw, with no
left or right wandering, but did tend to pull to the canopy on downlines,
requiring some down-elevator pressure. Because of this, rolls
on the down-line are affected, giving the airplane a nasty wobble. I
may experiment with mixing or some upthrust to help fix the problem
later.
I had the balance set slightly aft of the recommended starting
position but well within flying specifications. Moving the balance
forward will help the pull on the vertical down-line if it doesn’t
completely eliminate the problem. The balance point will also affect
the feel in inverted flight, the need for rudder in rolling maneuvers,
and the amount of mix needed to adjust for coupling. I may
experiment with that later.
From my initial experiences, I think the Aeroworks Ultimate
would make a great platform for IMAC (International Miniature
Aerobatic Club)-style competition.
3-D Freestyle: 3-D on the Ultimate is not for beginners. Although
high-alpha flight is controllable with the strong ailerons, the model
rocks rapidly, needing quick responses and a keen eye. An
experienced 3-D pilot can get on the stick in short order with some
practice and the airplane will do almost any 3-D maneuver, but this is
probably not the best model for those who want to do 3-D for the first
time.
Holes in supplied landing gear were drilled too large from the
factory. Mike shows 5/16 x 1/4-inch bushings and washers used to
mount the gear.
The Ultimate’s fuel tank is mounted on separate platform, as a
module, then bolted in place using blind nuts. Mike wraps vent
line toward rear of tank to prevent overflow during flight.
DA-100 engine was mounted using polyurethane standoffs cut
from kitchen cutting board. Electrical components are protected
from vibration and wear with neoprene sleeves. Braided steel
spark-plug wires are protected with nylon automotive wire wrap.
Make sure all electrical connections are well secure.
Inverted high-alpha flight is doable
with the Ultimate, but, again, you have to
be on the ball with the ailerons and know
the rudder corrections; the model can roll
out quickly. Outside Waterfalls had a
tendency to roll out on the last quarter, and
inverted flat spins take a little finesse and
some modulation on the elevator and
throttle.
Because the roll rate is so fast on this
airplane, Blenders can be extremely
violent. Imagine the model rolling at a rate
you can’t even count, and then it explodes
into a blurry ball and just stops like it
reappeared from warp drive! Kind of
scary.
Torque rolls and hovering are a blast
and come easily with this 33% Ultimate,
but beware: once its thrust vector hits the
vertical balance point, the model will
rotate rapidly. A 5° tilt in any direction
will stop the torque roll.
Aeroworks indicated that it has had the
best success when the airplane is outfitted
for “3D mode”; that is, to move the CG
roughly an inch behind its center point and
increase the elevator throw to
approximately 65°. Setting the model up
like this could remove some of the rollout
problems I was having. But I found the 3-
D performance perfectly acceptable at a
“normal” 3-D setup of a neutral balance
point and only 45° of elevator throw.
The Ultimate biplane can get wild
doing ultrafast snaps and rolling in a blur.
Tumbles are crazy tight and knife-edge is
amazing with the ability to do
extraordinarily tight knife-edge loops and
Figure 8s. I’ll continue to experiment with
3-D flight, and in the meantime I’ll enjoy
what it does well right off the board.
It seems that the Ultimate can be set up
as either a good precision aircraft or a
good 3-D aircraft, but it may be difficult to
set up to do both well in the same flight. It
is not like a scale monoplane, but you
already knew that. It’s best to capitalize on
its strong points and enjoy the uniqueness
of a high-performance biplane. Whether
you want a competition model that stands
out in a crowd or an outrageous Freestyle
airplane, the Ultimate can be set up to
excel.
