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Got some gaps in the foam board...how to rectify?

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Got some gaps in the foam board...how to rectify?
Posted by OracleUsr on Saturday, January 22, 2011 5:34 PM

I just painted and lay down the foam board on top of the plywood (for now, might get rid of the plywood later once I can get some time to build a true table).

My problem is that when the hardware store cut the foam board, it was not a clean cut and there are gaps in the board.  The worst of it, I might put some water there to make it less noticeable.

What really concerns me is that the plywood is not level, even though the top of the foam board appears to be, at least on the side where there's a drop.  I've shimmed the plywood board with some old Reader's Digest mags and it's helped a bit, but I'm afraid I might not be able to glue the foam board to the plywood.

Anyone have any suggestions?  The board is a 4x8 board, cut up into 4 sections so it would fit in my car.  The board is painted brown (Ace Hardware used a shade called Clinton Brown) and I do have foam-friendly glue to use on the bottom.

I want to do this right.

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Posted by gandydancer19 on Saturday, January 22, 2011 5:48 PM

If they cut a 4x8 piece of foam board, why can't you put it back together like a jigsaw puzzle?  You may have a seam or two, but shouldn't have any large gaps.

If its small gaps or seams, you can use latex caulk.  You might have to use a couple of coats because it will shrink some.

For larger gaps, you can get a can of spray foam insulation and spray into the gap.  But be aware that it is messy stuff.  After it has dried over night you can trim it down where it has expanded out the top.

Elmer.

The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.

(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.

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Posted by woodman on Saturday, January 22, 2011 8:38 PM

Instead of gluing down foamboard on my layout. I screwed the 2" foamboard down using 2 1/2" drywall screws with fender washers. The screws will pull the foamboard tight against the plywood and seat themselves below the surface of the foamboard. I them went over the screws with Spackle and Spackled any seams on the foamboard. It worked out great. I screwed down 8- 2'x8' sheets of foamboard. I am now in the process of laying my roadbed. and risers.

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Posted by CTValleyRR on Saturday, January 22, 2011 9:09 PM

Oracle,

Wanting to do it right is a great goal.... but there are so many ways that will work that I wouldn't go into paralysis over doing things just so.

First of all, what is your plywood sitting on?  Your benchwork underneath the plywood should be level.  I put adjustable feet on mine so that I can level it.  Honestly, though, you don't need both plywood and foam underneath your layout.  If the plywood is seriously warped, chuck it.  You might be able to flatten it by screwing it on to your benchwork (slight undulation in your layout will not be a big issue, and you can always rasp the foam down to level it).

As others have stated, you can use any of a number of products to plug the gaps between your foamboard, or just ignore them.  If you plan to put water where the gaps are, you can use plaster cloth and hydrocal or papier mache to seal cover it.

 

Connecticut Valley Railroad A Branch of the New York, New Haven, and Hartford

"If you think you can do a thing or think you can't do a thing, you're right." -- Henry Ford

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Posted by cowman on Saturday, January 22, 2011 10:33 PM

Plywood in noted for not staying flat by itself.  That is why most folks make a frame of 1" x 3" lumber tor it to sit on.  When screwed to the frame the plywood will be flat and yur doam should sit on it flat.

For gaps between the sections of foam there are several things you can do.  I would recommend a can of spray foam, for small gaps.  There is a high expansion version for filling large gaps, but I don't think that is necessary.  You could also use lightweight spackeling compound.

My computer is having the hick ups.  Not sure what's up, but hope this comes out OK.

Good luck,

Richard

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Posted by OracleUsr on Saturday, January 22, 2011 10:52 PM

I'll let my Facebook page album do the talking.

 

http://www.facebook.com/album.php?aid=34035&id=100001184090862&l=02f5208d44

It's sitting on top of sawhorses right now, and I'm sure that's part of the problem.  I could screw the foam board to the plywood, but wouldn't that cause the foam board to be unlevel?

If not...yeah, that might work.

