Recommended wood for ceiling layout

I would not use MDF for a span of any sort. In a span, the top of the board is under compression and the bottom is under tension. Because MDF has no grain, the only thing holding the tensioned part together will be the glue. Think about how cheap bookshelves sag over time; those are MDF or something a lot like it.

Half inch plywood sounds a little wimpy to me. The thicker the plywood, the farther apart you can put your wall brackets. I might go with 5/8". The more plys it has the less likely it will be to warp. I have 5-ply 5/8" plywood on my layout, and I wish I had gone with a better grade. Not thicker, just more layers.

For the 5'9" span, I would go with solid wood. If you think about it, in plywood half of the grain runs at 90 degrees to the direction of the tension, which means that only half of the plywood is helping you. With solid wood, you get the whole thing. I would use a pine board of 1" nominal (3/4" actual) thickness. Then I would cut a couple of strips, also out of 1" pine, maybe an inch and a half wide, and as long as the pine board. Glue and screw them to your board, running the long way. Whether you fasten them above or below the board is your choice. Think of what a girder bridge looks like on a real railroad, that is the basic idea.

When buying boards, look for something that has straight grain. Look at the edge of the board. The grain lines should make it all the way from one end to the other; if it looks like the grain runs off the edge of the board, leave that one there. Small knots won't hurt anything, but avoid boards with large knots on or near the edge. Look at end of the board to make sure it is not cut right out of the middle of the tree. Those like to warp, or twist, or split, after you get them home. Then, since you don't need much, instead of rifling through the pile of cheap stuff, you might just buy a better grade board and be done with it.

If it was me I would at least 3/4" C-D plywood and band the outside edge. For banding you would either need a table saw with a fine blade or a jointer to get a straight edge. I haven't checked lately but I use to be able to get maple veneer plywood for 25 bucks a sheet but I suspect those days are long gone.

Pete

I aready had cheap 1/2"x12" (?10"?) white laminated shelves up when I decided to put track up high. My longest unsupported spans are about 4.5' over a window, & 3.5' over a door. No warp in about 7 years, but I don't park on the spans either. The spans also have two brackets spaced about 1'-1.5' on each end, the shelf is secured to them solidly and they give extra cantelever support  parallel to the wall that way.

I fit two lines with sidings in between, but starting from scratch I would do a single line. The lines away from the edge couldn't be seen well. I didn't want to put up new shelves, so I graded and elevated the line nearest the wall. (grades were needed because the lines share a leg on one wall. A voltage drop via diodes, relays & track pressure switches does block stops for anti collision)

When I put the shelves up, being level wasn't in my thoughts as it held my large VW models. I measued off the crown molding/ceiling which wasn't level. In the long run, one grade was steeper than intended so it limited me to one direction running.with longer trains. The ground level is good for either direction though.

   Done again, I'd use 1 line width, and a clear 1" lip or fence/railing, to stop "dives". On the straights too. Derails in the curves have always gone to the outside towards the wall. My only derail dives were on the straights. (3 all survived, 2 cast steamers, and a bash that was reglued.)

Dont forget the curve's outside overhang at pilots and cab and that it extends past the curve a few inches.. I used a rough cut 2x4 with ¼" strip of scrap to space the 0-27 from the wall, but an E-33 rectifier intermediatly taps one wall very lightly at times. No paint loss to wall or pilot rail, but I see a light wall scrape and can hear it tap at times. For O-31 and larger the 2x4 & 1/4" shim should be enough as larger curves have less overhang (note: a rough cut 2x4 is thicker than a finished cut 2x4, both are actually under 2" too)

I measured my window span, it is 5'3" between brackets.

Your track type might make a difference. The elevation not counted, the ground level line and sidings, being tubular track, and screwed down well are adding support too. I never considered that before.

"My ceiling layout space is around 5' 9" x 17'.  While the sides and one end will be able to be supported by walls along the edge, the one end of the loop will have to go across the 5' 9" span.  I'm considering whether I need to put a couple small brackets to secure to ceiling joists for that span"

Personally I would select a nice tight grained wood with no knots.  I like oak, birch, maple, or even beech or walnut.

For the span, can you look at making out of steel that is brake pressed and hemmed, possibilities are endless to turn this into some form of bridge span.

J Daddy posted:

"For the span, can you look at making out of steel that is brake pressed and hemmed, possibilities are endless to turn this into some form of bridge span.

I wish I could, but this span has to include the end curves of the oval.  I have a 4' double track bridge that I will put into one of the long straight sides.

ceilingtrainkit.com

SteamWolf posted:

ceilingtrainkit.com

Interesting.  Way more than I'd want to spend, and a little too rustic looking.  Looks nice in the right setting.  

Adriatic posted:

Your track type might make a difference. The elevation not counted, the ground level line and sidings, being tubular track, and screwed down well are adding support too. I never considered that before.

Will be all Gargraves since that's what I have left from my old layout.  Once I finish building this, I'll sell all my remaining Gargraves track and Ross switches.  That will help offset the cost of the wood and brackets for this ceiling setup and maybe help pay for some HO track.

nickaix posted:

I would not use MDF for a span of any sort. In a span, the top of the board is under compression and the bottom is under tension. Because MDF has no grain, the only thing holding the tensioned part together will be the glue. Think about how cheap bookshelves sag over time; those are MDF or something a lot like it.

Half inch plywood sounds a little wimpy to me. The thicker the plywood, the farther apart you can put your wall brackets. I might go with 5/8". The more plys it has the less likely it will be to warp. I have 5-ply 5/8" plywood on my layout, and I wish I had gone with a better grade. Not thicker, just more layers.

For the 5'9" span, I would go with solid wood. If you think about it, in plywood half of the grain runs at 90 degrees to the direction of the tension, which means that only half of the plywood is helping you. With solid wood, you get the whole thing. I would use a pine board of 1" nominal (3/4" actual) thickness. Then I would cut a couple of strips, also out of 1" pine, maybe an inch and a half wide, and as long as the pine board. Glue and screw them to your board, running the long way. Whether you fasten them above or below the board is your choice. Think of what a girder bridge looks like on a real railroad, that is the basic idea.

When buying boards, look for something that has straight grain. Look at the edge of the board. The grain lines should make it all the way from one end to the other; if it looks like the grain runs off the edge of the board, leave that one there. Small knots won't hurt anything, but avoid boards with large knots on or near the edge. Look at end of the board to make sure it is not cut right out of the middle of the tree. Those like to warp, or twist, or split, after you get them home. Then, since you don't need much, instead of rifling through the pile of cheap stuff, you might just buy a better grade board and be done with it.

Good point on the MDF.  I'll hit up Lowe's and/or Home Depot and see what grades and ply options they have in stock. 

I would use 3/4" birch plywood and band the edge with 3/4" screen bead molding.

I made a "G" shelf layout at our club. I used 3/4" plywood. On the backside and front side, I glued and screwed 3/4" x  1.5" oak strip to help installation and to stiffen for any possible sag.