I’m beginning to secure my subroadbed to the risers on my L-girder benchwork. The subroadbed is 1/2" plywood.
Despite being careful in cutting, many of the joints don’t meet seamlessly, and I’m sure when I secure them the tops won’t be completely flush either.
I assume it’s important to eliminate gaps and otherwise assure a smooth joint vertically and horizontally between subroadbed sections. What’s the best way to do that? One poster suggested wood filler; would that stay put or shrink and/or pop out over time?
I use an additional horizontal piece under the subroadbed at the joints extending 6-8 inches from the joint and secure with glue and screws. I sink the screws far enough so that I can use a belt sander to smooth the transition even more. I never used wood fille as my layout is in the garage and I think the expansion/contraction problems would be exagetated.
Since you are using L-girder construction, follow Spidge’s advice about a splice plate under the subgrade material - but screw up from the underside and DON’T glue it.
I used Spidge’s method on my half-a-garage layout. When I was given title to the whole garage, I found a few spots where I could have reused pieces of properly-shaped cookie-cut subgrade if I could have flipped them over. Glued-on splice plates made that impossible. [sigh]
You can compensate for a less-than-perfect surface on the underside of subgrade. The top has to be as even and smooth as possible. Using a belt sander is NOT overkill, but it does generate a lot of fine dust.
I use splice plates under the subroadbed. I glue AND screw them together - the screws from the top down into the splice plate. I try to minimize my time crawling around under the layout.
I don’t even worry about horizontal gaps - as long as they’re under about 1/4 inch I figure it’s good. The roadbed and track will span the gap with no problem.
I do make sure I have very good vertical alignment - I don’t want any vertical kinks in the track! After cutting the subroadbed and splice plate, I use a shaper (basically a rasp that you pull towards you to remove material) to remove the broken splinters along the cut. Two reasons for that - First, to make sure I don’t have a raised edge that will keep the splice plate and subroadbed from sitting absolutely flush on the contacting faces, and second because my those tiny little splinters will invariably find their way into my skin if they’re sticking up to snag me. I also brush off the subroadbed and the splice plate to make sure no wood chips or sawduct gets caught between them.