THE RH RIBS AND SPARS
As with the left wing, I decided to assemble the right wing in an order different than the plans called for. The first item on my agenda to make a wing out of a box of aluminum parts is to de-burr the edges of all of the ribs. After that is accomplished, the ribs needed to be straightened. The vertical legs of each rib are never quite 90 degrees to the web so they have to be bent with a wide billed tool. I have 2 sizes of these “sheet metal pliers.” The photo below right shows the narrower of the 2. After the vertical flanges are straight, the fore and aft or horizontal flanges need to be straightened and fluted.
The photo above left shows that the straightening and fluting process is complete on the trailing edge ribs. In the photo above right I have just began to straighten and flute the leading edge ribs. This is a tedious process and I am always glad when it is over! I don’t know why that I have a enough patience tackle a project as large as building an airplane but, no patience for these ribs.
The next item on the agenda was to locate the W-731 tie down bar. On the left wing I mislocated this part and had to scrap it. I was a little more careful with this one. The problem that I had on the left wing was that I assumed that the outer edge of the bar aligned with the outer edge of the spar reinforcement. You know the old saying about “assume” (ass-u-me). On this tie down bar I located the upper outboard hole per the drawing and then I drilled it with a #12 drill bit. I put a centerline mark on the bar backside and cleco’d it two the spar (upper LH photo). I then Match drilled all of the holes after ensuring that the lines on the bar were centered in the holes in the spar. Next I counter sunk all of the 3/32 holes in the spar, including the nutplate holes (upper RH photo).
I have read that many people have had a problem with a chattering countersink on the nutplate holes on the spar. The problem is that the spar is not thick enough to counter sink for a #8 screw. I used the same procedure that I used on the left wing. Step one; I enlarged the screw holes to 3/16” diameter. I then counter sunk each hole to the proper depth with a 3/16” countersink. The pilot of the counter sink did not completely penetrate through the screw hole so the counter sink did not chatter.
If you’re metal is too thin for the counter sink, the pilot area of the counter sink will penetrate beyond the hole which will allow the cutters to “walk” inside the area that is to be counter sunk. This is how the “chatter” begins. In the photo at left above you can see two countersunk holes. Notice that there are no chatter marks. In the photo at right above I am checking the depth of the counter sunk holes with a scrap piece of sheet metal that has been dimpled for a #8 screw.
The next step was to locate the access panels to the spar. The holes for the access panels, as with most of the holes in this airplane, come pre-drilled in the spar and the access panel. As with the fuel tank attach holes, these holes are dimpled in the panel and counter sunk in the spar. The difference is that the panels use #6 screws in the spar instead of #8. The spar is too thin to countersink for a #6 screw also. Instead of enlarging the holes to 3/16” I enlarge them to 5/32” and counter sunk them to the proper depth for a #6 screw. I did not take any photos of the process for the access panel screw holes but it is basically the same process as the fuel tank countersinks. The two photos above show the access panels cleco’d to the spar.
The photo above left shows what I thought was a good idea but when you get to the wiring section of this wing, you will see that it did not completely work. What I decided to do was to pilot drill the ribs for snap bushings of two different sizes. I drilled two 1/8” holes in one rib. I then clamped this rib to another rib and transferred the holes. I transferred the holes to all of the rear ribs in this manner. Theoretically I would be able upsize these holes to the right size for a snap bushing. More on this in the wiring section. The Photo at upper right shows all of the leading edge and trailing edge ribs during the etch and alodine process.
The photo above left shows the right hand main spar and the rear spar hanging in the paint booth after they were primed. I etched and alodined the rear spar prior to priming it. The main spar I cleaned with MEK. It is an anodized and does not need to be etched and alodined. The photo above right shows all of the leading edge and trailing edge ribs after they were primed.
After the primer dried there were some details to accomplish prior putting the spar in the wing stand. First on the agenda was to assemble and install the W-731 tie down bar. I say assemble because prior to bolting it on, four nutplates get installed. The nutplate rivets go through two spacers P/N W-726 that of course I forgot to take a picture of. They are fabricated per drawing 15A. These nutplates are for the bolts that hold the aileron bell crank to the spar. Next came the installation of all of the nutplates for the fuel tank skin (K1100-08) and the access panels (K1000-06). There are a bunch of nutplates and if you don’t have a pneumatic squeezer you are going to be there for awhile. I have one and it sure makes short work out of the nutplate installation.
