Floyd Getz
Aug 28, 2002, 01:00 AM
<blockquote><center>
<table border="1" cellpadding="4" cellspacing="0" width="80%" bgcolor="#D5EAFF">
<tr>
<td width="50%" align="center"><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/outside4.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/outside4_s2.jpg" border="2"></a></td>
<td width="50%" align="left"><strong>Specifications</strong>
<ul>
<li><strong>Weight:</strong>11.5 to 13 ounces (Test plane = 11.9 ounces w/ 8 cell battery pack)</li>
<li><strong>Length:</strong>20.5 inches</li>
<li><strong>Wingspan:</strong>29.5 inches</li>
<li><strong>Wing area:</strong>140 square inches</li>
<li><strong>Wing loading:</strong>11.5 to 13 ounces/sq. foot</li>
<li><strong>Motor:</strong>WattAge 370, geared 3.67:1</li>
<li><strong>Prop:</strong>WattAge 7x5.5</li>
<li><strong>ESC:</strong>WattAge IC-15 (15 amp)</li>
<li><strong>Battery pack:</strong>8-cell 800mAh 5/4AAA NiMH</li>
<li><strong>Radio Required:</strong>4+ channel FM (ailerons, elevator, rudder, motor)</li>
<li><strong>Servos:</strong>2 Hitec HS-55 (elevator and rudder), 1 HS-50 (ailerons)</li>
<li><strong>Receiver:</strong>4-channel pico-type, FM single conversion (GWS 4P used)</li>
<li><strong>Manufacturer:</strong><a href="http://watt-age.globalhobby.com/">WattAge</a></li>
</ul></td>
</tr></table></center></blockquote>
<p><big>Introduction</big></p>
<blockquote>Back in 1984, I remember seeing something in the news about Russia's Sukhoi Design
Bureau coming out with a piston aerobatic plane (the SU-26) that was taking the competitive
aerobatic world by storm. This design was further refined into the SU-31, a craft that enjoys the
highest thrust-to-weight ration of any production piston aircraft, a rate of climb in excess of
3500 fpm and the ability to handle +12 and -10G's. This same plane has continued to dominate
the competition with six out of the top ten finishes in the 2000 World Aerobatic Championships.</blockquote>
<blockquote>I checked with Mike Greenshields at Global Hobby who said that a high trust-to-weight
ratio and sporty looks is exactly what the folks at WattAge were shooting for when they designed
their Sukhoi SU-31. They've managed to achieve that often-elusive goal by mating a lightweight
airframe with a geared 370 power plant on eight NiMH cells, a combination that produces an
impressive climb rate and exciting aerobatic capabilities. This little semi-scale model truly
lives up to it pedigree.</blockquote>
<p><big>Kit Contents</big></p>
<blockquote>The Sukhoi SU-31 kit box contains:</blockquote>
<blockquote><ul>
<li>Airframe Components (EPS fuselage, Depron-type wing and tail feathers)</li>
<li>370 Motor/Gearbox Assembly with 7.5.5" Prop & Spinner</li>
<li>Landing Gear</li>
<li>Control Rods and Horns</li>
<li>Wing Hold-down Rods and Inserts</li>
<li>Plastic Canopy and Cowl</li>
<li>Decals</li>
<li>Black & White Instruction Manual with Photos</li>
</ul></blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/kitparts5.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/kitparts5_s.jpg"></a></center></blockquote>
<blockquote>What you'll need (that's not in the kit):</blockquote>
<blockquote><ul>
<li>Assembly tools</li></ul>
Electronics gear:
<ul><li>An 8-cell flight battery pack (i.e., WattAge 5/4AAA NiMH pack)</li>
<li>15 amp ESC w/ BEC </li>
<li>3 pico-size servos (Hitec 50 or 55, Cirrus CS-10 or GWS 101) </li>
<li>4 channel micro Receiver (GWS 4-P, Hitec Feather or Cirrus MRX-4)</li>
<li>4 channel FM Transmitter</li>
<li>Battery Charger (one that can properly charge NiMH cells)</li>
</ul></blockquote>
<blockquote>The contents of this kit reflect a nice bit of attention to fit and finish of the parts. The fuselage,
cowl, and wing come pre-painted. The wing halves have a protective plastic layer on the leading
edge and pre-cut ailerons. The fuselage features molded spaces for mounting of electronic
components. The result is that construction of the SU-31 requires very little foam cutting and
removal on the part of the builder.</blockquote>
<p><big>Assembly - Wing</big></p>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingjoin1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingjoin1_s.jpg"></a></center></blockquote>
<blockquote>
The Sukhoi's wing is molded Depron-type foam with pre-cut ailerons. Preparation of the wing
structure involves just a few simple steps. The wing halves are joined with epoxy or other
suitable (foam-friendly) adhesive. Mine required minimal sanding for a nice flush fit.
