Stub Spars Completed

The stub spar’s machine countersinking is completed and after making craters in the stub spars for an entire day, it was good to do a little riveting to break the monotony. At some point the wing spars will need to be countersunk for the flush rivets and that will be time consuming because the spars have lots and lots of rivet holes … but that is a task for another day.

Each of the W-1208C stub spars receive a W-1208B stub spar doubler plate that, prior to riveting, receives countersinking for three holes at the inboard edge of the spar. Because this end of the stub spar is really a tab that mates with the fuselage, the three rivets here must be totally flush on both sides of the stub. Because of this, these three rivet holes are countersunk on both sides thus allowing the shop head of the rivet to form in the countersink. This results in the shop head being formed flush to the surface being riveted.

                                         Machine countersinking the three holes on the stub spar’s inboard tab.

                                                  Front and backside of the countersunk tabs on the stub spars.

                            View of the front and back of the stub spar tabs after flush riveting. Note how the
                            countersinking on both sides of the spars created flush rivets on both sides.

The rivets called out for riveting the stub spar doubler plates onto the stub spars are AN470AD4-4 rivets. Once inserted into the rivet hole, they looked a little short to me so measured them with the rivet gauge and decided the rivets should be the next size longer. I made a substitution and riveted the parts together using AN470AD4-5 rivets which made for a nice looking rivet.

                 Rivet gauge with the AN470AD4-4 called for in the plans … the rivet should touch the gauge.

                                       Rivet gauge with the substituted AN470AD4-5 rivet …. a much better fit.

                                      Completed left and right stub spar assemblies waiting for wing assembly.

The four W-1216 flaperon hinge brackets were the next items to get assembled. Each of the four hinge brackets are made from a W-1216 L&R bracket. Here again the plans called for AN470AD4-4 rivets which also looked short … so once again the rivet gauge was used to measure and sure enough, it was short. Because it is a flaperon hinge bracket, decided it best to once again install the proper sized rivet which is the AN470AD4-5 rivet.

Flaperon hinge bracket with AN470AD4-4 rivet being measured with the rivet gauge … note the rivet is quite short.

                               Flaperon hinge bracket with AN470AD4-5 rivet being measured with the rivet gauge,
                               note the perfect sizing which is why I used this size rivet instead of the 4-4.

                        Riveting the flaperon hinge brackets with the pneumatic squeezer using AN470AD4-5 rivets.

                                      Front and back of finished flaperon hinge brackets … the open rivet holes
                                     will attach the brackets to the inside of the wing structure later in assembly.