Spar blanks ready, metal fitting parts ready to paint. The rear spar is only 1/2" thick. The front spar 5/8" thick. On the lower wings the thicknesses are switched. On the lower wings the front spar is 1/2" thick and the rear spar is 5/8" thick. The thicker spars are where the flying and landing wires are attached.
Drilling the spars using old spar and fittings as a guide.
Spars for right upper wing with root fittings finished.
Spar reinforcements at the interplane attachment and flying wires attachment point. Front spar reinforcement are 5/16" thick. Later B models had 3/8" reinforcement here.
These wings have the thinnest spars I have ever seen in a real airplane. The rear spars on the upper wing and the front spars on the lower wing are only 1/2" thick. The other spars on this aricraft are a whopping 5/8" thick! The thin spars have something else I have never seen before; a "lateral buckling support". This is a 3/8" X 1" spruce piece attached to the spar from the wing root to the interplane strut. It is on the rear of the spar on inboard of the fuel tank and on the front of the spar outboard of the fuel tank. This transforms the spar into somewhat of a T section. These are nailed in with 1 1/2" nails. I drilled a pilot hole for these. A small rivet gun with a back driver set is a great tool for these "larger" nails.
Attaching the root rib. The two other ribs in this photo are out of place. They are there just to make sure the fore-and-aft spacing of the spars are correct.
This compression member (aka drag member, drag strut, compression strut) is just outboard of the fuel tank bay.
The web on the strut is 45o two ply spruce 1/8" thick. I made this material by gluing together 3/4" spruce, ripped, then glued together so that the grains are 90o to each other, ripped to a little over 1/8" thick then planed to 1/8". I planed to get two pieces of this ply out of the 3/4" spruce, but the second piece fluttered in the planer and messed up the end. Quess I need a thickness sander, ie, a minor excuse for a major power tool!
The Beech drawing B17212, which apparently applies to later versions of the B17L, has this listed as being 2 11/32" high with a 1/16" popular plywood web and 1/2" X 15/16" spruce struts. On my aircraft, this is 3" high with 1/2" X 7/8" struts. The difference in height can be traced to a difference in vertical position of the lateral buckling support. The rear of this compression member is attached to the buckling support.
Here's the compression member ready to be glued in.
Compression member installed. Another 1/8" plywood gusset will be attached on the underside once the wing is flipped.
This compression member is a single piece of spruce. In my original wing this was 1" X 1". The previous owner of this project had already made the drag members to Beech drawing B17212 which specifies a 1 1/8" square strut for this member.
Installation puzzle
The Beech drawing B17212 must apply to later versions has this listed as 1 1/8" X 1 1/8". In my original wing this was 1" X 1". The preivious owner of my project had already built this part. In this case I used his part. With the 1" X 1" strut the tabs that overlap the end spruce blocks looked a little thin.
This compression member is located at the interplane and flying wire attachment point.
Installing this compression member was tedious. Some of the bolt heads are covered by the ends on the spruce. With the bottom AN4 bolts in, the member is rotated as far to the left as possible to install one of the AN5 bolts. To get the other AN5 bolt in, its bushing has to be pushed forward in order for it to enter at an angle.
Would have to break wood to get these bolts out now.
Details
This compression member is attached to the spar with 3/16" plywood gussets on the top. There are also 1/4" gussets on the botton which will be installed when the wing is turned over.
I used shear nuts on the upper left and lower right AN5 bolts in this fitting. This was done to make sure there was adequate clearance for the flying wires. The original fitting has 3/8" tube rivets at the corners of this fitting. The other orginal wings, which have had repairs, have the tube rivets replaced with AN5 bolts and bushings. These bolts show signs of the being ground down for clearance.
Rear Fitting
The last compression member is very simple compared to the other one. It is just a single 5/8" X 0.035" steel tube. It is as if Beech wanted to use as many different ways of building a compression strut as possible. Of course, couldn't be like Stearman or Piper and make them all the same and easy to manufacture.
The Beech drawing B17212, which apparently applies to later versions of the B17L has this listed as a 7/8" X 0.035" steel tube.
An additional vernicle was added just forward of the rear spar. This addition was done either in the later B models or with the C models. This looks like a reasonable addition. As you can see the top cap strip has caved in some on the old rib.
Drag and anti-drag wires were cadmium re-plated along with various other wing parts, including some odd sizes Cessna turnbuckles used on this Beech.