Why were icebreaker ships still made of wood, not metal, into the 20th century? Shackleton's Endurance and Amundsen's Fram were made of wood, not metal.  Yet I can find no explanation of why, even though most other ships had long since been built from iron and/or steel.....
 A: I don't know the history of ice breakers so I can't confirm that this was their reason, but...
Steel back then contained high concentrations of impurities that made them an order of magnitude more brittle than today. This is especially problematic in cold water.
It has been suggested that the Titanic's fate may have been different had they've used a higher quality steel. There is also the famous example of the SS Schenectady, a ship that split in two while moored at a dock due to the cold conditions causing a brittle fracture.
A: When you are talking about an icebreaker, it is a very specific ship design with certain needs. It is also a vessel that will be pushed to its limits.
There is a general reluctance in the engineering community to adopt new bleeding edge technologies. Considering the secutity of tried and tested techniques that is understandable. Generally the greater the risks, the more the customer and public need to be assured that things will work out right. A centuries old technology provides that. It may ne a poor substitute but as its limitations are known, control measures can be engineered to meet the required performance specification. Investors feel more confident dealing with the predictable.
Experimentation in construction operates under the guise of quantity is a quality in and of itself. Although steel construction was not that novel at the turn of the 20th century, until production had demonstrated reliability in the 100s and 1000s, it was not trusted with risky costly ventures.
The builders who built the endurance did a spectacular job and everything about their approach to building it demonstrated reliability and trustworthyness. Unfortunately it wasn't designed with the rounded keel to enable it to pop up when under pressure, relying on its strength instead.
A: Wooden ships better withstood the crushing force of the ice when they were iced up for the winter. It sounds counter-intuitive, but it was found that wood was better than steel. This is not to say that wooden ships couldn't be damaged, sometimes they were.
