The Wings – Page 4

I fabricated the 7A “sister” ribs and glued them into place on both wings after drilling three ½” vent holes in them. I also drilled two of the same sized vent holes in the 2A ribs as I had forgotten to drill them prior to installation. I also glued on the ¼” nail strips to top and bottom of front spars leaving 1/8” or so between nail strips and ribs for ventilation.

I glued the ¼” square corner blocks to the shortened rear rib sections of ribs 3-6 leaving a small bit of overhang into the notches that had previously been cut. I did this to make sure I had some “adjustment” room in case I needed it to make the aileron mounting spar flanges fit properly. I measured and cut the stock for the bottom mounting flanges first. After notching the flanges to go under the caps of ribs 2 and 7, I made sure the flange was straight by measuring the distance from the leading edge of the rear spar to the flange at different points along the flange. I also made sure that the bottom of the flange would be level with the rib webs after the cap strips were sanded down to the webs of ribs 3-6. After some minor sanding adjustments of the corner blocks, I glued in the bottom flanges.

I deviated from the plans sequence slightly at this point. The plans say to glue the top flange into place and add the doublers, drill for the aileron hinges and add nut plates later in the process. I decided that it would be much easier to glue in the doublers, drill the holes and add the nut plates before the flange was glued to the wing. We’ll see.

I measured and cut the stock for the top flanges and notched the ends to fit under the caps of ribs 2 and 7. I measured for the placement of the aileron hinges and marked the flanges for them. I am using 2” stainless steel hinge material and had them cut 4” long with one end of the pin welded in place. The hinge holes are in the center (vertically) of the hinge halves for both wing and aileron sides but the holes are staggered horizontally for screw head clearance. Holes are .167 for the 8-32 screws called in the plans. I now centered the four, 6” x 3/8” x ¾” doublers on the center lines for the hinge locations and glued them in place. I then positioned the hinges on the flange/doubler and clamped the hinge in place temporarily to mark the hole locations on the doubler. (To make sure the hinge would be flush with the top of the wing, I laid the flange/doubler on its side on the workbench and sandwiched a piece of 1/8” plywood the same width as the flange between the flange and a vertical surface and butted the hinge against the vertical surface.) Using the drill press, I drilled the holes in the doublers for the hinges.

Although the plans don’t call for it, I added 1/8” plywood to the forward side of the flange/doublers. I felt like this would give the hinge doubler area more strength with very little weight penalty. After gluing on the plywood, I back drilled the hinge holes. I then used some 8-32 screws to hold the nut plates in place while I drilled the small holes for their mounting screws. After applying two coats of sealer under the nut plates, I used #2 x 3/8” cap screws to hold the nut plates in place. I only put one mounting screw in the nut plates for now so that the nut plates would swing clear of the hinge holes. I did this so I will be able to back drill the hinge holes when the plywood face of the spar is glued on.

I glued in the top aileron flange after carefully checking for alignment. The angle of the flange is also important here because of the square corner that should be formed by the top of the rib and the face of the mounting spar. I cut the face plywood and glued it to the flanges. I then back drilled the aileron hinge holes thru the face plywood. I notched the top of ribs 3-6 for the top piece of the mounting spar. The plans show this plywood covers the cap strips of ribs 2 and 7. I did not cover these caps. I stopped at the midpoint of the ribs to leave a glue surface for the “box” plywood around this piece. After gluing on the top plywood, I cut and glued on the plywood covering the top of ribs 2&2A and ribs 7&7A, making sure the plywood, when mounted, would be level with the trailing edges of the other ribs.

Flipped the wing to do the same on the bottom side. Sealed it all with Clear Coat.

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