Brendan. Happily I've never owned one. Nor built one. Wood, plywood, composites, aluminium, steel but not ferro. I have met people, amateurs and pros who made it. I even seen ferro boats in construction. As naval engineer I learnt the basis for building in ferro as the method is used for several applications in marine engineering of harbour installations.
There is a good record for simple barges built with coefficients of civil engineering, basically floating boxes. When you have the steel molds, the vapour heating for an accelerated cure, and when weight is not a major concern it's pretty good. The main cost on barges is the hull.
For boats where weight is a very major concern it doesn't work compared to simple steel welded with a cheap stick welder. If ferro was just as good as ordinary steel and best of all cheaper, we would see many ferro cement boats and ships. However ferrocement boats are rare, almost oddities. That's a fact. Why?
Simply because the material is not good enough for boatbuilding for a lot of reasons, the first one being structural. That's my opinion (I'm not alone).
For yachts and fishing boats it's not so cheap when you make the final sum. Very labor intensive, and the method is not so simple if you want a good quality for a high sea boat. Finally it's simpler to weld a steel plate on some flats and angles than cementing a mesh laboriously installed on a structure of welded steel bars, and waiting 28 days for the cure, plus the delay for drying.
A bunch were built in France in the 70ties. In terms of percentage very few survived, maybe less than 3%.
I have surveyed several (3 or 4 for eventual buyers, 2 fishing boats made by a pro shipyard as expert for legal problems and a few for people asking me if it was interesting to restore them).
Except one made expensively in Holland, having more steel and epoxy than cement and so heavy that it was a bad sail boat and not a good motor boat, all the others were junk after a few years at sea. Internal corrosion, and structural problems.
The two 15 meters fishing boats, were made by a specialist of concretes and ferro with the best of the best materials, on design by a good naval architect with lots of engineering and consultants. The FAO gave its blessing, the fishing authorities talked about revolution in boat building.
They resulted being heavy, too costly to make, and expensive to exploit. After 7-8 years of work they began to show signs of fatigue with a myriad of hairline cracks on the cyclic stresses points. Thus the legal liability problems and the survey made by several specialists in different domains. The builder was not happy when he saw the results after so much work and tooling investment. The "owners" were not happy. The Credit Maritime, the financier and final owner because of the mortgages, was not happy at all.
Unanimous verdict; unsafe, there was not more the structural integrity needed for a safe working boat, and the boats were aging very fast. Finally the boats were salvaged and the hulls destroyed. A wood fishing boat lasts 30 years at least, as polyester and steel. These ferro were junk at 8 years, after an unsuccessful career. Maybe very bad luck, maybe somewhere engineering mistakes, maybe simply the material is not for fishing boats with vibrating diesel engines.
Morality, when you say the word ferro about fishing boats in Brittany, everybody grabs a cross and spills holy water. There were on 2013 4537 commercial fishing boats in France. None in ferro cement.
In Cuba as I have heard myself from Cuban naval engineers they stopped after horrific experiences, the excellent Cuban rum surely made the stories more epic. But the Cuban need urgently cheap fishing boats, if ferro was the solution they would be making them by dozens. Idem in Central America.
We should ask the Chinese, they made thousands when the Great Party decided in the 70's that was the way for a radiant future. How many survived at least 15 years? There is nowadays a ship building industry in ferrocement boats in China?
After a fast search there is plenty of literature on Internet; the FAO made in 1995 a book about ferro fishing boats, it's the most recent and some of the claims are grossly inexact. It looks like the rewriting of a 70s book. Also plenty of re-edited books, and PDF of studies, papers and so on. All that has been written during the 70's.
After; black out. I did not find any recent serious professional book or technical paper about ferro on working boats.
It seems that there are very few built now. There must be a reason. I guess it's because when you compare ferro with the other boatbuilding methods there are no advantage, but many real and potential inconveniences.
