LH RIBS AND SPARS

 

The left wing spar work started on August 3, 2003.  The first thing that I did was to locate the wing inspection panel holes and drill the spar for nutplates.  As with the tank countersinks, I felt that the spar was a little too thin for #6 screws.  I upped the holes in the spar to #21 and counter sunk the screw holes to fit the #6 dimples in the access panels.  I did not photo the process but I did photo the result.  The photo at left shows the three inspection panels cleco’d to the spar.  The photo at right shows the spar countersunk for #6 screws and 3/32” rivets.

Inspection panels cleco’d to spar Holes countersunk for #6 screws

The next project was to install the tie down bracket.  I promptly screwed one up by assuming that the plate aligned with the outboard end of each spar cap.  Looking at the photo below left it is plain to see that the holes are off in the tie down bracket.  A look at the plans shows a hole location for the top right hole.  Interesting concept, follow the drawing.  Guess I’ll try it.

Tie down bracket that was miss-drilled Drawing showing where the first hole should be

I took the other tie down bracket and drilled the first hole per the dimensions in the drawing.  Amazing.  The bracket fit like a glove.  The holes were symmetrical and everything.  I wonder if I will ever learn to double check the drawing.

Second tie down bracket with first hole per dwg. Spacers mfg. per drawing

The left photo above shows the second tie down bracket with one hole per the drawing installed with a cleco and a clamp.  The RH photo shows spacers that I made per the drawing attached to the bracket.  After these parts are primed, nutplates will be attached.  The next item I tackled is the rear spar.  Two very thick (.125”) doublers get attached to the spar.  These doublers actually form the rear spar to fuselage attach point.  The rear spar is in the left photo below.  The two doublers are cleco’d together in the right photo below.  The spar doublers did not require any work other than to de-burr the edges and the holes. 

Rear Spar Rear spar doublers

 The aileron hinge brackets were next.  The lower left photo shows the outboard hinge doubler clamped in place.  The right photo shows the inboard  doubler.

Outboard aileron hinge doubler Inboard aileron hinge doubler

The inboard doubler had to have a hole for the aileron push-rod installed to match the hole in the spar.  I forgot to take a “before” picture of the doubler.  The left photo below shows the outboard hinge bracket cleco’d in place with the doubler.  The right photo shows both hinge brackets and the wing attach fitting doublers attached with clecos.

Outboard hinge bracket and doubler assembly Rear spar and doublers cleco’d together

 

The aileron attach hinge fittings came assembled but I decided to disassemble them for etch, alodine and prime.  The photo at right shows the hinge fittings after disassembly.  Note the bearings.  Also note the recess for the bearings.  I will feel better with primer between the steel bearing and the aluminum hinge bracket. 

I was very careful not to elongate any rivet holes in the brackets when I drilled them apart.

  Aileron hinges disassembled

 

Main spar and aft spar in paint booth O.B. end rib, spar doublers, hinge brackets

After careful thought, I decided to prime the main spar.  I had been debating with myself for some time and I finally decided that even though it has a beautiful anodized finish, primer was made to minimize corrosion.  The picture at left above shows the main and aft spar hanging in the paint booth.  The aft spar was etched and alodined prior to prime.  The RH photo above shows the rear spar doublers, aileron hinge fittings and outboard end rib after priming.  These parts were etched and alodined prior to prime as was  the rear spar.

 

Both spars primed as well as other parts Nutplates installed on main spar

The left picture above shows the two spars as well as the rest of the parts that were primed at this time.  The upper right photo shows the main spar with all of the nutplates installed.  This is a major milestone since this is the first thing the plans tell you to do.  At this point in the assembly process I did not take as many photos as I usually do.  I don’t know why.  Anyway, the picture at right shows the aileron hinge fittings during re-assembly process.  This was straight forward and I did not have any problems.  I installed the inboard hinge and both doublers onto the spar right after this photo was taken.

