There's two potential shrinkage problems with foam:
One is the shrinkage caused by continued chemical reaction after it is initially formed. I would expect that, if it happens, it would have a diminishing effect over time. Hence the pronouncements about aging for 6 months.
Now, the reaction MAY not be diminishing. Some don't. Consider zinc pest, and the great sadness that it can generate years after manufacture.
But it does "feel" like the diminishing style of reaction. Anyway, this kind of shrinkage does happen. I have seen the results. Hopefully, doing the six month wait eliminates the problem.
The other is continued and continual shrinkage and expansion caused by temperature variations. It exists, also. I saw it happen with my module, where the widths of cracks in the scenery surface over the foam changed with temperature. The cracks widened when it was hot. And narrowed when it grew cooler. The module was stored in an unconditioned space. I observed it when the temperatures ranged from 50 degrees to 90 degrees.
It seems likely that foam on a layout in a conditioned space would have minimal problems with the above.
Ed
markie97 I have started an expansion of my layout and was planning on using 2" and in some areas 1" thick foam insulation board, the kind you buy in Home Depot or Lowes. After reading comments in the foam core discussion thread I have some concerns about expansion and/or contraction. Should I be concerned? Where can i get a digital or traditional book on just setting up the basics before actually laying track...for example the proper way of setting the diffferent types of foundations, track beds, etc?
I have started an expansion of my layout and was planning on using 2" and in some areas 1" thick foam insulation board, the kind you buy in Home Depot or Lowes. After reading comments in the foam core discussion thread I have some concerns about expansion and/or contraction. Should I be concerned?
Where can i get a digital or traditional book on just setting up the basics before actually laying track...for example the proper way of setting the diffferent types of foundations, track beds, etc?
rrebell No shrinking to speak of if it is aged at least 3 months (measure the peice against stated size to find out if it has sat around long enough).
No shrinking to speak of if it is aged at least 3 months (measure the peice against stated size to find out if it has sat around long enough).
I'm certainly in the clear then. I only have time to model in the winter. My foam has seen two Winters without track. I measured the 8ft length of the base. It's only short a sixteenth of an inch I can accept that. I'm led to believe the only place one would have possible problems is a garage layout with extreme temperature swings. My own layout in a conditioned environment is just fine.
carl425 rrinker Cutting out stips of plywood and attaching it to risers I would not call cookie cutter. When you look at what's left of a sheet of plywood after cutting sub-roadbed pieces from it, it looks like a sheet of dough after you've cut cookies out of it. Too bad you can't ball it up, roll it out again and cut more cookies.
rrinker Cutting out stips of plywood and attaching it to risers I would not call cookie cutter.
When you look at what's left of a sheet of plywood after cutting sub-roadbed pieces from it, it looks like a sheet of dough after you've cut cookies out of it. Too bad you can't ball it up, roll it out again and cut more cookies.
Interesting concept. I thought about that too. Then I thought outside the box. Why buy WS risers if I don't have to. I love foam. My layout is 100% foam. After I cut out my cookie cutter. It occurred me don't throw away the rest of the jigsaw puzzle. Put the puzzle pieces back in spaced up with foam ribs at the appropriate levels. So I did. Now I don't have to carve down far to the lower levels or Build up very high to the upper levels. I have a lightweight wood frame that my foam layout will insert into when I'm ready to do so. My calculations is my 4x8 layout will weigh 40 to 50 pounds when I'm done. It is an N gauge layout. Almost the whole layout is 2% grades maximum. Radius 18 minimum. 16 hidden. Here's a picture of a portion of it so you can see what I'm talking about.
You guys all have a wonderful 4th.
Don't sweat the small stuff
rrinkerCutting out stips of plywood and attaching it to risers I would not call cookie cutter.
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
Everything? What if yooou ARE modeling the flatlands? And stacking up scraps of foam with a dab of glue or caulk is pretty quick way to build a base for hills and so forth.
Check Bill Darnaby's articles, foam makes it super easy to have main and sidings at different levels along with all the ditches - one of his articles shows a hot wire cutter be made that carves the subroadbed as well as the drainage ditches on both sides. Pretty slick.
