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knome · 08-09-2003, 11:16

Hello folks! I've been lurking for a bit, and I thought I would jump right in with a hull materials post. What am I thinking?!?!

There have been several long, authoritative sounding posts by Jeff H. While I am sure his post seems correct from his side of the dock, the reality is very different.

"My take on ferro-cement is that it is, in fact, pound for pound the weakest of all of the commonly used boat building materials. "

Jeff! You couldn't be more incorrect! A properly made FC hull is stronger than any other material or method except steel! With a compresive strength in the high teens of thousands, demonstrated and not remarked, this cannot be debated.

The issue with FC hulls, and the decline of FC as a building material is twofold:

1) Badly designed and/or constructed FC hulls

2) Basic perception

"Rocks don't float!" people think.. when all the while they are taking cruises on steel cruiseships. So thats the basic perception problem.

The other problem is more of an issue. You see, with Ferro you just CANNOT do it wrong and come out with anything usable. You CANNOT cut corners. You CANNOT use too much water. You CANNOT take 2 days to plaster. You CANOT cure it wrong. Any of these things, done incorrectly, could easily compromise the hull.

Case in point, a professionally designed ferro hull was lovingly crafted by an amateur builder. He did a fantastic job on the armature but when he plastered he didn't insure the sand he used was washed sand, and so salt got into the mix. Now in concrete this is not too much of an issue, but with FC.. OOF. His hull was spalling and refused to cure properly. He had to jackhammer the material out and redo it properly.

Anyhoo, as a result of these amateur designed and/or built boats where quality was not observed, FC has gotten a very bad name. I have never owned an FC boat, but have seen a stress test of a 25 year old Samson built hull. That is, a fella was swinging a sledge hammer at it trying to redo a section that had gotten puncture damage. I could not believe how strong that stuff was. In most cases, in order to get the plaster to fall off the whole armature, he had to swing the sledge five or six times, and that was just the OUTER plaster.

Another case, a 100+ year old FC barge was broken up in the UK recently, and the steel was not rusted. Not a bit. And it took hydraulic wrecking machines to do it.

Let me address a couple of Jay's points:

"Ferro-cement's weight comes from a number of sources. First of all, no matter how small the boat, there is a practical limit to how thin ferro-cement can be. ferro-cement needs to have a minimum thickness in order to have sufficient depth of material to protect the reinforcement from moisture. Because of this boats below 40 to 45 feet are generally considered too small to use ferro-cement efficiently. (i.e. they weigh way more than they would or should in some other material.) "

Ok Jay lots of errors here. First of all, a 32 foot ferro boat broke the world circumnav racord in the early 1980's. And its not 40-45 feet, its 30 feet thats considered the lowest limit for oceangoing boats. There are FC dinks at around 10 foot. As far as the weight issue, that's simply not so. The plaster is supposed to barely cover the reinforcing, like an 1/8" of material that is grouted on after the basic fill.

This being said, smaller ferro boats are indeed a bit heavier than their wood or lightly built FG counterparts, but not by loads. And if you get a professionally designed FC boat that was done by Hartley or Samson, or a real NA you should be fine.

"Ferro cement requires a high level of skill and a large labor force to build properly. The best materials, either galvanized or epoxy coated steel reinforcing rod, are very expensive making a well built ferrocement hull more expensive to build than a glass boat."

Building an FC boat requires so little skill its not funny. We're talking about using wire ties and mesh.. how does that translate to high skill? And if you follow the boiler plate process provided by the designers to begin with, you wont run into trouble plastering. Plus, I never knew that galvanized steel rebar was expensive... Also, the only 'labor force' you need is when you finally need to plaster. Then you need about 12 people, including 4+ professional plasterers. For 2 days. Also, you never use epoxy coated anything rods! The rust on the rods and mesh is what causes the proper bonding for the elastomeric properties to manifest..umm.. I mean the steel needs to be rusty for the thing to work

Sorry! Engineering showing!

I won't get into the rest.. this is getting very long!! But sufice to say, yes FC has low resale value, but this is a market thing, not a real value thing. And yes, FC boats are not trivial to survey, but then wooden boats are hard too. It is easy enough to require the seller to expose the armature in some location specified by a surveyer. This is easily patched back to new condition.

My point is, FC is not a bad material to build a boat from. It 's just not popular, and cannot be mass produced because it is a labor heavy process.

If anyone would like to know the real story of FC, I suggest you cough up a few pennies for Colin Brookes' "Ferro Cement Boatbuilding" which is offered for sale at http://www.ferroboats.com/

Jeff, I am sure you are very experienced but I'm sorry.. the tens of thousands of successful FC boats over the years, boats that have hauled cargo and people over oceans reliably and safely even when having encountered rocks and reefs, are a testament to FC as a good material to build boats from. It only takes one counterexample to disprove a hypothesis Jeff, and I think I can provide thousands! The general feeling about FC has been manufactured by culture as well as ticked off builders and designers who found they couldn't cut corners on Ferro and survive.

