Riveting Rib Attach Clips Onto Left Spar

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.