More negative level

Because foamcore has not a lot of thickness  I would use some foam in the 1/2" or1" thickness, you would be able to obtain more negative scenery Under the track level.

Second foam is sure less expensive, and if you use the blue one, it have really a good density and resist better at any agressive punch than foamcore.

Dimensional Stability

I'm currently reading Joe Fugate's Trackwork book in the Run Like a Dream series - there was a table in there citing expansion of various roadbed materials due to either heat, and humidity.  As I recall that table had an entry for foam core.

You might be able to find coefficients for thermal and humidity expansion on the manufacturer's web site too, if you have a specific brand in mind.

Removable Section with Track

At time frame 19:27 in this video Ken Patterson shows a modular section that is removable from the layout...
 

I posted a reference to this video over on another subject thread,....and wanted to make a note that this removable section included some track sections

This removable section appears to set down onto a plane old plywood table top.

And yes this removable section has some raised terrain (relatively thick foam construction). But why couldn't it also be a much thinner, flatter 'terrain' built of 3/16" foam-core??

And I do realize there appears to be quite a variety of foam-core products with different 'facing sheets'. I am NOT including the paper faced foam-cores in my potential selection. I have made reference to 2 products,..

1) the one used and proven by Prof_Klyzlr here on this forum,...3A I believe it was referred to

2) the ultracore one that was reference by my local sign shop.

I'll try to do some more research on these varieties to determine what best to use.

As I have mentioned previously I picked up a LOT of scrap pieces from that sign shop that had been tossed out back of their shop when they were moving a new laser cutter inside. It sat there in the pouring rain and hot FL sunshine for at least 3 weeks before I picked it up. I brought a lot of it home and left it sit outside in our VERY humid summer weather for 3 months now,...but covered over with a tarp. IT HAS NOT WARPED, NOR SOAKED UP MOISTURE YET. And it is now sitting stacked up on its edge leaning against my other stowage shed with nothing but a piece of sheet metal covering it from direct rain. It is still not warping, nor soaking up water......I'm amazed.

I used 1/4" Foamcore

Under my staging yard with 10 tracks on the lower level. It is 2' wide by about 20-25 ft long. Everything else is on cork over 1/2 inch plywood. It has been down for about 15+ years in my basement. NEVER had any problem with dimensional shift. . Since it is somewhat hidden I just used a staple gun to fasten it to the plywood and track nails to attach the code 100 flextrack. I used 1/4" thick to approximate the thickness of the cork. It was a far cheaper alternative than cork over that entire expanse.

Only two things I wished I had done differently was to paint the foamcore with a dark color BEFORE I laid down track. The second was to allow for some expansion/contraction in those long lengths of flextrack. As they say, Hindsight is always 20/20.

Espee over Donner

Foamcore

One thing to be aware of is that foamcore will warp if one side of it is painted or gets wet. It will return to normal if you also paint the other side, or even just moisten it with a paint brush dipped in water.

Joe S

I used cheap dollar store

I used cheap dollar store foamcore with a method I developed for grades on an N-scale layout. I cut the "ramp" for a constant 2% grade and pushed it down over finishing nails that followed the track center line on the plywood base. I cut sub roadbed from the same foamcore, removed the top and glued it to the ramp. Then I went back adding cut to fit supports along each side, wherever I felt. Low temp hot glue was my adhesive of choice and though I didn't keep the layout long, there was nothing wrong with it. It proved to be quite substantial. For N-scale anyway.

dollar store?? that's rarely even FLAT

Foamcore distributors in the USA

thanks, prof

Fome-Cor® Board

per that search....   https://graphicdisplayusa.com/products/fome-cor/
 

Fome-Cor® Board is the industry's leading paper-faced foam board for more than 40 years.  It is comprised of extruded polystyrene foam with clay-coated white or kraft black paper facers. Made In USA.

• The original graphic arts foam board with a great reputation for performance
• Perfect for die cutting and provides a compressed edge that stays closed
• Quick service on cut-to-size orders, including large sheets up to 8' x 10'
• Uniquely embossable for 3-D effect displays
• Cuts easily and cleanly, even by hand
• Extremely lightweight
• Well-suited for screen printing or digital direct print applications

Interesting that the black stuff is NOT coated. I found that today when I inspected some of those many scrap pieces I collected,...the black pieces were NOT stable, and were much more susceptible to warping.

Also noted: Painting Do not expose core to solvent-based paints

Just to verify Prof_Klyzlr, this Fomecor product is the one you prefer?

"Interesting that the black stuff is NOT coated"

That is why, in addition to bracing, I Krylon coat both sides of the black foam board I use. The top side gets the heaviest coating. Just made sense to me as I knew I'd be putting a lot of water based treatment on it.