Although the 33% Aeroworks Ultimate
biplane was the subject for this article, it
was not meant to be a kit review, but
rather a collection of thoughts that could
be adapted to other Giant Scale aerobatic
ARF kits. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
Manufacturers:
JR radio equipment:
Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 352-1913
Toll-free: (800) 338-4639
Fax: (217) 355-1552
www.horizonhobby.com/
Engine, mufflers, propeller:
Desert Aircraft
1815 S. Research Loop
Tucson AZ 85710
(520) 722-0607
Fax: (520) 722-5622
www.desertaircraft.com/
4-inch Ultimate spinner:
Tru-Turn Precision Model Products
100 W. 1st St.
Deer Park TX 77536
(281) 479-9600
Fax: (281) 479-9090
www.tru-turn.com/
33% Ultimate biplane:
Aeroworks
401 Laredo St. Suite D
Aurora CO 80011
(303) 366-4205
Fax: (303) 366-4203
www.aero-works.net/
Edition: Model Aviation - 2005/06
Page Numbers: 33,34,35,37
(Editor’s note: This is the second of a two-part series, the first of
which was published in last month’s issue.)
MOTOR-BOX CONSTRUCTION: The instructions mention some
longitudinal reinforcement pieces for the motor-box construction, but
the photographs look as if the covering is removed from the side of
the aircraft when they’re installed. The airplane was originally
designed with the front hatch removable so that those pieces would be
fine to fit into place, but with the present design it is impossible to fit
those pieces into the fuselage without some deconstruction. So even
though the parts are there and the instructions discuss it, the bracing is
left out.
The instructions advise to measure for the motor-box length and
cut them to fit, but I left the motor-box sides at full length. Right
thrust is already calculated, but you must mark the thrustline and
calculate the centerline offset on the firewall so that the engine will
still exit the cowl in the center. I did this and drilled the firewall for
blind nuts for the engine before it was glued into the model.
Once the motor-box sides are in place, the firewall is supposed to
be gusseted with spruce triangle stock, but the factory supplied only
balsa. If you go out and find some 1/2 spruce triangle stock and epoxy
it in place, you’ll be fine, but I had already glued the balsa into the
motor box. Rather than tear all that out, Aeroworks suggested that I
bolt some 3/4-inch angled aluminum to the outside of the motor box—
a perfect solution.
Landing Gear: The instructions for the
landing-gear installation were vague. The
gear is clearly swept, but there is no mention
of which orientation the sweep is intended
for! Then there is the matter of the bolt holes
that are predrilled in the gear. You are
supplied with 10-32 cap screws and blind nuts
to mount the gear, but the gear is drilled to 5/16
inch. The No. 10 cap screws’ heads pass right
through! Sweep the gear toward the rear of
the airplane. The axles should be almost even
with the LE of the bottom wing at the root.
Aeroworks indicated that the latest
production run was complete and all of the
kits were drilled like this. The company
suggested that I drill the holes a little larger
and use some wheel collars as a sleeve in the
oversized landing-gear holes and use a hefty
fender washer under the cap screw.
Instead of doing that, I found some 5/16 x
1/4-inch aluminum bushings at the hardware
store that fit perfectly, and I found the right
size of washer to work with the gear. Either
way will yield the same results.
Gas Tank: Putting together a proper gas tank
is one of those things you probably won’t see
June 2005 33
According to the author, this model is a dream to fly. It tracks like a competition aircraft,
yet it can be set up to fly 3-D with the best of them.
Although the Aeroworks 33% Ultimate biplane’s span just
exceeds 6 feet, it is still a fairly large airplane, making it perfect
for a 100cc engine.
Giant Scale Aerobatic
ARF Building Tips by Mike Hurley
Part 2
Photos by the author
use the fitting because it’s a solid mount and it’s neat. You can close off
the vent during transportation and moving the model in and out of the
shop. The vent is kept open during flight and storage so the tank doesn’t
deform or rupture.
The pickup line goes directly to the carburetor. I use a “T” fitting in
the pickup as a fill line. Just exit the side of the fuselage or the cowl and
plug it off with a fuel dot. You cannot flood the engine during fueling
with this method. Gasoline carburetors have a needle and seat that
won’t allow gas into the system while the engine is not running.