Reinforcement is accomplished by a few strips of clear packaging tape, plus the addition of two
peal-and-stick wing reinforcement boards, one on the trailing edge and the other across the top.
The result is a stiff, strong, and lightweight wing.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingtape2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingtape2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingboard1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingboard1_s.jpg"></a></center></blockquote>
<p><big>Fuselage and Motor Mount</big></p>
<blockquote>
The fuselage comes with top (blue) and bottom (white) halves that epoxy together easily. The
wing hold-downs are of thin aluminum tubing that are mounted through and glued into holes that
you drill (by hand) through the EPS. Measuring the right spot to drill can be just a little
confusing at first until you figure out exactly where it is that they want you to measure from, but
as I looked it over a few times and referred back to the manual, it became evident. To prevent
the EPS from tearing due to the stress that will be placed on the wing in flight, the kit includes
nylon inserts that press into the mounting holes prior to sliding in the aluminum tubing. The
wing is temporarily mounted at this point with bands to allow for proper sight-alignment of the
stabilizer/tail assembly.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusehalves2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusehalves2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusejoined.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusejoined_s.jpg"></a></center></blockquote>
<p><big>Tail and Elevator</big></p>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horiz1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horiz1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horizsquare.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horizsquare_s.jpg"></a></center></blockquote>
<blockquote>
The Depron horizontal stabilizer is reinforced with a fiberglass spar rod that epoxies to the
trailing edge. The elevator is hinged (with a 1/16" gap for free movement) using clear packaging
tape. To insure a good fit into slot in the rear of the fuselage, a foam spacer is added. The
horizontal stab then attaches in the slot once proper alignment is confirmed. A slight amount of
sanding was required to achieve this. The rudder hinges much like the elevator, but without
the spar. A tab on the front of the vertical stab fits into a slot on the top rear of the fuselage and
is epoxied in once a 90-degree alignment is established. Overall, installing the tail assembly was
simple and the instructions covered each step well. A nylon tailskid is provided, but a steerable
tail wheel would not be hard to devise.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/airframe2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/airframe2_s.jpg"></a></center></blockquote>
<p><big>Under the Cowl</big></p>
<blockquote>
Mounting a geared 370 and landing gear to a lightweight EPS foam fuselage must present
designers with certain challenges involving durability vs. weight savings. The folks at WattAge
approached this problem by using an integrated motor/gearbox housing that also serves as the
mount for the landing gear wire. The whole thing installs with three wood screws to a plywood
motor plate that glues to the front of the EPS fuselage. It's nice that the motor and gearbox
comes completely assembled right out of the box. This avoids the potentially serious problems
that newer builders might encounter if they had to install the pinion to the motor shaft and mate
it to the gearbox with proper alignment and lubrication.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/firewall2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/firewall2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/motor_mounted2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/motor_mounted2_s.jpg"></a></center></blockquote>
<p><big>Landing Gear</big></p>
<blockquote>
A "U" bend at the top of the landing gear wire presses into a slot at the rear of the housing and is
held against the plywood plate. The little plastic wheels that come with the kit are adequate for
smooth surfaces like concrete or asphalt. However, if you are planning on taking off or landing from grass
any rougher than a perfectly groomed putting green, other wheels are most certainly needed. I
had to switch to Hobby-Lobby LYT45 foam wheels and bend a new wire for them since our R/C
club field is cut from a Texas pasture. (If you've been to Texas, you know what I mean.)
</blockquote>
<p><big>Control Gear</big></p>
<blockquote>
The elevator and rudder controls utilize 1.5mm rods that attach to convenient "snap-on" control
horns. These horns slide through slotted openings and secure with a back-plate that clicks into
place. The plastic clevises that thread onto the control rods then snap into the forked end of
each horn. I also liked the rudder rod exit indent that's molded into the fuselage, which takes
the guesswork out of where to poke the hole in the foam.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail3.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail3_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/servos1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/servos1_s.jpg"></a></center></blockquote>
<blockquote>
The rudder and elevator servos sit side-by-side in an opening about halfway up the fuselage. Before finally
gluing the servos in as indicated by the directions, I would suggest waiting to check the
clearance of the aileron control rods. I ended up having to go back and re-mount the servos a bit
higher to make sure that there would be no interference.
