Lastspikemike Yes we are but extruded and bead are both closed cell foam structure. To shrink the sheets then the cells themselves must be gas permeable which seems odd to me. Extruded just creates the closed cells in continuous flow rather than popping up the individual cells and gluing them together. Conceptually I mean. The bead style are just expanded foam pieces stuck together after popping up and structurally the same as extruded, within each bead. https://www.buildingscience.com/sites/default/files/migrate/pdf/PA_Foam_Shrinks_Correction.pdf Newer foams are less gassy. Aged in storage for three months makes a difference apparently.
Yes we are but extruded and bead are both closed cell foam structure. To shrink the sheets then the cells themselves must be gas permeable which seems odd to me.
Extruded just creates the closed cells in continuous flow rather than popping up the individual cells and gluing them together. Conceptually I mean. The bead style are just expanded foam pieces stuck together after popping up and structurally the same as extruded, within each bead.
https://www.buildingscience.com/sites/default/files/migrate/pdf/PA_Foam_Shrinks_Correction.pdf
Newer foams are less gassy. Aged in storage for three months makes a difference apparently.
We are really talking two types of foam, extruded (pink and blue stuff) and expanded (beaded stuff). The extruded stuff will shrink much more than the beaded once cured. Seen the pink stuff curl up a bit even when held flat, not so with beaded stuff. All foam shrinks when first manufactured, once cured shrinkage is min. on beaded, not so much on extruded. With expanded this is due to shrinkage happening right after manufacture and many places age there stuff for a few days to make sure. Extruded has a more gradual process.
IDRickshould I use a Kreg pocket jig or an air nailer on the butt joints of the open grid?
The true key to rigid benchwork of superior strength is WOOD GLUE! Properly executed glue joints will actually be stronger than the wood it joins when cured. Wire brads or screws alone can never equal the strength and rigidity of glue joints. However, the brad nailer will prove to be a significantly faster means of assembling your benchwork. Put glue on the wood where it will create a joint and nail it together with the brad nailer. Just don't put ant strain on the brads until the glue cures. This is how I assembled my around-the walls single and double cantilevered benchwork with ope spans as long as 13 feet. No sagging or warping in over 10 years!
Hornblower
Some good points made Fred.
I would say I have to agree with you. Come to think of it I do remember researching extruded foam when I started my layout. I thoroughly went through the Owens Corning specs from their technical data sheet. I do remember reading about shrinkage due to outgassing after it is manufactured. The amount it shrinks is quite minimal.
The reason I never had any problem with foam on my layout is because it sat in my trailer a year after I completed a job before I started my layout.
There are actually building scientists that have devised methods of constructing buildings, commercial or residential. These fundamentals have been mandated into building codes over the years. Expansion and contraction is one of the biggest issues these codes were devised for. Temperature infiltration is another big one but I'm not going to get into that.
Vinyl siding has oval holes in it and roofing nails are used for fasteners not to be driven all the way tight so the siding can float on the side of the building as it expands and contracts from the fluctuation of temperature and air conditions. Extruded foam that is installed underneath the siding has to be installed with plastic ring nails usually manufactured in fluorescent green or orange so the inspectors can see them easily. These Fasteners allow the foam to float underneath the siding as the wood framing the foam is fastened to expands and contracts.
Even OSB roof sheathing is manufactured 1/16 of an inch shy of 8 feet. Sheathing installers tap-in 16 penny nails between the length of the sheets on the roof rafters temporarily as they put the next sheet on to leave an 1/8 gap for expansion and contraction of both the sheathing and roof framing. The inspectors look for the mandatory H-clips that are put between the width of the oriented strand board sheets installed so the roof sheathing does not buckle under temperature fluctuation.
I may be a little anal retentive sometimes but I built an inverted quarter inch Luan criss-cross frame for my layout benchwork. I used 90-degree elbow brackets and anchors in the foam for the fasteners so the foam can float on the bench work. The benchwork for our layouts is a much smaller scale as buildings but still has the same factors involved.