No warping here that amounts to anything. Of course I have a habit of putting pretty heavy structures on it!

Not a "preference" per-se

Dear Brian,

Not "my preference", just what I was able to get "last time I needed to stock up".
(well, actually, the last 2 times, but I use Foamcore extensively in my modelling and layout-building missions).

Previously (between 6 and 15 years ago) I literally used "whatever foamcore I could find locally at a decent price", I wasn't picky, and it all "just worked" as I needed it to...

That said, when it comes to any form of "how-to" or actionable reccomendation to and for fellow modellers,
I'm big on referencing specific makes/models/parts/components,
so others can "go forward with confidence",... 

...and at the price the _genuine 3A Composites_ Foam-Cor is
(AUD$10-13 per sheet, When bought in a stock 25-sheet carton,
I did some checking and that "UltraBoard" referenced elsewhere,
for a 16-sheet carton of 60x40x3/16 appears to be a bit over AUD$1200....)

...with known availability in the US, UK, and Aust
(I hate the perennial problem of having to "translate" the latest-and-greatest overseas-modelling tool/material/chemical/paint/etc into "local equivalent"
and _hoping_ it works the same,....

...in this case we _know_ we can all use the guaranteed same-stuff,
thus eliminating one variable from the "success/fail equation")

I'm quite comfy reccomending 3A Composites Foam-Cor by name for _appropriately designed_ and _properly constructed_ modelling applications.
(If someone finds a different material that's readily-available,
at a suitable price,
that works for them,
I'm not going to stand in their way...

...I just have over 20 years and 10+ touring/exhibition layouts,
with multiple 1000s of kilometres-travelled,
100s of shows and load-in/show/load-out/store/repeat cycles,
and zero damage to report,
which says "Foam-core works")

Happy modelling,
Aim to Improve,
Prof Klyzlr

Exspansion / Contraction observation

As discussed previously on another subject thread, it is very likely that it is NOT the track itself that is expanding/contracting that much, but rather the substance it is attached to. Would you have any opinions/observations about the 'problems' you experienced with this? Was it dramatic, etc??

Expansion

Dear Brian,

You seem stuck on this "differential expansion" issue, but when it's the _rails_ which are clearly buckled
(too much rail in not-enough linear length, where both rail-ends are anchored firm),

And the modules base-material<> end-plate and PCB rail-anchor-points are (still) exactly where they were first (properly and carefully) assembled, what leads us to blame the base material?

I'm not sure I get it....
(what is deemed "theoretically likely" may not actually align with "the observable-in-the-field fault conditions")

Happy modelling,
Aim to Improve,
Prof Klyzlr

Expansion, it’s not just for rails.

According to the table on the 5th page of this document:  https://psec.uchicago.edu/thermal_coefficients/cte_metals_05517-90143.pdf

The expansion coefficient of nickel silver is between 9 and 10 ppm per degree F depending on the exactly ratio of the alloy.  PPM in this case does in fact refer to parts per million - so 1 foot of nickel silver rail will get 0.000010 feet longer for each degree you heat it.  So if your basement varies by an extreme 40 degrees from coldest to hotest (say 50-90), a 10 foot length or rail where you’ve soldered all the joints so it acts as a unit will change length by at most 0.048 inches, or roughly 3/64th of an inch.  That’s just enough to cause some trouble if you haven’t allowed some expansion gaps here and there.

But everything else also expands with temperature, and some things expand with increasing humidity - sometimes vastly more than the expand with temperature.  Foamboard also changes size with temp (but negligeably with humidity).  The materials used to construct the room you’re putting your layout in also change size with temp and humidity.

With everything expanding and contracting it’s not surprising that some odd movements happen depending on what each thing is pushing or pulling against and where you have or haven’t glued and screwed everything together.  The model rail tendency to blame it on all rail expansion because the recall hearing the prototype has trouble with that along distances that are 1000 times greater is just silly.  Sure, rail expansion plays a part, but only a small part in the vast symphony of size change that goes on with everything in our basements.  Including the very rulers we might like to try to measure some of the changes with.

It’s easy to misinterpret what happened

Put two 8’ long pieces of plywood 1/8” apart end to end on a long table.  Now glue a piece of track along the whole length.  Now push the two pieces of plywood together closing the gap (thus simulating expansion due to humidity and temperature with the two ends pushing on something like same concrete walls that don’t move as much).  The track will buckle in exactly the same way that people attribute to rail expansion.

Figuring out what really happened is not at all easy when everything changes size and moves. 

