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CARF-Models Extra 330SC (3.1m)
use too much force, otherwise a phenolic hinge post inside
might break loose. Alternatively you can use 4mm carbon
tubes which definitively will have to be greased.
You have a choice of elevator servos. Anyway you should
use only hi-power digital servos with more than 280Ncm
torque. We recommend JR DS8911 or Futaba BLS152 or
BLS172 which fit perfectly in the milled servo cutouts and
supply enough power for extreme maneouvers.
To obtain sufficient elevator throws, quite long servo output
arms are needed (about 50mm). We advise to use full metal
servo arms, for example SWB or Secraft. These arms clamp
onto the servo output shaft with no lost movement (slop) at
all. These are high quality, properly engineered arms, and
are available from many good hobby stores. Anyway you
must not use any plastic servo arms or output discs with
extensions. The extreme torque of the current hi-torque
digital servos can strip the plastic splines - which will result in
immediate flutter and destruction of your Extra.
Install the servos by using the 2.9mm Ø x 13mm sheetmetal
screws provided in the kit. Centre both elevator servos using
your R/C and mount the servo arms, making sure that the
arms are both at 90° to the bottom surface of the stabs. Do
not forget to add a drop of Loctite to the bolt that secures the
arms to the servos. Make sure that your servo arm slots
allow enough space for maximum throw. Otherwise extend
them using a cutter.
The linkages between the servo arms and elevator horns are
made from the 75mm x M3 all-thread with a ball-link on the
control horns. You can fit a single-sided ball-link onto the
aluminium servo arm. Alternatively you can also use clevises
with aluminium pins in aluminum servo arms. We highly
recommend that you apply a little grease on these joints to
give smooth movement and prevent any inclination of the
aluminium pin to bind in the servo arm hole. Secure the
clevises by a M3 nut provided in the kit.
It is important that the linkage is exactly in-line with the
phenolic control surface horns in the elevators, as any 'side-
load' or 'twisting' could weaken or even break them, causing
flutter and destruction of your Extra.
The last step to finish your stabs is to partially static-balance
the elevators by gluing 20 grams of lead inside the mass-
balance area in each elevator half, which helps to prevent
any chance of flutter that could destroy your Extra.
Rudder
The rudder is 100% completed, with the phenolic hinge posts
and the dual phenolic rudder horns already glued in place at
12
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Linkage with a ball-link on each
side
Linkage with a ball-link on the
control horns and a clevise in
the aluminium servo arm.
Glue 20 grams of lead inside
the mass-balance area in order
to static-balance the elevators
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