I've yet to hear about that. De-masts i know about were always weather ndition related. Mates parents yacht(8m/27') is mid 70's(thats what, 50 years old?) and mast and boom still havent broken. and his own racing yacht(10m/30') with is about 20 years old with a racing life is also still going strong. Masts dont 'suddenly' snap.
They break under pressure, certainly. Alloy tends to tear and then snap off. I've broken a mast in a World Soling Championship of Queberon / France. I'm Australian, so I leased a boat. It was a few years old, and the mast had age hardened and become brittle. It's a known issue. Another Australian racing there was John Bertrand, and he also broke his mast in the same race. John later won the America's Cup, for the first time defeating the USA. The breeze wasn't very strong either that day.
The "Ocean Race" is still on now. There have been two broken masts, one boat retiring from the competition. I own a Sunfast 3200, and I sail in single handed. Obviously its setup for short handed racing. One of the things people traditionally like about a mast that goes through the deck and sits on the keel, is that if the mast breaks with such a setup, the remains of the mast can still be used to rig up a jury rig and sail to land. While a mast that sits on the cabin top, being able to do that, is far more unlikely to be able to be jury rigged after breaking at sea. Just an example of popular thinking on boats that go to ocean.
One of the reasons I bought a folding electric bike, is so that I can put in inside my boat. And also to ride to the yacht club - it takes me 14 minutes to get to my boat now, but over 20 coming home. I reckon I might be able to get home in 14 minutes from the boat with the electric bike. Going home from the yacht club is uphill!!
Masts do do break but its normally because of something else failing that causes too much strain. But masts do age harden. They are alloy, and its a very known issue with alloy. The Comet airplane could have made Britain the dominant air manufacturing giant after World War II. But after two years, the jet airplane's lovely large almost square windows fatigued and cracked, and the planes started crashing. They did not fly for a couple of years and it hurt Hawker Dehavilland a great deal. Boing would later say but for the Comet, the same issues would have killed the 707. Metal fatigue they called it then. Or work hardening. Alloy works and then becomes brittle and are more likely to break. Spinnaker poles of yachts are not much supported, and they just snap under conditions they have endured often before. Due to age hardening.
Ask those people you know who own boats, they will tell you about alloy hardening, if they are racing sailors. Racing yachts also are designed for the masts to bend. One reason is to optimise performance. Cruising boats though, have much more rigid masts, which are thicker, and not intended to bend much at all. The boats you describe sound like those sort of boats. While they are less likely to break, the facts are that their alloys would have changed characteristics over the years. If I was crossing the Pacific or the Atlantic etc., if that was my boat, I likely would not replace the mast. But I'd go right over the rigging, all the stay attachment points, to establish where issues had arisen. In Australia, we have to replace our rigging every 10 years, its an insurance demand. At the same time, the mast is gone right over by professional mast riggers.
These guys broke a mast too in the current Ocean Race, and they when getting back into the race, broke the world record for monohull sail boats, covering 640 nautical miles in 24 hours. That's almost an average spped of 50 KMH. or over 30 MPH. Without peddling too (that would be cheating!). Just 5 people on board. Check the 2 minute video:
But their mast failure was a carbon composite. They tend to sort of explode when they break, rather than sort of tear which is what alloy does.
Titanium is used on some bikes because it does not age harden. Neither does cast iron, but that is not suitable for bikes!!