</blockquote>
<blockquote>
Lightweight radio gear is a must for a plane of this size and type. An extra couple of ounces
could make the difference between a good performer and a dog. Hitec HS-55 servos are a good and
economical option for the elevator and rudder. The GWS Pico servo or the Cirrus CS-10 (both
are 0.19 ounce) would also be good choices. I've had good success with the GWS 4-P receiver
(about 0.1 ounce), so I ordered one for this plane, and it's worked nicely. The Cirrus MRX-4 or
Hitec Feather could also do the job. I wouldn't use heavier radio gear than that if you want a
plane that's going to perform as designed.
</blockquote>
<blockquote>
The ailerons are controlled by torque rods via a single servo mounted into the top of the wing.
The torque rods run through small groves that you cut into the foam and secure with tape
covered by a reinforcement board. I departed from the instructions a bit by securing the servo
in the foam using ProBond instead of the brass collets and mounting screws as recommended.
Care needs to be taken so that none of the aileron control mechanism contacts the side of the
fuselage once the wing is attached.
</blockquote>
<p><big>Cowl, Canopy, and Final Assembly</big></p>
<blockquote>
The Sukhoi comes with a molded and pre-painted plastic cowl that you simply trim and sand
smooth. It secures to the fuselage with screws into plastic mounting boards glued onto each
side. Since it's made of a very thin and light plastic, the cowling had a couple of dimples that I
never could get to smooth out. I'll take lighter weight and a few minor blemishes versus
something that looks slightly better but adds needless weight. After the cowling is on, you can
install the prop and spinner. I found that when I tightened the prop nut, it tended to bind against
the gearbox housing. Removing a small amount of plastic from the rear of the prop hub solved
the problem. I later used a black permanent marker to color the spinner and the front of the
cowling so it would all match the black prop and canopy.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/prop1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/prop1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/stockgear1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/stockgear1_s.jpg"></a></center></blockquote>
<blockquote>
The canopy is clear plastic that you trim and sand the edges just like the cowling. It mounts to
the fuselage in the same manner as well. The instructions don't mention anything about painting
the canopy, but the photo on the box and website show a shiny black one, which looks very nice.
A couple light coats of gloss black spray enamel to the inside (not the outside) of the canopy
produced the desired results.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/canopy2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/canopy2_s.jpg"></a></center></blockquote>
<blockquote>
The Sukhoi comes with a hard molded plastic tray to hold the battery pack on the underside of
the wing, which was excellent for ventilation and easy pack changing. After trimming/sanding the tray
and checking proper alignment, it epoxies to the wing. In addition to holding the battery pack in
place, the rear part of the tray is a flange that insures proper wing alignment. The edges of the
tray also serve to keep the rubber bands from digging into the foam wing. The pack is held in
the tray with crisscrossed rubber bands. I would suggest adding a couple of small pieces of
Velcro to the tray, just enough to keep the pack from sliding out from under the bands during
aerobatics. I discovered the need for this the hard way. Several flights into testing, I pulled out
hard from a split-s, the pack slid out from under the bands, but fortunately stayed connected to
the ESC so that I could make a semi-controlled landing (the CG had shifted big-time) with the
pack dangling from beneath the Sukhoi.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/batt-tray2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/batt-tray2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/battery-bands.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/battery-bands_s.jpg"></a></center></blockquote>
<blockquote>
The Sukhoi comes with a nice set of decals that, when combined with the pre-painted fuselage,
result in an attractive aircraft that didn't require a bunch of time or effort covering or painting.
Of course, extra decoration is an option. Chris, one of our club members (BarnBuster50 on E-
Zone), added a few light coats of red to his for a different look as shown in the photos below.
</blockquote>
<blockquote>
The weight of the finished Sukhoi came in at 11.9 ounces with the stock 800 NiMH 5/4AAA pack.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/weight1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/weight1_s.jpg"></a></center></blockquote>
<p><big>Setup and Flight</big></p>
<blockquote>
The Sukhoi's center of gravity is set 1-5/8" back from the leading edge of the wing at the side of the fuselage.
