Author Topic: 3/8" ply under 1/2" foamboard; is this ok?  (Read 1608 times)

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videobruce

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3/8" ply under 1/2" foamboard; is this ok?
« on: March 14, 2012, 08:32:10 AM »
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Using 3/8" plywood with 1/2" rigid foamboard over it on a around the wall layout in N scale (34" table depth) using cookie cutter construction, is this a problem with the flexing, expansion & contraction of the plywood in a non temperature controlled basement?
 Temperature varies from 55 to 75 degrees, but humidity has varied from 45 to sometimes close to 100%, but there is a dehumidifier, so high humidity will probably be 75 to 80%.

 I was concerned with overall weight of the plywood and thickness of the foamboard when it comes to work with linkage of turnouts. I also have no plans to 'dig down' below the top of the foam for scenery reasons which is why I choose 1/2" over 1".

John

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #1 on: March 14, 2012, 08:35:00 AM »
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It should work .. just make sure you have stiffeners cross braces every couple of feet ... I use 1/8 luaun in some sections .. no problems.

Most people tend to overbuild benchwork .. unless you are planning to stand on it, the only need is for enough stiffness to keep the track from flexing ..

videobruce

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #2 on: March 14, 2012, 10:40:59 AM »
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Most people tend to overbuild benchwork .. unless you are planning to stand on it, the only need is for enough stiffness to keep the track from flexing ..
Like using 3/4" ply as I just saw a thread with photos of someone using 3/4" for HO scale.?   :o

Funny you mentioned this as that is the main reason I choose 3/8" after a story I read from a UK model railroader stating Americans have this tendency of overbuilding. I'm just worried about doing the opposite.
« Last Edit: March 14, 2012, 10:42:34 AM by videobruce »

nscalemike

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #3 on: March 14, 2012, 01:11:53 PM »
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I agree it should be fine, I used 1/2" with 2" foam on top with no problems so far.  I have my supports every 16".  My bigger question is the 34" depth on an around the wall shelf.  Reaching back 34" will be difficult at best, impossible at worst.  Haven't seen your plan so it may work, but I've found any trackage over 20-24" from the front is just asking for problems.

Mike

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #4 on: March 14, 2012, 05:10:18 PM »
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I build my modules with 3/4" beaded foam (which means it's basically non-structural) over 1/4" plywood. I try to make sure the track is never more than 6" from the support framing under the plywood--which isn't hard when the mainlines are usually within 6" of the front edge of the module. :)
Rob M., a.k.a. Zox
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3DTrains

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #5 on: March 14, 2012, 07:08:59 PM »
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I believe 1/2" ply is fine, so long as it's cabinet grade to reduce warping.

Also, Murphy's Law dictates that problems will always occur in places where you can't get to. Mike is right - anything outside 24" reach is asking for trouble. 30" or so is possible, but only when foreground scenery is minimal (no trees, buildings or other sleeve-catchers), or that you have very long arms and the layout is at less than optimal height - ie: too low. Plenty of access hatches/popups can help overcome this, however.

kelticsylk

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #6 on: March 15, 2012, 11:48:50 AM »
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I'm actually using 1/4" plywood underlayment with 1/2" foam. The top of my benchwork is recycled 2x4 spaced on 12" centers. No problems in the year or so it's been up. I'm also using the half inch foam to make splines to support my roadbed. That also seems to work fine.

Frank Musick

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #7 on: March 15, 2012, 01:34:52 PM »
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I usually use 1/4" ply with a minimum of 1" of foam on top, and use 1X2 framing and cross bracing every 12" or so, using wood glue and small screws to attach it all the wood together. it's usually strong and fairly light.
Mike

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videobruce

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Re: 3/8" ply under 1/2" foamboard; is this ok?
« Reply #8 on: March 23, 2012, 10:15:38 AM »
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My bigger question is the 34" depth on an around the wall shelf.  Reaching back 34" will be difficult at best, impossible at worst.  Haven't seen your plan so it may work, but I've found any trackage over 20-24" from the front is just asking for problems.
That has been a concern. I do have long arms and I have 'reached' over many times. It will be a issue, but I have to deal with ti since I need that depth for the layout to work, especially at each end for the curves.