Features:
• Offset
• Lobster back bend
• Angle branch
• Branch pipe
• Mitre
• Beak
• Taper
• Off centre branch
• Breeches piece

Simple and easy to use app which saves a lot of time. All dimensions are in mm and divisions are 12,24,48 or 96.
All duct/pipe diameter sizes are outside dimensions.

Offset:
There are two ways to use this. Input the required angle and it will give you the end pattern heights, the middle section length and an overall height which includes 50mm ends.
Or you can use the angle finder helper by inputting a desired height which gives an angle to try out. Input the new angle and press calculate again. It will give you the new dimensions or tell you if the height you gave is not possible for obvious reasons(too short). If you are not using the angle helper you must enter 0 in this field as default.

Lobster back bend:
Using the centreline dimension instead of radius and count the number of half segments needed.
Must be an even number. One full equals two halves, so 3 full and 2 halves equals 8 halves.

Breeches piece:
Same diameter, three way

You can save your results to a file for printing.
I am using PeriPage thermal printer with their free app
Added Hindi and Korean translations, might not be accurate