There are other ways to go up and down that don't require using a jigsaw to cut patterns out of plywood, and then fit risers in and hope there are enough to not allow things to sag. All is not perfect with cookie cutter or cutting individual pieces of plywood subroadbed - I consider those two different things. To me, cookie cutter is you start with a flat sheet of plywood and you cut around outlines of ares to be raised or lowered, most of it ends up staying connected but with some parts rising higher than others. Cutting out stips of plywood and attaching it to risers I would not call cookie cutter.
All is not perfect in the world of l-girder and open grid, otherwise no one would have even bothered trying foam. Each has advantages and disadvantages. No one method is perfect for everything.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
One thing I still don't get about foam...
Open grid and L-girder evolved to get us away from the "Flatland" look of tabletop railroading. Why would someone want to go back to the tabletop when the open grid/L-girder with cookie cutter sub-roadbed makes everything from scenery to wiring easier and more flexible?
Here's something I think we all CAN agree on:
IF you are going to use foam, store it for at least 6 months before installation.
My sections are still all together despite sitting on my basement floor for over 2 years now, in widely varying humidity - rather damp in the summer since there is no insulation or vapor barrier on the walls, dry in winter because it's naturally dry plus heated. None of the foam has come unglued. None of the frames have warped. And that's 2 layers of foam glued to one another, and that is glued to 1/4" plywood. 1x4 and 1x3 framing.
Working on providing O C Specs first ones came out blurry
In my opinion it's not the foam that's shrinking it's the moisture in the wood framing that shrinks or expands. All construction materials come with a high percentage of moisture. This is indeed true fact. That's why there's problems with newer homes and mold. Wood is not kiln-dried like in the old days. Adhere your foam with a flexible caulk to it's base and even spend the extra money to use a higher grade 1 by 4's for your Framing and you'll be fine. If the foam floats on its base it will not be affected by the expansion and contraction of what's going on underneath.
Take it easy don't sweat the small stuff
Re extruded foam board shrinkage: I have seen it on some 2ft x 4ft modules that were foam within a wood frame. In some cases, the shrinking foam caused the glue joint to break. In other cases, where a very strong glue was used (Gorilla is among them), the foam split or the wood frame was bowed.
Most modules do not experience the shrinkage. As near as anybody can tell, the shrinkage from off-gassing is highest immediately after manufacture. Six plus months after manufacture, most of the shrinkage has already taken place.
FWIW, in the cases I personally observed, some of the pink foam modules had shrinkage issues, but only one of the blue foam ones did (a 4ft x 4ft blue foam in frame Christmas layout I had built had the frame bowed). My explanation is that in my neck of the woods, Home Depot carries the pink foam, and Lowe's carries the blue. Home Depot has a much faster turnover of foam board than Lowe's, and hence the foam board would be newer.
Based on what I have observed, the 2% is a maximum figure. What I have observed is in the 1% range or less - enough to pull the glue joint apart but not much more.
Based on a lot more than the shrinkage issue, I have gone away from extruded foam use for my modules and layouts. I am currently using 5mm plywood frame construction with 3/4" plywood end plates - very similar to what the Sipping & Switching Society uses. I use open top grid with 3/4" plywood subroadbed that runs from end plate to end plate. Scenery shell is to be Bragdon foam on screen wire for very light weight.
And I am experimenting with foam core construction of a module (will not be Free-mo).
Fred W
My layout is in the basement, humidity and temps do change a little with the seasons, and has been up and running since 2010, and no problems.
Mike.
My You Tube
carl425 superbe As for them being a fire hazard a dropped hot soldering iron produced a cave like opening. It all happened so fast I only remember a slight odor. Clearly the dangerous off-gassing from the foam has caused you to suffer permanent memory loss.
superbe As for them being a fire hazard a dropped hot soldering iron produced a cave like opening. It all happened so fast I only remember a slight odor.
Clearly the dangerous off-gassing from the foam has caused you to suffer permanent memory loss.
Glad to hear my memory loss is connected with model railroading. I thought it was because I'm 88.
