INDUSTRIAL DEVELOPMENT - 3 - NATIONAL METALLURGICAL

With terrain base covering almost the entire railroad, it was past time to fill in other scenery holes--industries served on the railroad.  Prompted by a proposed clinic presentation for the now-cancelled NMRA-PNR Convention in Eugene scheduled originally for mid-April, I launched upon developing railroad-served industry in the Eugene and Springfield area.  I began in Springfield with National Metallurgical.

National Metallurgical, later Globe Metallurgical Inc., refined silicon.  Taking advantage of cheap hydro-electric power, the plant began in 1954 with a single furnace.  By 1959, a second furnace was added.  Operating from 1967 as National Metallurgical, a third, more efficient furnace replaced the first two in 1975.  After several corporation changes, the plant was purchased by Globe Metallurgical Inc. in 1993.  The plant is gone today, but it served throughout the years of interest to my modelling.

With the plant gone today, my modelling efforts relied on very sparse information.  I began with the 1977 SPINS diagram for Springfield which identified the spur serving the plant as National Metallurgical.  One of my regular operators, a retired SP railroader, recalled servicing the plant and noted locomotives were not allowed inside the unloading shed.  That tidbit indicated the plant had an unloading shed.  For additional background and possible detail on Springfield industries, I was directed toward a book produced by the Springfield Chamber of Commerce:  Springfield, Between Two Rivers, published in 1999.  This wonderful book on Springfield has many single-page descriptions of Springfield businesses.  The page on Globe Metallurgical Inc. provided the history of the plant and two small photos.  One photo showed operation of one of the furnaces.  The other was 2x3-inch street-side view of the mill complex.  That single photograph combined with my knowledge of industrial processes (admittedly incomplete!) and the report of an unloading shed led to my "imagineering" of the plant for my model.

To model this industry, I chose to go back to an old modelling technique--the use of printed paper surfaces.  I recall building structures as a teen and into my college years using printed brick and cinder block paper glued to cardboard for full structures and scenery "flats" against backdrops.  Today's version of this comes via computer programs and files with photo-realistic "textures."  For this project, I chose the steel buildings collection of .pdf files from Clever Models: http://clevermodels.squarespace.com/catalog-pg-25x/  As .pdf files, this package was very useable on my Apple MacBook.  

Clever Models' Steel Industrial Building collection provides a number of "kits" for various corrugated steel structures as well as "texture" sheets for development of one's own model designs.  When I bought the package, I was looking at one mill building, a moderate-sized structure, but found their large steel mill better suited my needs for the core structure of my silicon refining mill.  Indeed, my final industry design uses pieces from four of the "kits" in the collection.

The core of the plant is a tall mill structure.  I built this by printing the "Big Steel Mill" building pieces on 65-pound cardstock which I cut out and laminated to foam-core poster board.  This was a large structure that had the rough proportions and size I could surmise from that one small photograph in the Springfield book.  The interior of the foam-core structure was braced with balsa strips.  I cut in a large roll-up door (featured in the kit) on the track side of the building--unseen in the book photo.  

The core mill building under construction.  The siding was laminated to foam-core board, braced with balsa wood strips.

The mill building core was flanked by side sheds.  These sheds were larger than the side sheds in the Clever Models kit, so I designed my own using more sheets of the central mill structure sides and ends.  Since these were imagineered, I chose not to build them as heavily as the core building.  I wanted to leave myself freedom to discard one of these structures if I got better information on them or found I needed to modify them as I created the complete industry scene.  This led me to build them without a foam-core interior, but still with significant balsa strip reinforcement.  Following construction advice from Clever Models, I used a lot of gap-filling CA glue for the joints.   I added doors and windows to the side structures with details printed on paper.  This contrasted to the use of cardstock printed and cut-in details on the mill core building.  

The side sheds for the mill building shown under construction.  The printed cardstock walls were built up using balsa wood strip interior framing.

