P r o d u c t R e v i e w Frank Granelli
Frank Granelli, 24 Old Middletown Rd., Rockaway NJ 07866
December 2004 55
JUST WHAT THE model-aviation world needs: another Extra ARF.
If there are not yet a million such kits available, there soon will be.
From small 25-size Extra 300s to monsters that are nearly half the size
of the full-scale aircraft, most model manufacturers offer at least one
version of this popular and successful aerobatic airplane. There are
almost as many different Extra models as there are P-51 Mustang kits,
and there are a million of those. But maybe the situation is not entirely
as it appears.
Dave Patrick Models (DPM) has been manufacturing a version of
the Extra 330L for sometime. It has proven to be a formidable Scale
Aerobatics competition aircraft and, with some minor modifications,
has won more than its share of contests. DPM has incorporated some
of these “field” modifications, added a few more, and produced a new
Extra 330L that should be even more competitive.
This improved DPM Extra has been expected; Mr. Patrick has been
designing and improving winning aerobatic competition aircraft for a
long time. Competition designs cannot remain static; new airframes
arrive on the contest scene each season, and existing airframes are
redesigned and improved in light of new technology and maneuver
requirements.
Successful competition models are always pushing the performance
envelope. This competitive drive develops the powerful engines,
stronger servos, lighter airframes, and other enhanced products that
sport pilots also enjoy. A good competition Aerobatics model makes
one of the most capable and easiest-to-fly sport models too.
Before finding out if this new 330L is as good as, or even better
than, the previous model, I had to “assemble” it (not “build” it—most
of that was done when I received the kit). Quickly examining the
contents shown in the photos reveals that this kit was more prebuilt
than most ARFs, but it was short of being an RTF because it required
radio and engine installation and some gluing. Maybe the DPM Extra
330L should have been called a Ready-to-Fly Almost (RFA).
The wing halves were not glued together; they were just slid onto
an aluminum spar (wing tube) that was already mounted in the
fuselage. The same method was used for the adjustable stabilizer. I
only had to epoxy the vertical fin in place and then add the control
surfaces.
Setting up the control surfaces and incidences was the most timeconsuming
part of construction. All of the tedious, exacting building
This model looks powerful from the front. The Extra 330L should
make your fellow Aerobatics competitors worry.
Dave Patrick Models Extra 330L ARF
Out of the box, roughly 90% of the main airframe work is done.
Wing halves don’t even need to be glued; this is a plug-in wing.
All fiberglass parts are supplied prepainted. The hardware is of
excellent quality. It’s a well-thought-out package!
Pros:
• More ready to fly than most ARFs.
• Professional-grade accessories.
• Winning competition-class flying abilities.
• Excellent 3-D capabilities.
• Easy to fly and terrific sport aircraft.
• Extremely attractive appearance.
• Extra-strong but light construction.
• Detailed photo instructions with complete
setup and trim information.
Cons:
• At a loss to think of anything.
Photos by the author
12sig2.QXD 10/25/04 10:42 AM Page 55
56 MODEL AVIATION
I drilled a 1⁄16-inch hole in the bottom of each stabilizer and through
the main spar. I tapped the spar for 4-40 thread and installed a bolt on
each side to lock the stabilizer in place. I installed the elevators
according to the book’s great instructions, using the supplied lightened
control horns and Mylar hinges.
I was pleasantly surprised by the extremely high quality of the
supplied hardware, including the ultralight and strong nylon-bushed
control horns, the 49-strand pull-pull cable, the locking clevises, and
the strong “Pattern-style” hinges. An experienced competition pilot
would choose these items.
In fact, the entire kit’s quality was impressive. The firewall was
held in place using aluminum corners for durability. Control horns used
four mounting bolts for the same reason. This entire package was
designed for heavy competition use and extreme durability without
added weight. Just how strong this light aircraft was would be proven
later.
Shaking Those Tail Feathers: It was time for the big debate: how to
best control the elevators. The kit allowed two methods, one of which
was the conventional two servos in the tail. The other was a forwardlocated
servo using pull-pull cables to the elevators. The latter
technique saves roughly 2 ounces of tail weight, avoids the problem of
synchronizing the two servos, and is technically more elegant.
