Fabric Covering Wing 2 of 8

Fabric bottom wing B

With the wing turned upside down, the first length of fabric was draped over and glued on the trailing edge with a one inch glued turnover section on the topside of the wing. The bottom trailing edge of the Northstar Wing incorporates a very gracefully formed “S” shaped aluminum profile. The fabric in the “S” shaped profile must be glued down along it’s entire shape otherwise the fabric would stretch across the curves after shrinking. Before gluing down the trailing edge, the fabric was precisely cut out to fit over the large aileron and flap protrusions.  Also, prior to gluing the fabric down, a pencil centerline was drawn on the leading edge where the top and bottom pieces of fabric would eventually meet and overlap each other for a glued two inch overlap. After the trailing edge fabric was attached and dried,  glue was then applied on numerous edges where inspection covers occurred and around the tank cover openings. The photos above show the fabric as it was glued over these edges. Please note the fabric is loose and was not shrunk down yet. Poly Fiber instruction suggest one inch of fabric slackness after the fabric is glued down prior to shrinking.  On the upper left photo there is a protrusion that was not cut out. This is an eye bolt used for a flying rope connection for the aircraft when on floats.  The protrusion was only an inch or so above the surface allowing the fabric to be cut out after the fabric was shrunk.

While the fabric attachment was fairly routine on the trailing and leading edges it was quite different on the wing tip edges.  This was especially true on the compound curves where fabric would otherwise bunch up. To avoid this, the iron was heated up to a low heat setting and the fabric was dry formed (without glue) which included clamping, heating the fabric, pulling the fabric around and repeating this until the fabric was shaped to follow the curve.  Excess fabric was then trimmed away and the fabric was clamped and glued in place until dry.

Before starting on the topside of the wing, you use your iron on the fabric edges where the bottom and top fabric glued edges will overlap to take out any wrinkles or imperfections.

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Assembly Details

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 The wing spar brackets on the fuselage must be 30″ on center to agree with the spar attachment points on the wings.  This has to be a precise fit.  Unfortunately my welding experience or lack thereof caused me to not compensate for all the distortion that can happen during a weld and thus I ended up with a fractional difference between the spar brackets.  Fortunately Morgan Williams had an easy solution using a series of thin precision made aluminum plates stacked between the aluminum spars and the steel attach brackets accommodated the measurement difference to thus make a precise fit.  

The Northstar wing like the standard Super Cub wing uses the forward wing strut to carry the aileron cable up to the wing. I wanted the aileron cable concealed and run inside the leading edge zone of the wing.  The lower right photo shows a preliminary rigging set-up of the proposed forward pulley location and it’s necessary alignment of the pulley behind the spar. The carry through hole in the spar had to be kept  small and avoid interfering with the adjacent hard riveted reinforcement plate.

The lower left photo shows the aileron hinge bracket located at the rear wing strut attach point and it’s alignment with the aluminum wing compression strut. Also note that there is an additional steel tube strut providing additional triangulation strength where the wing struts will be attached. The hinge bracket, compression struts and the rear wing strut bracket all come together in a collective assembly of precision made aluminum and steel plates all held firmly together with AN stop nut hardware.