The crib was a good idea and has worked out well. Cantilevering it from the wall was a very bad idea. I had commercial slides so I could slide it two feet out from the wall, duck underneath and work on the other side of the layout. I got sick of ducking under it and nothing ever got done on my layout. I later built different benchwork on wheels that should have been done in the first place.
I have been known to think backwards at times but it seems to me the fascia of a layout is most firmly attached to the sides of the benchwork frame or crib as some call it, and the foam floats in between. If the benchwork crib contracted, the fascia would be pulled tighter to the foam. If the benchwork crib expanded, the fascia would be pushed away from the foam leaving a gap.
Good hardwood floor installers know the winter time is the best time to install a hardwood floor when the air is dry and after the flooring acclimates to the air in the room. Installing a floor when it's humid, the floor shrinks the next winter leaving gaps.
Expansion and contraction are definite considerations to consider when building a layouts benchwork.
Especially Shrinkage
TF
A lot of research has gone into foam shrinkage by the modular folks who used framed foam modules for ease of construction and light weight. Over the years, there is mounting evidence that extruded foam does shrink as off-gasses after manufacture. Manufacturers admit it, and I've seen the modules where the glue joint has broken, the foam sheered, or the frame actually became curved where the glue and foam held.
It's not the wood because even 36" long modules using plywood-only frames have experienced the shrinkage pulling things apart while other modules using pine frames stay intact.
Most of the shrinkage occurs in the first 18 months after manufacture, and the majority of that most occurs in the first 6 months. But the cumulative effect can be enough to be noticed (and be destructive), particularly if you bought and used the blue or pink stuff right after it was made.
The only "cure" is to age the stuff before you use it - from experience the foam needs to age for at least 6 months for the shrinkage to be minimal and of no consequence from that point on.
For what it's worth, extruded foam is like many plastics that shrink with age. The cracked plastic gears in our model locomotives are another example of shrinkage with age. The plastic gear shrinks but is blocked by the metal shaft. Eventually the shrinkage stress cracks the gear.
As an aside, that "new car" smell is the plastic in your car off-gassing.
Fred W
A number of years ago I had a 2 inch slab of pink foam shrink on me. It buckled the track that was glued to it. The foam was not on plywood. I'm building a new layout now and as a precaution I'm cutting saw kerfs across it every 2 feet. They are cut about 90% through from the bottom side. The foam is on OSB this time. It may not be the answer but it makes me feel better.
George
IDRick Respectfully speaking, I did have separation at seams between foam pieces and separation between fascia and foam. The 5x9 benchwork followed the specs for a tabletop layout in Wescott's Model Railroad Benchwork. The top was 1" extruded foam over 1/2' plywood. I followed a MR article on how to build benchwork with a foam top. I don't recall which adhesive was used, it was either Liquid Nails for projects or carpenter glue, probably the LN. The top was weighted with college textbooks and left that way for a week. As far as I can tell, I did everything correctly but still had the separation develop over time. The layout was in a basement with temperature varying only a few degrees throughout the year and low humidity. My bottom line is I want to use foam in my next layout but want to do all I can do to prevent separation along the fascia. I will be building the benchwork in sections and the foam top will be a single piece, thus no separation between foam seams within a section. How do I prevent separation between the foam:fascia and foam:endplates? The anecdotal article (mentioned in OP) suggested that using two foam layers with 90-degree difference in seam orientation would prevent/minimize movement of the foam with benchwork expansion/contraction. Seemed plausible to me but then I'm a dairy scientist not an engineer, carpenter, or experienced layout builder. That's why I asked here...
My bottom line is I want to use foam in my next layout but want to do all I can do to prevent separation along the fascia. I will be building the benchwork in sections and the foam top will be a single piece, thus no separation between foam seams within a section. How do I prevent separation between the foam:fascia and foam:endplates?
The anecdotal article (mentioned in OP) suggested that using two foam layers with 90-degree difference in seam orientation would prevent/minimize movement of the foam with benchwork expansion/contraction. Seemed plausible to me but then I'm a dairy scientist not an engineer, carpenter, or experienced layout builder. That's why I asked here...
