Discussion in 'Boat Design' started by tdw, Feb 26, 2005.

  1. tdw
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    tdw New Member

    Was wondering if anyone knows about using ferro-cement over insulfoam (expananded polystyrene) as a frame?
  2. gonzo
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    gonzo Senior Member

    Do you mean as a mold?
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    D'ARTOIS Senior Member

    I have some experience with ferrocement boats: I sailed one from Holland to France - all sorts of accidents during the voyage and some in relation to the building material.
    The way you pose your question gives me the idea that you are not completely aware of the building-process. Ferrocement is no resin that stiffens the woven and that can be formed over or in a mould - male or female moulding.
    That doesn't apply to Ferrocement, a process that works differently.

    Ferrocement was during a short period popular in the "hippy-scene" in the early '70's till mid '80 a material used sometimes in a professional environment but mostly by amateurs.

    Ferrocement does have two main problems, no actually 3, now I recall.

    You start with the buiding of a frame of steelbar that functions as the basic reinforcent - it replaces the tranversal/longitudinal reinforcement in common structures.
    On this framework you attach a number of layers of chickenmesh we call it "dubbeltjesgaas" Wynand will know what I mean - the more layers - the stronger your reinforcement/the boat;
    Than the cementing starts up and that is a one-go process: you start it and finish it in one sequence - there are, as natural, the necessary exclusions, but in general this is the way it goes.
    You start inside or outside by pressing the cement in the wiremesh, making sure that no gaps,voids or whatever are formed during the cementing process.
    Afterwards you fair the hull.
    Result: a rotproof, corrosionproof and in general strong hull.

    The negative points are not many but the ones existent are serious:

    1) hull becomes more often than normal too heavy;
    2) low resistance against high impact loads;
    3) close to irrepairable;

    Nontheless, quite a number of yachts have been build this way and circumnavigated the world.
    As I said, I sailed one from Holland to France; it sailed like a bric and in the middle of the Biscaya the boat fell from a wave and the gasoil tank ripped open and the engine came loose from its foundation.

    I shall not repeat the ferocity of this voyage, but here I was faced with the irrepair-ability of Ferrocement.
    I spent in total 3 months on this boat and a few years ago I saw her still
    intact in Aigues Mortes, France.

    Gentlemen, my 0,02.....
  4. yago
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    yago __

    I have seen another way to build ferro in France. There was a small yard somehwere near Bordeaux, st. Jean something.. and I helped cement boats there on two occasions.

    They would first set up a male mould plug, upside down, from junk wood. This was then covered with cheap clear plastic cover. On top of this they tacked the wire mesh through to the wooden mold. once done, they would hire lots of cheap labour (me) and we would crawl all over the hull with vibrators while they poured the cement. Other guys were inside, with flashlights sticking knitting needles through where they noticed that the beton had not completely penetrated to the plastic. After hardening, the hull was turned ouver, the wood ripped out and the tack grinded off.

    The result were very good looking, modern hulls, that were considerably thinner and lighter than build in the tradional upright wire-basket way. They were then epoxied and faired and the hulls looked really great.

    What always worried me though was that the element that provides the strength (the meshing) is hidden and can not be inspected, except drilling carrots through the hull. Difficult to buy or sell second hand...

    As for ferro-boat stories, don't get me going..

    There was a guy in Yarmouth, Isle of Wight, who had build a 40 foot ferro ketch with an enourmous deckhouse, because he was so tall and he had raised the cabin floor up to about the waterline, until it reached over the full beam, so that he could fit his home furniture in, couch and all... Sailed it too, around the Solent and I believe once across the Channel. Eddie something, nice guy to hang out with at the King's Head with until closing time.
    I still remember how he considered to set up some bulkheads from Rigips (plaster panels) rather than from half-bricks to save weight! I know you will not believe this, but it is THE TRUTH!! :p
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    D'ARTOIS Senior Member

    Unfortunately Yago, I believe you.

    But in earnest - you always end up with a hull that is way out to heavy. Fair or not fair - whatever the "experts" will say, put it on a balance and than the truth will slap you in the face,
    This unfortunate 37' that I sailed from Holland to France, about 2500 nm, was profesionally built, weight: 12.000 kgs!!!!!

    BTW was it in St. Jean de Luz?
  6. yago
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    yago __

    I think so, but you know, 25 years and all the local red wine ... ;)
  7. yago
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    yago __

    No.. actually I think it was St Jean 'Angle, and the boats were called "Grisby" or something .... yes???
  8. Andy
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    Andy Senior Member

    D'Artois, you make some good observations about ferro. I have sailed a fair amount recently on a ferro-cement 35ft cruising boat, and I would disagree with you on a couple of points. The most major of these is repairability - ferro boats are easy to repair!!! As long as you are able to slip the boat and make the repair before rust becomes a major problem, then it is a simple matter of either replastering (for small repairs) or simple welding of the mesh before replastering. The boat I sail on had exactly this treatment 3 years ago after landing on a rock.