The Hatch: I was unhappy with the way the hatch fit out of the box.
The rear canopy former was too large, so the canopy didn’t match to the
turtledeck very well. The aft hold-down tabs are supposed to fit tight in
the fuselage but had quite a bit of play. Attempting to tighten those rear
bolts would surely have led to a broken tab, and one of the hold-down
bolts wouldn’t engage because of misaligned holes. So a little work was
in order to clear those things up.
I sanded the rear canopy former to fit the turtledeck. That took
approximately 10 minutes. For the tabs to fit I had to add 1/32 plywood
to the outside of the tabs, but before that I popped the blind nut out of
the tab that didn’t line up and plugged the hole with a dowel. Then I
added the plywood and sanded to get a nice, snug fit. After that, all that
was left was to redrill the plugged tab, using the fuselage as a fixture,
and reinstall the blind nut.
I want to pass along a building tip that makes a great deal of sense
when working with ARFs. Use a machine screw into a blind nut
whenever possible and try to avoid using wood screws, especially into
balsa. If you have many wood screws in your airplane and have access,
change them to bolts with blind nuts.
As a final step, use the appropriate thread locker on all machine
screws and cyanoacrylate on wood screws. The only exception I can
think of is propeller bolts; I don’t use thread locker there.
The Finished Product: I’ve discussed many things I had to fine-tune or
adjust with this model, but I haven’t touched on the things that worked
or fit exceptionally well. The vertical fin’s construction and the way it
integrates into the rear of the fuselage is outstanding, with a tight fit and
perfect alignment. Likewise for the horizontal stabilizers; the fit to the
fuselage sides is perfect, and there is no slop in the joiner tubes or
alignment pins. In general, the aircraft has excellent fit with tight joints
and no slop.
For a factory-built ARF, all of the incidences were amazingly close.
I doubt if my adjustments made much difference in flight. The quality
of the fiberglass parts, the wood, and the construction overall is firstrate.
And as I mentioned, there’s no cheap or inappropriate hardware or
materials anywhere in this kit. The same cannot be said for all ARFs.
You can see where some experience with building and with large
aerobatic models may pay off when building an ARF. Much of this
model’s fit and finish work is left to the builder and without clear
Finished motor box augmented with aluminum angles for
strength. Because Mike prefers no air pressure inside fuselage,
he covered all lightening holes with clear MonoKote.
Since gasoline engines tend to vibrate, Mike recommends
replacing wood screws with blind nuts. Here, blind nuts are used
in tabs attaching cowl to fuselage.
Four servos were located in rear of fuselage. After length of
servo wiring extensions were calculated, all four leads were
taped to wire fed through provided fiberglass wiring tube and
fished through tube together.
34 MODEL AVIATION
in any instruction manual. Most modelers are supposed to know how
to do that, but every year I hear of another airplane going down
because of fuel tank-problems. I used a 32-ounce Du-Bro tank for this
model.
I like a tight-fitting stopper cap and really horse the screw that
holds it all together (without deforming the stopper). With the OEM
plastic caps, overtightening will cause the cap to collapse. So I use the
machined aluminum caps from SWB. Be sure you use the gascompatible
red rubber stopper that comes with the tank.
The first part in assembling the tank is to solder a barb to the
internal end of the pickup tube. This is important to keep the clunk
line from falling off inside the tank. You can get the barbs from Du-
Bro.
If you have to cut the copper tubes, be sure to chamfer all of the
edges to relieve any sharp corners that may cut into the Tygon tubing
during use. I use Tygon tubing from Du-Bro and Easy Flex from
Aerotrend; both are 1/8 inch in inside diameter.
Be sure to secure all of the hoses with a nylon wire tie. Bend the
copper portion of the pickup tube down inside the tank a bit; this will
put the flexible portion of the pickup in a central location so that the
clunk line will be the same length upright, inverted, or in any
orientation. Make sure the clunk moves freely inside the tank and
reaches the back corners as closely as possible without hindering any
movement.
