Starting homasote spline roadbed (rather than foam board)

Last week I started putting in the “brackets” and roadbed under the new roadbed.  This supports from Madrid to Perham Junction and back up the Barnjam branch.  I will not go into the details of the design.  That is for another post, this one is more about the choice of homasote spline for the roadbed.

First of all, I really like foam as a roadbed support.  I was part of the Eastern Loggers, one (if not the) first Foam layouts.  Click here to see the layout design.  To my knowledge the techniques were developed by John Burchnall back in 1980 or so.  He never published an article, but did give many clinics at NMRA Conventions, Regionals, and Shows.  As a kid (14-20 years old), using my Eastern Loggers experience, I build small layouts with foam including extruded foam.  None of those layout got beyond grading but foam is my experience.  Bill Darnaby made foam based construction mainstream when he used extruded foam to build  his large Maumee layout and then wrote about it in MR (two articles).  MR staff and others went on to build layouts and write about them. It’s my understanding that John’s clinics inspired Bill Darnaby to try foam construction.  There was also a fellow who built an 100% foam HOn3 4×8′ layout and displayed it at conventions and shows.  He had products for foam construction.  (as a narrow gauge enthusiast I liked his layout).  I used foam on the sections of my first SR&RL layout and expected to for this too even though my layout design is a complicated nolix with mushroom.  Bill Darnaby’s layout is a nolix as is the n-scale B&O Chillicothe sub built by my friend Paul.   My thinking…If they could do it…why no me?

However, as construction started I got concerned about a few things.  Frist of all, using extruded foam was making it to complicated to ensure smooth grades through the curves.  This Sn2 SR&RL has 1.7% grades and if I accidentally go much higher than that, the finicky forney’s may come to a halt.  Secondly, I got concerned that the foam would not contour properly through the corners.  Finally, what roadbed would I use?  Cascade Roadbed, the most recent producers of milled homasote roadbed, has closed business.  There are other products I could use for roadbed and I could cookie cutter something.

Given my concerns, I’ve decided to try homasote spline.

I first became aware of homasote spline from Allen McClelland’s V&O layout (visit and articles) and layouts built by others who have been on his work crews (Gerry Albers is one local modeler who uses it on his VGN layout).  I’ve become aware that there are multiple spline techniques.  A MRH article describes a few different spline construction types/materials and their pro’s and cons.  Review it if you want to know about the other techniques.  I’m choosing to try Homasote splines for the following reasons:

  1. No need to add roadbed (cork or homasote) to the top
  2. Screws together with drywall screws, no glue required
  3. Will hold spikes for hand laid track
  4. Homasote is available in my local Home Depot and possibly Lowes (look for it with insulation as it is sound insulation)
  5. Can be thin enough for multi-deck (Jeff Ott has used it to build a huge Mussaubi Range GN layout with multiple decks.  He is/was a real railroad track specialist)

I’m not aware of published articles on homasote spline but I’m sure there are some.  To learn about the construction, I watched Matt Goodman’s youtube videos.  He has several videos that show and describe the construction on his layout.

  • Homasote Spline Cutting Fixture
  • Layout Update 5 – The last half shows some completed roadbed, and the stops.  The roadbed rests directly on the roadbed
  • Layout Update 6 – Shows the first run, but also shows constructed roadbed, double tracking.  It also shows him fitting foam around the roadbed
  • Layout Update 7 – Shows him constructing roadbed
  • Layout Update 8 – Spine Painting and Off-Layout Assembly – Shows him build roadbed off-layout with a jig and adding it to the layout.  You see him driving screws, marking where they are.  So simple.
  • Layout Update 13 – Bypass Construction
  • More videos – Matt has many more videos that show construction.  Just look as his Layout Updates on Matt’s YouTube channel.

At this time, I’m trying the screw together technique.  I’m starting with the section of the layout from Madrid to Eustis.  Part of it is hidden track under Barnjam branch, so could not be built of foam anyway.  I figure I have nothing to loose.  If it does not workout I can revert to foam based roadbed.

For Sn2, I plan to use three 1/2″ homasote strips to form the roadbed.  It’s a bit wider than I want.  I’m plan to use a knife to shave the edge at 45-60 degrees to represent the slope of the roadbed as seen on Mainline railroads and yes the SR&RL.  The SR&RL did all it could to keep it’s track dry and above ground level.  Maine winters were harsh and I presume the the freeze and thaw cycles played havoc on any roadbed at ground level.

Here are a few photos showing the start of brackets and roadbed.

The brackets extending from the wall. They are 1/2″ (nominal) plywood and stick out 16″ from the backdrop. At the sink it narrows to 10″. The grade coming up from Madrid is roughly 1.7%. I do not put in every bracket, instead I put one in every 3-4 feet. This is because there is a 1/8″ tolerance on the height as I install them, by filling in later brackets after the roadbed is in I reduce the chances of a sawtooth support.

Here is the first homasote spline from Madrid toward Reeds. This will all be hidden under Barnjam branch mill site. This is 1.7% grade.  You can see where I cam back and added the intermediate brackets.  I’ve not yet determined how I’ll support the corner.

Forming the curve. I cut plywood to 36″ radius on inside and outside to use as a form. The form is clamped to the spline to form a curve. Then spline is screwed together with drywall screws. The spline here is 4 wide. The extra width was added to space the masonite protector a finger width width away. The masonite protects will keep the rolling stock from falling off the back should a derailment occur. The front will be protected too, possibly with acrylic or 3″ foam extension forward. That way I can get my hands in and re-rail cars if needed.

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