    "Maragay" is often mistaken as a wooden boat, both due to her classic lines and due her hull undergoing extensive epoxy fairing prior to launch. Only her hull is ferro, which helps keep the weight to acceptible levels whilst keeping the centre of gravity low. Her hull is immensely stiff, both structurally and from a stability point of view, and in common with many other ferro boats, she really moves like a freight train throught the water.

    It is certainly harder to insure a ferro boat than it is to insure even a wooden boat, as a number of badly built hulls gave the method a bad name in the 70's. That said, there is at least one ferro friendly insurance broker in Britain who claims to have never received a claim other than due to operator error (like landing the boat on a rock...). Second hand value is not great either, but that makes a good ferro boat a great buy. Certainly I dont know of any ferro owners who dont love their boats and appreciate the strength of the material.

    If one can get over the idea that concrete really can float, I think ferro done well is a useful boatbuilding material.
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    D'ARTOIS Senior Member

    Andy, I agree with you on the stiffness of the hull - that is beyond any discussion, however regarding repairability I have my doubts and I explain why.
    First of all my experience derives from two angles, the first one is that I had to explain th guys joining our seminar back in '88 the value of the different building materials. Therefore I observed the building of Ferro boats not far away from Rotterdam, a few of them were made there.

    Beyond doubt, the hulls have a very high initial strength. When I arrived in the situation that the boat fell from a wave during a short blow in the Biscaya, the gasoiltank was split open and the engine had cracked one of the 4 supports.
    The engine was mounted in the midle of the boat, under the table of the salon.
    This was the old Perkins 4.108. In any case I tried in La Coruna to repair the gasoil-tank and the broken engine bracket, that was partly integrated inside the hull and welded on an intern steelbar. That boat aws probably at that time about twenty or so years old, and all those years the concrete around the engine was absolutely saturated with oil and grease. Nothing but nothing
    could be attached on that spot without setting the boat on the hardstand,
    getting the motor out and start thinking what to do. This is one.

    The same story with the gasoiltank that was an integrated part of the hull; the substance in gasoil, that can solidify, - I forgot the name now - had also made the gasoiltank irrepairable and I bought a inflatable or collapsible tank that was mailed to me in La Coruna.

    In Spain, Benalmadena, were I had to leave the boat for the owner to enjoy his holiday with his precious Dutch girlfriend. Fortunately he used the boat only as swimming plarform so when I came back I could started to try to repair the broken strut from the engine. I was lucky thatb the boat had a solid keelsole and iDrilled a hole and sunk in a bolt with a thermohardening ancre, the sort they use in the engineering of bridges.
    Whilst doing this work, somebody from the Capitaneria came and asked if I was willing to look up a boat that was in a hangar that was also made from ferrocement.
    That boat had collided with the local passengerferry bthat goes to Ceuta, and one of the sides was entirely cracked. The whole portside of the boat was cracked, not broken in, but cracked. The interior reinforcement of wiremesh hold everything together. The damaged area was about 3 metres in length,
    so I told him that I could not advise - I didn't have the precise knowledge of such big repairs were succesfully to execute.
    Second bonding on ferro is extremely difficult. I know there are ways to do it but one of my brother in law's owns a concrete factory and I know from experience that second bonding of concrete are bad bonds.

    A few days ago this topic ran on SA (Sailing Anarchy) look at the rating those guys give in connection to ferro - and what will make you using concrete as building material while there are other materials? Traditionally better suited.

    I hate the constant 5 knots the boat did, even at force 7 in the Biscaya, the log did no more than 110 miles (best) in 24 hours.
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    FAST FRED Senior Member

    Most ferro boats were advertised at 6 or 9 lbs per sq ft of hull surface, came out closer to 13 to 15 "As Built".

    AIREX in far stronger scantlings would be under 3lbs.

    There is also NO WAY to survey a concrete hull.

    Caviat Emptor!!!

  11. MikeJohns
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    MikeJohns Senior Member

    Xray, and chip hammer, you chip away the inner plaster to expose the mesh in a few areas and have a look inside the layup. The xray gives a good inside picture.

    I like the long lasting nature of the material, it is the only one I know that can be left for years without maintenance or proplems. I have a freind who injects 100% epoxy grout into ferro cracks at high pressure. Same process they use on structural cracked concrete very easy and good system.

    A few Australin boats had 4 or 5 layers of CSM and resin applied to the inside for better impact resistance for antarctic work some of these were LLoyds rated for ice.

    I had a ferro boat too (Hartley Fijian) the engine vibrated the engine moutning webs to death and I had to crush out all the plater and repair them, but the repair held up very well.