The manual says that you can set it forward or back as much as another 1/4", giving a fairly
decent range for operational CG. After getting used to the flight characteristics of the Sukhoi, I
enjoyed the increased responsiveness that came with moving the CG back to 1-7/8", but I'd
hesitate to go back any farther than that. There is a section in the manual concerning lateral
balancing, but I decided to skip that since the corrective action is to add weight to one of the
wing tips, something I am loath to do to a plane of this size and weight unless absolutely
necessary. Of course, the book gives control throw measurements for test and sport flight.
</blockquote>
<blockquote>
Considering that this is a 3/4 pound aircraft with a geared 370 in the nose, I was expecting
exciting flight characteristics. The Sukhoi didn't disappoint. After range testing, CG, etc., I
placed it on the paved driveway at a friend's ranchette, trimmed in a little right rudder and gave
it the juice. After a short take-off roll of about eight to ten feet, the Sukhoi rotated briskly. This little
plane climbed easily at about a 45-degree angle. It wasn't long before I had to ease off the
throttle and bring the Sukhoi back around so as to not lose orientation on it. I must say that this
plane tracks very nicely for a small (29.5" span) aerobatic ship. You have to pay attention to it
because of its size and quickness, but it doesn't suffer from instability problems.
</blockquote>
<blockquote>
The aerobatic abilities of the Sukhoi make it a fun flyer that seems to get better and better with
each outing. It will roll at a decent rate and snap when you ask it to. With the thrust that the
geared 370 achieves, nice large loops, outside loops and stall maneuvers are easily
accomplished. The Sukhoi will just about hold a knife-edge, but not quite. Aileron rolls are
moderate, but it snap rolls quickly.
</blockquote>
<blockquote>
When trying out a new plane or power set-up, I always like to hear comments from other flyers
who are watching, especially the glow guys. When I first flew the Sukhoi at our local R/C club,
one of the other members who watched it perform immediately ordered one for himself. As
lawyers (who usually know just a few pithy Latin phrases) say, "Res ipsa loquitur" (that speaks
for itself). He customized his a bit by painting some of the white areas red. I noticed that this
helped with visibility while trying to keep track of the small yet quick Sukhoi.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both5.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both5_s.jpg"></a></center></blockquote>
<p><big>Videos of the Sukhoi in action</p></big>
<blockquote><ul>
<li><a href="/articles/ezonemag/2002/aug/sukhoi/takeoff.mpg">Take off</a></li>
<li><a href="/articles/ezonemag/2002/aug/sukhoi/fly_by.mpg">Fly By</a></li>
<li><a href="/articles/ezonemag/2002/aug/sukhoi/lowpass.mpg">Low pass</a></li>
</ul></blockquote>
<p><big>Durability</big></p>
<blockquote>
For a 12-ounce foam plane, the Sukhoi can take a fair amount of hard use without significant
damage. The molded wing is especially strong and capable of handling a full range of
maneuvers. On the occasion described above (when the battery pack slipped out), I expected
significant structural damage, but found the Sukhoi intact except for a busted-off tail. I glued
the tail back on, added a small bit of Velcro to keep the pack from sliding, and was back in
business in short order.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/gearcrunch.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/gearcrunch_s.jpg"></a></center></blockquote>
<blockquote>
Landings (even good ones) on any rough surface with the stock wheels are likely to cause damage.
As the photo shows, this causes the gear wire to press back against the bottom of the motor
mount and splinter it. Switching to larger wheels and adding a bit of reinforcement to the very
bottom part of the motor mount enables the Sukhoi to land on grass or other rough surface
runways. Several landings on Texas field grass also caused a couple of small stress cracks in the
EPS fuselage just forward of the wing, but they were easily fixed with a dab of ProBond, and
haven't reappeared.
</blockquote>
<p><big>Conclusion</big></p>
<blockquote>
If you're looking for a well-flying, aerobatic parkflyer foamy that won't cause your wife to hunt
you down and inflict bodily harm upon you when she gets the credit card statement, the Sukhoi
should be tops on your list. WattAge has put together a kit that builds well, is attractive when
finished, and flies very nicely. Straight out of the box, it achieves the kind of performance that
makes you want to leave it stock and simply enjoy flying it. I think that's just what I'll do.
