Back on the RV12 again, this time to repair some damage to the lower cowling. I usually enjoy airframe work but this repair might not be much fun. The RV12’s thin fiberglass cowling is held to the structure with piano hinges and removable pins, this is a strong and aerodynamically safe way to hold the cowlings on; however, the hinges are attached to the thin fiberglass of the cowling using countersunk aluminum rivets. Bucking rivets into fiberglass is delicate work under the best of circumstances but with at least one rivet pulled through, I may have to do a fiberglass repair.

After pulling the cowl and getting it to the bench, I grabbed a #42 drill bit, slightly smaller than the #40 of the rivets, center punched each one and drilled into the shank. Using a center punch and a hammer, I drove each rivet out of the hinge and inspected the cowl. To my surprise, none of the holes were too damaged to hold a new rivet. I have to give props to Vans for their well put together and detailed plans. I ordered bare hinge from aircraft spruce and had it in hand in only a few days thanks to their distribution center just down the road. Unfortunately, this is where the “experimental amateur built” nature of the RV reared it’s head. The plans say to set up the lower cowling and trim before drilling for the hinge. It appears they had not finished trimming when they laid out the rivets on the cowl, then realized their mistake later and patched and re-drilled several holes. This resulted in the layout being relatively poor. With my other option being to patch all the holes and re-drill the cowling, I elected to use masking tape to hold the cowling in place and transfer the holes to the new hinge. This lead to sub-optimal edge spacing but until I have the time to spend a week on fiberglass work, it will have to do. In order to reduce the chances of the same failure, I drilled and countersunk one extra rivet on the overhang of the hinge.

After a quick test fit with clecos, I bucked the rivets and reinstalled the cowling, the new hinge fits great and the cowling fits more closely to the airframe now that it has been properly adjusted.