5 Transitions-No Seams
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Study the shop drawing. Remember that the first number for the duct size is always what we “see in the view”. The second number is the depth, or hidden view.
- From the given information on the drawing, we decide if we will make the fitting in 2, 3 or 4 pieces. This example is 2 pieces because it only slopes on 1 side.
- Calculate the blank size for the 2 pieces
- Body or large piece
- We have been given a length of 8”. The second dimension comes from the perimeter which includes the 2 sides and the bottom to form the “U” shaped piece. From the large opening dimensions, we add 6” +4” + 6”=16”. So our blank size is 16” x 8”
- We have been given a length of 8”. The second dimension comes from the perimeter which includes the 2 sides and the bottom to form the “U” shaped piece. From the large opening dimensions, we add 6” +4” + 6”=16”. So our blank size is 16” x 8”
- Top or small piece
- We are given the depth as 4”. The length must be calculated because of the slope of the top piece, so we use A² +B² = C². With the given numbers, we get √(8²+2²)=8 ¼”, so our blank size is 4” x 8 ¼”
- We are given the depth as 4”. The length must be calculated because of the slope of the top piece, so we use A² +B² = C². With the given numbers, we get √(8²+2²)=8 ¼”, so our blank size is 4” x 8 ¼”
- Body or large piece
- We’ll only draw out the body in this case because there is no layout required for the top piece, so we’ll draw the blank size or shear it and draw the arrow for airflow
- Working like it is a piece of straight duct, we work from one side, marking off the perimeter at each end and draw in the lines
- At one end, we will mark outwards from the two lines drawn in the last step, the smaller opening size. In our case, the 4” dimension
- Connect the points to create the sloped sides