The slots in the surface of the control horns
are cut too large. See the text for an easy
The author made a cutout to allow for engine
clearance and cooling. Note that the rear of the
cowl is made in such a way that the bottom two
cowl mounts are not usable.
Powering the SR- 9
is this rear-exhaust
36cc gas engine.
control horn pieces into the
elevators and the rudder, I ran
into the first major problem.
These horns are smaller than
those used on the wings, but
the precut slots are so big that
the horns are swimming inside
I contacted TBM and we
decided to use the control
horns and fill the rest of the
opening with epoxy mixed with
microballoons. After trimming
the length of the horns to fit the
slots, everything was epoxied
into place and it fixed the
The manual shows that the rudder
should be epoxied into position next,
but I advise putting off this step.
A heavy-duty tail wheel is included,
which requires some assembly as well
as some measuring so everything works
properly. The aluminum plate that the
wire runs through had to be drilled out
to accept the 1/8-inch wire.
The prebent wire has extra length.
It’s designed to extend through the
outer cover, through an aluminum
mounting plate, through a plywood
plate, then through another hole
predrilled in a rib that is further up
into the rudder.
Once cut to length, this wire also
needs a few flats cut to match the
positions of the wheel collars. At this
point, everything can be bolted into
position except the tail wheel. Take a
few minutes to install the pull-pull
wires that steer this assembly.
After everything is mounted in
position, the rear cover, tail wheel, and
wheel collars are attached. Although
the manual doesn’t say to bolt on the
landing gear struts until later in the
build, now is a good time to do so. It
will give you a firmer foundation for
the next step.
This is why I mentioned postponing
attaching the rudder. During the engine
and cowl installation, you can stand
the fuselage vertically, setting it on the
fin. It provides a flat, solid surface. And
having the second landing gear struts in
place gives you support when propping
up the fuselage against a vertical
surface such as a wall or door.
TBM supplied an engine with the
review kit: the Pterodactyl PTE36R
36cc gas engine. It’s a rear intake,
rear exhaust, single-cylinder
engine and it mounts on four
To figure out the engine’s
mounting position, I skipped
forward in the manual and
epoxied the cowl ring into
place. This requires sanding
flat the area on the front of the
fuselage where the ring mounts.
Take a moment to wick in
some thin CA around each of
the blocks on the mounting
ring. A few of the parts were
moving around slightly on my
piece, so make sure nothing
falls off on yours. Be careful not to get
CA in any of the threads.
After the CA cured, I took some
time to position the cowl and get an
idea of how the engine would fit. The
cowl will take a bit of trimming to
allow the muffler and the front fins of
the head to clear.
The engine needed to be spaced
11/2 inches out from the firewall to
allow the cowl to fit properly. No
wood is included in the kit for this, so
I designed a spacer from plywood and
You can download a diagram from
the www.ModelAviation.com website.
Paint it with clear polyurethane to
fuelproof it. To bolt the spacer to the
fuselage, I picked up a set of four 1/4-20
x 2 bolts and matching t-nuts.
Now is the time to finish the steps I
skipped. I mounted the rudder servo,
epoxied the rudder into place, and
installed the pull-pull cables. There’s
48 Model Aviation OCTOBER2012 www.ModelAviation.com