Ferro Cement Hulls ?

[cooper]

It is with a great deal of sadness that I report the designer and builder of my boat, Kan Walker, builder of the famous walker H28 (fiberglass) is now in serious ill health. You will find many examples of these tough little boats all over the place. They have circumnavigated several times, and there are plenty of examples that now live in NZ. Kan has been one of the finest designers and builders of ferro boats. The only reason he changed to fiberglass was market forces. His last and personal boat "Ali Khan" is a super light weight aluminum 38 footer . This boat is full of the ideas of a life time, including a "opening garage" in the transom so that he and his wife could launch and retrieve their dingy with ease.

[Alan Wheeler]

The H28 is the cheapest means of entering the cruising market here in NZ. There are many ont eh market and they go for around the medium of NZ$30K for a GRP hull and as low as NZ$20K for a timber hull. Wonderful entry level boats. One of our "lurkers" on here has just taken ownership of one and I do hope David and his wife will actually start posting soon. I want to be kept informed of the journey ahead of them.

[AuzzieM]

Getting back to reality with the Ferro-Cement discussion. I own one, I live aboard one, The previous owner and his wife lived aboard for 20 years, sailing all over, NO COMPLAINTS, GREAT BOAT.
I would like to purchase a larger ferro yacht in a couple of years, and unfortunately have noticed prices creeping up, probably due to people finally realising that low maintenance costs and longevity of well built ferro hulls is worth considering.

[Silverado6x6]

Good sunday morning all, I am adding my $.02 on this from an outsiders perspective, I do not currently own a boat but have worked on them periodically as a mechanic and operations engineer.

What I do for a living is managing a concrete batch plant in Alaska, other than delivering concrete by truck we also make concrete septic tanks, our tanks are proven to outlast any steel one on the market, only fiberglass or composite tanks come near or exceed the longevity of concrete. We use additives both chemical and composite to increase strength of concrete such as polypropylene fibers or as we call it in the trade fibermesh, also there is new types of reinforcing materials that will not corrode made from engineered plastics. There has been a lot of advances in concrete spurred by the rising cost of steel and fiberglass, as an intersting fact was years ago Anchorage had a nearby volcano erupt and the suround area of town recieved over 2" of coarse volcanic ash similar in size to small grape nut cereal, it was very very hard, the city collected as much as they could and used it in future sidewalks, ther is a section of highway that was paved in the 60's with a similar blend, usually our roads only last 5 years because everyone drives with studded tires half the year and wears grooves in the roads, the asphalt that had the ash in it was noticeable better at not wearing out.

So to sum this up if I was to consider building a ferro boat I would research using a fibermesh additive, composite reinforcing and an aggregate mix of high strength bonders other than rock possibly silica or even to go totally futuristic kevlar or spectra, the goal is to have binding agents that are immune to corrosion, to have the highest PSI rating possible.

There was an episode recently on TV called "Smash Lab", they proved that spraying a coating of bedliner material's like Herculon on both sides of a cinderblock wall greatly supported it during a car bomb blast, the building stayed basically intact. I would heavily research into that as well of coating the inside hull of a ferro boat with some of this bedliner material like Scorpion, Herculon or such.

[Jolly Roger]

The first boat I ever bought was a ferro cement Endurance 40 ketch, from Windboats in England, complete with Loyds hull certificate and lovely teak decks. She was built like a tank with twin danforths on half inch chain through hawsepipes, like a ship. We lived on her in the Med' for seven years and never had a scrap of trouble. She weighed in at 20 tons and took a bit of moving, but once she got going she would slice through those short Mediteranian seas like butter. One thing I noticed when sailing on friends glass fibre boats, how quiet ours was. We once took the ground on a beach and had to have her towed off. When I dived on the spot the next day there was a whopping great indentation in the sand like a whale had been sleeping there - not a scratch on the hull. We kept her in good repair and sold her for exactly the same as we paid for her seven years later.
If you find a good one, which suits your accomodation needs, and meets survey - go for it.
If there is anyone out there who knew "Tranquility Base," in the Med' contact me. Roger.

[Alan Wheeler]

Silverado, your post has made interesting reading and some of those ideas could well improve a hulls strength. However, be aware that the strength in the cement itself is not the secret. It is the combination of the steel and cement and the combinations ability to send stresses along it to dissipate impact energy. Many of the earlier hulls went awry by builders not understanding that and thought that if they made the cement thicker, they made the boat stronger. The chicken mesh is there only to tie the cement to the steel and although I say this with caution, having fibre materials in the cement mix could well improve it's "adhesion" to the steel. The only issue I can see would be adhesion of the cement to the fibre. You wouldn't want microscopic capilleries that could allow water to wick along between the cement and plastic fibre mating edge.

[Silverado6x6]

The septic tanks we build are roughly 2" thick in walls and floors, we use a very heavy gauge wire mesh that is shipped flat, off hand I think its a 5 or 6 inch squares, maybe 8 or 10 gauge wire, at lifting points, corners and floor we add rebar. Obviously the ferro boats are built differently and with a different mix design, what I am implying is that there are materials now to reduce internal corrosion. As I said I know nothing about ferro boats but I do know a fair bit about concrete, and if I were to build a ferro boat I would research options of using wire of either galvanized, stainless or even non ferrous.