It is possible the wood moved but impossible to test, given the age of the layout! I didn't purchase the wood far in advance and let it acclimate for a significant time in my basement. Rather, it was only a few days from purchase to benchwork construction during the summer months. The foam had direct contact with MDF fascia and the 1/2" plywood. I would not expect much movement with either material in our moderate temperature, low humidity basement.
Is there a reasonable way to test when it is "safe" to cut and construct with 2x 2 and 1x3 stock? The material in my layout did not warp but I have experienced warpage in 2x2 and 1x3 in my garage, stored flat. The new layout will be in the basement but the shop is in the garage. PITA to haul downstairs to acclimate, carry up to the shop to cut, then haul back to the layout room... Mrs does not want construction dust in the house...
York1 Because I know nothing, I went to the "end all source of knowledge of the universe", Wikipedia! (Don't yell at me. It's an attempt at a joke.)
Because I know nothing, I went to the "end all source of knowledge of the universe", Wikipedia! (Don't yell at me. It's an attempt at a joke.)
Track fiddler All I've got to say is bull pucky. Foam don't shrink. You could bury it underground like they do and it'll take 30 years before it starts to decompose. I've kept tabs on foam. A seven foot length shrank 1/16 of an inch over three years Building materials come to the lumber yard up to 60% moisture. Building materials are categorized as cellulose. All cellulose materials have a high content of moisture. That is a problem as wood and man-made materials out of wood shrinks as it dries. I remember an article in Model Railroader magazine years ago. A modeler did a spline lamination of some sort of cellulose materials. It didn't take long and when the spline material dried out, the track buckled severely. I don't think modelers started to put foam over wooden bench work years ago for the heck of it. The foam fluctuates to the shrinkage and then later expansion and contraction of wood. Cellulose material has been known to drink and expel moisture since the beginning of time. Foam laughs at it. I don't know who wants to reinvent the toothbrush in some magazine as an author but you can't always believe what you read. Foams expansion and contraction rate is extremely minimal. Modelers have been using it over bench work to buffer out movement underlying it since the 80s. At this point I wouldn't reinvent the wheel either. How you fasten foam to cellulose materials does matter as well Respectfully speaking for what I know TF
All I've got to say is bull pucky.
Foam don't shrink.
You could bury it underground like they do and it'll take 30 years before it starts to decompose.
I've kept tabs on foam. A seven foot length shrank 1/16 of an inch over three years
Building materials come to the lumber yard up to 60% moisture. Building materials are categorized as cellulose. All cellulose materials have a high content of moisture. That is a problem as wood and man-made materials out of wood shrinks as it dries.
I remember an article in Model Railroader magazine years ago. A modeler did a spline lamination of some sort of cellulose materials. It didn't take long and when the spline material dried out, the track buckled severely.
I don't think modelers started to put foam over wooden bench work years ago for the heck of it. The foam fluctuates to the shrinkage and then later expansion and contraction of wood.
Cellulose material has been known to drink and expel moisture since the beginning of time. Foam laughs at it.
I don't know who wants to reinvent the toothbrush in some magazine as an author but you can't always believe what you read.
Foams expansion and contraction rate is extremely minimal. Modelers have been using it over bench work to buffer out movement underlying it since the 80s.
At this point I wouldn't reinvent the wheel either. How you fasten foam to cellulose materials does matter as well
Respectfully speaking for what I know
Respectfully speaking, I did have separation at seams between foam pieces and separation between fascia and foam. The 5x9 benchwork followed the specs for a tabletop layout in Wescott's Model Railroad Benchwork. The top was 1" extruded foam over 1/2' plywood. I followed a MR article on how to build benchwork with a foam top. I don't recall which adhesive was used, it was either Liquid Nails for projects or carpenter glue, probably the LN. The top was weighted with college textbooks and left that way for a week. As far as I can tell, I did everything correctly but still had the separation develop over time. The layout was in a basement with temperature varying only a few degrees throughout the year and low humidity.
rrebell I use beaded foam, it dose not shrink one cured enough to even see.