 

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Posted by OracleUsr on Saturday, January 22, 2011 10:54 PM

I thought this project was going to be a lot harder, but so far, no kinks in the track.  And, rail nippers are great for cutting rail joiners off.  Wish I had thought of that in the first place.

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Posted by OracleUsr on Saturday, January 22, 2011 11:07 PM

The board is off on one corner, and it may be my house.  I checked the foam board with the level on that end and found it WAS level, just not the plywood.

I honestly don't have the time or the will to make a frame and/or a table to do this right.  My father has offered his services, but he gets as busy as I do, if not more so, and he lives an hour and a half away.  Hence the sawhorses.

The cut in the foam was done with a handsaw and was not a clean cut, much as the guy who cut it tried to make it one.

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Posted by J.Rob on Saturday, January 22, 2011 11:48 PM

With out a sub-frame of some type under your plywood it will never be flat. The time you spend on the sub-frame will be well worth it later as it will give you a place to run your wires and help keep everything else in line and stable. Not doing this will cause everything else you do to flex and crack constantly. If the carpentry skills needed to do this as well as the tools are not something that you have now you may decide to develop them or you can purchase some ready made bench work from one of the advertisers in MR. I have never used it but it comes precut and ready to assemble with just basic tools, it is also available in different sizes.

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Posted by Hamltnblue on Sunday, January 23, 2011 9:23 AM

I also used drywall screws with fender washers.  For uneven joints or to hide joints in general try using plaster cloth. 

Springfield PA

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Posted by CTValleyRR on Sunday, January 23, 2011 9:57 AM

OracleUsr

The board is off on one corner, and it may be my house.  I checked the foam board with the level on that end and found it WAS level, just not the plywood.

I honestly don't have the time or the will to make a frame and/or a table to do this right.  My father has offered his services, but he gets as busy as I do, if not more so, and he lives an hour and a half away.  Hence the sawhorses.

The cut in the foam was done with a handsaw and was not a clean cut, much as the guy who cut it tried to make it one.

Oracle --

This kind of contradicts your earlier statement that you want to "do it right".  While there are many ways that will work for you, you absolutely must construct some kind of more-or-less permanent framing under the layout.  Also, you will probably find the sawhorses to be much too low, and will cause all kinds of ergonomic problems as you start laying track and installing scenery.

If you don't, you're heading for all kinds of trouble down the road as your layout shifts due to lack of adequate support.  Plywood on sawhorses does not meet the standards for adequate support.

As someone else pointed out, there are several sources of pre-fabricated benchwork, Sievers (http://www.sieversbenchwork.com/), Mianne (http://www.miannebenchwork.com/), Woodland Scenics (http://woodlandscenics.woodlandscenics.com/show/category/ModURailSystem) and probably some more that I don't know about.  Unfortunately, it's pretty expensive.

It's really not hard to make your own, though, and there are several good books on the subject, as well as a lot of Internet resources.  While it can be done with basic hand tools, it's sure a lot easier if you have the proper power tools.  I put together the benchwork for my 10x15 C shaped folded dogbone in a weekend.  Lumber cost was approximately $150.

While your desire to get up and running is commendable, my very strong advice to you would be to put the layout construction on hold for a while until you have a firm foundation on which to build.

Connecticut Valley Railroad A Branch of the New York, New Haven, and Hartford

"If you think you can do a thing or think you can't do a thing, you're right." -- Henry Ford

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Posted by jwhitten on Sunday, January 23, 2011 8:45 PM

J.Rob

With out a sub-frame of some type under your plywood it will never be flat. The time you spend on the sub-frame will be well worth it later as it will give you a place to run your wires and help keep everything else in line and stable. Not doing this will cause everything else you do to flex and crack constantly. If the carpentry skills needed to do this as well as the tools are not something that you have now you may decide to develop them or you can purchase some ready made bench work from one of the advertisers in MR. I have never used it but it comes precut and ready to assemble with just basic tools, it is also available in different sizes.

