The 30 Mile Dimples

There are six F-1212 step ribs, three left and three right. The six F-1212 ribs required deburring and some dimpling. Per the plans, the two F-1212 ribs that will become the centermost two ribs receive 120 degree dimples along the entire top flange of both ribs … because they will become a portion the tunnel and a removable cover plate will sit on top of them. The bottom most rivet hole in the forward flanges of the outer most rib on each side also received a 120 degree dimple. In addition, all of the F-1212 L&R ribs received 120 degree dimples in all the rivet holes of the bottom flange to accommodate the flush rivets being used on the RV-12 project.

                Using the Scotch-Brite wheel to remove burrs and smooth edges on one of the six F-1212 step ribs.

                                                 Dimpling one of the F-1212 ribs with the pneumatic squeezer.

                    Bottom flange of all F-1212-L&R ribs were dimpled for flush rivets being used on the RV-12 project.

And now for the 30 mile dimples … overall the DOG Aviation procurement department has done a great job amassing the necessary tools and specialty items required to bring the RV-12 to fruition. One tool which was overlooked was a set of #40 dimple dies for 3/32” rivets that are the type with the holes in them used with a hand rivet puller … or the type that has the dimple dies welded onto the end of a vice grip. The shop is outfitted nicely with various dimple die sets for #30 rivets but only has one set for making #40 dimples using a typical rivet squeezer with a yoke.

As luck would have it, the W-1226-L&R floor pans required quite a few dimples … however, there were two dimples on the front edge for a nutplate that the tools in the shop just could not reach. The edge on this piece of metal is bent way more than 90 degrees so there is not enough clearance for the squeezer yoke to get low enough to allow the dimple die to align with the hole.

This photo shows how the tight bend interferes with the squeezer yoke preventing the dimple die from getting low enough.

Tom to the rescue …. I contacted a fellow RV builder who is building a Van’s RV-10 (a beautiful four place aircraft). Tom lives around 15 miles away and had two types of #40 dimple dies that would do the job … so the two F-1226 floors were packed up and carted over to Tom’s house and dimpled there. The tool that was used to make the dimples resembles a vice grip which has a set of dimple dies welded onto the end of the jaws. Fortunately, there was just enough room for the tool to fit and the rivet holes for the nutplate on both floors were successfully dimpled. Sadly, I forgot to take my camera to Tom’s so don’t have photos of the tool used to form the dimples or of his project to share. Thanks Tom!!!.

                              Dimples in the F-1226-L&R floors made at Tom’s house are circled in red.

The last item to be worked on before the next primer session is the W-1202F bulkhead. The edges were deburred and Smoothed on a Scotch-Brite wheel then the nutplate rivet holes on the top flange were dimpled. In addition, the bottom flange and the side flanges were dimpled for the 120 degree flush rivets being used on the RV-12 project.

                               Making 120 degree dimples in the bottom flange of the F-1202F bulkhead for flush rivets.

                                  Pile of parts ready for cleaning, scuffing with a Scotch-Brite pad and priming.