Dear Lain, propably the lifting bracket would pass through to a stronger structure as the propeller weight
would exceed twenty tons for sure.
Also ,Threebs, many thanks for sharing so great photos.
Tom,yes this practice was used in the shipyards and drydocks,but great care had to be taken during preparation to ensure the thread both internal and external had not been damaged and was well lubricated.I well remember using
special internal scrappers,triangular files and emery cloth in freezing fingures to get it just right for our old chagehand Charlie Buick at the Caledon Shipyard Dundee.We seemed to spend weeks fitting the tailshaft ,drilling out the lignum vitea bearing and fitting the prop. while fully exposed to the elements. the next job was then the fitting ogf the steering gear. I was really pleased when I finally got to sea.
I expect that this lifting bracket was made of cast steel.
The rectangular shaped flange would than be riveted to the hull with a (web)frame on the inside in line with it. Welding was not an option in the years this vessel was built.
The present solution on larger vessels is that lifting padeyes are penetrating the shell and are integrated with the internal structure.