Section 17 – Wing Skins

11/24/09 – While working on the Section 16 stall warning, I pulled out a skin to check placement and alignment of the sensor.  On the inside of the skin, I found some blackish discoloration which appears to be some form of oxidation. 

I’ve posted this photo to the VAF forums for some advice.  I’m hoping that I just need to polish and prime the affected area.  We’ll see.

Update:  So far the consensus is that this is cosmetic and should be cleaned, buffed, or scuffed off.  I’ve found similar discoloration in the leading edge area of a couple of skins now.  In each case, the discoloration is found under an area of bubbled-up blue plastic, and is limited to the dimensions of the bubbles.  It does not seem to come up with MEK, but scuffs right out with scotchbrite.  This seems to be a non-issue, but I will shoot this photo to Van’s for their take on it.

12/1/09 – Got back to work after a Thanksgiving trip to Oregon (and a Monday series of trips to the bathroom…with the stomach flu).  Peeled the exterior plastic off of 1203-L and removed the interior discoloration with a blue scotchbrite pad.  I polished all discoloration until the metal was bright and uniformly colored.  Then I re-cleaned with MEK and primed with the NAPA 7220.  I found a small nick and a scratch on the exterior side which will be sanded and primed tomorrow.  Short night, since my wife now has what I had yesterday.  Ick.

12/2/09 – Took the night off to read a book.  A word about my skin prep.  I will be scuffing clean any area which shows any level of discoloration/staining/oxidation.  The skin will be scrubbed clean with MEK on a towel.  I’ve found that the blue marking ink and the plastic’s adhesive need to be carefully cleaned off.  Any scuffed areas will get a solid coat of primer, with the remainder of the skins getting a light coat.  I’m still using the Napa 7220 primer, which is self-etching.  I’m not scuffing the skins (other than otherwise noted), as the interior of the skins will not be subjected to wind/weather/movement, etc.  Also, all mating surfaces will be primed on both surfaces.  Ultimately, I’d rather leave the alclad layer alone than improve the primer adhesion.  I figure the weight penalty will be a pound or two across both wings.  Hell, if my wings end up overweight, I can always reskin them or build a new set while I’m flying with these.  Sure, it’s taken me a year to build these.  Next time, I could probably do it in a month.

1/12/10 – Happy New Year.  A nice post from Phil reminded me that I haven’t updated for awhile.  I’ve been dealing with flu (mine and family’s), an acute flareup of a chronic back problem, Christmas, New Year, some urgent duck hunting, and other life-related issues.  I have also now completed ALL of my pre-checkride flight requirements for my PPL!  Last Friday I spent 3.4hrs on a solo cross-country from Redlands to Blythe to Thermal to Redlands, taking me to 5.1hrs of PIC time.  Now I “just” need to do my written, oral, and flight tests for my ticket.  Looks like I’ll have the PPL before I’m done with the plane

Progress has been made, though.  I have prepped and primed all of the lower skins for the left wing. In my prep work I focused on making sure the skins were blemish free and sanding/polishing the edges smooth and tool-mark free.

I have installed the inboard-most skin and am ready to do the outboard skin.  I’ve been hampered slightly by the unfortunate rusting of my clecos.  Boo.  The poor little clamps somehow got moved under a rain downspout and were significantly rusted before I noticed.  Luckily, I found a great product called “Evapo-Rust”.  Okay, stupid name but awesome product.  It works through chelation (sequestration of the offending rust particle, in this case), and ONLY attacks iron rust.  It purports to have no impact on aluminum, and I worked to confirm this by submerging an alclad scrap in the stuff for about a week.  No effect on the alclad was noted.  On the other hand, the rust stripped right off and the clecos work perfectly (I followed up with a shot of WD-40)  Riveting seems to be going smoothly.  I’m happy that I can use the pneumatic riveter on these, rather than the hand-puller I used for all of the rib-related rivets.

