Read 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?
My layout is a 5x9 tabletop with two foam seams (1 inch extruded foam over 1/2 inch plywood). It is in the basement, temperature does not vary greatly, never above 70 degrees with low humidity. After 20+ years there is a 1/16 inch wide crack at the seams. Foam separation from the fascia is now 1/16 to 1/8 inch. Double layering and offsetting may have prevented or maybe not…
The next layout will be wall-mounted with narrow shelves and will be built in sections. Would double layering prevent cracks at the seams or any tips to prevent cracking at sectional seams?
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.
Honestly, I’d just go with my good old drill and screw bits if the only use of an expensive tool is going to be benchwork assembly. The hundred bucks I’d spend on the Kreg jig or a nail gun could go towards the layout instead.
I’ll use a nailgun because I already own it. But, I bought it for home projects, so it gets more use than getting sidelined as soon as the benchwork is done.
Sounds like a lot of work to cut the foam and glue in that manner, and depending on the dimensions, wasteful of foam.
Ken Patterson (Youtube) claims his foam shrunk just as you describe. That’s not what the foam manufactures say, but as he just lays it on the table, one can’t blame the benchwork. I believe he thinks that painting the foam prevents that, but I can’t swear to it.
David Popp uses glue and a nail gun for the MR projects.
It’s free floating on the frame, not glued down. The track should hold it together. In fact the track does hold itself together but there are gaps between the foam.
Hi Dave, my title was a bit cryptic… Sorry about that! Love your Rotisserie thread! Cliff notes would be good!
Did not really impact the trackwork as the foam seams were not near track joints and I had not soldered rail joiners so was some available slack for slight movement. The foam separation along the fascia was more bothersome to me based on appearance.
Forty seven years house building and remodeling, foam eventually shrinks a little. There is no building material that is 100% stable. Everything deteriorates, just glance at the mirror next time you walk by. We would all be grateful to only expand or contract by 16ths and 32nds.
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.
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.
This open grid was improvised to allow for a rounded-end on a peninsula…
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
Respectfully, your picture above has 11 visible butt joints (screws through a flat surface board into the end grain of another board). Linn Westcott calls this attachment a butt joint in “Model Railroad Benchwork”.
I am planning to build a sectional layout. The sections will be 6 feet long by 2 feet wide with 3" wide boards and topped with 1/2 inch plywood. Cross braces will be placed every 18" and attached to the side rails with an air nailer, deck screws, or pocket hole screws. The only way to not have a butt joint is to cut dados in the side rails and glue. Unfortunately, I don’
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.
Depends on your definition of a butt joint. For me it would be joining end grain to end grain or edge grain to edge grain. In metal work it would be end to end welding. Opinions vary. Technically, nobody uses joinery jointing any longer except for these two types of butt joints. So calling every non joinery joint a butt joint adds little to the description. Modern glues make joinery skills pretty much obsolete. Except for end to end or edge to edge joints (although even edge to edge are rarely joinered now, just glued and trued through a planer)
Only end grain to end grain wood joints require some sort of joinery technique of which scarfing is by far the easiest per unit of strength. The ready availability of very long longitudinal “fingerjoint” planks pretty much makes scarfing unnecessary and any reasonably spaced grid benchwork can be built from some pretty short planks, if you wish. I’m not sure why grid benchwork isn’t just built from 4" x 1/2" plywood strips ripped out of a sheet because that solves a lot of these issues.
Modern glues make old fashioned joinery unnecessary for things like concealed benchwork grids. Pilot holes aren’t really required when screwing softwoods together, although fir/hemlock can be a bit of a nuisance in some applications. I would always pilot drill end grain in anything under 1.5" wide.
Otherwise, just glue and screw and the structure will be sound.
For any sort of cabinet joint nowadays the most you need is a rabbet or dado groove for easy “squaring” and additional glue surface.
While I admire dovetails, and especially hand cut real triangular ones, they really aren’t necessary any longer and certainly building model railroad benchwork to joinery standards is pretty much a waste of effort and time. Hardboard fascia and paint will cover anything visible quite nicely. Well, except for the butt joints in the hardboard…
Hmmm I’ve been using foam on layouts of various shapes and sizes for decades and never had a “foam separation issue”. So might be an instance of solving an non-existent problem.
I cannot help you with this one. I most often use L-girder construction so there are no butt joints. When I do have to use a butt joint for some reason I just use standard wood screws, countersink, and screw them together.
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, I used the definition from Linn Westcott’s book and my proposed joints match his picture of butt joints in tabletop benchwork. 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. Your picture showed that you used them in your benchwork and they have worked well for you in your beautiful layout. I suspect my butt joints will be acceptable in my proposed layout, I was leaning toward pocket holes as they are commonly found in some of the commercial benchwork components but others have stated use countersunk wood screws (easier and cheaper by far).
only if you overlap the boards, scarfing. To be a butt joint it has to butt. I’m not trying to start an argument either. The term butt means “end” (ya think?) so implies the joining of two butt ends. I know it is also somewhat confusingly used to describe joining one butt to a face…
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.
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.