    Don't build a new boat in Ferro unless you want a low maintenance live-abaord to moor in a backwater, then it may be advantageous. Otherwise you lose you time investment when you try and resell.
  12. Columnist
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    Columnist New Member

    A different take

    I recently met up with an old friend who had built a 50+ foot Ferro Cement Schooner over 30 years ago. He has a company now installing cell phone towers in out of the way places using satellite connections where no other phone lines exist. His boat has been rammed three times while sinking one of the ramming boats his boat sustained no damage other than having to repair the paint. Before GPS he had been grounded on reefs and pulled from a couple beaches still the hull sustained no damage. His hull is only ½” thick in most places. He had to change engines to a Sabb with variable pitch propeller. His boat has many hundreds of thousands of miles under the keel and he has since treated the bottom with copper impregnated epoxy.

    I went on the first shakedown cruise but I had many obligations such as a family, job and boats to build so I could not continue in all the high adventure. He built the boat in Alviso California near San Jose. Our shakedown cruise took us out the golden gate and up the coast of California. While his boat was still in the San Francisco Bay he was invited to the master mariner schooner race until the officials were told it was a Ferro boat. They only accept traditional material boats. By looking at it they could not tell it was built from Ferro Cement. We did set off around a few races with some of the schooners that were already practicing and the Ferro boat was light and very fast compared to traditional built boats. Although an 80 foot water line should beat a 50 foot water line but that was not the result

    If built using the proper techniques a Ferro Cement Hull will be as light as GRP and much lighter than planked wood and steel hulls. What is needed is some very real schooling about Ferro Cement boats because they are a fantastic medium to build from. Sure if you use old telephone poles for masts and full Ferro cabins you will have a heavy boat, also if your Ferro Hull is an inch thick you have not made a good Ferro boat because it is not designed to be that thick and heavy for strength.. In fact a study done a few years ago by national magazine showed that more home built Ferro cement boats have done circumnavigations around the world than traditional wood boats since 1968! How can so many boats and cruisers have been wrong?

    Most of the negative attitudes about Ferro Cement come from people without experience and or from poorly built boats. Chicken wire does not make a good Ferro boat. Welded wire such as used in cages for rabbits or other small animals make much better support because you don’t need eight layers to make it strong two or even three layers are all that is needed. You can build a strong long lasting Ferro Cement boat and if you can not sell it for a profit in the USA you can sell it overseas where they have very high resale value.

    I write a monthly column for a few boating magazines about new tools for boat building. I have built many boats and seen many boats after they have been sailing for years. Ferro Cement hulls have the best looks in my opinion after long use than most others. All of the faults I have heard about Ferro Cement Boats can be put over on steel hulls plus you must worry about rust now. There is no completely perfect substance to build a boat from but if you combine materials you can make a perfect boat that will not need the care other materials could use in different parts of a boat hull. That is only my opinion but I consider my experience from building al types of boat hulls. Maybe I should build a reed boat next?

  13. PAR
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    PAR Yacht Designer/Builder

    Ferro cement boats were first built around the 1850's, some still survive and floating today. During WWII pretty large vessels were built of the material. Carefully cured mortar to over 8,000 PSI over a steel mesh and rod matrix, results in a structure that is tough, strong, will not burn, resistant to chemicals, not affected by ice and gets stronger with age.

    That's the good news. Ferro got it's bad rep from the building craze of the late 60's, where children only a mother could love nested in backyards around the country. Chicken wire was substituted for the welded mesh, non-continuous pours for the plastering work were performed and other sins contributed to the "wonder" material back sliding in yachting communities. Furthering this, were promoters pushing the process in an effort to sell franchise rights rather then produce well founded yachts.

    Though many good yachts have been built of this material, like the ones by English Windboats, Ltd. to Lloyd's approval, the reputation has been dead in this country for some time. Europe is catching up with this opinion, for a number of reasons, difficult and expensive surveys being one.

    I must disagree with Columnist in the resale value of ferro yachts. They hold the lower end of the slip, not the upper end plus the sales and construction statistics clearly bare this out.

    Anyone interested in the method should try to find Jay Benford's book on the subject "Practical Ferro-Cement Boatbuilding" it covers the methods and correct ways to build lighter, stronger ferro yachts. Benford Design Group or Tiller Publications may still have a copy around.
  14. FOsorio
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    FOsorio Junior Member

    I am very interested to get hold of this book or any manual that could guide me in the proper building of a good ferro cement boat. I live in the Philippines where we have low priced labor, lots of good sand and not so expensive portland cement. So a ferro cement boat would be the most advisable for us to build.

  15. CDBarry
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    CDBarry Senior Member

    I have sent a paper copy of the three part US Navy ferro manual to the board, but I imagine it won't be easy to get up.

    Have patience
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