4/3/11 – Yup, another year-plus hiatus.  It is what it is, I suppose.  I spent last weekend and part of this one cleaning dust, oiling clecoes, and reorganizing.  Today I cleaned the outboard lower skin, which had been clecoed in place for the last 12mo’s, waiting for me to get back to work.  The clecoes had bled oil onto the ribs and skins, staining/discoloring them in numerous places.  There was no pitting or corrosion, so I cleaned the skins with non-corrosive purple Simple Green.  To get the remaining color spots out, I buffed the exterior of the skins with gray ScotchBrite along the rivet lines and shot a thin coat of Napa primer over the scuff lines.  Not pretty, but better than oil staining, and will ultimately be removed and/or covered by painting.  I also shot some Napa primer on the rear spar to remove the oil drip appearance.  So, the rear spar is now Stewart Primered and Napa primered in places.  Should be solid.  No significant scratching, deformation, or (any) corrosion was noted during cleanup.

It was nice to get back out to the shop.  A new canopy has been ordered for the tent.  Hopefully this canopy will see the completion of Chapters 17 and 18, and the beginning of the fuselage or the empennage, whichever comes next.

Tech Inspection

11/22/09 – The plan is to arrange for an EAA tech counselor to take a look at my wing skeletons before I put on the skins.  In all honesty, I question the need for this with the RV-12 kit.

11/23/09 – Called the local tech counselor and made arrangements for him to come check my work tomorrow morning.  Whee!

11/24/09 – Swing and a miss.  The tech counselor blew off our morning meeting.  When I eventually got ahold of him, he said he’d come by tonight.

Update:  I’m a little concerned about the local tech counselor.  When I contacted him this morning, he said that he’d forgotten about our meeting at 10am (which we’d scheduled only 14hrs before).  We agreed on 6:30pm tonight for the inspection.  Note that these were his chosen times.  At 1:30pm I got a call on my cell phone from the counselor, asking me why he couldn’t find my address (he’d written it down wrong).  I corrected the address for him, but told him that I was now at work because we had agreed on 6:30pm.  “Oh.  Okay.” was the response.  At 6:30pm (and on)…no tech counselor.  To say that my confidence level with this guy is low would be a dramatic understatement.  I will be looking for another nearby counselor to sign off on my wing skeletons.  Obviously, this won’t happen before Thanksgiving.  Oh well.

Section 16 – Stall Warning

11/19/09 – As mentioned below, I began on the stall warning assembly.  I deburred and final drilled the two mounting plates.  I trimmed and deburred the two large angle brackets.  It looks like my supplied parts include a different set of washers than called for in the revised plans, so I’ll need to figure that out.

11/20/09 – Cleaned, etched, and alodined the aluminum parts of Section 16.  Marty Santic’s blog helped me with the washer issue (he’s an RV-12 builder that has a similar kit to mine, but his is flying already).  I should be able to construct the stall warning with the materials available.

11/22/09 – Primed all aluminum parts and assembled the stall warning switch assembly.  Fabricated the terminal blocks.  I was ready to install the various assemblies, but I need to buy some #18ga wire.  Doh.  It’ll give me something to do while I’m setting up the tech inspection.

11/23/09 – Finished the bulk of this section.  Installed the stall warning, but did not attach the wing skin to check alignment because the wing was on sawhorses, not on the table.  The odds of getting Melissa out in the backyard in the 40 degree weather just to switch out wing skeletons were quite low, so I left the test fitting for tomorrow.  I ran the wiring for the stall warning and installed both terminal blocks (one per wing).  I did not install the string down both wings, simply because I didn’t have any string in the shop.  And the last thing left undone is installing the nuts on the left wing’s terminal bracket.  Turns out that the kit came with 2 of these nuts, while the plans require 4 of them.  Hmm.  I looked at the plans about 8 times to make sure it wasn’t my fault, but I seem to be in the clear.  So I will call Van’s tomorrow and request a couple of the required locknuts.  Hopefully the nuts will be waiting for me when I get home on Sunday after Turkey Day.

So, left undone for Section 16 is:

1.  Cleco on the wing skin and check alignment of the stall warning switch. – Completed 11/24/09

2.  Install the string in both wings per plans. – Completed 11/24/09

3.  Obtain and install the two locknuts required for the left wing terminal bracket.

11/24/09 – Spent a little time on the plane waiting for my no-show tech counselor.  I ran string through the grommets in both wings and checked the stall warning.  All looks good.  My only question is whether or not the stall warning tongue should rest on the skin, or if it needs to sit above the lower edge of the cutout.  This is how it looks currently: