ZIM
Approximately 18 inches. Some people less, some people more depending on long one's arms are..
That's a problem iffen you are trying to build something that needs to be consistent in measurements for fitting..
12 people working and 12 different board lengths all supposed to be the same..
I wouldn't want to be on that boat out in depths..
I know that was a common way of doing things. The 18 inches I referenced was not set in stone. It is a number used by many Professors as being close to what a "cubit" was in length generally was.
I doubt anything was a snug fit or air tight if we just everyone's elbow to fingertip measurement..
On average the foot and a half seems to be pretty much what that length turns out to be but their is some slight variances..