The unloading shed used a Clever Models Car Barn from the Steel Industrial Building collection.  This structure kit was the right size for what I thought would be used.  It is an open structure for which Clever Models provides an interior sheet.  I laminated the interior and exterior walls.  I then added styrene strip framing to overlay the framing of the interior images.  I built both the car barn core and its side shed, cutting holes in the side for the conveyor belt assembly leading to the mill core building.  

Siding pieces for the "Car Barn" used as an unloading shed.

Framing the unloading shed interior.  Styrene strip was attached to the building interior, overlaying the printed framing.

Building the unloading shed.  The shed sides have been formed into the complete structure.  The side-shed is built up as siding laminated onto foam-core board.  Holes have been cut into the siding for the conveyor system.

With the core structures completed, I turned to details.  The Springfield book street-side photo shows an external stair set zig-zagging to a high location on the end of the core building.  Alongside that was a high-mounted bin that received sand from the conveyor belt from the unloading shed.  I used Tichy staircase platform and railing sets (#8208) for the zig-zag stair case.

I must make a brief shout-out to Tichy on this.  I needed a half-dozen of these staircase sets--more than commonly available at my local hobby shop.  Further, I wanted them "now."  I placed an order with Tichy over a weekend.  I had them in my mailbox by Wednesday.  Tichy packed and shipped and the USPS delivered in a half week, crossing the country!  I will continue to obtain parts through my hobby shop when I can, but for a case like this, I will not hesitate to order direct.  Kudos to Tichy Train Group!  https://www.tichytraingroup.com/Home.aspx

I built the staircase up as three sub-assemblies.  Each consisted of two platforms and two staircases with their associated railings.  I was able to handle these subassemblies as I glued them to the end wall of the mill building.  I doubt I could have handled an assembly of all six staircases and platforms as one installation step.  The subassemblies were painted before attaching to the mill building end.  

The exterior staircase for the central mill building was built up over a simple drawing.  I looked at a four-staircase installation (left), but quickly went to the prototype's six-staircase design.  This fit the Tichy parts better.  The end railings for the platforms was the limiting part on the sprue.  Tichy supplies only one per sprue set.

The sand bin was a simple box, mounted to the wall with diagonal braces underneath.  This was simple styrene sheet construction.  The book photo appears to show a small platform with railing on the side of the bin, so I built the bin platform a bit larger and added railings left over from the staircase project.  A quick coat of paint and CA glue for mounting completed the job.  The conveyor was a Walthers 933-3149 conveyor set. 

Street-side view of the completed mill complex.  Unfortunately, all that great detail--the stairs, and conveyor system--appears on what appears to be the back side (away from the aisle) on my railroad.

Final details for this round of construction were a rooftop vent on the core mill building and an exhaust stack.  The rooftop vent was scavenged from the Clever Models small streel mill kit.  I joined two of the vent sides for a longer vent, something easily done with paper construction.  I built the vent around a pair of pieces of balsa strip wood.  The exhaust vent was formed from 5/8-inch dowel.  I needed miter cuts to form a 90-degree bend.  I started with my compound miter saw, but found its saw blade was too rough for the job.  Instead, the protractor guide on my band-saw gave me great control with smooth cuts.  I formed a cap from cardstock and attached it with wire legs.

National Metallurgical seen from the track side and aisle on my railroad.

Another view of the National Metallurgical complex from the track side.  I added a sign high on the building core.  Such a sign would be unlikely for the prototype plant but is useful for my operating crew.  This does away with the folded index card sign that has occupied this space for the past eight years.

Arranging the structure pieces on the layout filled a major hole in my Springfield scene.  It was fun to return to an old-school modeling technique using paper texture on a cardboard interior, albeit with the modern twist of desktop publishing and printing with a computer file.  The folded index card industry name can be retired and a full three-dimensional structure complex has taken its place.  Over time, I will add more detail, but the important gap-filling has been done!

EUGENE TURNTABLE - 2 - TURNTABLE BRIDGE

Construction of my turntable and associated track and service facilities continues as a long-term, many-step process.  I previously reported the preparation of the turntable pit:

https://espeecascades.blogspot.com/2019/11/eugene-turntable-1-pit-preparation.html

The next step was construction of the turntable bridge.  