Track Distortion

My basic point was (is) that very often model railroaders want to blame track 'distortions' on the metal rail itself,...while most in depth analysis usual blames the plywood or foam base that the track is attached to as much more of the culprit.

I'm trying to avoid these 'distortions' by thoroughly sealing up my plywood decks/shelfs, and looking at any other materials I might be attaching track to,...including this possible use of 'fomecor' stuff. What is the best product brand?,...and are there special considerations that need to be addressed?? After all I would NOT be happy if I chose the wrong product and had to go back and remove all this underlying 'foam-core'.

YES, I certainly plan on having expansion joints in my trackwork,...after all we are using multiple feeders which should account for electrical continuity down the lengths of rail.
 

My goal with this 'research' into the foam-core products is to determine how the track sections will end up remaining good in acceptable alignment over a number of years when track might be mounted on those removable sections of foam-core that would be bases for structures that are removable from the layout. I'm also wondering, investigating, how it might all remain in alignment if multiple turnouts cross those 'boundries', etc??

Defending dollar store foamcore

Notice where I said I removed the top layer of paper on the dollar store foamcore when I used it as sub roadbed? The reason is twofold. #1, it's not attached that well and water based scenery will separate it from the foam quite easily which is a mess especially if roadbed and track are attached. #2, my experience is that ripples are caused by the paper and it's quite flat otherwise.

Us model airplane guys have found all kinds of creative uses for various types of foam and foamcore, dollar store and otherwise. Lot's of inspiration and ideas of what you can and can't do with it on those sites.

I'm here to tell you that even dollar store foamcore will work for N-scale sub roadbed in certain applications. I know, I've done it. I cannot comment on HO and larger because so far I've only used it for scenery profile boards and support since my scale change a few years ago. As Robert Ripley was fond of saying, "Believe it or not".

"YES, I certainly plan on

Hi Brian   Given the relatively small area of layout and your planned expansion joints I don't think you need to spend too much time looking for ways to reduce expansion.  Plain old plywood is not gonna move enough to open or close unsoldered rail joints enough to wreck a train. I'd just build with whatever proven stable material you can get easily, plywood, pink or blue foam, homasote, glued up splines, etc. then add enough expansion joints and move ahead with layout building. The clock is ticking so I'd not waste time reinventing the wheel if a layout is the desired goal.....DaveB

in the defense of materials and science

What are the equipment for the research? Here and in other posts related to the expansion or contraction due to the temperature changes or even humidity in unregulated or partially regulated environments, the only equipment used is composed from the thermal coeficient and the four basic mathematical operations. We are in 21th century and that equipment wasn't enough centuries ago. The knowledge gathered through the scientific methodology is threwed and we return to the dark ages.
The rail buckling is caused by the stress caused by the restrained expansion and the imperfections of the rail. For the evaluation of the stress more physics and mechanics are needed. Forces depends on the modulus of elasticity, the crossection, the length, the restraints and the temperature change.
https://www.engineeringtoolbox.com/stress-restricting-thermal-expansion-d_1756.html
/> How they can have welded long rails in the real railroad? https://en.wikipedia.org/wiki/Track_(rail_transport)#Continuous_welded_rail
/> If i dont know how to fix rail on ties, the ties to the roadbed, the roadbed to the subroadbed i can't avoid the failure from thermal expansion. To transfer the forces of a restrained long rail i have to know the forces. To avoid the buckling i have to know the forces and the behaviour of an elastically restrained rail. The elastical restrain depends on the connection between the rails and the ties, the connection between the ties and the roadbed, the connection betweent the roadbed and the subroadbed  and the properties of each material and the relations - laws which defines the materials behaviour. I have to specify the temperature extremes and the "rail neutral temperature".
I can't use inappropriate materials, in an inappropriate way for a specific environment and then blaming the materials for the failure. I can't use materials affected by the humidity in an environment wihere the humidity varies more than the material can sustain without changing in an unwanted way. The materials don't fail, they don't try nothing to prove. People fail when using the wrong materials in wrong ways.
They have a saying here, "You can't make a whip from shit. Even if you do it you can't crack with it. Even if you crack it will return to you."
It's too hard or (and) unnecessary a such kind of research? If yes, then i have to stay with common practices. Do i like to experimenting? Ok, then i have to specify the experiment and its parameters in a way to be replicable and attempt to find the relations between the involved parameters.
Good luck sincerely 
 

Coroplast

Thinking of my RC hobby again, I should mention Coroplast. If it's been mentioned then I missed it. Much like corrugated cardboard but plastic. Used a lot for small outdoor signs and another thing used by the RC guys to build planes.