However, I know my limitations. I have enough trouble just getting
a single pull-pull rudder to center. I would probably never be able to
work was done. After installing the radio, engine, fuel system, and
pushrods, it was flying time.
Assembly: Following the excellent 59-page, photo-illustrated
construction book, the first assembly step was installing the
horizontal stabilizer. It featured fully adjustable incidence using
stabilizer-mounted adjustment screws that locked onto a fuselagemounted
aluminum adjustment rod. Having an adjustable stabilizer
is crucial for a competition aircraft.
The fuselage mounting holes were preinstalled for the main spar
tube and the incidence adjustment rod. The adjusters were factory
installed in each stabilizer half. Before gluing the incidence
adjustment rod in place, I test-installed the spar, incidence rod, and
stabilizer halves to make sure that all were square.
Once they were square, I removed a stabilizer half and glued the
adjustment rod in place on that side. When dry, I reinstalled that
stabilizer half and repeated the process on the other side. This
ensured perfect alignment. Make sure that the adjustment screws
contact the flats of the adjustment rod. If the flat area is not large
enough, you can use a small file to easily extend the flat area in the
soft aluminum.
To complete the stabilizer installation, I propped up the fuselage
until it was level (using the fuselage fin plate as a leveling guide). I
set the stabilizer incidence to zero using an incidence meter. The
instruction book showed how to achieve this result without an
incidence meter.
Start of low-altitude Slow Roll. “Top” rudder control is already in.
Little rudder is needed for level, 10-second Slow Rolls.
Look carefully at the rudder. Only roughly 15% of available
rudder control is required to maintain level knife-edge flight.
Wing and stabilizer halves mount onto aluminum spars. Field
assembly is simple, fast, and requires just two nylon bolts.
The attractive and colorful Extra 330L would be an outstanding
choice for a first large Scale Aerobatics model.
12sig2.QXD 10/25/04 10:43 AM Page 56
56 MODEL AVIATION
I drilled a 1⁄16-inch hole in the bottom of each stabilizer and through
the main spar. I tapped the spar for 4-40 thread and installed a bolt on
each side to lock the stabilizer in place. I installed the elevators
according to the book’s great instructions, using the supplied lightened
control horns and Mylar hinges.
I was pleasantly surprised by the extremely high quality of the
supplied hardware, including the ultralight and strong nylon-bushed
control horns, the 49-strand pull-pull cable, the locking clevises, and
the strong “Pattern-style” hinges. An experienced competition pilot
would choose these items.
In fact, the entire kit’s quality was impressive. The firewall was
held in place using aluminum corners for durability. Control horns used
four mounting bolts for the same reason. This entire package was
designed for heavy competition use and extreme durability without
added weight. Just how strong this light aircraft was would be proven
later.
Shaking Those Tail Feathers: It was time for the big debate: how to
best control the elevators. The kit allowed two methods, one of which
was the conventional two servos in the tail. The other was a forwardlocated
servo using pull-pull cables to the elevators. The latter
technique saves roughly 2 ounces of tail weight, avoids the problem of
synchronizing the two servos, and is technically more elegant.
However, I know my limitations. I have enough trouble just getting
a single pull-pull rudder to center. I would probably never be able to
work was done. After installing the radio, engine, fuel system, and
pushrods, it was flying time.
Assembly: Following the excellent 59-page, photo-illustrated
construction book, the first assembly step was installing the
horizontal stabilizer. It featured fully adjustable incidence using
stabilizer-mounted adjustment screws that locked onto a fuselagemounted
aluminum adjustment rod. Having an adjustable stabilizer
is crucial for a competition aircraft.
The fuselage mounting holes were preinstalled for the main spar
tube and the incidence adjustment rod. The adjusters were factory
installed in each stabilizer half. Before gluing the incidence
adjustment rod in place, I test-installed the spar, incidence rod, and
stabilizer halves to make sure that all were square.
