THE LH WING SKINS

 

I started the left wing skin installation on October 14, 2003.  The photo below left shows me reaming the lower wing skin holes to size.  The inboard skin had to be trimmed where it met the fuel tank skin.  The picture at right below shows the beginning of a deviation from the plans.  I had been debating whether or not to attempt to make a one piece skin for the top of each wing.  I have seen other RVs with one piece skins and I thought that they looked good.  I decided to give it a try.  The picture at right below shows the .032 2024 T3 aluminum that I ordered right after I opened the box.  The aluminum was damaged!!!  I decided to see if there was enough of an un-damaged area to use to make the skin.  Low and behold, if I was careful there was just barely enough un-damaged area to fabricate the upper wing skin in one piece.

Checking and fitting lower wing skins Aluminum damaged in shipment.

The photo at left below shows the upper wing skins supplied with the kit cleco’d to the .032 2024 T3 aluminum after I transferred all of the holes to it from the inboard skin. There are two rows of fasteners along the seam where the inboard skin is overlapped by the outboard skin.  I was careful to drill only the row that picked up the rib where the skins overlap.  I cleco'd the outboard skin to the inboard along this seam.

Inboard skin cleco’d to aluminum sheet Outboard skin added on

Next I transferred all of the holes in the outboard skin to the aluminum sheet.  After these holes were drilled I scribed a line on the aluminum sheet around the perimeter of the skin.  I trimmed away the excess material to the line and de-burred the edges.  Next I held my breath and cleco’d the “new” skin to the wing to  check for fit.  It fit like a glove (photo below left).  Now if I can only rivet it on without deforming it too much. I did not mention it before but the reason that I used .032 is that this is the thickness of the original inboard skin.  The outboard skin is .025 but it would be considered to be a good practice to have the one piece skin be the same thickness as the thicker of the two skins that came with the kit.  The next item on the agenda was to remove the protective coating on the outside of the skin along the rivet lines.  The photo at right below shows the process.  I left the skin cleco'd to the wing and put masking tape along the lines where I wanted to remove material.  Then I used the soldering gun to melt away plastic on each side of the rivet line along the edge of the masking tape.  By the way, I stopped using the "trigger" type soldering gun eventually.  It is intermittent duty and I have burned one of these up already.

“New” one piece upper wing skin Removing protective coating.

Now it was time to dimple the rivet holes in the new one piece skin.  Because the sheet was so large, I set the platform up on the floor.  I had the skin lay on a piece of plywood to help protect it (below left).  The next item was to etch, alodine and prime.

Dimpling rivet holes in new one piece skin Skin and inboard doubler primed

The smaller sheet in the right photo above is the doubler that re-enforces the skin at the inboard end.  This doubler is necessary because this is where people step to enter the plane.  I cleco'd the skin and the doubler to the wing and was now ready to rivet it on.  First, I would need a riveting partner.  What better riveting partner than my life partner, Mary.  She had never bucked a rivet in her life but after this day was over, she would not have that heavy burden to carry around anymore.  The photo at left below shows Mary in her riveting attire, all bundled up because it was cold outside.  I caught her in the act of blinking her eyes and I did not know it until later.  I should have taken more photos.  The photo at right below shows the upper wing skin riveted in place.  We shot 390 rivets together and had to drill out less than 10.  Mary did very well on her first riveting project.  Within 10 minutes she could tell if a rivet was too high, too flat or bent over.  The riveting took 2 hours and 15 minutes.  That is very quick for a first timer.  That is very quick for anyone actually.

Mary the riveter LH upper wing skin riveted on

What a milestone this was.  After the new one piece upper wing skin was installed, I did not get back to the left wing until March 11, 2004.  On this date I moved to the bottom skin.  As previously stated,  I had already checked for fit and reamed the rivet holes to size.  I also did some minor trimming where the inboard skin met the fuel tank skin.