An important reason for my selection of a Diamond Scale turntable was that product most closely matched the Eugene, Oregon turntable.  The prototype turntable still exists and sees limited use in spite of the down-sizing and almost elimination of that once large yard and locomotive service base.  In particular, the Eugene turntable featured a deck girder bridge with a rounded-top turntable arch.  The arch served to convey power to the electric motors for the table.  In the model form, that same arch will serve as part of the track power circuit.

The Diamond Scale turntable bridge is built up around a rotating core consisting of a shaft held by two bearings and a center block.  The primary bridge structure consists of wood girders that straddle the center block and end pieces which serve as mounting points for the turntable drive dolly models.  Bridge ties are glued to the wood bridge girders.  A pair of brass strips are attached near the center of the bridge to support the bridge arch.  One of my project delays involved getting appropriate 00-90 screws to affix the straps with.  In hindsight, I could have substituted pins.  A cosmetic plastic girder set is fixed to the exterior of the wood girders.

Turntable bridge girder built up and mounted on the center block and shaft assembly.  The green wire will bring track power up through the shaft in parallel to a similar circuit using the bridge arch.  Two brass straps straddle the center of the bridge.  These will support the bridge arch.

The turntable bridge ties were laid out on double-stick tape on the template provided by Diamond Scale.

The turntable ties were glued to the bridge girders and weight applied while the glue set.

The bridge dollies have been built up and are awaiting installation.  Note the wire dangling near the center of the turntable bridge at the top of the photo.  That wire is soldered to both of the near-center brass straps to convey power from the bridge arch to one of the bridge rails.  The other rail will receive power from the bridge dollies, including the Tomar wiper seen here.

Bridge dolly mounted on the end of the bridge.  A wire is attached to the wiper at each end and through a mounting screw to the dolly.  These wires feed the "right hand" rail on the bridge when looking toward the control cab.

Aligning the rail on the turntable bridge proved an interesting challenge.  For my first attempt, I carefully measured to find the center of the end blocks.  I then laid the rails using these locations (both ends).  When I tested the bridge, I found turning the bridge 180 degrees did not align with the pair of tracks (approach and roundhouse exit) that I tested with.  This was undesirable.  

The first three roundhouse tracks at Eugene aligned with three approach tracks allowing locomotives to run straight through the turntable into those roundhouse tracks which then exited into the back shop.  Although I do not have space for the back shop, I still wanted to be able to run locomotives straight through over the turntable into the first three roundhouse tracks, regardless of which end of the table faced the roundhouse.

The solution was to use my four feet long straight edge to align the turntable center, ends and the extended tracks.  I was able to get very close, with a slight bit of tolerance created by chamfering the ends of the turntable bridge rails as called for in Diamond Scale's instructions.

Aligning approach and roundhouse tracks with the turntable bridge.  Use of the four-feet straight edge provided center marks that could be used to lay the rail on the turntable bridge.

Once the rails were on the turntable bridge, I could complete its assembly.  This included bridge handrails, walkways, the control cab, and the bridge arch.  I chose to paint the handrails white to match photos of the Eugene roundhouse and turntable shot in the mid to late 1950s.  Before that time, the handrails likely were basic wood, perhaps with some treatment.  By the 1960s, the handrails appear to have weathered and had pieces replaced such that they take on the same grungy appearance as early photos.  Even later, the wood handrails were replaced by pipe stanchions and cable.  The interim period with white handrails was quite striking and fit well with my prime modeling year focus for this area--about 1958 when the new diesel sand facility was built.  Photos taken at the end of steam locomotive operation also show the white handrails.