Once they were square, I removed a stabilizer half and glued the
adjustment rod in place on that side. When dry, I reinstalled that
stabilizer half and repeated the process on the other side. This
ensured perfect alignment. Make sure that the adjustment screws
contact the flats of the adjustment rod. If the flat area is not large
enough, you can use a small file to easily extend the flat area in the
soft aluminum.
To complete the stabilizer installation, I propped up the fuselage
until it was level (using the fuselage fin plate as a leveling guide). I
set the stabilizer incidence to zero using an incidence meter. The
instruction book showed how to achieve this result without an
incidence meter.
Start of low-altitude Slow Roll. “Top” rudder control is already in.
Little rudder is needed for level, 10-second Slow Rolls.
Look carefully at the rudder. Only roughly 15% of available
rudder control is required to maintain level knife-edge flight.
Wing and stabilizer halves mount onto aluminum spars. Field
assembly is simple, fast, and requires just two nylon bolts.
The attractive and colorful Extra 330L would be an outstanding
choice for a first large Scale Aerobatics model.
12sig2.QXD 10/25/04 10:43 AM Page 56
December 2004 57
get elevator halves to center and move exactly alike at all times. I
chose the two-servo method.
The servos installed easily, and I used two 1⁄8-inch-diameter carbonfiber
control rods with titanium ends instead of the supplied 4-40
threaded steel rods. The vertical fin was attached after I completed the
stabilizer/elevator installation. The front of the vertical fin was offset 1⁄8
inch to the left to counteract engine torque. The instructions and photos
made this easy.
Before gluing the vertical fin in place with epoxy, I removed the
overlapping plastic covering material from the bottom of the fin. This
ensured a firm, complete bond.
I removed the stabilizer halves but left the main spar in place. I
leveled the fuselage using the spar tube. I installed the fin with 30-
minute epoxy, making sure that it was vertical to the spar. After the
epoxy dried, I installed the rudder. Then I inserted a thin piece of
cardboard between the vertical fin top and the rudder to ensure proper
clearance.
I installed the prepainted fiberglass tail fairing (there was no plastic
in this kit), and tail-feather construction was complete. So was
approximately 65% of the construction work since most of the rest was
completed.
The rudder servo, receiver, switch, and battery mounting board was
installed at the factory. However, since I planned to install a light
engine and had already used two rear servos, I repositioned the battery
pack just behind the firewall and above the fuel tank for extra nose
weight. The throttle-servo mount was supplied, but not installed, to
allow the builder to position it as necessary for the engine being used.
In the extra-light but strong structure, the formers were the
minimum size but were made from light plywood. The turtledeck was
made from a balsa/foam laminate for extra strength without additional
weight. Taping the antenna to the turtledeck eliminated the excess
weight of an antenna tube.
Once the rudder servo was in place, I installed the pull-pull cable
using the premade fuselage holes. The rudder’s servo arm was extra
large, to allow “3-D-style” rudder movement. Whenever a pull-pull
rudder system is used, the length of the rudder control arm must equal
the distance between the holes used in the rudder’s two control horns.
Since the cables must run in a straight line, without narrowing or
“pinching” anywhere, the cables’ fuselage exit points must be located
where the fuselage’s exterior width equals the servo control arm’s
length. Therefore, I had to move the fuselage cable exits forward 1⁄2
inch on this model. This straight-line installation ensured that the
rudder centered perfectly every time. Since the Extra’s rudder
possessed enormous power, centering was critical.
Finishing the Extra: It was time to install the engine. I mounted the
prepainted fiberglass cowling in place using the factory-drilled
mounting holes, and then I measured the distance from the firewall to
the front bottom of the cowling. The cowling’s bottom section
extended out farther than the top. Mine was 5.83 inches. I clamped the
engine to one of the engine-mount beams and set it 1⁄10 inch farther out
to ensure proper spinner clearance.
I had to be careful because there was a left and a right engine
mount. I drilled the engine mounting holes and bolted the engine in
place. Then I positioned the other engine-mount half and drilled the
mounting holes, and then bolted the engine to it as well.