The photo just below at left shows another person I am introducing to the art of building an airplane.  His name is Dr. Tom Graves.  He is the chairman of the Airport Authority in Gallatin and also a good friend.  He is seen here dimpling the rivet holes in one of the lower wing skins with a pneumatic squeeze.  At right below I can be seen dimpling the holes in the inboard lower wing skin with the “C” frame tool.  Dr. Graves also helped with the removal of the protective coating on the external side of the lower wing skins.  He seems to enjoy the building process and is wrestling with the idea of building his own machine.  You will see his picture in more photos as the project rolls along.

Dr. Tom Graves “Sheetmetal Technician” Dimpling the bottom skin rivet holes

The photo at left below shows the outboard lower wing skin after it was etched, alodined and primed.  The inboard skin under went this process at the same time (no photo).  Below right is a photo of the 3 access panels that are attached with screws when the lower wing skins are riveted to the wing.  These panels called “Inspection Panels” allow for internal wing inspections with their removal.  They also allow access to otherwise impossible to get to rivets during the lower wing skin installation.  The photo also shows the pitot tube mount structure which will be discussed in another section.

Outboard wing skin in the paint booth Access panels and pitot tube mount brackets

Here (below) are  two photos of parts called air gap seals.  These are simple in concept: reduce the airflow between the aileron or flap and the rear wing spar and you will reduce drag.  They probably help reduce the stall speed a little too.  The left photo below shows them both cleco’d in place, looking outboard from the trailing edge wing root.  The other photo shows them in the paint booth after they were etched, alodined and primed. 

Gap seals in place Gap seals primed

The photos below show the installation of the gap seals, starting with the inboard seal.  My able bodied assistant in the pictures is James Graves.  He is the son of Dr. Tom Graves pictured earlier.  James is a senior in high school this year and is very much considering aviation as a career.  I am teaching him to buck rivets in these photos.  The one thing I like about building this airplane as opposed to maintaining corporate airplanes, which is what I do, is that there are no time constraints.  In the real world of aircraft maintenance, everything is billed on a “time and material” basis.  If a project takes too long the customer will be upset thus I will be upset.  If I train someone on the job the customer will not want to pay for his time even if he or she is productive.  With this project I can take all the time I want to teach someone some basic skills.  I am not racing the clock here.

James and I attaching a gap seal Another view of James and I.

The photo at left below shows the left wing with the gap seals riveted on.  It is now ready for the lower wing skin.  The pitot tube and the wiring are all in place (See section titled appropriately enough “Pitot Tube and Wiring”) and the wing box is ready to close up.  Why did I call it a box?  Because that is what the ribs, spars and skins form when assembled, a box.  The other photo shows the inboard skin partially cleco’d in place.  The forward edge of the sheet is held off of the ribs and spar with several strips of masking tape.  This allows me to get to the rivets at the rear so that I can buck them.

Wing ready for bottom skins Inboard skin ready to rivet the aft rows

The photo below left shows me shooting the rivets in the inboard skin by myself.  It is early Sunday and most righteous men (and women) are at church at this hour.  I should be there too but this is a particularly quiet airport on Sunday mornings and I like to work in peace sometimes (when I am not teaching or working with someone else, that is).  The photo below right shows that I have successfully riveted the right lower inboard skin on and the outboard skin is cleco’d in place.  I did not seek help to install the skins but right after I finished the inboard skin I received a volunteer.  The 3 large holes in the skins are the places where the access panels get installed with screws.

Solo riveting the bottom skin Inboard skin completed

The photo at left shows the volunteer.  It is Dr. Tom Graves.  He showed up later in the afternoon and I showed him how to use a rivet gun.  We installed the outboard skin in a relatively short order.  Dr. Graves got the handling of the rivet gun down pretty fast.  Normally, I like to have someone new hold the bucking bar for a while until they get a “feel” for riveting but Dr. Graves picked it up quickly and there were no rivet set marks on or near any of the rivets.  

Well now!  The left wing riveting is done save for the flap and aileron.  Pitot tube installation and wing wiring are next.