Part of the preparation consists of scuffing the rivet lines where the ribs and tank stiffeners will sit. If you dimple the holes first, you will have a hard time doing this afterward. In addition, I’ve wrote myself a note to “break” the aft top and bottom edges of the tank skins prior to dimpling the holes. Doing so through dimpled holes is nearly impossible. Ask me why I know…
I may have said that previously but buying the DRDT-2 tools is a must (www.experimentalaero.com). I’ve read many posts on VAF’s forum from guys who have punched a hole with the standard “C-frame” dimpling machine. It may happen with the DRDT-2 if you’re not careful but it is unlikely to happen compared to its counterpart tool.
Some may have heard that there are dimple dies made especially for RV’s fuel tanks. There are good scientific reasons for using these but some builders have reported either issues or discontentment from their use. For a while I wish I had bought a set of these when I encountered problems with rivets sitting unevenly in the dimpled holes. I’ll explain that in more details later on. Bottom line is I’ve used standard sub-frame dimple dies and the fuel tank rivets turned really great.
Rivet lines are scuffed generously before dimpling the skins.
