From the original, there are only pictures on wich you can relate the thickness of the planks. In the “Bluenose old photo ...” thread, you can find some. Relate them to the arms and hands of the workers .
In The Sage (page 42) of the BN-II is written:
“Planking 3 1/2” thick, hardwood, average about 6” wide. Lenght of planks ranges from about 25 to 30 feet”.
At the specifications on page 18 is written:
“18 Planking: Topside 3 1/2”, bottom plank of 3” hardwood.
Hopefully this will help you. @Heinrich : Perhaps you can place this thread to the BN Main Support Page?