Trig formula for splayed box

[Richard_C]

We have 2 concurrent active threads with the same question going here, this one and the one now hijacked from an original question about windmill hoppers, titled "Compound Mitre Angles". People have tried to help on both.

I'm fairly good with trigonometry and calculations generally, but I have followed both threads and like many I can't visualise what the real question is so haven't suggeted a solution. I wonder of the problem is the use of the term butt joint - might it be a mitred joint?

Woodchippy777 - people on this forum are very wise and very helpful, but when they ask for a sketch or a better explanation of the problem its because they need it to be able to help.

 

[Inspector]

By a butt joint he is asking for the sides and ends to tilt out. Instead of a miter joint in the corners it is square to the face of the adjoining board plus whatever angle adjustment is needed to allow for the slope of the hopper. In other words tilt the sides out while keeping the end square to the bottom and then tip the ends out with the sides butting up to the face of the end boards.
Am I making sense or adding to the confusion? I get what he is after but don't know the math and don't know the right terminology to find a calculator.

Pete

 

[--Tom--]

So this? (As a splayed box is just a section of a pyramid)

https://benkrasnow.blogspot.com/2008/09/determining-proper-angles-to-cut.html?m=1

 

[user 43606]

All worth the search

 

[galleywood]

End of post?

 

[Rupesh]

I have a book called 'Tage Frid teaches Woodworking' Joinery:Tools & Techniques from Taunton Press isbn 0-918804-03-5
This has splayed dovetails well described & taught.