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Get the muffler and see if the fuselage sides will permit its
installation. If there is enough room, skip the following few paragraphs
and go on to the section on setting up the throttle. Chances are there
is insufficient muffler clearance; I don't know why, but many ARFs do
not provide enough. Now what do we do?
Mount the engine in place. Plug
the intake and exhaust holes, and cover the entire engine with a plastic
bag. Use a straightedge and a sharp modeling razor knife to cut the
covering. Make the cut slightly larger than required. Carefully peel
back the covering and apply some low-tack painter's masking tape to
protect the covering.
Use a razor saw to make the vertical cuts that are
visible in the picture. Score the wood for the horizontal cut and then
use a 1/2-inch hobby razor chisel to cut through the tough plywood.
Nudge the other end of that chisel handle along with a tack hammer. You
finally get to hammer away on something!
Remove the offending wood piece
and masking tape. Carefully position the covering over the new slot and
iron in place with a hobby covering trim iron. Cut any overlap away and
use this excess to cover the inside vertical parts. Some wood has to
show but is rarely noticeable once the muffler is installed. Coat any
exposed wood parts with five-minute epoxy to prevent fuel damage.
If you
can locate new covering that is the same color, using it is preferable.
But usually either the colors do not match or purchasing an entire roll
is required, which can get expensive for 2 inches worth of material.
After all that work to install the muffler, you don't get to bolt it on
just yet. Hook up the throttle linkage instead. This was also covered in
the "From The Ground Up" engine series and is reprinted in Sport
Aviator, but the basic idea is simple. Use the transmitter—always extend
the antenna at least four sections when "bench-running" the transmitter
to protect the radio-frequency output section—to set the throttle servo
at full throttle.
Connect the throttle pushrod so that the carburetor is
fully open. Make sure the throttle stick and trim lever are on high.
Lower the throttle stick all the way. The carburetor barrel should
remain open approximately 1/16 inch. Lowering the throttle trim lever
(or using the engine-shutoff button) as well should fully close the
barrel opening.
A computer transmitter makes this easier. If one is not
being used, make any adjustments by changing the servo arm holes or
throttle barrel holes. The farther out from the servo arm's center, the
greater the amount of throttle movement. The farther out from the
throttle arm's center, the less the throttle moves.
Click on photo to view large image with caption
Next you install the
nose wheel. The Hobbistar 60 has a fairly strong nose-gear strut; many
ARFs and RTFs do not. But even relatively strong nose-gear struts have a
problem on grass runways.
Because of the need for a shock-absorbing
spring, the actual strut—the part that extends downward to the axle and
wheel—is offset from the center, usually by approximately 1/2 inch. That
means every bump tries to turn the wheel off course. It is sometimes
difficult for a new pilot, or any pilot for that matter, to keep the
airplane's takeoff roll in a straight line on bumpy grass.
Dual-strut
nose gears are available that prevent this problem. Fults makes the one
used in this installation (model RF400). The two struts are equidistant
from the center post, ensuring that the bumps do not transmit a turning
force.
The dual struts are also stronger and, although they do flex, can
withstand harder landing forces without deforming than a single-strut
nose gear can. Make sure the firewall has the extra bracing I discussed
if you are going to use this stronger nose gear.
Although the Fults
nose-gear kit includes mounting bearings, it is usually easier to modify
the bearings that are premounted on your ARF. Using the Fults' mounting
bearings would require drilling new mounting holes in the firewall.
That's too much work for me. The Hobbistar's mounting bearings only need
to have their holes enlarged. The dual-strut nose gear has a
thicker-than-usual center post. Fortunately this is an easy job.
You can
dismount the Hobbico nylon bearing as shown or try to enlarge the hole
while it is still mounted. Use a high-speed hobby tool and a 3/16-inch
ball cutter to enlarge the nylon hole. If you have a drill press, use a
3/16-inch bit to enlarge the nose-gear bearing hole in the aluminum
engine mount. If not, carefully use a hand drill to try to make the hole
as straight as possible.
Remount everything and make sure it all fits.
Remove the nose gear for now.
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