confusion (STILL) on angles...need help

[myxpykalix]

This is what i'm trying to do is get all my angles precise so that i can create a tight lid in order to keep bugs and critters out of this feed box.
2178.jpg shows the deminsions 48" in back, 36" in front with a 10" flat top. I was going to buy this anglefinder to gauge the angle of incline in the front so as to then cut the same ange on the flat top edge so that the lid lays flat on that incline angle.
2179.jpg shows the two angles
full size render.jpg shows with the arrow the surface i need to find angle to.
Because my tablesaw will not tilt to that angle to cut and the jigs i've created to hold it still are not precise enough here is what i want to do.
I want to buy the angle finder, find that angle then program into my shopbot to 3d carve this angle.
I will have to go down and use artcam but i don't recall if it will lat me program an agle to make basically a 3d angle and cut it.

Normally this shouldn't be such a head scratcher but lately i'm getting more and more confused and need help...
https://www.amazon.com/AccuRemote-Di...l+inclinometer (https://www.amazon.com/AccuRemote-Digital-Electronic-Magnetic-Protractor/dp/B006JR8XBG/ref=sr_1_4?ie=UTF8&qid=1477359456&sr=8-4&keywords=digital+inclinometer)

(I couldn't get pictures turned over....)

[guitarwes]

Probably would be a good tool to have going forward.

What is the maximum tilt degree of your table saw? This angle I'm looking at in your drawings shouldn't be more than 60 degrees or so I would think (which is a 30degree angle on both pieces).

If it is 60 degrees and you can afford to do it, put another piece of plywood on the Shopbot and run a thru-cut profile path with a 60 degree Vbit cutting the pieces to the size they need to be (or leaving it a little proud and then rip the square edge down to fit with the table saw.

[8Ball]

Any cad type program will give the exact angle. What is the length at the bottom? With that and the dimensions you already have, it would be simple to figure the angle.

For the table saw, build a tall fence (12" should work) and rip the angles with the board on edge. That will decrease the angle that is required to make the cut. If it's 60 degrees flat, it would be 30 degrees on edge.

[8Ball]

I did a quick check, without knowing the length of the bottom, I used 25".
The top of the lid comes out to 51.3 degrees and the bottom of the lid is 38.7 degrees. That's using no angles on the front or top boards, just a straight cut.
Those two angles will equal the 90 degrees. Although, I would cut them at 51 and 38 respectively to eliminate binding.

Both cuts can be made on the table saw. Set blade at 38 degrees and cut the bottom edge of the lid laying flat, then cut the top with the lid standing on edge.

That angle is based on the bottom length being 25". It will be different if the length is different.