The turntable arch was built up from a number of white metal castings.  This proved a tedious task, as the various geometric elements precluded laying it over a template for assembly.  I needed to glue each joint with CA and let that joint set before moving on to the next joint.  The couple of days it took me to assemble the bridge arch seemed to summarize my entire experience with the turntable bridge assembly--not difficult, but tedious.  The turntable arch was mounted by soldering it to the underside of the pair of near-center brass straps.  I also soldered the end of the thick magnet wire that completes the center arch circuit from the feed tube at the top of the arch to one of the brass straps.

Mounting the bridge arch by soldering tabs at the base of the arch supports to the undersides of the near-center brass straps.  The magnet wire connected to the feed tube at the top of the arch has been soldered to the strap in the upper right position in this photo.

After a tedious construction effort, the turntable bridge has been installed!

Completed turntable bridge installed.

LET THERE BE LIGHT!

One immediate impact of my recent terrain-forming effort at Cascade Summit was the elimination of the light paths filtering down through the still-open bench-work at that upper level to illuminate the scene below which climbs up out of Oakridge to McCredie Springs.  I had always planned to provide additional lighting for this "land down under," but had never gotten to it. 

The "land down under" without lighting now that the Cascade Summit Terrain has been formed in the scene overhead.

When I began construction in 2012, I thought I might use single-tube florescent fixtures, but did not pursue that seriously as other work always had a higher priority--at least as long as that light continued to filter down to the scene.  With the terrain above now blocking the light, I needed to do something--now!  Fortunately, LED lighting has come a long way since 2012, with affordable solutions readily available.  I considered modern tube-style LED fixtures, but their cross-section size, mounting concerns, and relatively higher cost scored against them.  LED strips seemed the way to go.  

I looked at several supply sources for LED lighting strips.  I ended up selecting the strips from MicroMark.  A big factor in this choice was the recommendation of a fellow model railroad friend of mine in Virginia, Paul M.  Paul had used the MicroMark system to light the lower deck of his two-deck railroad.  I have since found a fellow model RR owner locally who has also used the MicroMark system, but it was Paul's recommendation that drove me.  I liked that the MicroMark system was well-engineered and had UL-tested components. 

I still delayed, as I needed to select a color temperature to match the 5000 deg-K lighting used in the rest of my railroad space.  MicroMark has three LED light temperature ranges, two of which bracket, but do not match my desired color.  The need to solve the lighting problem--now!--drove me past that hurdle to place an order.  I selected the 6000-6500 deg-K strips rather than the warmer 4000-4500 deg-K strips also available from MicroMark.  I previously experienced "warmer" (lower color temperature) florescent tubes in some new fixtures added after initial construction--tubes with a similar 4000 deg-K rating.  They were noticeably warmer (and quickly replaced with the correct tubes!), so I shied away from the warmer lighting for the current LED project and selected the bright-cool 6000-6500 deg-K strips.

The area beneath Cascade Summit now lit with 6000 deg-K LED light strips.  Note the color difference in this picture between the overhead warmer-lit scene and the bright-cool lighting below.

As illustrated in the photo above, the color temperature does make a difference, at least in photographs.  In person, the difference is barely noticeable.  Far more important is that there is light on the scene below the Cascade Summit overhang.

I mounted the LED strips to pieces of 1x2 lumber with a 3/4-inch cove molding on the edge forming a roughly 45 degree angle.  If I were to do this over again, I would simplify this to ripping a 1x4 using a 45 degree saw blade angle--no need for the complexity of the cove molding.  Indeed, the self-adhesive on the back of the LED strips does not attach to the cove molding, so I hold the strips in place with wire ties.

LED strips mounted on 1x2 lumber with cove molding edges. 

The LED strips provide needed lighting and are safely out of the way overhead.  I have a few minor adjustments to make at the ends and I may fill the molded cove with adhesive caulk to provide a flatter surface for the LED strips.  I may also need to provide a small amount of valence for the lighting, though that did not seem to be a distraction in the first operational test during the February 1 operating session.  For now, I am happy to have light on the Montieth Rock scene and the climb up out of Oakridge.

Mike L. guides Amtrak Number 11 past Montieth Rock in this now well-lit scene underneath Cascade Summit.