The vent curves up to the top of the tank just behind the stopper.
Make sure it can’t be blocked off by the inside wall of the tank.
Outside the tank I loop the vent line back behind the rear edge of the
tank so that fuel cannot pour out while in flight. You’ll be surprised
by how much your fuel consumption will be improved with this
simple loop!
The vent simply exits the bottom of the cowl to a B&B fitting. I
instruction at times. But for me, those steps left up to the builder
ensure a better finished product.
I’ve done enough of the work on this airplane to know that all the
parts fit well, its alignment is spot on, and there’s nothing left to
question. This ARF is as solid as any of the aircraft I’ve built, and it’s
just as good as many of them.
The guys at Aeroworks were always there and happy to help with
my questions. I’m probably one of those perfectionists who really
shouldn’t build an ARF; but for a perfectionist, I’m pretty darn
pleased with the finished product. In fact, I’m downright stoked! I
don’t see this Ultimate as an ARF anymore; it feels like any airplane I
would have built, and I think the finished model’s quality is what
gives me such confidence.
Flying: As all biplanes do, the Aeroworks Ultimate takes a bit more
time and effort to field-assemble. At first it seemed as if the flyingwire
setup would make life easier, but so far I’ve had to readjust them
after every flight. I’m reasonably sure there will come a point when
they will settle in and stay taut.
I went with a three-blade propeller because the Ultimate’s
advertised flying weight was 24-25 pounds, but mine came in at 27
pounds, 10 ounces. At our mile-high altitude here in Denver, a 100cc
engine on a three-blade at that weight isn’t going to have all the power
I wanted, but I’ll give the three-blade a couple flights before I switch
to the two-blade. The three-blade Mejzlik 25 x 12 was noticeably
quieter than my other DA engines with two-blade propellers during
the first flight tests.
I had not prerun the engine or made any adjustments to it before
going out to the field. Once the DA-100 was primed, it fired and
started easily. After a few minutes to let it warm up, we did a range
check with the engine running and inspected the throttle response. The
engine was a tad on the lean side but responded well, so I made the
first flight without a single adjustment or tweak of the needle.
Precision Flight: The Aeroworks Ultimate is rock solid and grooves
like a Pattern airplane. The ailerons are extremely effective and rolls
are axial. I hadn’t even looked at the recommended throws; I set
everything to max for the first flight and adjusted from there according
to performance. I don’t recommend that you do this unless you have
considerable flying experience and feel comfortable with extreme
throws in flight. I dialed down the throw on the ailerons for the next
few flights, and I’ll be dialing up the exponential on the next outing.
The rudder is also effective but accurate, meaning that finessing
the yaw on this airplane was easier than on some other models I’ve
flown. The elevators are not overly powerful but adequate. There’s
little pitch coupling and even less roll. I’ll worry about mixing that out
when I get a little further along in the trimming process.
At the initial balance point, inverted flight is a thing of beauty. The
airplane doesn’t drop right away and gives me time to feel for exactly
the right amount of down-elevator pressure, delivering a seamless half
roll into a direct horizontal line. I felt that it required only slight
pressure on the stick to hold the line. Unless you are doing an
extremely slow roll, rudder input is just not needed to control the line
in a roll.
Up and down vertical lines had good tendencies in yaw, with no
left or right wandering, but did tend to pull to the canopy on downlines,
requiring some down-elevator pressure. Because of this, rolls
on the down-line are affected, giving the airplane a nasty wobble. I
may experiment with mixing or some upthrust to help fix the problem
later.
I had the balance set slightly aft of the recommended starting
position but well within flying specifications. Moving the balance
forward will help the pull on the vertical down-line if it doesn’t
completely eliminate the problem. The balance point will also affect
the feel in inverted flight, the need for rudder in rolling maneuvers,
and the amount of mix needed to adjust for coupling. I may
experiment with that later.
