sentences:  Merchant ship owners were attracted by the savings made possible by copper sheathing, despite the initial outlay.As the coppering was expensive, only the better owners tended to invest in the method, and as a result the use of copper sheathing tended to indicate a well-found and maintained ship, which led to Lloyd's of London charging lower insurance premiums, as the vessels were better risks.From this stems the phrase "copper-bottomed" as an indication of quality,
  
  Coppering was more commonly used on merchant ships sailing in warm waters.