Above left is a photo that shows the first trailing edge rib installation. See the “Leading Edge” section for installation of leading edge ribs prior to trailing edge rib installation. Photo above right shows several trailing edge ribs installed. The arrow points to a glaring error. This rib was installed up side down. How embarrassing! Fortunately, no one but me saw it. I drilled the rib off and reinstalled it correctly. No harm, no foul, as they say. Putting these ribs on after the leading edge ribs were installed was much easier than the procedure the plans call out.
The photo above left shows the wing stand bracket in place. This is my own design. The bracket is held on with two bolts. The holes are drilled prior to installing the rib. The bracket is clamped to the rib with its upper surface parallel and even with the flange that attaches the rib to the spar. Then two 3/16” holes are transferred from the bracket to the rib. Two AN3-4A bolts, two AN970-3 washers (inside next to rib), and two AN365-1032 nuts are used to hold the bracket to the rib. Picture above right shows the rear spar cleco’d in place.
I riveted as much of the rear spar as I could at this stage. I found out on the left wing that some things should not be installed yet. Specifically the aileron attach brackets should not be installed yet. They interfere with a few rivets from the upper wing skin to the spar. I have not installed the aileron bracket doublers at this point either. Also the W-707D rear spar doubler plate should not be installed yet. In the photo above left where you see clecos is where these parts will ultimately go. The wing is ready to go into the stand. Above right shows the wing sub assembly in the stand. I leveled the spar and checked that the wing was not twisted by using the same plumb bob procedure that I used on the left wing (Ref: LH Wing Ribs and Spar).
The photo above left shows the outboard aileron attach bracket doubler in place on the rear spar. The photo above right shows the center aileron attach bracket doubler cleco’d in place. I could have and should have located these two doublers when the wing was on the bench, but I didn’t. It didn’t take too much longer but it would have sure been easier if it was already done before the wing went into the stand.
The center aileron attach bracket gets a hole cut into it that matches a hole in the spar. This is where aileron push-pull tube goes through the rear spar from the bell crank in the wing to operate the aileron. As I did with the left wing I disassembled the aileron attach brackets. I etched alodined and primed the individual parts (RH photo above). Notice the part with the large round hole in it in the photo. This is the landing a light lens retainer bracket. There are no other landing light parts in the photo. That is because they were all primed previously. This part was missing when I primed the other parts. I believe that I accidentally threw it away when I removed the landing light parts from the box that they were shipped in. I had to order another one. It cost $10.00. The shipping cost $6.00. The lesson was priceless.
The photo above left shows the outboard aileron attach bracket doubler partially installed. Four countersunk rivets go into four dimpled holes. To the right above is a photo of the inboard aileron attach bracket doubler, cleco’d in place. At this point in time the upper wing skin has been riveted on. You can see the shop heads on the spar flange in the photo. The wing is out of the stand and on a bench. See “The RH Wing Skins” for details of the skin installation.
In the photo above left you can see that the outboard aileron attach bracket has been re-assembled and it is now cleco’d to the rear spar. It is obvious to see why the four outboard rivets in the spar needed to be flush. The aileron attach bracket angle (with two clecos) covers these four rivets up. The arrow in the photo is pointing to one of the rivets that would not be possible to install with the aileron attach bracket in place. The photo above right shows the inboard aileron attach bracket riveted in place. The arrow is pointing to another rivet from the upper skin to the spar that would have been very difficult to install if this aileron attach bracket were already in place. I made this mistake on the left wing and as of that date on these two photos I have not figured out how I am going to solve it. Anyway, I don’t have to solve it on this wing because I learned from the last wing.
There are two rivets that get countersunk in each aileron attach bracket. This is on the drawing but not covered very well in the plans. I actually had to drill these two rivets out in the left wing after I installed button head rivets first.
The four photos above show the final details of the “Ribs and Spar” section. Upper left is the W-707D spar doubler plate. You can see that it would have interfered with five rivets that attach the skin to spar. The next two photos (Upper RH and lower LH) show the W-721-R flap brace. The inboard end had to be trimmed at an angle but otherwise the installation is straightforward. The last photo Shows the W-724-R aileron gap faring just prior to riveting. This was also a straightforward riveting project.
And there you have it. All of the work is now done on both spars and all of the ribs. Constructing the leading edge is next.