There are 10 (5 pairs) of rib mounting clips
that the builder attaches to the left spar and they were clecoed onto the left spar during
the previous work session. The clips are attached to the front and rear of the
spar and share the same mounting holes. Because the pneumatic squeezer could
reach most all the rivets of the outer three pairs of mounting clips the
decision was made to use AN470AD4-5 solid rivets in place of the LP4-3 pop rivets
the plans call for. The remaining two pairs of rib mounting clips did not have any
lightening holes, thus the pneumatic squeezer had no access so the rivet gun
was dusted off and the rivets were set using a bucking bar.
Using the pneumatic squeezer to attach rib clips
onto the left spar with solid rivets.
For the two pairs of clips the pneumatic squeezer
could not reach, a rivet gun and
bucking bar was used to rivet the attach clips
onto the left spar with solid rivets.
There are eight pairs of rib attach clips that come
already preinstalled on the left spar by the factory. These clips are located
in the areas of the spar where the extra layers of spar doubler plates are
located. Only the two outer holes of the clips are riveted onto the spar using really
large rivets … the inner three holes are left for the builder to rivet onto the
spar with LP4-3 pop rivets. Unfortunately, placing solid rivets into these
holes and using standard riveting techniques is just not possible because the
clips on the opposite side of the spar prevent bucking bar access. The two
photos bellow will illustrate the problem. The first photo has a blue tube
placed into one of the rivet holes of the rib attach clips (the paper towel is
just there to eliminate the reflections). The second photo shows the blue tube
sticking out the opposite side of the spar and the interference the clip on the
opposite side of the spar creates.
Blue tube placed into one of the rivet holes of
a factory installed
rib attach clip to illustrate the clearance issue seen in
next photo.
The blue tube can be seen beneath the rib attach
clip on the opposite side of the spar … this
lack of access necessitates the
use of pop rivets because there is no clearance for a bucking bar.
While adding rivets to the factory installed rib
mounting clips per the plans, one of the LP4-4 rivets used to attach the inner
most rib attach clip onto the spar created some grief when the mandrel broke off
way outside of the rivet. The rivet did not look fully set to me so the broken mandrel
was driven through the back side of the rivet and then the rivet was drilled
out and replaced with another rivet. This was the first pop rivet that has
needed to be drilled out thus far.
The mandrel of one of the LP4-4 rivets used to
attach the inner most rib
clip to the spar broke off outside of the rivet and
needed replacing.
Because of clearance issues, the mandrels of the
rib attach clips needed to be slightly bent
and a wedge used so square pressure
can be applied to the pop rivet while it is being set.
Using the pneumatic rivet gun and wedge to set
the LP4-3 rivets with the
slightly bent mandrels that attach the rib clips onto
the left spar.
All rib mounting clips fully riveted onto the
left spar and ready for ribs at a later date.