However, models designed for aerobatic competition, whether it’s
precision Aerobatics (Pattern) or Scale Aerobatics, are judged using a
strict, unforgiving set of criteria. There are no allowances for
performance shortfalls. Competition aircraft must have perfect axial
rolls, only minor knife-edge direction changes, powerful rudders,
absolutely no roll coupling, incidence-adjustment ability, light wing
loadings, and other demanding flight abilities.
If the aircraft is weak in any area of flight, it is practically useless as
a competition machine. Pilots cannot compensate for an aircraft’s poor
flight performance while flying in competition. The aircraft and the
pilot must work to perfection to win.
Although the DPM Extra 330L would make a great sport aircraft, it
was designed for Scale Aerobatics competition; therefore, I judged its
performance harshly and looked for even the slightest chink in its
flying armor. I found that its flight abilities are the closest to a modern
Pattern aircraft that I have ever experienced in a Scale Aerobatics
machine.
O.S. Max 1.60 FX Engine
I had a new O.S. Max 1.60 FX two-stroke sitting
in a box. This engine is fast becoming extremely
popular among Pattern pilots, although many wish
that O.S. would also make a rear-exhaust version.
The 1.60 FX has proven to be powerful and reliable,
and it is lightweight at just 32 ounces.
DPM warns against using any of the smaller
gasoline engines in its Extra 330L ARF because of
their low power-to-weight ratios compared to larger
glow engines. Since the 1.60 was within the
recommended size range and was lighter than the
larger glow engines, I installed it.
It proved to be a good choice. The Extra required
just 3.5 ounces of nose weight. The next larger glow
engine was 5-6 ounces heavier than the O.S. and
would have required tail weight. The 1.60 FX saved
approximately 7-8 ounces of total weight. But I
wondered if it would be powerful enough for 3-D
and International Miniature Aerobatic Club
competition.
I should not have worried about power. I propped
the engine to turn 8,900 rpm on the ground using an
APC 16 x 10 competition propeller since the 1.60
achieves 3.7 horsepower at 9,000 rpm. I thought the
larger airframe would prohibit a big rpm increase in
the air and that vertical climbs would force the
engine to turn more slowly. Dumb. The first takeoff
was vertical to higher than 500 feet. Airspeed was a
bit too fast for excellent competition performance,
but the climbs and hovers were impressive.
To help slow the aircraft and increase vertical
performance even more, the people at Mejzlik
suggested that I try one of its 18 x 6 carbon-fiber
propellers. Airspeed was reduced roughly 15 mph
and felt just right for competition. But the vertical—
that nearly out-of-sight vertical—and the super-fast
recovery from hover can lay a permanent smile on
your face.
There was no need for a fuel regulator, as is
required with some of the larger engines, because
fuel flow was consistent at all tank levels.
The O.S. 1.60 FX, which is the most economical
and fuel efficient of all the larger two-stroke glow
engines, proved to be the perfect match with the
Mejzlik propeller. Just remember to read the
instructions and set the idle correctly. MA
—Frank Granelli
12sig2.QXD 10/25/04 10:43 AM Page 57
58 MODEL AVIATION
I have flown several dozen Extra designs,
including 40%+-size models, and I even own
a few. None of these other designs has the
ability to “point” (hold a straight line during
rolls, down- and up-lines, and straight flight)
that a Pattern aircraft has. This airplane does
and does so right off the building bench, with
almost no trimming required. The 330L went
exactly where it was pointed and never
complained or varied during a maneuver.
Straight Slow Rolls were so pretty and
required so little rudder and elevator input
that it was possible to become distracted
admiring them and forget that I was the one
flying the airplane. Even 10-second Slow
Rolls were outstanding.
Snap Rolls showed no tendency to recover
off-line. Each time this Extra stopped snap
rolling exactly on heading without requiring
opposite rudder input before the snap began.
Snap Roll speed was moderate, making it a
bit easier to stop the roll in a wings-level
attitude. There was a definite “stall break”
(nose pitch-up) before entering the snap that
would eliminate Snap Roll “zero scores” from
even the most discriminating judge.
Point Rolls—4, 8, 16, and 32—were fun.