</blockquote>
<table border="1" cellpadding="4" cellspacing="0" width="80%" bgcolor="#D5EAFF">
<tr>
<td width="50%" align="center"><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/outside4.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/outside4_s2.jpg" border="2"></a></td>
<td width="50%" align="left"><strong>Specifications</strong>
<ul>
<li><strong>Weight:</strong>11.5 to 13 ounces (Test plane = 11.9 ounces w/ 8 cell battery pack)</li>
<li><strong>Length:</strong>20.5 inches</li>
<li><strong>Wingspan:</strong>29.5 inches</li>
<li><strong>Wing area:</strong>140 square inches</li>
<li><strong>Wing loading:</strong>11.5 to 13 ounces/sq. foot</li>
<li><strong>Motor:</strong>WattAge 370, geared 3.67:1</li>
<li><strong>Prop:</strong>WattAge 7x5.5</li>
<li><strong>ESC:</strong>WattAge IC-15 (15 amp)</li>
<li><strong>Battery pack:</strong>8-cell 800mAh 5/4AAA NiMH</li>
<li><strong>Radio Required:</strong>4+ channel FM (ailerons, elevator, rudder, motor)</li>
<li><strong>Servos:</strong>2 Hitec HS-55 (elevator and rudder), 1 HS-50 (ailerons)</li>
<li><strong>Receiver:</strong>4-channel pico-type, FM single conversion (GWS 4P used)</li>
<li><strong>Manufacturer:</strong><a href="http://watt-age.globalhobby.com/">WattAge</a></li>
</ul></td>
</tr></table></center></blockquote>
<p><big>Introduction</big></p>
<blockquote>Back in 1984, I remember seeing something in the news about Russia's Sukhoi Design
Bureau coming out with a piston aerobatic plane (the SU-26) that was taking the competitive
aerobatic world by storm. This design was further refined into the SU-31, a craft that enjoys the
highest thrust-to-weight ration of any production piston aircraft, a rate of climb in excess of
3500 fpm and the ability to handle +12 and -10G's. This same plane has continued to dominate
the competition with six out of the top ten finishes in the 2000 World Aerobatic Championships.</blockquote>
<blockquote>I checked with Mike Greenshields at Global Hobby who said that a high trust-to-weight
ratio and sporty looks is exactly what the folks at WattAge were shooting for when they designed
their Sukhoi SU-31. They've managed to achieve that often-elusive goal by mating a lightweight
airframe with a geared 370 power plant on eight NiMH cells, a combination that produces an
impressive climb rate and exciting aerobatic capabilities. This little semi-scale model truly
lives up to it pedigree.</blockquote>
<p><big>Kit Contents</big></p>
<blockquote>The Sukhoi SU-31 kit box contains:</blockquote>
<blockquote><ul>
<li>Airframe Components (EPS fuselage, Depron-type wing and tail feathers)</li>
<li>370 Motor/Gearbox Assembly with 7.5.5" Prop & Spinner</li>
<li>Landing Gear</li>
<li>Control Rods and Horns</li>
<li>Wing Hold-down Rods and Inserts</li>
<li>Plastic Canopy and Cowl</li>
<li>Decals</li>
<li>Black & White Instruction Manual with Photos</li>
</ul></blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/kitparts5.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/kitparts5_s.jpg"></a></center></blockquote>
<blockquote>What you'll need (that's not in the kit):</blockquote>
<blockquote><ul>
<li>Assembly tools</li></ul>
Electronics gear:
<ul><li>An 8-cell flight battery pack (i.e., WattAge 5/4AAA NiMH pack)</li>
<li>15 amp ESC w/ BEC </li>
<li>3 pico-size servos (Hitec 50 or 55, Cirrus CS-10 or GWS 101) </li>
<li>4 channel micro Receiver (GWS 4-P, Hitec Feather or Cirrus MRX-4)</li>
<li>4 channel FM Transmitter</li>
<li>Battery Charger (one that can properly charge NiMH cells)</li>
</ul></blockquote>
<blockquote>The contents of this kit reflect a nice bit of attention to fit and finish of the parts. The fuselage,
cowl, and wing come pre-painted. The wing halves have a protective plastic layer on the leading
edge and pre-cut ailerons. The fuselage features molded spaces for mounting of electronic
components. The result is that construction of the SU-31 requires very little foam cutting and
removal on the part of the builder.</blockquote>
<p><big>Assembly - Wing</big></p>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingjoin1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingjoin1_s.jpg"></a></center></blockquote>
<blockquote>
The Sukhoi's wing is molded Depron-type foam with pre-cut ailerons. Preparation of the wing
structure involves just a few simple steps. The wing halves are joined with epoxy or other
suitable (foam-friendly) adhesive. Mine required minimal sanding for a nice flush fit.
Reinforcement is accomplished by a few strips of clear packaging tape, plus the addition of two
peal-and-stick wing reinforcement boards, one on the trailing edge and the other across the top.
The result is a stiff, strong, and lightweight wing.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingtape2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingtape2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingboard1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/wingboard1_s.jpg"></a></center></blockquote>
<p><big>Fuselage and Motor Mount</big></p>
<blockquote>
The fuselage comes with top (blue) and bottom (white) halves that epoxy together easily. The
wing hold-downs are of thin aluminum tubing that are mounted through and glued into holes that
you drill (by hand) through the EPS. Measuring the right spot to drill can be just a little
confusing at first until you figure out exactly where it is that they want you to measure from, but
as I looked it over a few times and referred back to the manual, it became evident. To prevent
the EPS from tearing due to the stress that will be placed on the wing in flight, the kit includes
nylon inserts that press into the mounting holes prior to sliding in the aluminum tubing. The
wing is temporarily mounted at this point with bands to allow for proper sight-alignment of the
stabilizer/tail assembly.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusehalves2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusehalves2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusejoined.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/fusejoined_s.jpg"></a></center></blockquote>
<p><big>Tail and Elevator</big></p>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horiz1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horiz1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horizsquare.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/horizsquare_s.jpg"></a></center></blockquote>
<blockquote>
The Depron horizontal stabilizer is reinforced with a fiberglass spar rod that epoxies to the
trailing edge. The elevator is hinged (with a 1/16" gap for free movement) using clear packaging
tape. To insure a good fit into slot in the rear of the fuselage, a foam spacer is added. The
horizontal stab then attaches in the slot once proper alignment is confirmed. A slight amount of
sanding was required to achieve this. The rudder hinges much like the elevator, but without
the spar. A tab on the front of the vertical stab fits into a slot on the top rear of the fuselage and
is epoxied in once a 90-degree alignment is established. Overall, installing the tail assembly was
simple and the instructions covered each step well. A nylon tailskid is provided, but a steerable
tail wheel would not be hard to devise.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/airframe2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/airframe2_s.jpg"></a></center></blockquote>
<p><big>Under the Cowl</big></p>
<blockquote>
Mounting a geared 370 and landing gear to a lightweight EPS foam fuselage must present
designers with certain challenges involving durability vs. weight savings. The folks at WattAge
approached this problem by using an integrated motor/gearbox housing that also serves as the
mount for the landing gear wire. The whole thing installs with three wood screws to a plywood
motor plate that glues to the front of the EPS fuselage. It's nice that the motor and gearbox
comes completely assembled right out of the box. This avoids the potentially serious problems
that newer builders might encounter if they had to install the pinion to the motor shaft and mate
it to the gearbox with proper alignment and lubrication.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/firewall2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/firewall2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/motor_mounted2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/motor_mounted2_s.jpg"></a></center></blockquote>
<p><big>Landing Gear</big></p>
<blockquote>
A "U" bend at the top of the landing gear wire presses into a slot at the rear of the housing and is
held against the plywood plate. The little plastic wheels that come with the kit are adequate for
smooth surfaces like concrete or asphalt. However, if you are planning on taking off or landing from grass
any rougher than a perfectly groomed putting green, other wheels are most certainly needed. I
had to switch to Hobby-Lobby LYT45 foam wheels and bend a new wire for them since our R/C
club field is cut from a Texas pasture. (If you've been to Texas, you know what I mean.)
</blockquote>
<p><big>Control Gear</big></p>
<blockquote>
The elevator and rudder controls utilize 1.5mm rods that attach to convenient "snap-on" control
horns. These horns slide through slotted openings and secure with a back-plate that clicks into
place. The plastic clevises that thread onto the control rods then snap into the forked end of
each horn. I also liked the rudder rod exit indent that's molded into the fuselage, which takes
the guesswork out of where to poke the hole in the foam.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail3.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/tail3_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/servos1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/servos1_s.jpg"></a></center></blockquote>
<blockquote>
The rudder and elevator servos sit side-by-side in an opening about halfway up the fuselage. Before finally
gluing the servos in as indicated by the directions, I would suggest waiting to check the
clearance of the aileron control rods. I ended up having to go back and re-mount the servos a bit
higher to make sure that there would be no interference.