Aft ribs during straightening and fluting Aft ribs cleco’d in place

I can’t believe I was lax in taking pictures at this point.  Oh well, I will describe what went on.  After I installed the aileron hinge doublers and the inboard aileron hinge bracket, I riveted the inboard rear spar doublers to the spar.  Once this was done I straightened and fluted the remaining 13 aft ribs.  The outboard rib was straightened and fluted previously because it was needed in the process of locating the outboard aileron hinge doubler.  Its attach holes use flush fasteners.  The plans call for countersinking the outboard aileron hinge doubler holes that attach to the end rib through the spar.  I did not feel that the material was thick enough so I dimpled the doubler, the spar, and the end rib instead.  I did not install the doubler yet.  I decided to wait until I had riveted the rest of the spar together.  I left it cleco’d together for now though.  I then cleco’d the other 13 ribs to the main spar and the aft spar to check for fit.  See the upper RH photo.

 

Aft ribs etched and alodined Aft ribs primed

Next on the agenda was to etch, alodine, and prime the aft ribs.  The left photo above shows the aft ribs after etch and alodine.  The right picture shows the ribs after prime.  At this point I was thinking about assembling the ribs to the spar using the fixture I had made several months earlier.  I was getting antsy about using the fixture but I decided it still is not time to move the wing into it.  I riveted all 13 of the aforementioned ribs to the main spar on a work bench.  The outboard rib could not be installed yet.  I actually took a photo of the rib installation in progress. 

Riveting ribs to the main spar Attaching the rear spar to the aft ribs.

The picture at the left above shows the start of the rib installation.  I finished attaching the aft ribs to the main spar with the spar clamped 90 degrees to the work bench surface.  To attach the rear spar, I put the main spar on the floor on some blocks.  I cleco’d the rear spar to the ribs and noticed that some holes in the second and third ribs did not line up at all.  I checked the plans in a panic, knowing that I had missed a step or had installed the wrong ribs or something.  The plans identified these ribs and said to drill new holes and forget about the unused holes.  The 2 photos immediately below show these holes.  Obviously, these ribs were designed for a different wing and adapted to this wing design.  It probably saved Vans Aircraft a lot of time and money by using less tooling.  I am assuming that saving was passed on to me so I accept this unusual construction step without too much complaint.

2nd  and third ribs with misaligned holes Close up of a misaligned hole

 

Outboard rib cleco’d to main spar Outboard ribs attached to spars

I had to straighten, flute, etch alodine and prime one forward rib to attach the aft outboard rib to the main spar (photos directly above).  The forward and aft outboard ribs are riveted together through the spar.  The reason that I needed to rivet these two ribs on now is because I will attach a bracket to the aft rib to hold the spar to the assembly stand.  Also, these rivets weren’t exactly easy to shoot and they would have been worse with the wing in the stand.  You can see that the rivets are very close to the web of the ribs but because I installed them at this point, I was able to move the aft rib sideways to get the rivet gun to the rivet head.

Left wing aft ribs and spar assembly Left wing with one skin cleco’d on

The picture above left shows the left wing skeleton ready to be placed in the assembly fixture.  The photo above right shows the outboard lower wing skin cleco’d in place.  The reason I put the skin in place at this time was because I wanted to make sure that it would fit after the ribs were riveted to the two spars.  I just wanted to make sure that I was not going to have any problems later.  It fit like a glove.  I needn’t have worried but my philosophy is to double check and make sure.  When I force myself to do this, I am seldom disappointed.  

Outboard stand attach bracket installed Wing in the assembly fixture

Above left is the bracket I described earlier.  It's function is to hold the spar to the assembly fixture at the outboard end.  I carefully drilled it so that it was exactly parallel to the spar itself.  The photo at right above shows the wing skeleton in the assembly stand.  See the tools section for more about this stand.

Rear spar support String to check that spar is straight

Above left is a picture of the threaded rod that I used to support the rear spar in the middle.  To make sure that the spar was straight, I stretched a piece of string from one end to the other across the rivet holes.  I adjusted the rod until the holes all lined up with the string at the same point (blurry photo above right).  No, the spar is not warped.  The camera lens distorted the picture.

Installing the fuel tank Checking for twist with plumb bob

Next, I attached the fuel tank (above left).  I am using a DeWalt battery powered impact tool on slow speed with the dial set to 7 so that I do not heat up the bolt due to friction.  The number 7 setting is safe to prevent over-torque.  Last but not least, I checked the assembly to make sure it was not twisted.  More about that in The Left Wing Skin section which is coming up after the Leading Edge section.