The ignition was installed on the side of the
fuselage box using its rubber grommets and the
battery used was a Turnigy two cell Lipo installed
aft of the wing spar. The ignition supplied with the
MVVS is for 6 to 8.4v so a two cell LiPo suits perfectly. The engine box was pre sealed with thinned
epoxy resin at the factory, but it’s worth sealing the
edges of the cut out you’ll need to make on the firewall for the carburettor to fuel proof it as well. The
MVVS ignition is interesting in that you can connect
a choke servo directly to the ignition and the ignition will modulate the choke servo as required to
start the engine. A location inside the airframe opposite the throttle servo is there if you wish to install
a choke servo, however I opted for the simple solution of a manual choke as described in the assembly manual. The rod to actuate the choke exits
under the cowl behind the muffler.
The fuselage has a tunnel for a canister muffler
should you wish to go that route and will accommodate an MTW canister or RE3 tuned pipe. The
aluminium landing gear has been bent to facilitate
the canister method but I opted to use the MVVS
Pitts muffler as I had it on hand and the power produced by the engine on this muffler is more than
enough for the airframe. The manual gives guidance of roughly where to cut the cowl to allow for
clearance and cooling for the engine. I added
some light weight carbon fibre cloth to the cowl
around the engine cut outs I’d made to stiffen the
glass work at the edges as I felt long term vibration
could take its toll. This was not a defect with the
kit, just a bit of over precaution on my part. The
front of the cowl is closed to airflow to act as a baffle, which is painted black with a small opening at
the front for cooling of the engine. It’s good to see
the cowl supplied this way as many manufactures
of round cowl aircraft have the whole front open.
This can sometimes lead to overheating due to an
incorrect ratio inlet to outlet air.
The rudder is installed with a thin piece of
piano wire that joins the flat pin hinge halves and
it’s secured by the installation of the carbon fibre
sprung tail wheel assembly. Follow the manuals
advice here and use a cordless drill on low speed
to install the wire. I also found I needed to add a
drop or two of sewing machine oil to the wire to
get it to pass through all the hinges properly.
Wheels and wheel collars are already installed
on the main gear and only the wheel pants need
to be installed. I had to slightly sand one wheel
pant with the drum sander on the Dremel to get
them to sit at the same angle. Make sure you use
a drop of Loctite on all metal-to-metal fasteners
such as the wheel pants screws or they will vibrate loose. It also pays to just check that all
nuts, bolts and screws are tight as supplied by
the factory. I didn’t find any to be loose, but better
to be safe than sorry.
Wing and horizontal stabiliser assemblies are
completed at the factory and only require unwrapping and sliding onto their respective aluminium
wing and tail tubes. The fit of the wings and tail
feathers to the fuselage side was great and the
wing - tail alignment was spot on. Plastic servo
keepers are included to keep connections together when flying. Where I did spend a bit of time
was ensuring that the elevators and ailerons were
perfectly straight and symmetrical. As with any
film covered open structure model, control surfaces can warp and a bit of time with the heat gun
and reverse twisting will get them back in shape.
Look at the model from the rear to check that they
are straight and the same on both sides before
your first flight so less trimming will be required.
The model can be built in the time advertised
but don’t rush it, get everything in and secured
properly as per the manual. My model weighed
10.58kg (23.33lb) completed which is just under
spec and to be expected with the MVVS, as it’s
quite a bit heavier than the DA-85. No other
weight was required for balancing and I balanced
the plane at the forward centre of gravity. Take the
time to read all of the setup advice in the rear of
the manual. I needed to adjust one elevator horn
by a turn to get equal deflection and use the rates
suggested. I really liked the control throws given
for both setups and feel it’s a great place to start.
The Flying
With a wing area of 1762sq. inches, the wing
loading came out at a very respectable 30.5
oz./sq. ft. Taking off with these types of models
is a very straight forward event and the Sukhoi
was no different. With sensible application of
power, the model tracked straight with only the
slightest of right rudder needed during the initial
spool up. Taking the time to set the control surfaces to neutral and ensuring no warps were
present paid dividends as only one click of down
trim was needed to trim the model. It was evident
just after rotation that the power of the engine
was more than enough, so after a couple of circuits to check slow speed handling, stall and
centre of gravity it was on with the show.
As I’d balanced to model for precision aerobatics, inverted flight required the slightest touch
of down elevator to maintain level flight. Tracking
on up lines and down lines was straight as an
arrow, proving Hangar 9 had got the engine
8
Airborne