(page 15-06) Space crises postponed

By hoisting the left wing spar with all ribs attached up near the rafters I temporarily put off running out of build space and am proceeding with the right wing.  Almost all of the rivets attaching the ribs to the spar can be pulled with the pneumatic puller, which makes things proceed quite rapidly.  The closely spaced ribs near

the inboard end require the hand squeezer because of the lack of space between ribs.

I discovered that once the ribs are attached to the spar any curvature due to inadequate fluting is easily corrected, verifying my earlier decision to not be overly anal about absolute flatness in the fluting stage.

In their current configuration, the spar-rib structure is quite flimsy and I'm looking forward to attaching the skins.  Once skinned, I'm thinking I can continue to store the wings as they are now -- one on the work table and one suspended from the rafters.  The suspended wing will be turned upside down to allow use of the tie-down ring.  As noted earlier, there's a tapped hole on top but this would require drilling a hole in the skin to expose it.  As a full-fledged aero-nerd I could never bring myself to drill the hole in the top skin.

(page 15-05) Mistake in the build manual

Page 15-02 step 9 shows one nutplate and one W00028 doubler plate installed on a nose rib, yet page 15-05 and 15-07 refer to the nose rib with three nutplates.  After puzzling over this a bit  and studying all the

revisions, I contacted the Mothership and they confirmed that there are no longer any nose ribs with three nutplates.  These pages refer to a previous configuration and are now in error.  I'm RV-12 builder 593 and I'm sure hundreds of builders have encountered this, yet no revision has been issued.  I don't understand it.  This explains why the Homebuilt Help video didn't match what I'm doing.  It referred to the earlier configuration.  Those guys at Homebuilt Help need to keep up a bit better as well, but considering how inexpensive their product is, I forgive them.

RIP my favorite tool, the pneumatic rivet puller which came with my Isham RV-12 tool kit.  I never knew who actually made it since Isham re-branded it.  It became necessary to refill the hydraulic reservoir frequently, so I ordered a replacement from the aviation division of Harbor Freight for a mere $40.  It works great.  Can't beat the price.

It's a bit tricky figuring out which ribs go where on the spar, but the actual installation is easy.  As seen in the picture, almost all the ribs for the left wing are installed.  Space is a major problem.  Don't know the solution unless I evict the car from the garage.

(page 15-04) Wing ribs

Attaching ribs to wing spars seemed fairly painless and straight forward until I discovered that I had somehow managed to attach the rib-attach angles to only one side of the spar.  When page 15-04 called for clecoing and then riveting nose ribs to the rib-attach angles starting at the outboard end of the spar I got that familiar sinking feeling that accompanies the realization that I had made a mistake.  Looking back at page

13-03, I saw clearly that attach angles go on both sides of the spar.  I have no idea how I missed it.  The good part is that everything that needs to be redone is completely accessible and involves pulled rivets which are much easier to drill out than squeezed rivets.  The bad part is that there are 50 rivets that must be drilled out.  Fortunately, I have acquired great skill at drilling out rivets, so it didn't take long to accomplish.

The real pressing problem is where I'm going to store the left wing  spar with ribs attached when it's time to do the right.  I put a 3/8-16 eye-bolt into the previously-drilled-and-tapped extrusion intended for the tie down and used it to hoist the right spar up to the rafters until I'm ready for it.  I'm hoping the wings can be stored in a similar fashion.

(page 15-02) Wing OCD (obsessive-compulsive deburring)

Deburring all the wing ribs is a bigger job than I previously suspected.  The lightening holes require use of the little curved, freely-rotating deburring blades (I don't know what they're officially called), the small flange cut-outs require a tiny rat-tail file, and I'm doing the flange edges on a Scotch-Brite wheel mounted to a drill

press (visible in the previous post).  The build manual calls for flattening all the ribs via fluting, and I quickly learned that it's easier to debur before the fluting process.  The edges of the flanges are cut in a scalloped pattern so the flanges are scalloped in two dimensions after fluting.  The picture at right shows the fluting tool and the tool I used to remove fluting.  After fluting the first 10 or so nose ribs, I settled on this procedure which went more quickly: lightly flute every bay between holes, then decrease or increase the fluting where needed as indicated by laying each rib flat on the work bench.  The main ribs require a lot less fluting.  I found that lightly fluting the seven bays between the embossed stiffeners in the web was near perfect with no correction.

Since the fluting didn't require and solvents or lubricants and didn't produce any aluminum chips, I was able to escape the horrendous cold that has descended on the sunny south by moving the fluting operation into the house.  The Spousal Unit (my beautiful and patient wife Karen) was none too pleased but allowed it considering the temperature in the garage.

The description in the build manual of the various operations to be performed on the ribs is somewhat confusing, and the situation was not helped by viewing the Homebuilt Help videos, which don't agree with the manual.  I couldn't find a revision on Van's site which would explain this discrepancy, so I went with my best interpretation of the manual.

The bare ribs come in two flavors labeled W-1208-R and W-1208-L.  I assumed, of course, that the L referred to ribs for the left wing and the R referred to ribs for the right wing.  Wrong.  All the nose ribs for the left wing are labeled R with one exception.

Off topic  The engine for my antique car recently came off the dyno: 544 hp @ 6600 rpm, 486 ft-lbf at 5000 rpm.  I was a bit disappointed in the torque number, but it'll probably be hard to get it to hook up anyway given the limited rim width.

(sections 14 and 15) Where's the global warming when I need it?

