Thickness of benchwork plywood?

[howmus]

QUOTE: Originally posted by Robert Knapp
I would like to add to this. Check out the ply at a local quality lumber yard first. They will carry a far better grade of ply than the big box stores. Plywood, whether 3/8 or 1/2" can be found in Douglas fir graded for underlayment (3/8, 1/2 PTS or termed plugged and sanded). This is still a relativly inexpensive ply for the quality. Most big box stores will have only pine and found to be inferior.

Absolutely! A few years ago I bought some plywood at a local HugeCo "we sell cheaper" (meaning quality) store. The plywood was purchased to be cut up to make stands for a backdrop for a Christian Rock Group sponsored by the Presbytery. When it was cut it completly delaminated. I took a couple sections back to them and they said they were really sorry and would replace it (with more from the same pile of crap). When the replacement sheets did the same thing, they said, "Oh these aren't really made to cut and should be used whole". Yeh! Right! IMHO go to a quality lumber yard (the kind owned by people in your community who care about the stuff they sell to you) and get quality (5 ply) plywood that will not warp or fall apart on you. In the long run it will be a lot cheaper.

[WilmJunc]

I am currently using 3/8" plywood supported 16" O.C. Once everything is connected it becomes quite strong.

[riverotter1948]

This is exactly the forum I've been looking for. I recently moved to the Midwest where humidity definitely is a problem. For my first attempt at a new layout I used Mianne benchwork and 5/8" B/C plywood as recommended by MR et al. First thunderstorm we had (100% humidity), the 2' x 6' sections I had cut and screwed into the benchwork warped almost 2" east-west; pulled those wood screws out like they were greased. The fellow at Home Depot suggested I consider laminate (you know, compressed sawdust); he said that stuff never warps. Doesn't sound right to me. Thanks to everyone for sharing their thoughts on this. P.S. What is "OSB"? Sorry to be so dumb; I'm in information technology (IT) & we're acronym crazy, too.

[selector]

Any manufactured or natural wood product, unless it is completely sealed in a non-porous medium, will begin to change shape as the ambient humidity changes. That is why layouts in garages and basements, and those in non-air conditioned homes, will have problems with continuity, displaced and separated structures, dislodged castings, and faults along the terrain that mirror the San Andreas fault....unless they have a decent dehumidifier nearby.

I don't know why a person wouldn't spend $200 on a dehumidifier, and spend another $30/year operating it, to protect a much more substantial investment in their hobby.

[pcarrell]

Larry Boyd brings up a good point.

I used 1/4 inch luan with 1/4 inch foam sheets over the top. I placed this on a boxed framework of 1x4's and used 1x3's for cross braces on 12 inch centers. I'm using the cookie cutter method. I just built this a few months ago in a climate controlled room. I don't climb on the layout, humidity isn't an issue, and the temperature is constant year round.

My question is will this be enough support for the long haul or should I make an I-beam setup to go under the luan between the 12 inch supports?

I want it to last but I don't need a 2 million pound monster in my train room.

[Leon Silverman]

Riverotter:
Checkout www.howelumber.com/osbply.htm. This explains the difference between OSB (Oriented Strand Board) and regular plywood. Plywood has the wood grain appearance whereas OSB looks like chips of wood laid in random directions. OSB should be cheaper since it can be made from small trees. It has about the same strength as plywood of similar thickness but will lose strength is countersunk.

[selector]

P. Carrell, yes, what you describe should be plenty strong for light trains and structure, such as plaster cloth mountains, especially with the 12" support spacing underneath. One question, though: how long are the 1X3's that are spaced 12" apart? In other words, how wide is your layout, because I am assuming that those 1X3's are like floor joists in orientation? If they are longer than about three feet, and oriented on the flat side up against the luan, then a stronger beam running longitudinally under their centers might give them a bit of insurance from over-time sag.

[pcarrell]

selector,

The layout depth, and consequently the supports, are 4 feet deep and they are not layed up on their sides. They stand up with the skinny side on the top and bottom. They are cut to fit within the 1x4 frame and they are double screwed on each end with 4 inch deck screws countersunk into a pilot hole. Seemed pretty solid to me but with the luan being only 1/4 inch thick I didn't know about sagging over time.

The scenery will be light and will be mostly plaster soaked paper towels except for a pop out hatch that will be foam board (2 inch thick).

The setting is late 30's coastal and near coastal backwoods Maine and so trains will be mostly short (10 or 12 cars at the longest).

Any more input is welcome as I right now have a plan, 1/3 of the track down, and a head full of ideas.

I'd rather make changes now then later, so bring it on!

[pcarrell]

Oh, I used only quality wood for the benchwork (clear poplar).

[Bikerdad]

If you live anywhere that has either a hardwood dealer or a sheet goods dealer, go visit them. Last week, my buddy purchased 6 sheets of 5'x5' 1/2" Baltic Birch plywood from McKillican's (they have stores in several states) for $20 each. 1/2" BB is 9 ply, shop grade (i.e. paintable and stainable) both sides. BB is available in other thicknesses as well.

[selector]

P. Carrell, I think you are okay.

It really isn't the luan sagging, especially if it is well supported, as I believe you are, but the thinner luan sagging because your 1X3's are immeasurably sagging over time when they are too long and/or not supported well enough near their middles. However, in your case, they should be good on their edges as you describe, like joists.

What you could do, with a few minutes of your time, is use a level and straight-edge to mark the 1X3's average middle-span sags (if there is any) at each of the end beams of your bench. Put a mark with a date. Three months later, repeat the measurement and see if you can detect any sag. If more than 1mm in three months, I'd say you were slowly losing the struggle against Mother Earth. You would want some form of support along them.

[pcarrell]

Excellant idea selector! Time to dig out the straight edge again.