 

I agree. You really need to spend some time building a suitable benchwork. It isn't as hard as it seems and it's well worth the result. One of the easiest methods is the "L-Girder" approach where all you have to be able to to do (mostly) is glue/screw boards together at right angles. Many people use 1x4's for the upright segment and 1x3 or 1x2's for the horizontal segment. Place the horizontal board along the edge of the upright segment and glue / screw it in place along the line. You can see many examples of how to do this on Google, or even using the search right here on the MR forums. Building legs is not hard either. One the L-Girders are made, just screw some joists across a pair of them and then clamp on some 2x2 or 2x3 or even 2x4 legs and you're ready to go. I like using clamps myself, at least until I'm sure, because its easy to adjust the height or move stuff around. Eventually you'll want to glue / screw the legs also and probably add some braces.

There's a good book about building benchwork by Linn Wescott (a former MR editor, now deceased) that you would probably benefit from:

How to Build Model Railroad Benchwork

 

John

Modeling the South Pennsylvania Railroad ("The Hilltop Route") in the late 50's
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Posted by OracleUsr on Wednesday, March 9, 2011 6:10 PM

One of my coworkers has graciously offered to build me a proper railroad table.  He's built some strong tables for my work plant that are 4x8 and he said he could build one relatively easily.

I think I'll go with that.  I've got three buildings done for the layout already (Walthers LifeLike Ace Supermarket and KFC, then a Walthers Cornerstone Pizzeria).  Looking forward to tacking some of those signs Tomkat's put up on the side of the pizzeria.

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Posted by CTValleyRR on Wednesday, March 9, 2011 7:48 PM

Excellent.  You will be very glad you took the time to get something sturdy under your layout.    Give some thought to the height.  Mine stands 48"; some people like higher, some lower, but I wanted a height that my kids could see without too much trouble but that would be high enough for me to work on comfortably.

At the risk of offering unsolicited and unwelcome advice, get in there and help your coworker do the construction, and ask lots of questions.  I firmly believe that much of the fun of this hobby is in stretching our limits and mastering things we thought were beyond us.  If you'd told me ten years ago that I would be painting backdrops with an airbrush, I would have laughed at you.  Wanna guess what I'm doing tonight?

Connecticut Valley Railroad A Branch of the New York, New Haven, and Hartford

"If you think you can do a thing or think you can't do a thing, you're right." -- Henry Ford

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Posted by B&O SteamDemon on Thursday, March 10, 2011 5:12 AM

I have built several modules for a club layout and I use a sub-frame and have it so that the blue board foam sets down into the frame so it's flush with the outside frame pieces.  I have no problems with warpage and cuts down on the weight issue too, as far as gap filler goes, I used spackle to fill in any small gaps I had, I took some pages from an old phone book and used them as fillers in the gap and then spackled over them to finish and smooth the gaps out.  Looks fine and unless you are a mouse running around under the modules you will never know what was used.  Hope this helps.

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Posted by TheK4Kid on Friday, March 11, 2011 12:15 AM

I used 2 inch thick 4 by 8 foot foamboard for my layout.

I built a bed lattice type framework, three tables 6 feet wide by 8 feet long, bolted them together, and custom cut my foamboard to fit. My layout presently is 6 feet wide by 24 feet long, all three tables bolted together.

I have bolt on legs with screew adujusters for leveling.

I used a glue from Menards that comes in caulk gun tubes, great stuff! to glue my foamboard to the

lattice frames.

I may move my layout later on so it is totally portable and strong at the same time.

The tables easily go up the basement staircase if I ever have to move them

My layout is also totally a walk  around layout, every point easily accdessible at 45 inches above the floor.

As far as any gaps.

Expanding foam for insualtion is a good way to go. Fill the gap, let it expnd and dry, then trim it off and perhaps a light sanding.

The insulating foam willadhere well to regular foam board

 

The K4Kid

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Posted by cv_acr on Friday, March 11, 2011 1:30 PM

OracleUsr
It's sitting on top of sawhorses right now, and I'm sure that's part of the problem.  I could screw the foam board to the plywood, but wouldn't that cause the foam board to be unlevel?

I would say that's entirely the problem. Even thick (3/4") plywood needs nice strong bracing underneath it to keep it level and rigid.

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