I use beaded foam, it dose not shrink one cured enough to even see.
IDRickCliff notes would be good!
Hi IDRick,
I have started the 'Cliff Notes' version of the thread:
http://cs.trains.com/mrr/f/11/t/287007.aspx
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
IDRick DrWayne, I have a world of respect for you and your fine modeling skills! I greatly appreciate all the ways you provide assistance and encouragement to those of us with lesser talent and learning/developing skills! You are one of the top, must read posters in the MR forums. We're good, just a difference in definitions.
DrWayne, I have a world of respect for you and your fine modeling skills! I greatly appreciate all the ways you provide assistance and encouragement to those of us with lesser talent and learning/developing skills! You are one of the top, must read posters in the MR forums. We're good, just a difference in definitions.
IDRickliff Notes were a "Godsend" in the 70's. They summarized a long book in like 30 pages with a synopsis by chapter.
Okay, now I understand. In Canada we used to call them 'Cole's Notes' after the bookstore that produced them. They helped a lot of people.
I will consider your very valid suggestion. In fact, I did that before with another thread about upgrading a Walthers 90' turntable that got a little long in the wind too.
Just so you are aware, I currently have a partially torn tendon in my left shoulder which is severely limiting my abilities. I can type but not for long periods. Doing the 'Cliff Notes' version of the thread might be pushing my luck right now, but I would really like to do something in the future.
Thanks for the suggestion.
Cliff Notes were a "Godsend" in the 70's. They summarized a long book in like 30 pages with a synopsis by chapter. For me, I had a hard time reading Shakespeare but found that I could better understand if I read the book and its associated Cliff notes.
When I jokingly asked for cliff notes, I was saying it would be great to have a short summary on the key points of your rotisserie layout. I have bad knees and would love to work on layout sections mounted on a rotisserie rather than man handling pieces on a workbench! It's an awesome idea, Kudos! Your long thread had lots of twists and turns, typical and awesome for a close knit group like this forum!
York1 John
IDRick,
I'm glad you are enjoying my build thread. I am really frustrated right now because my recent injuries have stopped me from working on either the layout proper or doing any workbench sort of stuff. My shoulder is still weak and hurting after more than two months.
What do you mean by "Cliff notes"? I don't recall hearing the phrase before.
Thanks,
IDRick ...Shrug, was not trying to start an argument, was simply identifying my source and respectfully disagreeing with your statement that butt joints (per Westcott definition) are rarely used in benchwork....
I didn't reply in arguement, either, but rather referred to the term as used by an uncle, who both owned and ran a lumberyard and also built houses, and for him, a butt joint was butt-ends butting against one another, as Mike has mentioned. My father, a design engineer, had a similar opinion of the term.
While the main portion of my layout is open grid, most of the track and structures there are not directly atop the grid, but rather on risers, attached to the grid. Structures of any appreciable size are likewise on risers, with a platform suited to the structure's shape and size.The partial upper level, also open grid when built, is covered in 5/8" t&g plywood, so I guess, technically-speaking, it's no longer open grid.
Wayne
doctorwayneA butt joint occurs when the ends of two pieces are butted against one another.
doctorwayne IDRick Respectfully, your picture above has 11 visible butt joints (screws through a flat surface board into the end grain of another board). A butt joint occurs when the ends of two pieces are butted against one another. Unless the mating ends are modified to overlap one another, or a separate splice plate is used, overlapping both pieces, it's not the kind of joint most builders would use. Using your definition of butt joints would mean that most of the framing I built for my house is butt joints, but (no pun intended) if it had butt joints as I know them, it would have fallen down even before I had time to apply the exterior sheathing. Wayne
IDRick
Respectfully, your picture above has 11 visible butt joints (screws through a flat surface board into the end grain of another board).
