Working on the leading edges

 

With the top skins on the wings, it’s time to get down to working on the leading edges.  These seem likely to be the last parts I’ll finish before moving the project to Illinois.  Then, the whole thing will likely sit on the shelf until we move out in July.

Section 17 starts with a lot of part prep.  I built the cradle pieces and trimmed the nose ribs while I was waiting for bucking help on the wing skins, so it was time to do some initial fitting and match drilling.  I first sorted the ribs to make sure I had the correct ones for each side (and to make sure I had trimmed the right ones earlier).  I also had to trim the J-channel pieces.  I finally figured out how I had the reversed J-channel pieces for the wing top skin… it wasn’t reversed, it was a piece for the bottom skin!  Sigh.  Alas, I also discovered that I had cut my short W-00009B pieces (first page of the wing instructions) from the wrong piece of stock.  So, I realized that I needed to order two new pieces of J-channel (luckily I won’t need them until I get started on the tanks this July).

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You need to separate this splice strip from the tank skins.  It get riveted to the leading edge and then we use nutplates to screw the tank skin down.  The instructions suggest using a cutoff wheel to do this.  I had visions of cutting off my fingers and of gouging the tank skins, so I opted for something simpler.  This mini-hack worked great.

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Lots of dimpling on the ribs.  There is one more hole that gets match drilled later that will also need to be dimpled.  These dimpling pliers were a great investment.  I use them all the time for dimpling ribs and the edges of skins.  A lot easier to use than my squeezer or my DRDT-2.2015-12-05 11.55.27

On the left leading edge, you have to cut out a slot for the stall warning vane.  I considered just skipping it because I’m adding an angle of attack pitot tube.  I decided to leave it in because (1) it would be a real pain to add after closing up the skins and (2) the A-O-A has to be calibrated before it gives you good feedback.  Since my very first flight is all about calibration, it will be a good idea to have a dirt simple stall warning.  So, I cut the hole out.  Note the big holes on the ends.  Those are a #10 hole.  I didn’t have a #10 bit.  So I ordered a whole set of cheap Chinese bits from size #1 to size #60.  I’m sure they’re not real great quality, but there are a lot of these “drill one hole” parts of the instructions.  I have quality bits for the common sizes, but now I won’t have to wait a week each time I fail to notice yet another weird size bit.

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The clippers did a reasonable job clearing out the hole.  Then a lot of careful filing finished it off.

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Not too bad!

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You need to fabricate the J-stiffeners.  Lots (and lots) of holes to drill.  This is a traditional “blue-lining” job.  You drill one end hole, draw a blue sharpie line down the middle of the flange and then carefully drill and cleco your way across the stiffener.  Then you have to deburr everything….

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…. and dimple everything.  Luckily, this fit on to the DRDT-2.

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Then you need to dimple the skins… There are approximately 3 bazillion holes to dimple (and a dozen or so to skip).   Got the left skin done.  The right skin is waiting in the wings still partially assembled to avoid intermixing the parts.

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There are still more parts to prep.  Here are the brackets for the landing lights.  They were pretty rough and needed a file to smooth them out.  They get dimpled (they are deep enough to countersink, but I’m not going to try to second guess the instructions). They need to be painted flat black to help hide the landing light.  I was going to spray paint them, but then I saw a presentation on powder coating.  I’m going to try that next week.

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In preparation of powder coating the brackets (and in painting the ribs), I decided to make a mini painting booth.  This one is built out of a Home Depot wardrobe box.  It has a 20″x20″ filter wired in the back to help keep overspray under control.  The metal arm will work great for adding the ground wire for powder coating.

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The video I watch on surface prep and powder coating suggested that you wash the surface with Ajax or Comet.  The scotchbrite pad scuffs it up, but the Comet helps remove any grease and also removes any light oxide build up.  When you start, water beads on the surface so you know there is nothing for the primer to grip.

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After a bit of scrubbing, the surface is very lightly scuffed, but still Al-clad for maximum corrosion protection.  And it will really hold the primer (and black paint for the light bay).

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So now, I’ve got one leading edge ready for black paint and reassembly!

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Next up, I’ll paint the bay, prime the ribs (and paint the two in the light bay black), try powder coating the light brackets, and start the reassembly.

 

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