Fabricating hood scoop and bad at math... any help?

First, sorry for being long winded here... it’s really a lot simpler than I’m making it sound! I’ll try to get a diagram up later to show what i mean.

That triangle can go a lot of ways depending on how you want the finished product.

If you want the sides vertical like in the diagram, it can be a right triangle; it just has to be perpendicular to the hood, not to the top of the scoop like you have it now.

if you want the sides slanted like you have it mocked up, things get a little more complicated. You can either a) keep the top of the hood and the slanted back one rectangular sheet, in which case you will need to bend the sides where the triangle meets the oddly shaped quadrilateral. In this case the shape of the triangle will depend on how much you slant the sides. For instance, if you have the sides slanted 45* you will need an isosceles triangle. The shape of the triangle will change directly in proportion to however much you change the slant of the sides.

Option b) comes in if you want to keep the sides straight in line with each other. In this case the top and back won’t be able to be a rectangular shape. The easiest way IMO to cut that out would be to cut the sides like you want, then mark the top to fit.

I think about this sort of thing in terms of geometry so I don’t have any formulas for you, sorry.