FINISHING THE CABIN PAGE 1

 

 

The first step in this section was the installation of the F-749-L and F-749-R internal baggage panels.  The upper flange of each panel needed to be trimmed per the drawing.  The photo below left shows the right panel in the process of being marked for the cut.  The photo below right shows the panel in the process of being cut on the scroll saw.  The small block of wood in the photo was used to hold the panels down because the follower on the saw was too wide to miss the web of the F-749.  Incidentally, this saw works very well cutting aluminum.  I have cut aluminum as thick as .125 with it.  The only problem is that the saw blade can catch the material and since the saw oscillates, it can move the material up and down quite rapidly.  Some attempt must be made to keep the metal from moving vertically.  A small block of wood works very well if you keep pressure on it.  ( Don’t get your fingers in the way of the saw blade!)  

 

Measuring R-749-R for trim Trimming F-749-R on scroll saw

 

The photo below left shows the two forward baggage panels after they were trimmed.  The photo below right shows the right hand panels (fore and aft) cleco’d in place.  The fuselage is still upside down at this point.  It was much easier working on it sitting on a roll around stool than to bend over the side if it was upright.

 

F-749-R and F-749-L after trim F-749-R and F-750-R cleco’d in place

 

The plans call out to install the rear panel with "pop" rivets and the forward panel with button head screws.  At about this time I decided to install both panels  with screws.  Better yet, I decided to install these panels with flush head screws.  There is no structural significance to the decision.  I thought that the installation might look a little more sanitary. I knew going in that it would add considerable time to the installation, but don't forget, with me the building is the fun part.  I hope to fly it someday though.

 

Obviously, these panels and the structure of the airplane for that matter, are too thin to countersink for the #8 screws I decided to use.  Everything would have to be dimpled.  This meant that I would have to use dimpled nutplates.  The structure is thin enough that the rivet holes need to be dimpled too, which means that the nutplate rivet holes need to be dimpled.  The nutplates that Vans sells, P/N K1100-8, do not have dimpled holes.  They can be dimpled with a standard male dimple die and a reduced diameter female die.  The other option is to purchase P/N MS21049L08K nutplates for about $0.70 each.  I did both on this project.

 

Dimpling nutplate holes Nutplates already dimpled

The photo below left shows the structure in the baggage compartment with the dimpled nutplates installed.  Below right is a photo of the left baggage panels installed with flush screws.  I used P/N MS24694-S2 or -S3 screws depending on material total thickness.  Cost was .04 and .09 each respectively.  The screws that are included with the various kits are always several sizes longer than they need to be.  A screw should protrude through the nut and expose at least 1.5 threads.  Anything past the minimum is a waste.

Nutplates for the baggage panels Left baggage panels installed temporarily

 

Cabin seat floors cleco'd in place Outboard holes not drilled yet

The two photos above show the forward cabin seat floors cleco'd in place (F-739 and F-740).  The photo at right was taken just before I transferred the holes on the outboard edge of the RH seat floor panel P/N F-739 to the seat rib P/N F-715-R.

The two photos below show all of the seat ribs after the holes were enlarged to #19, dimpled for #8 screws and drilled for nutplates.  The nutplate rivet holes were also dimpled.  The nutplates are all installed in these photos.

Seat rib fastener holes......... ........with nutplates

 

Below left is a photo of the baggage ribs with all of the fastener holes nut-plated.  At right is the the F-706 bulkhead lower web with the same treatment.  Again I will say that I did not have to do this.  There is no structural significance to attaching thes parts with screws versus blind fasteners.  It is something that I wanted to do so I did.  All it gets me is the ability to removed the floor panels (which is unlikely) without drilling out rivets.

 

Baggage ribs nut-plated Nutplates on lower web of F-706 bulkhead

The next item to tackle is the hinge sections that hold the seat backs to the seat floors.  In the photo below left there are 6 hinges trimmed for the seat floors and two hinge sections trimmed for the seat backs.  The photo at right shows one of the seat floors with lines on it for drilling the rivet holes for the hinges.

All seat back hinges Seat floor rivet layout

 

Below left is a photo of the right seat floor drilled for hinges and the hinges are cleco'd on.  At right I cleco'd the two floors together.

 

RH seat floor, hinges in place Both seat floors cleco'd together

I transferred the holes from the right floor to the left floor which saved a little time (below left).  The other photo shows the seat back hinges all cleco'd in place.

Transferring rivet holes floor to floor All of the seat back hinges cleco'd on

 

It is time to start working on the seat backs.  The are four extruded angles on the seat backs.  The vertical angles, P/N F-637B-L and F-637B-R, have to have a .040 recess where they go over the hinge (drawing #30).  You can do this with a file which may take a couple of hours to do all 4.  I did it on the mini-mill (below left) in about 10 minutes total.  The upper horizontal angles, P/N F-637C, need to be radiused to nestle into the angle on the top of the seat back (drawing #30).  Again you can file these two pieces or maybe sand them but I put this radius on each angle with the tool pictured below right in the mini-mill.  Elapsed time was about 10 minutes. 

 

Recessing the vertical angle Putting radius into upper horizontal angle

Below left is the radius mill tool in action.  Below right is the finished product.  The photos and the narrative took longer than the process.  If you enjoy doing this kind of work then the more tools you have the happier you will be.  If you are in a hurry to fly then get past these steps with minimal expenditure.

Radius tool at work Finished product

 

The pictures below show drilling holes for the top and bottom angles and the seat back skin with the help of a rivet hole fan.

 

Drilling skin for bottom angle and hinge Drilling skin for top angle

The arrow below is pointing to wrinkled protective coating which will cause a problem with getting the upper angle to lay in side the angle on the seat back skin properly.  I removed the coating before I drilled the upper angle (below right).  These photos also show that the vertical angle pilot holes are drilled on this seat back.

Arrow points to wrinkled coating Coating removed, angle clamped in place

 

Below left is a close-up of the upper angle.  Notice how nice it fits into the radius of th angle on the seat back skin.  The photo below right shows that after all of the angle pilot holes were drilled on this seat back, the seat back was clamped to the other seat back and the holes were transferred to it.  This saved about an hour and a half of layout work.

 

Upper angle fit Seat backs drilled back to back

The next thing to do was to put lightening holes in the two seat back braces P/N F-838.  I put a center line on each part (below left) and then I marked four places on each line per drawing #30.  Idrilled a pilot hole at each mark (below right).

Center line on the seat back braces Four pilot holes in each brace

 

I set up the fly cutter with the proper radius and chucked it up in the mini-mill.  I put a block of wood beneath a seat back brace and started cutting holes (below left).  The wood is to prevent damage to the table of the mill and also the fly cutter bit.  This is a process where one does not hurry the cutting.  If the fly cutter digs in the mill is too powerful to keep from spinning the entire part.  Injuries can occur with attempts to speed the process up.  At right are the two finished products.  The weight savings is so small that putting these holes in for that reason is questionable.  However these holes make these two braces "look" like airplane parts so therefore the trouble is worth going through.

 

Cutting the holes Seat backs with lightening holes

The next step is to layout trim lines on the angles at the edges of the braces (below left).  I then cut the angles with a Dremmel tool (below right).