Fuselage Turtle Deck

 The turtle deck is the assembly of stringers which round the top of the fuselage behind the pilot cockpit.  This picture was taken in the WACO factory 28 June 1926, within days of my plane leaving the factory.  They have a lot of planes being assembled.  There are some of the turtle decks hanging on the far wall.

On the plane in the bottom left, there are some little blocks of wood at the forward ends of some of the stringers.  When I first saw these on my plane I thought they were a repair, but there they are, in the factory, in the exact same positions. More on these later.

The turtle deck on my plane is damaged a little but not bad for something that's 98 years old.

It's really pretty simple.  There are 11 stringers, 3 plywood formers, a spruce former at the aft end, and a piece of plywood covering the forward end.  The pilot seat looks like it rubs on it, but the seat actually hits the cross tube .

The light color spot is from a mud dauber nest, hangar rash.

An interesting little item is the hole in the lower right corner, behind the pilot.  I have a newspaper article from 1929 when they wired the plane with position lights powered by a dry cell battery. They flew it in the dark of night.  Braver than me.

The guy on the left is Benson Spangler, 2nd owner.  His son, Benson, let me handle the goggles dangling from his hand.  The other fellow is "Shorty" Nelson, the 1st owner

The trim piece along the edge of the cockpit is a piece of Hide-A-Tack welting, also call Tack Hidem.  Because of all the Model A Fords, it's still available.  It gets tacked on through the sewn gap in the middle and covers the tacks holding the fabric covering in place.

The front plywood cover piece is flush with the top of the stringers, which all stick up 1/8" above the formers.

The coolest thing I discovered when I got the fuselage in 1996 was the factory Construction Number 264 written in pencil on the back of the plywood cover piece.  The official serial number was stamped 1/8" high on the leading edge of the right hand flying wire fitting, which was welded to the lower longeron.  That's about a foot in front of where my fuselage was sawn in half.  It appears the factory wrote the number on the turtle deck of all the planes, where it was more easily seen by t he workers.  That fancy font style was only used for the drawing numbers on the oldest drawings.  Because of that hand written number I was able to get the records from the FAA and track down the son of the last owner.  I also talked to the fellow who cut off the front of the fuselage with a hacksaw, in 1939.  In the end I have lots of evidence that this really is fuselage number 264.

The bigger blocks of wood between the stringers were added in 1931 so they could install a WACO TEN headrest.  I don't plan to reinstall it.

The slim stringer former is notched to hold the stringers, which don't continue into the full plywood cover.  All the plywood is 3 ply 3/16" Mahogany.  The former is nailed to the front plywood cover from the aft side.

So here are those little wood blocks.  They provide places to install wood screws to attach the cockpit cowling

The blocks are each nailed to the former with 2 long aircraft nails.  There is no evidence of glue used anywhere on the turtle deck.  The blocks are hand shaped on the top so they don't poke out under the fabric covering.

The ends of the second former originally rested on  the top of the upper longerons.

The 3rd former is also plywood and rested on the longerons.

None of the formers were placed such that they were centered on the cross tubes.

You can see more clearly here that there are 3 different stringer shapes.  The center one is 3/4" x 1/2" so the fabric panels on each side were tacked to this stringer.  The 2 outer stringers are 3/4" x 3/8".  The others are all 3/4" x 1/4".  All stringers are spruce with a 3/8" radius on the upper edge.

All stringers are attached to the formers with a diagonal nail into the plywood.

The 4th (aft) former is made of 5/8" thick spruce.  The 2 side stringers are tipped at 30 degrees.  The rest are vertical.

This former was not attached.  The others were screwed to little steel tabs.  The 2nd and 3rd formers hold the stringers such that they put about a 1/2" sag in the stringers helping to hold the aft end down.  I used a straight line in this area of my 1927 photo of the plane and the sag is really there.

There are 2 little blocks of 5/8" square spruce on the bottom of this former to hold it from moving sideways.

The stringers are tapered for the last 6", to a height of 5/8", flush with the former.

There are 6 tabs for mounting the plywood formers, welded to the upper longerons.  They are made of .050" steel, 3/4" x 1-1/4".  They have a curved bottom to fit the 1" dia. longerons and are welded only on the aft side.

They are all tipped toward each other.  For the 1st former they are tipped so the holes are 29-1/2" center to center, and located 1/4" forward of the aft edge of the cross tube.

For the 2nd former the tabs are tipped so the holes are 23" center to center, and located 1/4" forward of the forward edge of the cross tube.

For the 3rd former the tabs are tipped so the holes are 17" center to center, and located 3/8" forward of the forward edge of the cross tube.

I've taken the turtle deck off the fuselage and have it downstairs in our embroidery shop.  I really didn't understand how long this thing is.  It's 1-1/2" short of 7 feet.

I've modeled the forward and aft formers in CAD and I'm working on the middle 2 formers.  When I'm done I'll have drawings for all the parts.  Then I'll start making parts.

Trimmed Trailing Edge of Ribs

 The ailerons use a folded ">" shaped piece of steel for the trailing edge.  Today you can buy a similar, aluminum, trailing edge material from most aircraft supply houses.  During WWI some of the aircraft, like the SPADs used a wire trailing edge.  That's how it's done on the NINE wings.

They use a length of 1/6" music (piano) wire for the trailing edge.  To hold it to each rib the wire is soldered to a strip of thin (0.020") copper, the width of the rib capstrips (3/8" for most ribs) and, about 3 1/2" long.  The copper is folded around the trailing edge of the rib and nailed to the upper and lower capstrips.  The noticeable thing about this method is that the tension on the fabric causes the wire to sag between each rib giving the trailing edge a scalloped look.  The wire sags in the shape of a Catenary Curve, like the cables on a suspension bridge (Golden Gate or Mackinaw).

To support the wire the ends of the ribs need to be square, not pointy, so there is a surface for the wire to bear against.

I had planned to make a fixture for the table saw, like I did for the Lead Edge wood on the nose ribs.  I forgot to do that and built the first 2 wings with pointy ribs.

I decided to make a fixture which would work for the ribs for these next 2 wings, but could also be used to go back and trim the ribs on the first 2 wings

After much rechecking dimensions the cut needs to be 20 3/8" from the rear face of the aft spar

For my fixture I used a piece of 3/4" plywood.  I need to cut out some holes in it to clear some diagonal braces on the wings so I needed it thick enough that it shouldn't break once I make those cut-outs.

There are 3 reference points to assure the fixture is in the correct position on the rib.  The 1st is the forward end of the fixture which rests against the rear face of the spar.  The 2nd, right behind it, is a block which holds the fixture in the correct vertical location.  The 3rd is forward of the trailing edge.  The rib sets down in the pocket resting on the 3rd stop.

I made a pocket, with another piece of 3/4" plywood,  just to get better control of the cut-off saw location and angle.  I wanted a nice square cut.

I used the square on these ribs to simulate the spar.

Once the rib was in the fixture correctly I clamped it in place at 2 of the vertical sticks.

A few gentile strokes with the X-acto Saw and the job is done, next rib.

A nice square end to each rib.

Look like I need to build wings.

The Shop Is Ready To Build More Wings

 I can't believe I've done nothing on the WACO all winter.  My little free time was spent on a sticky valve problem on the Fly Baby, now solved & ready to fly.

I kept thinking I could build the wings in the other room of the attic, not possible.  Instead I moved the sand blaster and metal band saw to the other room.  They and the ShopSmith sat where the fuselage is now.  I didn't want to take the fuselage back to the hangar.

I now have about 6 feet clear in the middle.  It worked for the other 2 panels, so I think I'm ready to get back working on these 2.