A butt joint occurs when the ends of two pieces are butted against one another. Unless the mating ends are modified to overlap one another, or a separate splice plate is used, overlapping both pieces, it's not the kind of joint most builders would use.
Using your definition of butt joints would mean that most of the framing I built for my house is butt joints, but (no pun intended) if it had butt joints as I know them, it would have fallen down even before I had time to apply the exterior sheathing.
IDRick Respectfully, your picture above has 11 visible butt joints (screws through a flat surface board into the end grain of another board).
IDRickRead an anecdotal article (non-MR related) today on foam separation issues. The author states that two layers of foam are better than a single layer for preventing separation and that joints should be offset vertically and horizontally. Is this true for a MR layout and is it worth the effort?
Finally, putting together an open grid box, should I use a Kreg pocket jig or an air nailer on the butt joints of the open grid? I will need to purchase the selection and it would most likely only be used with model railroad benchwork.
Use a drill/driver and screws on your butt joints. Drill a pilot hole when needed, to prevent splitting.
If you feel you need the pocket jig, so no screw heads show, that's your call.
I, myself, wouldn't mess with it. For furniture and finish work? Maybe.
As far as the foam shrinkage, I haven't had any problems, but the foam on my layout is made from random pieces from job sites, so they it all kinda overlaps each other.
Mike.
My You Tube
doctorwayne IDRick ...Finally, putting together an open grid box, should I use a Kreg pocket jig or an air nailer on the butt joints of the open grid?.... I can't visualise where or why there'd be a butt joint anywhere. When I make a section of open grid, usually 8' or 10' long, and at a width suitable for the available space and in consideration of the necessary aisle width, it gets set upon the support framing and fastened in place with short 1"x2" verticals, screwed to the support framing and the grid. The next grid section, and all subsequent ones, are attached likewise, and also attached to the grid already in place, using screws through the end cross-members. This open grid was improvised to allow for a rounded-end on a peninsula... Wayne
IDRick ...Finally, putting together an open grid box, should I use a Kreg pocket jig or an air nailer on the butt joints of the open grid?....
I can't visualise where or why there'd be a butt joint anywhere. When I make a section of open grid, usually 8' or 10' long, and at a width suitable for the available space and in consideration of the necessary aisle width, it gets set upon the support framing and fastened in place with short 1"x2" verticals, screwed to the support framing and the grid. The next grid section, and all subsequent ones, are attached likewise, and also attached to the grid already in place, using screws through the end cross-members.
This open grid was improvised to allow for a rounded-end on a peninsula...
IDRick...Finally, putting together an open grid box, should I use a Kreg pocket jig or an air nailer on the butt joints of the open grid?....
I can't visualise where or why there'd be a butt joint anywhere. When I make a section of open grid, usually 8' or 10' long, and at a width suitable for the available space and in consideration of the necessary aisle width, it gets set upon the support framing and fastened in place with short 1"x2" verticals, screwed to the support framing and the grid. The next grid section, and all subsequent ones, are attached likewise, and also attached to the grid already in place, using screws through the end cross-members.This makes a solid support for the layout, but one which is also readily disassembled if the layout needs to be moved or altered.
If the aim is to save materials by eliminating the cross-members at the ends of each segment of open grid, then the simple (and economical) solution is to use a leftover piece of the grid-making lumber to make a lap joint at the points where the open ends of the grids abut one another.
While I've decided to use some extruded foam for some scenic effects, most of my track is on cut-out 3/4" plywood roadbed, mostly curves. A lot of the structures are on plywood platforms, too, with the adjoining terrain represented by Durabond patching plaster over aluminum screen.The only portion of the layout with an actual top on the open grid is on the partial upper level, where I used 5/8 t&g plywood.There will be some landforms done with extruded foam, too, but I personally wouldn't use it as a sheathing material atop open grid, as it won't provide much rigidity should a section of open grid need to be removed or altered.
Seventeen years ago I did my bench with a drill and wood screws. I layered up foam to a total of 4", in steps, along a twelve foot span over plywood. Used no more nails for gluw, with weights.
No problems so far.