CASCADE SUMMIT TERRAIN

The cap is now on my railroad world.  Terrain rises up behind Cascade Summit placing this important operating point and scene into context with the rest of my railroad.  This was the last major terrain gap--and I do mean MAJOR!  I spent most of the past month filling this space with terrain.  I have covered my basic terrain forming techniques in previous blog posts, so I just kept terra-forming--and not reporting via this blog.  

The terrain for Cascade Summit rises behind roughly thirty feet of mainline track.  With the terrain scene depth averaging around three feet, that made for about one hundred square feet of terrain.  Anyone who has ever done model mountain forming will understand that as a significant area, especially for a crew of one (me).

I began the terrain effort at the wye tunnel.  I attached a styrofoam "bar" to the coved (curved) backdrop in this area to serve as a top brace for the terrain slabs.  I then began fitting foam slabs, beginning with one-inch thick slabs cut to four-inch widths.  half of these slabs needed to be tapered to account for the curve.  As I built up the terrain around the tunnel portal, I realized I needed to make the RR-West end of this assemblage removable so I could retain access to the tunnel portal and the terrain beyond it.  I worked on this area by climbing up on the Pope and Talbot scene below it and squeezing between the joists supporting Cascade Summit.  This was exhausting, with lots of contortions and climbing up and down a ladder.  I validated a goal not quite reached of completing all such work by the time I turned seventy.  I sure am glad this part of the layout construction is done!

Ridge support for wye tunnel terrain installed on the backdrop.

Basic terrain surface formed for the Cascade Summit wye tunnel.  The panel to the left of the tunnel portal is removable.

I next tackled the two ends, again with coved backdrops.  This time the cove was convex, so I needed to form terrain around the curves.  Since these ends reach down to track level and the plywood sub-base, I chose to build them up with layers of foam.  Shortly after laying the bases for both curves, I fit the base slabs for the remaining terrain in place with their ridge backing pieces which I will describe further below.  This helped me form and align the "pyramids" of foam slabs for the curved corners.  I also needed to tie into the existing terrain for Trapper Creek at the RR-East end of Cascade Summit.

Terrain base formed for RR-East Cascade Summit.  Trapper Creek is the gray area on the far right.  The two flat spaces are where the section foreman's and signal maintainer's house and the section gang bunk houses will be located.

Terrain formed at the RR-West end of Cascade Summit.  The base slab for the RR-West end of the scene extends between the corner cove and the wye tunnel panels.

The major terrain sections between the end curves and the wye tunnel were built as removable panels.  As seen in the photo above showing the RR-West end, I used a two-inch foam panel as the base and a 1.5-inch panel as the back ridge against the backdrop.  Triangular braces were attached to both panels for support, spaced where the backdrop vertical support posts were located--roughly on 16-inch centers.  

One area needed special treatment.  The track at Cascade Summit is located on the mountainside along Odell Lake.  At one spot near the terrain indentation used for the wye tunnel, a major rock formation juts out from the rest of the mountainside.  Indeed, the railroad builders had to blast a shelf for the railroad through the end of this rock formation.  I built this area up with additional layers of two-inch thick foam.

The area of the rock formation at Cascade Summit got three layers of two-inch thick foam to help form that rock.  Other areas got a second layer of the two-inch foam.  The rest of the mountainside formation can be seen with the slabs of one-inch foam spanning between the base and the backdrop ridge. The flat spot for the summit water towers is in the right foreground.

Cascade Summit base terrain formation with gaps filled with spray foam insulation.

After a couple weeks of effort, I applied the final foam touch of spray foam insulation filling the gaps.  I then removed the three large panels and finished forming the foam terrain using knives and a Stanley Surform ™ scraper.  I moved the panels to spots on the floor to apply Sculptamold.  As with previous terrain efforts, I mixed latex paint in with the Sculptamold.  This immediately provided a ground or rock color and ensures any open edges, punctures or holes drilled will produce a suitable terrain color and not white--a common problem with plaster.

Sculptamold being applied to the largest of the removable panels--the one with the rock formation, seen in gray.

