Ok heres how I did the stage/s
I snapped a chalkline for the back of the stage and found center
layed out 2 layers of 3/4" osb T&G staggered directions of seams between layers giving me a 16' wide x 8 ' deep layed out and screwed down "platform"
I made a compass out of a piece of 1x10x10' long pine board by tracing around my router base and routing half the wood out in this area so my router sunk in and was screwed too it then screwed the compass centered at the back middle and positioned the 1/4" bit at the inside of the groove of the T&G and routed through both layers in 3 passes to save on the bit overheating, your outside bottom step is done.
Move the compass back 1', rinse and repeat and your bottom step and stage top is done!!!
repeat the same process with 3/4" t&g plywood except I glued this and whipped out the finish nailer which Ill explain in a minute.
we are making the curved 2x4s now so we measure back 2" off our original 8' ( we want a lip on our stage) route the first route then use finish nailer and 1-1/2 nails or screws to "clamp" the 2 peices of wood together being careful not to go over the 3-1/2" depth( what I did was measure back my 3-1/2" and set the router bit to barely scratch the surface and made a full swoop showing my finished "2x4" ) then I nailed inside the 1st route and the scratch. Now route at the 3-1/2" wide mark and you have a complete 24' long perfect curved 2x4.
It gets slightly tricky here because I am cheap and wanted to conserve wood at $20 a sheet so I routed the first Stage 2x4 next, remember to drop 2" or whatever you want your lip at.
then I went back to the other stair 2x4 ( lets call this the bottom cord of our steps curved front wall, the top is already done ) you will notice you cant get a full sweep with what you have left but lay it out the same way coming up short a couple feet on the ends but dont worry you still have lots of wood left to finish these and if you just look at whats layed out you will see this clearly.
do this until you have 2 each for step and then for stage.
Now I layed the step and stage tops back down ( If I were you I would leave it from the beginning to save about 1/2 hour ) also when I routed I barely scratched the floor so I knew right where it layed back out .
Ready to build the step, lay bottom cord curved 2x4 down and screw it down in a couple places and cut 2x6 s from the front of this to the back of the stage 2x4 mine were 15" long and I think I cut 20 of them ( chop saw with a stop coming into play) then with a table saw or whatever cut 1-3/8" x 3-1/2 deep notches out of the end of the 2x6 ( thhis will flush up to the front of the 2x4 cords and sit on the floor as well as the top of the bottom cord and allow you to place the top cord down flush with the top of the 2x6) looking from the side of the 2x6 it will have like a 3" x 3-1/2" long extended peice right in the middle. I am probably confusing you but just look at the pics and notice the 2x6 joist are notched so they slide into the 2 2x4s but sit on the ground and flush to the top as well.
I layed these out at 16" centers on the front and used a calculator to figure the spacing on the back of these which was something like 13" then I used my Framing nailer with 3-1/2 nails and popped a nail straight through into the botom cord to stablize , layed out my top cord into the notched areas being careful to make sure I followed exactly flush and nailed these with framing nailer , you could use screws I sure, then I took a long board and screwed it about half way across side to side to stablize this monster so as to flip it over and nail the bottom cord on ,
Lay out your step wall on the floor , set your bottom stage cord on the back of the 2x6s nail it all together and fill in the blanks with 2x12 inside the stage area , then remake the 2x6 doohickies ( joists) except using 2x12 and doing the math , the sliding chop again come in real handy since I basically framed a square inside and then measured the top stage joist seperately 2 at a time ( left and right) thes had angles on the back but it was like 8 degrees, 16 degrees, 24 degrees up to like 48 degrees , its simple really if youve ever built anything with angle before and you will see what needs to be done clearly through the building stages
The plywood curved fronts are 5/8 ply ripped on a table saw at 5-3/8" wide
then using the trusty 12" sliding chop ( in my case a RIGID which has a depth of cut stop on it) I measured 1-1/2 " dots as in 1-1/2 markr dot ,3 dot,4-1/2 dot, 6 dot all the way to 96 " then I cut these 2 at a time to save time and marking ( again cant say enough about a 12" sliding chop) and cut about 3/16 deep at every dot across the 5-1/2 width , you may need help holding this because it gets flimsy about halfway , I used the trusty wife. Nail er on with the grooves in against the the wall , fill er up with sand or insulation, and put your top on and get Diana Krall or someone to come perform ! My wife asked where the poles were going when she was away and I almost let it slip and say over here and over......
If you have any questions or are going to build one send me a PM and we can exchange phone #s and I could walk you through it or help you if you get stuck.