novemberechoes
Member
Hi all,
Can anyone out there tell me how to determine the moment of inertia for two sheets of plywood that have been joined together? I've looked through the APA website and can't find anything specific. I'm not sure if I should calculate it as roughly the same as a single sheet of plywood of comparable thickness (best-case scenario), as simply double the value of a single sheet (worst-case scenario), or something in between. If specifics are helpful, I'm looking to combine two sheets of 19/32 CDX ply with face grains running in perpendicular directions.
Long story short the designer wants a platform that's thinner than standard framing allows (nothing new there, right?), so I'm looking at simply layering ply, as I've done before for certain turntables. On top of that however she also wants it cantilevered a minimum of 6" the entire way around, so I'm trying to do a calculation for a cantilever beam with a concentrated load at free end as a worst-case scenario.
Long story long, the designer wants a raked, circular platform, 18' in diameter, 2" in thickness, with 80+ 5" circles in the platform that light up. My plan is raked studwalls/joists with the cross-layed plywood attached like flooring. On top of that I'll do 3/4" foam that will have channels carved in it for rope lights. The whole thing will be lidded with 1/4" masonite with plexiglass circles inset to allow the rope light to shine through. All on a tight budget, of course. I think it'll look really neat when it's all done, but I'm guessing the director will want to stage people on the cantilevered sections quite frequently, and I'd like to give a firm answer in terms of number of cast members he can stage within a certain area of the cantilever.
Thanks in advance to any and all who might help. I've been reading posts on here for years but never posted.
Can anyone out there tell me how to determine the moment of inertia for two sheets of plywood that have been joined together? I've looked through the APA website and can't find anything specific. I'm not sure if I should calculate it as roughly the same as a single sheet of plywood of comparable thickness (best-case scenario), as simply double the value of a single sheet (worst-case scenario), or something in between. If specifics are helpful, I'm looking to combine two sheets of 19/32 CDX ply with face grains running in perpendicular directions.
Long story short the designer wants a platform that's thinner than standard framing allows (nothing new there, right?), so I'm looking at simply layering ply, as I've done before for certain turntables. On top of that however she also wants it cantilevered a minimum of 6" the entire way around, so I'm trying to do a calculation for a cantilever beam with a concentrated load at free end as a worst-case scenario.
Long story long, the designer wants a raked, circular platform, 18' in diameter, 2" in thickness, with 80+ 5" circles in the platform that light up. My plan is raked studwalls/joists with the cross-layed plywood attached like flooring. On top of that I'll do 3/4" foam that will have channels carved in it for rope lights. The whole thing will be lidded with 1/4" masonite with plexiglass circles inset to allow the rope light to shine through. All on a tight budget, of course. I think it'll look really neat when it's all done, but I'm guessing the director will want to stage people on the cantilevered sections quite frequently, and I'd like to give a firm answer in terms of number of cast members he can stage within a certain area of the cantilever.
Thanks in advance to any and all who might help. I've been reading posts on here for years but never posted.