Use gloss varnish.
If weight is not a concern, attach 90 degree angle brackets to the bottom that run the length of the layout, leave space for your saw horses. I did this on my O guage layout to stiffen the plywood. It works!, but... kinda hurts if you hit your head and may damage your racecar if the layout falls. Pretty awesome though to have a layout that drops from the ceiling.
Do you get cracks in the roads at points other than the seams between sections?
If that is the only areas that seem to crack you could try a little creative planning. As your river meanders along, have it go off the front of the layout one side of the seam and back on the other. Also swing away from the front and go behind a hill or clump of trees to hide "the spot". Bridges or buildings could also be used to block the view.
While experimenting you could also see if a strech of rough water rapids might hide the cracking.
Another thought, there is a product called Lexel that seems to stay flexible after curing. Might be more expensive expecially on a large project. Not sure if you could use it in just your trouble areas and Envirotex in the others. Might be able to hide the change in product using the same masking ideas as above.
Good luck,
Richard
Is your garage climate controlled? At least 1 Model railroad water product spiderwebs when it is exposed to cyclic temperatures. I dont remember which one that is, but you might want to test before committing. Also check out what MR did on the Virginian Project Layout (they used paint).
Pink foam......that's not a bad idea at all. Carve that out as sort of a buffer. Good idea. I like it!
I have no idea if Envirotex Lite would crack. It is tough and hard, but might be brittle. My approach would be to use pink foam for your river bed. Pink foam is quite stiff itself, and would resist flexing so that your "water" would not have to.
I would do a test of your chosen material. You could even make a small "practice river" on your bench. Once it's done, with multiple pours just like you'd do it for real, pull it out and try to bend and twist it.
It takes an iron man to play with a toy iron horse.
Need some advice from some people with more experience than I have. My dad and I are building a layout in my garage. It's a 17x12 layout that is on a pulley system. It's lowered onto sawhorses when we work on it and raised up out of the way when I need to park the racecar in the garage.
My question is this. While we have gone overkill on the framework to eliminate as much flex as we can, there is still flex. And unfortunately always will be. We did a 7' section of road using tile grout and while it didn't crack huge, there are some hairline fractures.(only on the road they look like they belong so it works out)
Water however. If I have plans for a river that spans the length of the layout.....cracks will completely destroy the look. I don't mind hiding some with fallen logs or other things like that. But are we crazy to even consider doing such a long water feature on a layout that has flex?
I just don't want to go through all the build process to do a river and then have huge cracks in it after a few raises and lowers! How much flex will products such as Woodland Scenics and others allow?
My only other brainstorm is to suspend the water. Cut out top of the main board and suspend the water in a chickenwire/plaster type set up. I don't think this is a guaranteed way to eliminate the change of cracks either though and would proove to be a lot more work.
Thought o wise sensai's?
Mike