[Alan Wheeler]

Internal corrosion is actually not an issue. I do know of some that were built with SST Rebar, but there is no need for the extra expense. The plaster mix has a very high concentration of lime and other chemicals that react with rust on steel. It has often been the case that when a hull has needed repair, breaking away the plaster has resulted in exposure of beautiful shiny steel as if it was brand new. Allowing the steel matrix to rust before the application of the plaster results in a great cement to steel bond. The rust streaks that sometimes are seen, are caused by the "ear's" of the wire ties too close to the surface. A grind back of that spot, treat and fill takes care of that. The chicken mesh is normally Galv. The main concern with the mesh is a small hole size. There has never been found a real substitute for the particular mesh used. Only one company in the world makes it. However, if you know of something that would do the job, you could be onto something. It's main purpose is to take impacts and send the stress out over a larger area. Maybe the fibre materials you suggest would do similar. I do like the idea of hard mediums used. I reckon the hard sand particles are also a great tribute to the strength. It is one of two reasons why a sharp sand is used. It compacts in closer as particle to particle making for a denser plaster and it has a flatter surface enabling better particle to particle contact and share of the stresses. Sand with sea shell in it never made a great plaster mix. it was not strong enough. Granite sand is great and I would say your volcanic sand would be good as well. But it may need to be crushed to reduce the particle size and to make the sand sharp. Smooth pebble type particles are no good.

[cooper]

Ahh , its getting better !! one day we will turn the corner completely. The relationship between steel and concrete is an interesting one. I have no imperical data (but I think you will find a few trillion bridges/ buildings etc will prove my point. Expansion and contraction at a similar rate subject to the same temperature.

[Silverado6x6]

There is a liquid additive we the drivers keep on board that we can add to the mix at the jobsite its loosely called "air" but its basically liquid soap, what it does is to introduce microscopic air bubbles into the concrete, the specs are in a narrow range and for the engineers at state job sites they test the loads, too much air entrainment lowers the PSI rating dramatically. The upside to having this minuscule "sponge" effect is it handle thermal expansion much better such as we have here in Alaska.


Rhinolinings Industrial



I keep thinking about that episode of Smash Lab and them blowing up treated and non-treated concrete block walls with urethane spray coatings like Rhino lining.

I am cheating here but its interesting reading:High performance fiber reinforced cementitious composites - Wikipedia, the free encyclopedia

And here is a link and images for the Paxcon Blast mitigation coating.
PAXCON® Anti-Terrorism Blast-Resistant Coatings

[Talbot]

I believe that you are possibly creating a new variant of the ferro boat. I can envisage a future where the boat is created using techniques similar to a fibreglass hull (i.e. without the chicken mesh former, but laid up inside a mould. this would allow a more fair shape, and get away from the use of rusty wire. A lot of the ideas you discuss are very interesting, but I suspect it will need a keen amateur to give it a try before a "proper" boat builder gets interested.
The need to create this in a mould will significantly reduce the number of amateur disasters which gave ferro its undeserved bad name.

[mangomuffins]

It's a ferro-cement revolution!!

What about a FC catamaran?

seriously... at least the hulls

mm

[Alan Wheeler]

Many have tried variations and failed miserably. Even those expanded cements that have the "air" in them. They don't work. The results were the reasons why FC hulls ended up getting such a bad reputation. That is because everyone gets confused with what it is all about. First of all, the name is actually incorrect. Ferro-cement is not the original name. The name is derived from the French word, "faircement". We evolved it into ferro-cement. However, the modern name is still quite accurate. I have said it before, this is important to understand. You have to think of these hulls as steel hulls. That is basically what they are Steel. Just not welded together is all. The cement is what holds it all the steel together. The cement is not the strength of the boat. It is the combination of the Steel and the cement and how it transfers loads.
The next important thing to understand is that the Cement is an additive to the plaster mix. The Plaster mix is NOT concrete. It has nothing to do with concrete other than it has cement in it. Even the idea of trying to compare bridges and tanks etc is wrong. The plaster mix is a high ratio of Portland cement. Portland cement is used for a very important reason.
FC is the oldest material other than timber, to be used in boat building. It can be considered the first composite material to ever be used. It was first developed back as early as the beginning of the 1800's and so has many many more years of people trying different recipies than any other composite material known. In the 70's, exotic materials (exotic for the time) were introduced to the plasters to give what builders thought woudl be extra strength. But all failed miserably. The real key is the lime and a few other key ingredients and how they fuse to the steel. The Plaster is all about chemical reaction. Right from the initial hardening, to adhesion to the steel, through to the "self healing" ability the lime creates and the way water acts on the material.

BEWARE of applying linings like Rhinoliner. I am very familiar with this product and although it quite possibly helps with bomb blasts against concrete walls, it could be the worst thing to do to plaster hulls. Many linings have fallen off plaster. Not that that is a problem to the plaster. In fact, plaster becomes harder and harder the longer it is cured and to cure cement, you need water. Water is actually a friend to cement and the better hulls are those that are not painted with anything for several years. Then and only then, paint is usually applied as an epoxy coat first. The reason is, it is usually the only thing that will stick to the cement long term. This gives a base for the paint system to adhere to. You won't get paint to adhere to Rhinoliner. And I have also seen Rhinoliner peel away from plywood in sheets. It may have enough adhesion to a concrete wall on land, but I imagine it would eventually come away from the side of a boat.
Personally, I would stick to the well proven tried and true method of FC building. The boats that are still floating today were all built that way.

[Silverado6x6]

OK by me, I guess their is also no place on earth to explore so we need not ever think of roaming off to another country? Sounds like a scene from The Truman Show.

You are so right but yet I have a tendency to not follow the predicted path to be counted, categorized and contained in an egg carton world of mass singular themed objectives dictated by omnipotent demi god beings that stand upon the shoulders of mindless flocks of cattlehumans.

Sorry my rant of the day.

[Alan Wheeler]

I certainly am not saying don't. Just be aware of the History and have a real understanding of the material. If you can find a better medium to build with, then great.