Radio Control Combat - 2004/03

144 MODEL AVIATION
BY THE TIME this column reaches print, the 2003 Radio Control
(RC) Combat season will have drawn to a close. It was a great season
with record-setting activity in Open and Scale Combat.
The season saw Slow and Survivable Combat (SSC) come into its
own with dozens of events being held across the United States. The
2003 season had more than 93 sanctioned Combat events in 28 states.
The 2003 National Aeromodeling Championships (Nats) in Muncie,
Indiana, saw Open Class B Combat become the third most popular
event in the entire discipline (and we are aiming higher in 2004!).
As a result of all that flying and fun, many models have seen dozens of
rounds and have been bumped, bruised, and whacked countless times
during the year. Now, between the 2003 and the 2004 season while the
skies are calm, it is a good time to perform critical inspection and repair
of your Combat models. Do it before this year’s season gets into full
swing.
As with their full-scale counterparts, the first step in ensuring the
safety of operation of flying models is a close and detailed inspection to
find any problems before they are critical.
I like to start with the wings. I visually check each wing for damage.
I follow the length of the wing, looking closely for cracks or dents that
may be visual signs of greater damage. Depending on the type of wing,
I either remove the servo or disconnect the linkages for the servo.
(Some of my servos are built in and require major surgery to remove.)
Using my knee, I support the top center of the wing and pull both
wingtips slowly up while looking at the leading edge. The wing should
flex uniformly along its length. Signs that it is bending or flexing
unevenly can be an indication of internal spar damage. Rotate the wing
and watch the trailing edge while performing the same test.
While I am putting stress on the wing, I look but also listen for any
pops or cracks that it might make. An audible click in concert with an
uneven flexing of the wing is an indication that there is a break in the
continuity of the spar or supporting structure.
I flip the wing over and test it again. This time I will be pushing
down on the wingtips rather than pulling up. Again, I watch the wing
from the leading edge and listen for any audible clues. I repeat the act
of pushing down on the wingtips, this time watching the wing from the
rear.
I’ve learned that it is important that the wing be tested in a positive
and a negative G test. I had an Me 109 wing that pushed the broken
spar together and seemed fine under one force, but with the force
coming from the other direction, the wing flexed at midspan like it was
hinged!
I then take the wing by the tips and rack the wingtips in opposite
directions. By that I mean that I twist the wing, with the leading edge
forced down in one hand and the leading edge forced up in the other. I
rack it back and forth several times, looking and listening for any sign
of weakness.
If I find a structural problem, the wing then moves to my
repair/rebuild table with notes that describe what I found during testing.
(I suspect that I am not unique in having a larger repair/rebuild area in
my shop than I have for building new models.)
If I’m satisfied that the wing is sound, I go on to test the linkages,
completely ensuring that the ailerons are in good shape and all of the
hinges are still intact. Thank goodness for the fiber hinges! They can be
used to retrofit and repair without having to disassemble the whole
wing!
While the servo is out or disconnected, I check the linkage hardware
and decide if it needs to be replaced. Broken gear teeth are the most
common problem I find. I then reinstall the servo/linkage and plug the
wing into the radio and check that the wing is ready for use.
Greg Rose, 1312 NW 196th St., Edmond OK 73003
RADIO CONTROL COMBAT
Mark McCool gives a model the close attention that is required
for a detailed inspection.
Bill Smrtic won’t have to test to find damage on his P-63’s wing!
Abrupt landings such as this one will require a complete
inspection and a detailed repair.
Checking the fuselage requires the same
attention to detail as the wings do. After
removing or disconnecting the servos, I start
at the tail, checking the attachment of the
stabilizer and rudder to the fuselage under
force from each direction. Again, look and
listen as force is applied.
With the tail, I think it’s a good idea to
check for cracks running with the chord. I
make sure to flex the elevator in different
directions to ensure that the connection
between right and left is good, paying careful
attention to the point at the front of the tail
where it joins the fuselage. This is a common
weak spot on many models.
Similar to the wing-flex test, I take the
fuselage by the nose and the tail and start to
twist. Twisting first in one direction and then
the other, I watch and listen for hidden cracks
that may appear under stress. I’ve been testing
a model as I am writing this, and I found a
small crack between the wing saddle and the
left rear wing-attachment dowel with this test!
This is a good time to check those dowels
or whatever wing-attachment system you use.
I spread and then compress the fuselage from
the model of the wing-saddle area, looking for
uneven flexing that may indicate a hidden
problem. Since they are already out, this is
when I check my servos and inspect the
linkages.
I get my hex wrench ready because I will
need it for the firewall forward. I remove the
engine and engine mount and begin my
inspection of the firewall itself. When I’m
satisfied it’s in good shape, I install the engine
March 2004 145
mount without the engine. I check every
mounting hole, repairing or resetting the blind
nuts.
Before I continue with the inspection, I put
the wings on the airplane and use the engine
mount to check alignment and thrust angles.
Finally, the engine is returned to the model
and the linkages are checked and replaced if
necessary. Pay careful attention to the
integrity of your pushrods. Even a slight bend
in the pushrod can give you an unwanted
differential in control movement.
After all of this, I reassemble the entire
model and give it the once-over with
launching safety in mind. Is the switch located
out of the way during a launch? If not, there is
no better time to relocate it than now. If it
can’t be relocated, I make sure that the switch
is oriented in a manner that doesn’t allow it to
be accidentally shut off while launching.
Having the switch work up and down,
completely perpendicular to the direction of
the launch, seems to work the best.
I check for any linkages that can snag a
hand while launching. This is especially
important on Open designs where many of the
control linkages are exposed.
I always take the time to replace bent wire
linkages that are potential “hand-grabbers”
with alternate linkages. Is there a nonskid area
from which to hold and launch your model?
Now is the time to install one.
One final touch: since I have just given my
model a complete going-over, now is a good
time to install a tether between the wing and
fuselage. Tethers do work, yet not enough
pilots use them.
The 2004 season gives every indication that it
will be a bigger year in RC Combat than the
record-setting 2003. Let’s make it a recordsetting
year for safety in RC Combat too!
Until next time, fly safely, fly Combat,
and don’t forget to check your six! MA