Computing compound angles

[temiqui]

Sorry if this is the wrong sub-forum, but there weren't many choices....

I am building a topper for my pickup truck out of foam, over which I will lay fiberglass.   I tried to make the design simple, but I sort of failed 🙂

Actually, I am only failing at the math of figuring out the compound angles involved, and/or at the fusion skill of measuring an angle between two discrete intersections.

The problem is simple on its face.  I have a rectangular shape I have sheared the edges of at 45 degrees.  So in each corner there is a trianglular intersection of faces...  there is a peaked roof at the top, so you can ignore the line coming in from the north...

Each surface is a piece of foam.  Obviously the cut for the edges on the sides of the pieces that join horizontal and vertical pieces will be 22.5 degrees, as will the edges on the horizontal and vertical pieces themselves.  And I naively thought ALL the angles would be 22.5, but of course where a 45 degree piece meets another 45 degree piece, there will be a different, sharper angle....  and I cannot for the life of me figure out what the math looks like to compute that angle!

Any help most welcome, thanks in advance!!

-eric

[jeff_strater]

Not sure if this is exactly what you are trying to do, but in this particular case, there is already a feature to do this.  I would not try to work out the angles on my own, just use Chamfer to do this for you.

[temiqui]

Thanks for the response!

I've created the object (although yours is an easier way for sure!) but how do I measure the angles, with reference to the resulting surfaces?  I need to cut those angles out of foam, and need to know what angle to set the cutting wire at.  None of the angles between existing edges is what I'm looking for...  I want angles between the surfaces, (and not clear how to measure that.)

Okay, by forcing myself to ask the question better, it occurred to me to try checking the angles between the surfaces.  Is this the actual correct angle between surfaces, 120 degrees?--I think it is.  When I would try doing the same kind of thing in sketchup, it always referenced one of the x,y or z axes, so it didn't occur to me that I could do this. 

So I think my cut should be at 30 degrees, not 22.5.   Does this seem right?  I knew it had to be a sharper cut, and that seems intuitively about right...

[etfrench]

Have you tried using the Measure tool?

[davebYYPCU]

Don't make it too complicated,  everything is 45 or 90.... for a box.

a mitre corner is 45 degrees, and the internal corner is just 90 deg from that.

Might help....

[etfrench]

Hmmm.  I think it depends on which faces have the panels.  It's easy enough to get the cut angles using planes, split body command, and the measure tool.

[temiqui · Accepted solution]

Wow, that is seriously cool, and something I will definitely use in future!!

For now, just being able to measure the angle between two surfaces  does the trick.

Thanks All!!!!