We all know that metal expands and contracts due to temperature changes and memebers have reported their track buckeling. There is no question about this.
But I have yet to hear a complaint about pink or blue foam shrinking. No doubt it may and or does when used for the purpose and in the environment it was intended. On a layout in a controlled environment with track and paint IMO it is very stable.
A 2% shrinkage on my layout would equal 3.36" X .96" and I think I would have seen some evidence of that.
Has anyone actually experienced any shrinkage and if so what were the results??
Bob
Don't Ever Give Up
FowlmereRR Since the appalling tragedy of the Grenfell Tower fire in London, there has been much in the UK press about combustibility of materials used in such rennovations. Today I read a piece about certain foam insulation board that was used behind the rainscreen cladding and, when ignited, emitted hydrogen cyanide gas. So, perhaps we should urge caution and apply large doses of common sense when choosing materials for our projects - it is all to easy, it seems, for a seemingly innocuous material to become a source of deadly fumes in the wrong circumstances. I am not an expert and I am sure that there are several types of "foam insulation board", and that not all of them may be hazardous. So please check first.
Since the appalling tragedy of the Grenfell Tower fire in London, there has been much in the UK press about combustibility of materials used in such rennovations. Today I read a piece about certain foam insulation board that was used behind the rainscreen cladding and, when ignited, emitted hydrogen cyanide gas.
So, perhaps we should urge caution and apply large doses of common sense when choosing materials for our projects - it is all to easy, it seems, for a seemingly innocuous material to become a source of deadly fumes in the wrong circumstances.
I am not an expert and I am sure that there are several types of "foam insulation board", and that not all of them may be hazardous. So please check first.
You know what else emits hydrogen cyanide when it burns? Wool. Cotton. Silk. Nylon. Leather. Pretty much everything.
Your mattress and carpet are bigger sources of it than your layout foam.
rrinker Thankfully these threads don't come up nearly as often as "the hobby is dying" or "what is the best DCC system" but we have been through all this before.
Thankfully these threads don't come up nearly as often as "the hobby is dying" or "what is the best DCC system" but we have been through all this before.
One of my favorites is the "exploding fan in the paint spray booth".
Robert
LINK to SNSR Blog
superbeAs for them being a fire hazard a dropped hot soldering iron produced a cave like opening. It all happened so fast I only remember a slight odor.
But seriously, I believe the fire related argument is based more on the gasses released by the foam when it burns rather than the fact that it is flammable.
superbe After 10 years there has been no shrinking or expanding.
After 10 years there has been no shrinking or expanding.
Sounds like your stuff might have been aged 6 months before you used it. Or so. Or perhaps your foam came out of the good end of the batch.
I do notice that, while the manufacturer said the product might shrink 2%, they did not mention a time span. Considering they are BIG, and all that, I find it odd that they acknowlege a shrinkage problem, but also neglect to share data.
Ten years ago I looked for 2" foam and had to settle for doubling up 1" foam. I glued them to the plywood and to each other with latex caulk. I ran a bead around the perimeters and diagonal beads from corner to corner.
After 10 years there has been no shrinking or expanding. As for them being a fire hazard a dropped hot soldering iron produced a cave like opening. It all happened so fast I only remember a slight odor.
IMO you can't beat foam for your layout top.
That was a sincere not a sarcastic post. 2 inch Owens Corning pink insulation foam board is widely used in Minnesota on the exterior framing of homes before siding goes on. It is rated don't quote me from 50 below zero wind chill factor to 100 degrees plus humidity. It is a very good product. It's called closed-cell for reason. It does not absorb moisture. It has a less expansion and contraction ratio than open grain wood by far. Nobody's siding is buckling up here because of this Superior foam insulation product.
