Sunday, March 27, 2016

Making the New Shin Panel (fig.23-32 P/N 0412117)

My computer died and one thing after another it's a year and a half later and I'm finally getting caught up on postings.
 The flattened panel was used to cut a new blank from 0.032" 2024-T3 aluminum.  I cut it with the grain aligned like on the original panel from a 4 foot wide sheet.

 The flattened panel was clamped to the new blank with 2x4s to hold it flat to the sheet of particle board under the new skin.  I wanted the 2 pieces a  flat as possible to prevent misalignment of the holes.

Using the Whitney punch with the nib ground off a 1/8" punch I started duplicating the holes.  Even though everything is clamped and can't move I like installing Cleco clamps as I go to assure nothing moves.

 The nut-plate holes were then duplicated at the aft end.

 The stiffener flange on each side is 1/2" tall and the bend for it starts 3/8" from the centerline of the rivet holes.

 To punch the holes along the side the flange was cut off on the band saw.  With the ends held in place with Cleco clamps each side was again clamped to the particle board and the rivet holes duplicated.  The Cleco's helped take out any wrinkling from the straightened damage.

 The next thing was to layout the cut lines.  Graphite lead should not be used to draw on aluminum so I used masking tape to draw the cut lines.
Even if you use long smooth edge snips to trim the curved cuts it's hard not to get small wrinkles form the snips.
One way to prevent this is to make the cuts with a band saw, or table saw for straight cuts and then file them smooth.

Just make sure you mask the back side to prevent scratching it on aluminum chips

 The finished blank ready to form.
 I accidentally damaged my blank and had to make another one.  This time I cut the long straight side cuts with a Plexiglas cutter and a straight edge clamped to the aluminum and the piece of particle board.  This is a trick the aluminum siding guys use.  The cutter has a hooked blade which scratches the aluminum and then you bend and break it along the scratch.  The 0.032" aluminum is as thick as this will work with and even then it takes several passes to get the scratch deep enough to fold and break.  If the scratch is deep enough to make a bump on the back side it will bend and break.  With 0.016" aluminum 2 passes is usually enough.  It works even easier with dead soft aluminum.

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