Buying and Owning a Ferrocement Boat

Courtesy - Hartley Ferro Cement Boat Owners Association Inc (NZ) - Ferro Flyer Newsletter

Every one seems to have an opinion on ferrocement boats. Some swear by them, others swear at them. Some people do know what they are talking about, some people sound as if they know what they are talking about and lots do not have a clue. I don't no many impartial experts on anything, let alone ferrocement boat construction, so all that could be done is to gather as many facts and as much common sense as possible, put it on paper and let you, the reader, make up your own mind. First of all, lets start off with what ferrocement really is.? Essentially, it is steel reinforced concrete. The term refers basically to a thin shelled structure consisting of a close-knit matrix of small diameter hi tensile steel rod sandwiched between layers of wire mesh, and embedded in a rich mortar cement which just covers steel matrix. Ferrocement is really a "hybrid" reinforced concrete, differing in the fact that the steel reinforcement matrix predominates rather than the concrete ( mortar). In reinforced concrete the steel is used simply as a strengthening addition. By altering the ratio of cement to steel we end up with a product that exhibits properties superior to those of either material separately. The tensile strength of ferrocement can be high, assuming an average figure of 5,340 lbs/sq in ultimate. The comparative tensile strength of high quality timber can reach about 6,000 lbs/sq in, but it must be remembered that this is only with the grain, while across the grain, tensile strength, from a structural consideration is almost negligible. Tensile strength of a ferrocement hull is in all directions, by virtue of the steel mesh reinforcement. Where compressive strength is concerned, a ferro hull can achieve an ultimate strength of about 12,000 lbs/sq in, in 28 days of curing, a figure which will increase with aging far more than can be obtained with wood. A particular characteristic of ferrocement construction is that it gains strength with age, rather than losing it. Detractors like to argue ferrocements failure at point impact. This may be true, but the damage is very little worse than grp or wood, tends to be localised and is very easily repaired at little expense, compared to grp and wood. Ferrocement hulls are fire resistant. GRP and wood will burn and melt, whilst a steel or alloy can buckle and distort. Only very high temperatures will damage ferrocement.The main reason is that the constituent materials, mortar and steel, have almost identical coefficients of expansion, which means they will expand and contract at the same rate with the changes in temperature. There is therefore no, or very little, cracking or separation at the steel/mortar interface.

A ferrocement hull is not damp and cold. The material has a very low thermal conductivity. this being the case, the rate of heat transference is low, thus allowing for the probability of the hull remaining cool in hot weather and relatively warm in cold weather. The material is, of course, impermeable, so there is no dampness, and there should be no leaks either. Condensation in a ferro hull is minimal, how often is the comment heard of cobwebs in the bilges of ferro hulls. Ferrocement is thought to be a heavy building material. Actually the weight disability disappears as the size increases. At about 30 feet in length, the length/weight ratio improves to the point where ferro boats can be built much lighter than equivalent wooden or steel vessels, and as light as those constructed with "hand laid" GRP So, after considering all of the above, why does it seem that so many people appear to be prejudiced against ferrocement as a boat construction medium? Why are there so many self proclaimed experts voicing their opposition? And why are there so few new ferro boats being built these days? Nobody knows for sure what motivates others to take a stand one way or the other, but could the following be some possible explanations? As regards to new construction, no longer is ferrocement the low-cost option. You need quality steel, mesh, cement, aggregate and these costs have risen significantly since the boom days of the 60 s and 70 s. More importantly the techniques used in quality construction are labour intensive, and this is an area where costs have increased greatly. Many of the fine examples of ferrocement construction available today were built by professionals, or by amateurs with professional help, or by amateurs with a truly professional and time consuming approach to the construction. Seldom are these attributes available today at a cost effective price. Initial reaction to the thought of building boats from ferrocement is usually cynicism. Most people relate to the term of ferrocement with thoughts of typical reinforced concrete structures, massive clumps of heavy brittle masonry, something you would construct a building or a footpath from, not a beautiful boat. Possibly people thought that a thin shell structure of mortar and steel wouldn’t be sufficiently impermeable, strong,or impact resistant, nor could it have the degree of flexibility required for this application. As you are aware all of these beliefs have proven to be incorrect, but they still come to mind for the uninitiated. What about the so called"experts"?? We had a seasoned cruiser and otherwise knowledgeable sailor tell us once that he didn't like ferro boats, "because the only time he was on a ferro boat it sank", how s that for logic? No thoughts about whether any other medium would have stayed afloat or not, no consideration about the abilities of the skipper or crew, just a simple "Don't confuse me my mind is made up". When you run into that "Yacht club or Broker expert" who bad mouths ferrocement, just ask how he/she came to their conclusion about the medium. Find out if they know anything at all about which they speak. Consider the facts above and ask them to specific about their criticism. Find out for yourself. Draw your own conclusions. Chances are, after all the study, reading, and checking you have done, you will have more knowledge of the subject than they. Each and every boat building medium has it's strong points and it's weak points, anyone trying to convince you differently is foolish. The only question should be "whats right for me".