Fabricating the Flaps


 Fabricating the flaps and ailerons required a special flat table fixture. I had my local lumber yard rip some flat MDF panels into very square pieces and then assembled them around  4 X 4 posts with adjustable leveling glides.  The Northstar Kit included several angle iron brackets that attached to the table top and would be used as squaring stops to keep the skins aligned with the spar and ribs during assembly. The preformed ribs and spar were attached off the table using plastic milk crates to support the irregular shaped parts during riveting.  The rib and spar assembly was then placed against the angle iron stops on the table for attachment of the preformed leading edge sheet metal.  This procedure was basically the same as was done for the leading edge metal on the wings.  The top edge is riveted first and the assembly is then turned upside down and ratcheting straps are used to pull the leading edge metal tight against the edges of the ribs and spar. When everything is tight and square the holes are drilled through the leading edge metal and structure beneath and cleco’d together.  The clecos and skins are then removed and holes are deburred and dimpled for flush riveting.  Almost all riveting was done with a pneumatic riveter gun using Avex brand rivets.

 The corrugaated sheet metal skins are attached to the assembly in preformed sections that overlap the ribs. Reenforced strapping tape is used to keep the trailing edge metal flat and tight against the table surface and stops. The corrugated sheets are then placed over the assembly and riveting lines are aligned with rib edges beneath. The convulusions of the corrugated skins need to be carefully placed to avoid locating them over a riveting line. The strapping tape was very useful to keep the skins down and flat.  Clecos were attached after each hole was drilled and then removed along with the corrugated skin. Each hole was deburred and skins were reattached using Avex dome rivets.  When completed, the Flaps and Ailerons were extremely straight, square and very strong.