After several days of setting and drying time, I moved the big panels back to the railroad.  Along the way, I cut hand-holds in their base plates to help with positioning and handling.  The biggest panel--the one with the rock formation--was still a bit wet, as I had to finish its Sculptamold a day after the others.  I ran out of paint--again.  That panel was noticeably heavier than the other two.  I really could have used another person to help carry and lift the panels into position, but a little bit of thought and use of our hand-truck helped me move them around and get them into position.  A key was to lift only one end of the panels at a time.  I also made creative use of the handrails for the Cascade Summit operator platform.

The "rock" panel balanced on the Cascade Summit operator railing prior to lifting into place on the railroad.

Terrain for RR-West Cascade Summit.

Rounding the curve into Cascade Summit RR-eastbound.

The Summit wye tunnel terrain.  Panel gaps will need to be filled as scenery is applied.  The ground area around the summit wye tracks has been filled in with Sculptamold.  The wye was slightly elevated from the mainline, likely reducing the amount of grading needed.  

The train order office and operator village at Cascade Summit with the water tanks on their concrete bases.  I will provide a base to raise the buildings.  Still to come is the beanery, to be located near the water tanks.  The beanery used a retired wood passenger car on the ground.

RR-East end of Cascade Summit with the section gang quarters.  Trapper Creek is on the far right.

Overview of the completed terrain at Cascade Summit, viewed from the RR-West end.

THE SKY'S THE LIMIT!

I completed--for now--the Cascade Summit backdrop project by applying spackle to the panel joints, sanding, and then painting the high backdrop.  Construction may be seen in the prior post:

https://espeecascades.blogspot.com/2019/12/cascade-summit-backdrop-construction.html

Most of this high (partial) backdrop received my basic "sky blue"--Sherwin-Williams "Blissful Blue."  The coved end corners needed a more complete sky blend, as they connect to other backdrop areas that have that full treatment.  The basic technique involves painting six color bands with blue-white mixes that range from the pure "Blissful Blue" down to one with 1:5 parts blue and white.  The still-wet paint bands are then blended together using a 2-3 inch-wide brush--one for each blending band.  I described this more fully back when I did the original stretch of serpentine backdrop winding around my main peninsula: https://espeecascades.blogspot.com/2012/11/backdrop-sky.html

The end corner coves may see the terrain edge come down to the backdrop base, so the full blend to haze is important.

Joint spackling underway.  The roll of fiberglass "tape" in the foreground was used to reinforce the joints.  Sanding the spackle was exhausting due to the confined space I worked within.  It also was dusty!  After the first pass through, I remembered to install drop cloths over the terrain on the lower level.

Sky blue base paint being applied.  The contrast to the blend toward haze at the horizon can be seen at the right side of the corner cove where the new sky blue base contrasts with the previously blended flat section to its right.  Trapper Creek is in the extreme lower right corner of this photo.  Three-dimensional terrain will descend to the creek and more detailed backdrop painting will attempt to convey the source of the creek.

Completed sky fade to haze.  The sky fade was done just for the full height section that is part of the corner cove.  The less-than-full-height backdrop to the left has just the base sky blue.  The terrain should reach closer to the top of most of the new backdrop except at the end corner coves.  Once the three-dimensional terrain is formed, I may need to add more mountain and forest painting to the backdrop above that terrain.

The Cascade Summit company village ready for three-dimensional terrain to be formed behind it.

I am ready to begin forming the three-dimensional terrain.   This will begin by enclosing the wye tunnel, followed by terrain around the corner coves.  The straight sections between those corners will be filled in last.  For now, the railroad has been cleaned up in preparation for the first operating session of the new year.

CASCADE SUMMIT BACKDROP CONSTRUCTION

The last major terrain gap on my railroad has been the missing mountainside behind Cascade Summit.  The prototype Cascade Summit is located just RR-West of the summit tunnel (Tunnel 3) and is located along the shores of Odell Lake.  The mountain pierced by the summit tunnel continues as a ridge flowing down to the lake.  This ridge provides the background for the Cascade Summit station site.  

