One of the first tasks  accomplished during construction of the cabin area was to rivet the F-705E-L & -R doublers to the F-770 side skins.  These doublers re-enforce the side skin where the wing spar penetrates into the fuselage.  Regretfully, I did not photo the process, but I do have a photo of the parts.  The photo at left shows the RH F-705E cleco’d to the center section vertical brace (arrow).  This part is thick to countersink so I countersunk all of the 3/32” holes.  The 1/8” rivets which surround the spar cutout are all button head rivets (P/N AN470AD4).   The row of rivets closest to the cutout (arrow, photo at right) are best installed before the skin is riveted to the F-704 bulkhead.


F-705E-R F-770 side skin


Before the side skins get riveted in place, there are a few details to deal with,  The left photo below shows a vertical brace, F-728-L & -R, between bulkheads F-705 and F-706.  It gets attached to the upper longeron and a skin stiffener, F-623-L &-R which is not shown here.  In the photo at right you can see that the flange that attaches to the F-623 on both of these braces has no edge distance on one hole in each part.  This is really the first miss-manufactured part that I have run across. 


Photo of additional structure in center fus. F-724-L &-R edge distance problem

To solve the problem I simply had to fabricate a repair to each brace to get the strength back.  The repairs are cleco’d on in the photo at left below and riveted on in the photo at right.  Naturally I primed these two repairs prior to installing them.  This simple repair was all I needed to get the strength back into the part. 


F-724 repairs Repairs riveted in place


The photo below left shows a longitudinal stiffener that is attached to F-704B and F-705 (arrow).  There is another longitudinal stiffener F-722-L & -R, one on each side of the fuselage between F-705 and F-706.  It can be seen cleco’d in place in photo below right (arrow).  The vertical stiffener that runs across the F-722-L that is shown is the F-724-L with the edge distance problem described above.  By the way, -L means this is a left part and –R is a right part.  In the wings and also in some parts of the fuselage there are –L parts on the right side and –R parts on the left???  This could be very confusing and I am easily confused.


F-720-L armrest F-722-L and F-724-L


There is a modification that gets accomplished on the upper longeron stiffeners, F-721B-L & -R, for airplanes with sliding canopies (which I will have).  It consists of putting a slot in the vertical flange as well as shortening it.  This modification is at the aft end.  The reason is to accommodate a plate P/N F-757-S on each side of the fuselage.  The plate also gets a modification.  The photo below left shows the slot.  Below right is one of the F-757-S plates undergoing modification. 


Modification to the F-721B-L F-757-S Modification


The photo below left shows the location of the installed F-757-S.  The photo at right is a Vans “gotcha.”  I drilled the outboard ribs for a -7 snap bushing previously.  When the side skin was cleco’d on, I saw another pilot hole and thought that I had not drilled for the snap bushing yet so I ended up drilling a snap bushing hole through both parts.  Drawing 22 shows to drill a 5/8” hole in the seat rib, drawing 28 shows to drill a 5/8” hole in the skin????  I haven’t decided what to do about this yet, if anything.  I will have to wait to see how I run wires and plumbing from the wing.


F-757-S installed How many snap bushing holes do we need?


I changed my protective coating removal procedure a little on the two side skins F-776.  In the left photo below, it is clear that the protective coating is still on the outside of the skin.  It has not been removed around the rivet lines.  In the right photo I have removed the plastic coating around the rivet lines. I did it while the skin was cleco’d on.  It was easier this way because these skins are so large.


RH F-776 prior to coating removal LH F-776 after coating removal


If the coating had not been removed then obviously these skins were not dimpled yet either.  These two skins are so large I set up the “C” frame dimpler on the floor.  I made 2 simple platforms the same height as the “C” frame platform to support the skins during the dimpling process (lower left).  These platforms worked very well.  As you can see looking at the other photo (lower right) these skins are so large that they require special care.  The added platforms worked to keep the skins relatively straight during the dimpling process.  If you let the skin overhang the dimpling platform you risk the danger of these skins developing a crease or worse yet the possibility of slipping during the setting of a dimple.  There are more photos of the platforms in the tool section. 


Dimpler with the 2 extra platforms Dimpling an F-770 side skin


In the picture below left you can see my new riveting partner.  She is my wife's sister, Sharon.  She was down from North Dakota where she and her husband operate a nice farm.  As hard as it is to believe from looking at the photo, Sharon has 6 children, three of whom are in college.  The oldest is working on her doctorate in Psychology.  As with Mary on the wings, Sharon took to bucking rivets like a fish takes to water.  I only had her help for a day but we managed to rivet the majority of both of the F-770 skins to the center section.  In the photo below right you can see that the fuselage is beginning to shape up. If you are building one of these don't be surprised if the last thing that you do every night and the first thing that you do every morning is to take a look at it, even on the days that you are not able to work on it.


Sharon, Mother of 6 and riveter extraordinaire The fuselage is taking shape


The photo below left shows a shot I took looking aft after the side skins were attached.  The next time I worked on the center section was in April of 2004.  The forward fuselage and the fuselage top skins received some attention in the meantime.  In photo below right shows the spacers that I used to keep the two halves of the F-704 the proper distance apart (Ref: Firewall and Bulkheads).  April 23 was the day that I finally got to remove them.


Fuselage, side skins attached F-704 spar spacers removed


Below are pictures of the problem that riveting the F-704 upright capstrips caused.  In the photo below left you can see that it will be nearly impossible to put solid rivets from the skin to the longerons above the capstrips.  There is one rivet installed already in the picture.  How did I do it?  In the picture below right is a bucking bar that I made from a piece of steel that is 12" long by 3/4" high by 1/2" wide.  (Actually I didn't make the bar.  I have a friend that owns a machine shop and he had this piece of steel left from a project he was making for a customer.)  I covered three sides of it with masking tape so that I wouldn't scratch up the surrounding sheet metal. 


Area above the capstrips Special bucking bar


I slid the bar into place and held pressure with a screwdriver (below left).  I had Mary shoot the rivets for me (below right).  This was her first experience with the rivet gun so I set the air pressure to the rivet gun to 40 PSI with a regulator.  This way she could pull the trigger and hold it in until I told her to stop.  We practiced on a piece of wood a few times until she felt that she could hold the rivet gun perpendicular to the rivet.  After we both felt she was ready, we shot the rivets.  We had no "set marks" in the skin and every rivet came out nice.


Bucking bar and screwdriver Mary with rivet gun


This completes the Cabin as far as we can go for now.  We now will move on to the Forward Fuselage.

UPDATE 12-21-2004

When I got to the finishing forward fuselage stage, I realized that these rivets couldn't be installed yet and I had to drill them all back out.  See the "Finishing Forward Fuselage" section to see how or if I was able to replace these rivets with solid rivets again.