From my initial experiences, I think the Aeroworks Ultimate
would make a great platform for IMAC (International Miniature
Aerobatic Club)-style competition.
3-D Freestyle: 3-D on the Ultimate is not for beginners. Although
high-alpha flight is controllable with the strong ailerons, the model
rocks rapidly, needing quick responses and a keen eye. An
experienced 3-D pilot can get on the stick in short order with some
practice and the airplane will do almost any 3-D maneuver, but this is
probably not the best model for those who want to do 3-D for the first
time.
Holes in supplied landing gear were drilled too large from the
factory. Mike shows 5/16 x 1/4-inch bushings and washers used to
mount the gear.
The Ultimate’s fuel tank is mounted on separate platform, as a
module, then bolted in place using blind nuts. Mike wraps vent
line toward rear of tank to prevent overflow during flight.
DA-100 engine was mounted using polyurethane standoffs cut
from kitchen cutting board. Electrical components are protected
from vibration and wear with neoprene sleeves. Braided steel
spark-plug wires are protected with nylon automotive wire wrap.
Make sure all electrical connections are well secure.
Inverted high-alpha flight is doable
with the Ultimate, but, again, you have to
be on the ball with the ailerons and know
the rudder corrections; the model can roll
out quickly. Outside Waterfalls had a
tendency to roll out on the last quarter, and
inverted flat spins take a little finesse and
some modulation on the elevator and
throttle.
Because the roll rate is so fast on this
airplane, Blenders can be extremely
violent. Imagine the model rolling at a rate
you can’t even count, and then it explodes
into a blurry ball and just stops like it
reappeared from warp drive! Kind of
scary.
Torque rolls and hovering are a blast
and come easily with this 33% Ultimate,
but beware: once its thrust vector hits the
vertical balance point, the model will
rotate rapidly. A 5° tilt in any direction
will stop the torque roll.
Aeroworks indicated that it has had the
best success when the airplane is outfitted
for “3D mode”; that is, to move the CG
roughly an inch behind its center point and
increase the elevator throw to
approximately 65°. Setting the model up
like this could remove some of the rollout
problems I was having. But I found the 3-
D performance perfectly acceptable at a
“normal” 3-D setup of a neutral balance
point and only 45° of elevator throw.
The Ultimate biplane can get wild
doing ultrafast snaps and rolling in a blur.
Tumbles are crazy tight and knife-edge is
amazing with the ability to do
extraordinarily tight knife-edge loops and
Figure 8s. I’ll continue to experiment with
3-D flight, and in the meantime I’ll enjoy
what it does well right off the board.
It seems that the Ultimate can be set up
as either a good precision aircraft or a
good 3-D aircraft, but it may be difficult to
set up to do both well in the same flight. It
is not like a scale monoplane, but you
already knew that. It’s best to capitalize on
its strong points and enjoy the uniqueness
of a high-performance biplane. Whether
you want a competition model that stands
out in a crowd or an outrageous Freestyle
airplane, the Ultimate can be set up to
excel.
Although the 33% Aeroworks Ultimate
biplane was the subject for this article, it
was not meant to be a kit review, but
rather a collection of thoughts that could
be adapted to other Giant Scale aerobatic
ARF kits. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
Manufacturers:
JR radio equipment:
Horizon Hobby Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 352-1913
Toll-free: (800) 338-4639
Fax: (217) 355-1552
www.horizonhobby.com/
Engine, mufflers, propeller:
Desert Aircraft
1815 S. Research Loop
Tucson AZ 85710
(520) 722-0607
Fax: (520) 722-5622
www.desertaircraft.com/
4-inch Ultimate spinner:
Tru-Turn Precision Model Products
100 W. 1st St.
Deer Park TX 77536
(281) 479-9600
Fax: (281) 479-9090
www.tru-turn.com/
33% Ultimate biplane:
Aeroworks
401 Laredo St. Suite D
Aurora CO 80011
(303) 366-4205
Fax: (303) 366-4203
www.aero-works.net/