Absolutely - do it!
Look around the web. You'll probably find good drawings to work from. Conversion to 1/72 or any other scale is easy. Here is a description, if not detailed drawings.
http://uboat.net/wwi/types/?type=UB+III
Just multiply the dimensions in meters by 39.37 to get the length in inches, then divide by 72 and you'll know exactly how big it's going to be. Then when you have proper drawings it's easy to resize them to match the scale dimensions and print them out, and you'll have a pattern.
You'll also need to find as many detailed photographs as you can, because it's the details that make the model.