I'm quite sure it would burn just like anything else.
rrinker Thankfully these threads don't come up nearly as often as "the hobby is dying" or "what is the best DCC system" but we have been through all this before. There used to be a video on YouTube of someone debunking the fire dangers of the pink extruded foam - basically with ost cobustion sources like a hot soldering iron or even a lit candle, the foam melts a hole around the heat source until the edes are far enough fromt he heat source as to be below the meltign temperature. It took them considerably effort to actually ge tthe foam to catch fire, and it quickly extinguished itself. The kid of foam I was always aware of as giving of hydrogen cyanide was the stuff foam coffee cups (the white ones) are made out of. This was way before extruded foam insualtion was available that I heard this, and still cringe any time someone throws one in a fire or burn barrel. There are other white expanded foams that don't, or else a hot wire selas it instantly - Woodland Scenics forms and risers and so forth they specifically sell a hot wire cutter for. There was also a vendor selling hot wire cutters who would always set up at the Timonium train show and would demonstrate carving with it in various foams, included the pink extruded stuff. No fumes. Less, actually, then you get by scoring and smapping it. No granted, if your house is buring around the layout, the foam will likely burn as well, it's not fire proof. But there are plenty of other plastic type materials inthe layout, not to mention objects in the home plus construction materials in the walls, floors, and ceilings. If you're in there breathing that stuff in, foam or not foam on the train layout isn't going to make a difference. Plastic or wood structure kits on the layout aren't going to make a difference. Acrylic vs solvent paints aren't going to make a difference. --Randy
There used to be a video on YouTube of someone debunking the fire dangers of the pink extruded foam - basically with ost cobustion sources like a hot soldering iron or even a lit candle, the foam melts a hole around the heat source until the edes are far enough fromt he heat source as to be below the meltign temperature. It took them considerably effort to actually ge tthe foam to catch fire, and it quickly extinguished itself.
The kid of foam I was always aware of as giving of hydrogen cyanide was the stuff foam coffee cups (the white ones) are made out of. This was way before extruded foam insualtion was available that I heard this, and still cringe any time someone throws one in a fire or burn barrel. There are other white expanded foams that don't, or else a hot wire selas it instantly - Woodland Scenics forms and risers and so forth they specifically sell a hot wire cutter for. There was also a vendor selling hot wire cutters who would always set up at the Timonium train show and would demonstrate carving with it in various foams, included the pink extruded stuff. No fumes. Less, actually, then you get by scoring and smapping it.
No granted, if your house is buring around the layout, the foam will likely burn as well, it's not fire proof. But there are plenty of other plastic type materials inthe layout, not to mention objects in the home plus construction materials in the walls, floors, and ceilings. If you're in there breathing that stuff in, foam or not foam on the train layout isn't going to make a difference. Plastic or wood structure kits on the layout aren't going to make a difference. Acrylic vs solvent paints aren't going to make a difference.
Amen brother. Thank you for your support.
FowlmereRRSo, perhaps we should urge caution and apply large doses of common sense when choosing materials for our projects - it is all to easy, it seems, for a seemingly innocuous material to become a source of deadly fumes in the wrong circumstances.
I also am no expert, but this is consistent with the advice about not using hot wire cutters on this foam.
It not the quietest or safest material out there. The MSDS shows the hazards. Best to check
i had a large problem occur with pink two inch years ago. The edges curled under a six inch width on both sides just rolled under pulling the rest up off the benchwork. Had to start over I dont use foam all the much Since then i have seen curled edges on foam a lotout on theconstruction sites i have been on . Not sure if it becacuse it is not cured right at the plant or something in shipping
shane
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
There you have it, folks:
Be concerned!
Don't be concerned!
Yikes!!
WHat they don't say is what the conditions are for maximum change - heat? Humidity? Combo? Under the maximum pressure of 150PSI?
There are some people using it in VERY hot climates with no problems. I've used it on two layouts now with no problem, and one of those was in a basement with very variable humidity throughout the year.
There is NO reason to be concerned with using foam. ANd you say long term? If it was a long term problem, Bill Darnaby's entire layout would have come crashing down already. He even has less support structure than many put under the foam. I believe his first foam board article appeared in MR back in 1995.
Here's the data sheet at the Owens Corning web site:
http://insulation.owenscorning.com/assets/0/428/429/431/0538f0de-3893-4e8a-a0c0-5de11b913061.pdf
For dimensional stability they say the maximum linear change is 2.0%. That's pretty scary... although I've never heard a model railroader report that much.