My Cascade Summit tracks were built on a benchwork table that extends out from the wall above the lower mainline which has begun the climb out of Oakridge.  This is a "half-mushroom" design feature.  The Cascade Summit benchwork extends five feet from the back wall to the operator aisle.  Cascade Summit tracks are located along the aisle edge, so no great reach is required.  One important use of the benchwork depth was to provide space for the summit wye, used in the steam era for turning helper locomotives.  The summit wye tail tack was located inside a single-ended tunnel.  

I thought I would begin my terrain project in this area by completing the tunnel liner for the wye tail and then encasing this area in terrain.  The deep scene and low ceiling height above the roadbed (two feet) means the terrain will reach the ceiling before reaching the back wall for this area.  My first thought was to build a back wall for the terrain using my standard terrain underlayment of insulating foam.  As I wrestled with this, I eventually realized I would do better with a very firm backing for the eventual top of the terrain--a backdrop.  This began a major construction project made more difficult by tight clearances.  

I began the terrain effort by completing the summit wye tunnel.  I previously reported on my modeling of the tunnel portal and initial tunnel liner in a post this past year:  

https://espeecascades.blogspot.com/2018/12/an-unique-tunnel.html

Several tasks remained.  First, I needed to paint and ballast the track, as access would be restricted or eliminated by the new efforts.  I then built a solid end of the tunnel.  I used three pieces of 1x4 to form a "U" roughly five inches long. Then I built a foam-core tunnel liner to span the space between the tunnel end and the portal and initial liner.  This foam core liner remains removable. 

Summit wye tunnel liner in place.  The track has been painted prior to ballasting.

I then turned my attention to the backdrop structure.  My Cascade Summit forms part of a large S-curve.  The backdrop needed to follow this same pattern.  This meant corner coves at the ends to meet the existing walls and another cove in the middle--right over the wye tunnel.  I began by building support structures for these curved backdrop segments.  I cut top and bottom profiles from plywood, temporarily screwed together to get a common curve.  Once separated, I joined the top and bottom plates with sections of 2x2.  The end corner pieces were full height for this area--about two feet tall, though I chose to leave a small margin between the ceiling and the backdrop structure.  The backdrop cove over the wye tunnel needed to provide clearance for that tunnel for subsequent maintenance.  This resulted in a modest height cove former, mounted on legs attached to the underlying benchwork joists.

Backdrop cove former mounted above the summit wye tunnel.

With formers for the ends and middle curve mounted, I filled in the rest of the backdrop structure, beginning with 2x2 posts for vertical support.  In retrospect, I should have built the straight sections off the layout as short "stud walls" which would have needed just a few screws to the existing benchwork joists to secure in place.  Ah, hindsight...  I braced the straight sections with knee braces which extend back to the actual wall.  The resulting structure is quite rigid.

Backdrop structure.

Finally, I applied hardboard "skin" to the structure, beginning with the coved portions.  I used most of my supply of hardboard scraps for this effort.  The cove over the tunnel and the straight sections are not full height.  Only the top needs to be continuous as my intent is to build terrain to very nearly the top of this backdrop structure.  I provided support for the bottom of this elevated backdrop edge by toe-attachments of 1x2 horizontal supports using a pocket-screw jig.

Skinning the backdrop.  One more segment is needed to fill the gap to the center (over tunnel) cove.

The curve that began it all--backdrop mounted above the summit wye tunnel.

After the construction adhesive sets, I will begin the process of filling and spackling the backdrop panel joints, filling the screw heads used to attach the panels as I go.  I chose to mount all of the current backdrop panels using construction adhesive and screws.  Earlier backdrop efforts used brads rather than screws for support as the adhesive set.  The limited working space this time and the nature of the support system drove me to use screws for this function.  

I plan to paint this new backdrop with my basic "sky blue," but may not do much of the fading to horizon haze used at lower elevations on my layout.  Stay tuned.