I am in the process of remodeling my layout room ,and building a whole new layout from scratch. The main reason is I was never really happy with my current 5x19x7 U-shape layout. The new room will be an L-shape in the garage taking up almost 3/4 of the footprint. The L-shaped room will measure 17' x 19' and be 7.5' wide on both sides. I have 5 inside corners and 1 outside corner that I want coved. What is the best way to do this? I want to keep the radius as small as possible. The walls are drywall and I can mud pretty good. I am looking for something that will be solid and yet thin enough so I can mud it and sand it without making a federal project out of it. BTW , once I get the shell of the room done I will try to start a progress thread of the layout. I have a real good vision of what I want to build, I just have to find the time.
I used thin Masonite on my former layout. Corner about 16 inch radius. I used a long piece of Masonsite with the corner in the middle of the sheet, and the tension on the corner sheet held by the sheets on each side of it. And I taped and floated the Masonite just like it was plasterboard. The corner of the room is straight over the peak on the courthouse tower. Unfortunately, the room where I am building my current layout does not allow that. It has windows flush against the corners of the room, which must be kept at least semi-reasonably accessible. So I must make due with square cornered background, and the portions of "sky" over the windows are hung on nails and removable. All background is on thin sheet styrene.
US Gypsum makes a product just for this purpose, well may be not specifically for layouts. But it is a gyp board product that flexible for doing coves. Not sure how tight of a radius it can do. You could also try scoring the back of a thin sheet of gyp board. Makes the scores parallel with the cove. About every 1" or so should do. Don't cut all the way through the board only about 1/3 of the thickness. Just a couple ideas.
Just released today, the April MRH has a curved corner article. You can get MRH for free and read it here http://model-railroad-hobbyist.com/magazine/mrh-2011-04-Apr About the article http://model-railroad-hobbyist.com/magazine/mrh-2011-04-Apr/coved_corners ratled
I have only one coved corner in my layout room. For the main walls, I used 1/2" GWB (drywall). The last 18" to the coved corner I used 3/8" drywall, and bent a piece of 1/8" masonite after trimming it to length into the recess. A little drywall tape and joint compound and it looks great. Pretty easy to do.
I used 1/8 inch Masonite. I moistened it with a spray bottle to help it form the curve into a 12 inch radius. Very easy to do many years ago. There may be a better way today.
As Soo Line says US Gypsum makes a product that is perfect . Some in the Drywall trade call it "Bendy board". Its 1/4 drywall that bends easy er. Most installers will wet down the piece of drywall and lay it over a sawhorse. It may take a couple of wettings to get the radius you want.....Mike
A friend of mine in Springfield Illinois used moistened Masonite to curve a 12 inch wide strip to a 6 inch radius for sections of his lighting valences. He said it took several days of re-wetting and tightening the shaping straps, and he hurried too much on one and snapped it, but I thought the finished product was beautiful.