</blockquote>
<blockquote>
Lightweight radio gear is a must for a plane of this size and type. An extra couple of ounces
could make the difference between a good performer and a dog. Hitec HS-55 servos are a good and
economical option for the elevator and rudder. The GWS Pico servo or the Cirrus CS-10 (both
are 0.19 ounce) would also be good choices. I've had good success with the GWS 4-P receiver
(about 0.1 ounce), so I ordered one for this plane, and it's worked nicely. The Cirrus MRX-4 or
Hitec Feather could also do the job. I wouldn't use heavier radio gear than that if you want a
plane that's going to perform as designed.
</blockquote>
<blockquote>
The ailerons are controlled by torque rods via a single servo mounted into the top of the wing.
The torque rods run through small groves that you cut into the foam and secure with tape
covered by a reinforcement board. I departed from the instructions a bit by securing the servo
in the foam using ProBond instead of the brass collets and mounting screws as recommended.
Care needs to be taken so that none of the aileron control mechanism contacts the side of the
fuselage once the wing is attached.
</blockquote>
<p><big>Cowl, Canopy, and Final Assembly</big></p>
<blockquote>
The Sukhoi comes with a molded and pre-painted plastic cowl that you simply trim and sand
smooth. It secures to the fuselage with screws into plastic mounting boards glued onto each
side. Since it's made of a very thin and light plastic, the cowling had a couple of dimples that I
never could get to smooth out. I'll take lighter weight and a few minor blemishes versus
something that looks slightly better but adds needless weight. After the cowling is on, you can
install the prop and spinner. I found that when I tightened the prop nut, it tended to bind against
the gearbox housing. Removing a small amount of plastic from the rear of the prop hub solved
the problem. I later used a black permanent marker to color the spinner and the front of the
cowling so it would all match the black prop and canopy.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/prop1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/prop1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/stockgear1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/stockgear1_s.jpg"></a></center></blockquote>
<blockquote>
The canopy is clear plastic that you trim and sand the edges just like the cowling. It mounts to
the fuselage in the same manner as well. The instructions don't mention anything about painting
the canopy, but the photo on the box and website show a shiny black one, which looks very nice.
A couple light coats of gloss black spray enamel to the inside (not the outside) of the canopy
produced the desired results.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/canopy2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/canopy2_s.jpg"></a></center></blockquote>
<blockquote>
The Sukhoi comes with a hard molded plastic tray to hold the battery pack on the underside of
the wing, which was excellent for ventilation and easy pack changing. After trimming/sanding the tray
and checking proper alignment, it epoxies to the wing. In addition to holding the battery pack in
place, the rear part of the tray is a flange that insures proper wing alignment. The edges of the
tray also serve to keep the rubber bands from digging into the foam wing. The pack is held in
the tray with crisscrossed rubber bands. I would suggest adding a couple of small pieces of
Velcro to the tray, just enough to keep the pack from sliding out from under the bands during
aerobatics. I discovered the need for this the hard way. Several flights into testing, I pulled out
hard from a split-s, the pack slid out from under the bands, but fortunately stayed connected to
the ESC so that I could make a semi-controlled landing (the CG had shifted big-time) with the
pack dangling from beneath the Sukhoi.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/batt-tray2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/batt-tray2_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/battery-bands.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/battery-bands_s.jpg"></a></center></blockquote>
<blockquote>
The Sukhoi comes with a nice set of decals that, when combined with the pre-painted fuselage,
result in an attractive aircraft that didn't require a bunch of time or effort covering or painting.
Of course, extra decoration is an option. Chris, one of our club members (BarnBuster50 on E-
Zone), added a few light coats of red to his for a different look as shown in the photos below.
</blockquote>
<blockquote>
The weight of the finished Sukhoi came in at 11.9 ounces with the stock 800 NiMH 5/4AAA pack.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/weight1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/weight1_s.jpg"></a></center></blockquote>
<p><big>Setup and Flight</big></p>
<blockquote>
The Sukhoi's center of gravity is set 1-5/8" back from the leading edge of the wing at the side of the fuselage.
