how do I prevent Warping

tjdreams Feb 3, 2014

  1. tjdreams

    tjdreams TrainBoard Member

    473
    607
    24
    Last summer I built a base that I thought would work out It's 42" long by 20" wide and 3/4 inch thick.
    It needs to be thin to fit into a guitar case but everything I've tried so far has failed.
    This last try
    I used 1/4 Birch plywood and 1x2x3/4 poplar lumber. I let it dry in the sun for 2 months, then used a plainer to get straight wood out of it. Making it 1x2x1/2.
    I then cut and 1/2 lapped all the joints and glued it to the plywood. I left it clamped in the jig for a week before painting it, at which time it was perfectly flat.
    4 months later in November it was still perfectly flat, thinking I was good to go I started laying track.
    Yesterday I pull it out to find my track work has buckled. Laying a 4 foot level across the top it has a 1/2" gap in the middle. Warped!

    Anyone have any ideas how I can prevent warping and still keep the base thickness 1 inch or less?

    IMG_2777.jpg IMG_2785.jpg
     
  2. robwill84

    robwill84 TrainBoard Member

    173
    2
    16
    I would try a 2" thick piece of pink or blue board foam insulation. At only 42 x 20 inches it will be pretty stable just on its own. Then you can use something like 1/8" MDF, cut to 2" thick strips, attached to the sides with liquid nails. I think you'll find this a better solution than dimensional lumber and plywood, both of which are prone to warping and probably working against each other in your situation. Good luck!
     
  3. robwill84

    robwill84 TrainBoard Member

    173
    2
    16
    Oh, and if you want a more solid top than styrofoam offers, top it off with a piece of 1/8" or 1/4" MDF board, again with liquid nails. MDF is much less prone to warping than plywood.
     
  4. markm

    markm TrainBoard Supporter

    804
    241
    21
    David,
    If you are set on using wood, right after I build and the glue is dry, I seal the wood with a spray sealer, usually shellac . Another possibly would be to glue an manmade material like plastic laminate to the back side of the plywood for strength.

    Other alternatives for wood, considering the small size would be 2x4' acoustic ceiling tile or 1/2" arts & crafts board (foam board with laminated paper surfaces (both properly sealed), or even a 3/4" piece of high density foam insulation.

    Hope this helps,

    Mark
     
  5. Z_thek

    Z_thek TrainBoard Member

    536
    7
    28
    There are multi layer plywood products, like apple-ply, fin-ply and various marine grade plywood that very stable, but fairly heavy. More advanced light weight materials are the foam core plywood products, like this: http://www.kerfkore.com/uploads/brochures/foamkorefr.pdf
    Some marine plywood suppliers carry smaller pieces, unfortunately the prices are high. The other way is to buy a full sheet from standard plywood suppliers and split the cost with other train nutZ.
     
  6. seabanna

    seabanna New Member

    3
    0
    10
    And when you seal the wood, seal all of it - the underside and the edges too. Hopefully that will keep any moisture from entering the wood. I've done this on small tables/platforms and have never had a warping problem.

    Hopefully this will help,

    Charles
     
  7. tjdreams

    tjdreams TrainBoard Member

    473
    607
    24
    I've tried using just a piece of Styrofoam even tried using 2 thin pieces glued together and they both warped in a matter of weeks.
    I'm not apposed to using anything as long as it's not too expensive and doesn't warp.
     
  8. emaley

    emaley TrainBoard Supporter

    327
    44
    9
    Try the pink or blue foam and laminate a thin sheet of masonite on both sides. Use a contact cement and get a good coverage. A composite like that should be very strong and light also.

    Trey
     
  9. David K. Smith

    David K. Smith TrainBoard Supporter

    1,211
    1
    22
    I have built several Z and N scale layouts of various sizes up to 24 x 48 inches using Gatorfoam board. For the base I usually use two layers of 1/2-inch thick Gatorfoam sheets laminated together with heavy-duty spray cement. I have had some of these layouts for years and they have not warped. They are very lightweight and plenty rigid. Gatorfoam is also moisture-resistant.

    http://www.foamboardsource.com/gatorfoams--gatorfoam.html
     
  10. JamesTraction

    JamesTraction TrainBoard Supporter

    195
    0
    17
    Most of these excellent examples are based on the torsion box concept. To recover your work, you might be able to add a thin plywood sheet to the bottom of your module, then clamping the assembly flat with weight (sand bags) or long clamping bars.
    James
     
  11. tjdreams

    tjdreams TrainBoard Member

    473
    607
    24
    Thanks for all the input everyone. A lot of good Ideas.

    From all your responses and a few emails I got I'm guessing I made 2 mistakes on this last attempt.
    #1 - I didn't reseal the wood around the holes I drilled for the wiring. Which may have ben my fatal mistake. As It didn't start to warp until after I drilled the holes.
    #2 - I didn't use (as James put it) the Torsion box concept. I should have put a piece of plywood on the bottom too

    The new plan
    A- cut 2 pieces of Birch plywood with the grain running 90* of each other
    B- pickup some more 1x2's Dry (come on summer time) plane flat, cut to size and 1/2 lap the joints like before.
    C- Give it all a good coat of oil based wood sealant (before assembly this time)
    D- Glue and Screw it all together with a layer of plywood on top and on the bottom.
    E- Use the warped one as a template to drill holes in the new one
    F- Give it a 2nd coat of wood sealant making sure to seal any holes I drill to keep moisture out.

    Anything else I should do?
     

Share This Page