How would I calculate this

[bassface]

I have to bring 110 sq inches of port area into my cabin, unfortunatly I have a convertible motor dead center of my trunk shelf so I need to split the ports, I have cutout the maximum amount of area that can safely be cut out of the trunk pan. I just wonder how irregular shaped ports can be caluculated and if its off a little how much of a difference would it make?

heres a drawing of kind of what im working with,

[LZTYBRN]

Are you planning on using the FULL area of that cutout, or just match it closely?

[bassface]

Are you planning on using the FULL area of that cutout, or just match it closely?

Yeah im going to make fiberglass ports molded into that shape.

[LZTYBRN]

Well you could either try to divide the area into a bunch of triangles and shit, or you could try this:

1. Trace the shape on a piece of cardboard

2. Draw a grid with lines spaced 1" apart.

3. Count number of squares completely inside the shape. (see pic)

4. Count number of squares partially inside the shaped. (see pic) Divide this number by 2.

5. Add numbers from steps 3 and 4. This is the approximate area in square inches.

Pic:

Here, the shape is the red line. The pink squares are completely inside, and the blue squares are partially inside.

[bassface]

Well you could either try to divide the area into a bunch of triangles and shit, or you could try this:

1. Trace the shape on a piece of cardboard

2. Draw a grid with lines spaced 1" apart.

3. Count number of squares completely inside the shape. (see pic)

4. Count number of squares partially inside the shaped. (see pic) Divide this number by 2.

5. Add numbers from steps 3 and 4. This is the approximate area in square inches.

Pic:

Here, the shape is the red line. The pink squares are completely inside, and the blue squares are partially inside.

Good idea lztybrn. Heres an actual pic of the f'ed up spot i had cut holes.

[bassface]

So far heres the box im am making for it, the white spots are sanding marks, not bubbles. I will cut out the front of box and build the ports then mold them into it, and re-enforce with about 1/4" more of fiberglass layers.