The manual says that you can set it forward or back as much as another 1/4", giving a fairly
decent range for operational CG. After getting used to the flight characteristics of the Sukhoi, I
enjoyed the increased responsiveness that came with moving the CG back to 1-7/8", but I'd
hesitate to go back any farther than that. There is a section in the manual concerning lateral
balancing, but I decided to skip that since the corrective action is to add weight to one of the
wing tips, something I am loath to do to a plane of this size and weight unless absolutely
necessary. Of course, the book gives control throw measurements for test and sport flight.
</blockquote>
<blockquote>
Considering that this is a 3/4 pound aircraft with a geared 370 in the nose, I was expecting
exciting flight characteristics. The Sukhoi didn't disappoint. After range testing, CG, etc., I
placed it on the paved driveway at a friend's ranchette, trimmed in a little right rudder and gave
it the juice. After a short take-off roll of about eight to ten feet, the Sukhoi rotated briskly. This little
plane climbed easily at about a 45-degree angle. It wasn't long before I had to ease off the
throttle and bring the Sukhoi back around so as to not lose orientation on it. I must say that this
plane tracks very nicely for a small (29.5" span) aerobatic ship. You have to pay attention to it
because of its size and quickness, but it doesn't suffer from instability problems.
</blockquote>
<blockquote>
The aerobatic abilities of the Sukhoi make it a fun flyer that seems to get better and better with
each outing. It will roll at a decent rate and snap when you ask it to. With the thrust that the
geared 370 achieves, nice large loops, outside loops and stall maneuvers are easily
accomplished. The Sukhoi will just about hold a knife-edge, but not quite. Aileron rolls are
moderate, but it snap rolls quickly.
</blockquote>
<blockquote>
When trying out a new plane or power set-up, I always like to hear comments from other flyers
who are watching, especially the glow guys. When I first flew the Sukhoi at our local R/C club,
one of the other members who watched it perform immediately ordered one for himself. As
lawyers (who usually know just a few pithy Latin phrases) say, "Res ipsa loquitur" (that speaks
for itself). He customized his a bit by painting some of the white areas red. I noticed that this
helped with visibility while trying to keep track of the small yet quick Sukhoi.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both1_s.jpg"></a>
<a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both5.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/both5_s.jpg"></a></center></blockquote>
<p><big>Videos of the Sukhoi in action</p></big>
<blockquote><ul>
<li><a href="/articles/ezonemag/2002/aug/sukhoi/takeoff.mpg">Take off</a></li>
<li><a href="/articles/ezonemag/2002/aug/sukhoi/fly_by.mpg">Fly By</a></li>
<li><a href="/articles/ezonemag/2002/aug/sukhoi/lowpass.mpg">Low pass</a></li>
</ul></blockquote>
<p><big>Durability</big></p>
<blockquote>
For a 12-ounce foam plane, the Sukhoi can take a fair amount of hard use without significant
damage. The molded wing is especially strong and capable of handling a full range of
maneuvers. On the occasion described above (when the battery pack slipped out), I expected
significant structural damage, but found the Sukhoi intact except for a busted-off tail. I glued
the tail back on, added a small bit of Velcro to keep the pack from sliding, and was back in
business in short order.
</blockquote>
<blockquote><center><a href="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/gearcrunch.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/aug/sukhoi/gearcrunch_s.jpg"></a></center></blockquote>
<blockquote>
Landings (even good ones) on any rough surface with the stock wheels are likely to cause damage.
As the photo shows, this causes the gear wire to press back against the bottom of the motor
mount and splinter it. Switching to larger wheels and adding a bit of reinforcement to the very
bottom part of the motor mount enables the Sukhoi to land on grass or other rough surface
runways. Several landings on Texas field grass also caused a couple of small stress cracks in the
EPS fuselage just forward of the wing, but they were easily fixed with a dab of ProBond, and
haven't reappeared.
</blockquote>
<p><big>Conclusion</big></p>
<blockquote>
If you're looking for a well-flying, aerobatic parkflyer foamy that won't cause your wife to hunt
you down and inflict bodily harm upon you when she gets the credit card statement, the Sukhoi
should be tops on your list. WattAge has put together a kit that builds well, is attractive when
finished, and flies very nicely. Straight out of the box, it achieves the kind of performance that
makes you want to leave it stock and simply enjoy flying it. I think that's just what I'll do.
</blockquote>