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Consequently, the forward fuselage
extended down, generating small, one
inch deep stress cracks (highlight in
black above) at the rear of the
equipment bays.
These cracks were filled with expanding
polyurethane glue. As a result of this
experience, we redesigned the firewall
keys to stiffen this area. With this type
of damage, adding epoxy or
polyurethane glue will add rigidity at the
cracks and completely repair the
damage.
Before and after making such a repair,
you should evaluate the airframe’s
integrity by attempting to twist or flex it.
You are searching for areas of
weakness like a section that moves too
easily – this can be a sign of internal
damage. The likelihood of there being
significant internal damage without
visible external (skin) damage is remote,
but still possible.
This incident, while extreme, proves the
airframe can flex a great deal under
impact forces and receive little, or no
damage. Despite the extreme flex of
the wings and aft fuselage (seen below
at the moment of maximum deflection),
there was no damage to these areas
and only the small stress cracks as
noted above.
How about major damage? Yea, we did
that too. On another occasion, after our
model veered off the runway at full
throttle, it cart-wheeled hard into the
ground, breaking in half.
The signs of damage are pretty obvious
in this case yet some damage was
initially hidden from view.
The first step in assessing the damage
is to remove the skins at a point were
the surface damage stops (perhaps a
logical panel line location).
Cut, then peel back the skin. It takes
about 10 lbs. of pull force to remove the
skin. You will note that virtually all the
adhesive remains on the skin. This
leaves the underlying airframe smooth
for the replacement skin and there will
be no net weight increase (except for
Summary of Contents for T-34C TURBO MENTOR
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