Ductwork surface area calculation problem

[tibor]

Hello,

I have a major in economics and I am creating an excel spreadsheet for quotations of sheet metal ductwork as my final thesis. I need to calculate weights for various types of ductwork produced in the company I chose for my thesis. In order to calculate weight, I need to know the surface area of ductwork parts. For many parts (pipes, elbows,etc.) I have figured out the formula for surface area myself, resp. found it on the internet. But there are some pieces I am not able to figure out how to get the surface area based on the input parameters.

You will find the pictures of the parts in the pdf attachment for which I need to get the formula for calculation of the surface area (in metric units). I would be very thankful if anyone of you could help me with finding the correct formulas.

Thank you very much for your time, help and effort.



Tibor

 

[Astronuc]

Most of the geomtries represent a frustum of a square pyramid. The surface are just trapezoids, or the remainder of cutting a smaller triangle from the top of a larger triangle, or some case, a given surface is represented by two or more triangles.

http://mathworld.wolfram.com/PyramidalFrustum.html

http://www.mathsisfun.com/geometry/pyramids.html