Meanwhile, here in the frozen North (Carolina), the temperature has been close to single digits several mornings in the last couple of weeks, and more of the same is predicted before sane weather returns.  This time of year, on average, the low should be around 31 and the high should be around 50.  I can live with that.  I'm not happy about it, but I can survive in it.  This brings to mind the dire predictions from the pundits

back in the sixties and early seventies, when they solemnly proclaimed that we should be preparing for the coming ice age.  I am not making this up.  Maybe they were right.  This is all made worse by the fact that we just returned from our yearly week in the Florida Keys (81 degrees, kayaking in the ocean).

The result: With three kerosene heaters in the shop, I'm still too much of a wuss to work much on the airplane.  I have finished with the stub spars and rear spars.  The 1/8th inch solid rivets all got squeezed with nary a drill-out.  The nose ribs required a huge amount of de-burring, and I'm close to installing them on the main spars.  This requires supporting the spars with saw horses while riveting the ribs.  I simply don't have room without evicting my car from the garage.  I don't have a solution yet.

(page 13-2) Wings continued

After priming the mating surfaces on the 20 rib-attach angles, said angles had to be riveted to the spar webs using pulled rivets (thankfully).  This would involve my favorite tool, the pneumatic puller. Problem was, the

rivets are very close to the angle flange, necessitating use of either the little wedges which were constructed as the very first step in the entire build (can't find them) or the tool shown in the first photo (wedge with a handle).  Using the wedge tool and flexing the angle a bit allowed all the rivets to be pulled without reverting to the manual riveter.

Since the rivets had to pass through the spar web as well as the angle itself (and sometimes another angle on the opposite side), hole alignment was an issue.  The custom hole-alignment tool (Vice-grips holding a 1/8th-inch drift whose tip I tapered) solved the problem, as usual. I prefer this to using a reamer or #30 bit, and I've found very few cases where this wouldn't work.

The next step involved machine countersinking 120 degrees all of the #30 holes on the slanted flanges of the stub spars.  Even though a countersink cage is used for this, I've always found it hard to get exactly the same depth on countersinks.   Van's suggests drilling a 1/4-inch hole in a scrap piece of aluminum and using this as a quick gauge for the larger diameter of the

taper, which I did.  It's still hard to make them identical.  Apparently, dimples in the leading edges of the wing skins fit into the countersunk holes.

The stub-spar doubler plates get riveted to the stub spar webs with 1/8th-inch solid rivets, requiring use of my Main Squeeze and jeopardizing my recently repaired rotator cuff.  Hole alignment again required a fair amount of effort.  The holes with clecos get left open at this point.

The six #40 holes within the inboard rounded portion of the stub spars get countersunk 100 degrees on both faces for "double flush" solid rivets.  Double flush, of course, means the countersunk rivet is squeezed using a flat set until the shop head is flush with the surface of the aluminum, leaving nothing protruding on either side.

The semester is officially over.  All grades have been turned in and, following last Saturday's commencement ceremony, a fresh batch of mechanical engineers has been released into the wild.  Theoretically, I should now have plenty of time to work on the airplane.  The antique car is, as usual, taking part of my time.  The engine for it is going together well as I continue to hemorrhage money.  Should be on the dyno within the week.

(page 13-02) A wing and a ....swear(word).

Or maybe a prayer to the god of aircraft construction that I'll do a better job inventorying the parts when the kits arrive.  With the empennage and fuselage kits, I inventoried essentially all the sheet metal parts and most of the bags, without always looking at every single part in each bag.

 I didn't count all the bolts, nuts, washers and certainly not all the rivets.  My thinking was that my time was better spent building, and if some small part was missing, I'd order it.  The small parts are cheap, and priority mail gets me the parts from Van's to North Carolina in two to three days.  This method worked surprisingly well, with only a couple of nuts or nut plates missing.  When the wing kit arrived, for some reason I didn't inventory anything.  I simply spread the various parts around the garage wherever I could find space.  I don't know why I did this.  Step one of the wing section of the build manual called for cutting apart an angle about two feet long into 20 smaller angles and putting these aside for later use.  You guessed it.  I couldn't find this angle.  Over the next three days, I spent at least three hours searching for the part.  On day two, having abandoned hope and cursing myself for my sloppy inventory technique, I made the decision to reorder but, fortunately, put it off for a day.  On the next day, I found it cleverly hidden out of sight on a box beneath a table.  I had to get on all fours to see it!  Inventory technique exonerated (except for the wasted time).

Step two called for cutting apart a stiffener plate.  Couldn't find it for two days.  The moral of this story is to do a proper job with the inventory and avoid this anguish.  With the fuselage kit, which has more parts and more different parts than any other kit, I made a notation on the inventory sheet telling where each part or bag was put.  I named the various cabinets and sets of shelves, then put that name next to the checked-off part on the inventory sheet (being an engineer, I'm surprised I didn't number them instead of naming them).  With the wing kit, I can't even find where I put the inventory sheet!  I am, at this moment, taking a solemn vow to do a better job with this.

Step three of the wing kit involved drilling and tapping four 5/16th-inch holes for the tie-down rings in the wing spars.  To better explain my fear of this, realize that the wing spars arrive as multiple anodized plates and angles beautifully riveted together.  Each spar is a thing of beauty.

 Doing anything to it makes me nervous, conjuring up visions of a vary large check which would be required to get a replacement.

The drilling and tapping went well.  As shown, the back of the tap handle accepted a 3/8th inch ratchet drive, which greatly facilitated the task.  Boelube was applied to the tap initially, and for every two rotations clockwise, I rotated the tap one rotation counterclockwise to clear the chips (a technique I learned as a student working in a machine shop).

You may be wondering why both top and bottom got tapped.  Best I can figure, it's to allow a hard point on top of the wing if a person is willing to drill the wing skin to expose it.  I'm thinking ahead to somehow using these to support the wings from the ceiling joists once they're finished.