The fuselage had enough knife-edge lift that
little rudder was needed during these
maneuvers. As do many performance aircraft,
the Extra 330L did need 1%—just 1%—of
up-elevator, mixed with left rudder, to fly a
straight line during right knife-edge. That is
not a great deal and presents no competition
problems. Left knife-edge was fine.
The Extra’s rudder was powerful enough
to perform knife-edge loops measuring
roughly 200 feet in diameter without a hint of
roll coupling. It is nearly impossible for a
pilot to “flop” a Stall Turn (fall forward or
over backward instead of rotating) with this
aircraft because of the powerful rudder.
Rolling Circles (not one of my strong
points yet) felt steady and predictable, and
some were even close to being round. Rolling
Loops (another of my weak points) were
straight, steady, and not all that scary. Before
flying this Extra I had been unable to
complete either of these maneuvers, so it had
to be the aircraft that did them—not me.
Vertical performance with the O.S. Max
1.60 engine was terrific. Vertical climbs from
level, stalled flight extended more than 500
feet up. During these maneuvers, the Extra
showed its only difference from a Pattern
aircraft that I could find: it required slight
right rudder input—roughly 10°—during the
second half of the climb to counteract torque
effects. This performance has been common
to all other Scale Aerobatics competition
aircraft I have flown.
Before switching to the carbon-fiber
propeller, vertical rolls topped out at roughly
300 feet. They extended higher than the
original nonrolling verticals with the carbon
propeller, which also seemed to reduce torque
effect.
This Extra exhibited excellent “braking”
in vertical down-lines. Even prolonged
vertical dives did not produce very high
airspeeds. Good braking allows the
competition pilot extra time to plan the next
maneuver while making the current maneuver
“present” better (look smooth and impressive
to the judges). I flew the Extra through the
complete Masters Pattern schedule, and it did
almost as well as my Pattern aircraft.
Okay, the DPM Extra 330L is great for
Aerobatics competition, but can the average
sport pilot fly it?
I can prove that its handling is exceptional.
Before reading the engine’s instructions, I set
the idle as I would for any other two-stroke
engine. Wrong! Therefore, my first 17
landings were power-off. Except for one, each
was easy. This Extra’s slow-speed handling
and great gliding ability removed much of the
drama from each landing. After setting the
idle correctly, the following 101 flights were
uneventful.
Do you want further proof of how easy
this aircraft is to fly? The instruction book
clearly stated that the modeler should reseal
all of the UltraCote seams with a modeling
iron because temperature changes during
shipping may cause loosening. Guess who
didn’t do that?
Approximately 10 minutes into the 27th
flight, the Extra started to drop the right wing
while yawing badly in that direction. I
brought the aircraft back to level flight and
began a landing approach because I thought
one of the aileron servos had gone bad.
As I made the approach, I noticed that I
was inputting nearly full left aileron and
roughly 75% left rudder. Despite the large
control inputs, the Extra was gliding slowly to
Since 1948 Fox Manufacturing
Company has been producing
high quality model airplane
engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
12sig2.QXD 10/25/04 10:44 AM Page 58
the runway as if it were on rails. As it landed gently, it was easy to see
that the entire top covering of the right wing had peeled away and was
flapping behind the wing like a sail.
Despite the loose covering’s drag and the airfoil loss on the right
side, the Extra remained fully controllable and easy to land. You can
probably imagine how easy it is to land with both wings working.
(UltraCote is strong. I reattached the covering, and it still looks new
after 81 more flights.)
Any competent sport flier can handle this aircraft and become a
better pilot for the experience. Good competition aircraft are the easiest
to fly well. The best competition airplanes make the pilot appear more
skillful than he or she might be. This Extra is one of the latter.
What about that one of 17 power-off landings that did not go well?
It is proof of this aircraft’s strength. During an inverted photo pass just
10 feet over high corn, the misadjusted engine quit. There was no time,
or altitude, to do anything but roll the aircraft level and stall it into the
corn.
My world went dim for a moment as the bangs and crunches of the
crash mixed with the sight of falling cornstalks. A 15-pound (with
fuel), 27% Extra does not go quietly into a cornfield. I prayed that the
photos already taken were good because this aircraft was history.
Dave must have had dumb, unlucky pilots such as myself in mind
when he designed this thing. The only damage—and I have many
witnesses—was one dent, not a hole, in the underside of the left wing
where it landed on top of a cornstalk. After 10 seconds with a heat gun,
all evidence of my idiocy was removed.
Competition aircraft are not supposed to crash well, but this one
did. I do not suggest that you try this, but it is nice to know that the
extra strength is there if you ever need it. After this experience I
realized just how strong this aircraft is, and I started flinging it about
the sky, doing all sorts of 3-D work.
Sudden cruise-speed stalls—called the Wall—were done without
tip-stalling. Inverted cross-controlled spins—the Blender—remained
level with a slow descent rate. Torque Rolls and Waterfalls were better
than I can usually fly them. The aircraft made my flying look better
than it was. More experienced 3-D pilots would have a ball
60 MODEL AVIATION
Bisson 1.60 Pitts-Style Muffler
I know I am not the first person to consider the O.S.
1.60 FX to be a perfect match for the DPM Extra 330L
because Bisson Custom Mufflers manufactures an
excellent “Pitts-style” muffler just for this
airframe/engine combination.
The special muffler—shown after 53 trouble-free
flights (mufflerwise, anyway)—features flexible
silicone tubing with attractive metal ends that are a
perfect fit in the Extra 330L’s bottom cowl outlet.
At 8,900 rpm with an APC 16 x 10 propeller, this
7.5-ounce muffler reduces noise levels to just 96
decibels at 10 feet, over grass. This is well below any
current or future International Miniature Aerobatic
Club noise standards and nearly Pattern-quiet.
Even better, the 1.60 Bisson costs roughly $60—
$140 less than a Pattern muffler. MA
—Frank Granelli
The fourpushing the performance envelope with this
aircraft.
My most daring 3-D maneuver was the
Harrier landing. I had never tried this fully
stalled, high-angle-of-attack landing before.
My first attempt actually worked, although
jamming the main landing gear extremely
hard onto the ground this way is not one of
my favorite things.
DPM provided many different levels of
control movements in the excellent instruction
book, from gentle sport flight to wild 3-D.
How to set dual, and triple, rates was clearly
explained. A complete competition trimming
guide was included so that every pilot could
get the best from the Extra.
Since the 330L had a fully adjustable
stabilizer, it was possible to adjust the
stabilizer’s incidence to remove all elevator
trim requirements, yet maintain level flight.
Required for competition flight, this ability
would also make sport flying much easier.
Now, after 108 flights, I still think DPM’s
Extra 330L is the most excellent Extra I have
flown. MA
Specifications:
Wingspan: 76 inches
Length: 74 inches
Wing area: 1,220 square inches
Weight: 14.2 pounds
Engine used: O.S. Max 1.60 FX
Wing loading: 26.8 ounces/square foot
Radio used: JR 10SX transmitter/JR PR955
S-PCM receiver
Servos: JR 4131 elevator/ailerons; JR DS8611
rudder; JR 501 throttle
Battery: 2000 mA, six-volt NiMH
Manufacturers:
Advanced precision composite propeller:
Landing Products
1222 Harter
Woodland CA 95776
(530) 661-0399
www.apcprop.com
Bisson Custom Mufflers
9 Moffat Rd., Parry Sound
Ontario P2A 2W7
(705) 389-1156
www.bissonmufflers.com
Dave Patrick Models
1811 E. 400 N. Rd.
Milford IL 60953
(815) 457-3128
www.davepatrickmodels.com
Mejzlik Modellbau
Borova 14
644 00 Brno
Czech Republic (Europe)
011 420 5 43218888
www.mejzlikmodellbau.com
Sonic-Tronics, Inc.
7865 Mill Rd.
Elkins Park PA 19027
(215) 635-6520
www.sonictronics.com
Tru-Turn Spinner:
Romco Mfg., Inc.
100 W. 1st St.
Deer Park TX 77536
(281) 479-9600
www.tru-turn.com