FC, once the Darling of materials is now the red headed stepchild, not because it is a bad material, but because folks realized that they couldn't make any money on it. So it is in everyone's very best interests to badmouth the material. And they have succeeded well, so much so that I dont believe many insurers are left in the US whom will even consider liability on FC, no matter WHAT the survey.

All bad news for FC owners, but then you can just sail to New Zealand and get insured

Good luck hunting!!

--T

08-09-2003, 11:16	#12
knome Registered User Join Date: Sep 2003 Posts: 8	Ferro is an excellent material Hello folks! I've been lurking for a bit, and I thought I would jump right in with a hull materials post. What am I thinking?!?! There have been several long, authoritative sounding posts by Jeff H. While I am sure his post seems correct from his side of the dock, the reality is very different. "My take on ferro-cement is that it is, in fact, pound for pound the weakest of all of the commonly used boat building materials. " Jeff! You couldn't be more incorrect! A properly made FC hull is stronger than any other material or method except steel! With a compresive strength in the high teens of thousands, demonstrated and not remarked, this cannot be debated. The issue with FC hulls, and the decline of FC as a building material is twofold: 1) Badly designed and/or constructed FC hulls 2) Basic perception "Rocks don't float!" people think.. when all the while they are taking cruises on steel cruiseships. So thats the basic perception problem. The other problem is more of an issue. You see, with Ferro you just CANNOT do it wrong and come out with anything usable. You CANNOT cut corners. You CANNOT use too much water. You CANNOT take 2 days to plaster. You CANOT cure it wrong. Any of these things, done incorrectly, could easily compromise the hull. Case in point, a professionally designed ferro hull was lovingly crafted by an amateur builder. He did a fantastic job on the armature but when he plastered he didn't insure the sand he used was washed sand, and so salt got into the mix. Now in concrete this is not too much of an issue, but with FC.. OOF. His hull was spalling and refused to cure properly. He had to jackhammer the material out and redo it properly. Anyhoo, as a result of these amateur designed and/or built boats where quality was not observed, FC has gotten a very bad name. I have never owned an FC boat, but have seen a stress test of a 25 year old Samson built hull. That is, a fella was swinging a sledge hammer at it trying to redo a section that had gotten puncture damage. I could not believe how strong that stuff was. In most cases, in order to get the plaster to fall off the whole armature, he had to swing the sledge five or six times, and that was just the OUTER plaster. Another case, a 100+ year old FC barge was broken up in the UK recently, and the steel was not rusted. Not a bit. And it took hydraulic wrecking machines to do it. Let me address a couple of Jay's points: "Ferro-cement's weight comes from a number of sources. First of all, no matter how small the boat, there is a practical limit to how thin ferro-cement can be. ferro-cement needs to have a minimum thickness in order to have sufficient depth of material to protect the reinforcement from moisture. Because of this boats below 40 to 45 feet are generally considered too small to use ferro-cement efficiently. (i.e. they weigh way more than they would or should in some other material.) " Ok Jay lots of errors here. First of all, a 32 foot ferro boat broke the world circumnav racord in the early 1980's. And its not 40-45 feet, its 30 feet thats considered the lowest limit for oceangoing boats. There are FC dinks at around 10 foot. As far as the weight issue, that's simply not so. The plaster is supposed to barely cover the reinforcing, like an 1/8" of material that is grouted on after the basic fill. This being said, smaller ferro boats are indeed a bit heavier than their wood or lightly built FG counterparts, but not by loads. And if you get a professionally designed FC boat that was done by Hartley or Samson, or a real NA you should be fine. "Ferro cement requires a high level of skill and a large labor force to build properly. The best materials, either galvanized or epoxy coated steel reinforcing rod, are very expensive making a well built ferrocement hull more expensive to build than a glass boat." Building an FC boat requires so little skill its not funny. We're talking about using wire ties and mesh.. how does that translate to high skill? And if you follow the boiler plate process provided by the designers to begin with, you wont run into trouble plastering. Plus, I never knew that galvanized steel rebar was expensive... Also, the only 'labor force' you need is when you finally need to plaster. Then you need about 12 people, including 4+ professional plasterers. For 2 days. Also, you never use epoxy coated anything rods! The rust on the rods and mesh is what causes the proper bonding for the elastomeric properties to manifest..umm.. I mean the steel needs to be rusty for the thing to work Sorry! Engineering showing! I won't get into the rest.. this is getting very long!! But sufice to say, yes FC has low resale value, but this is a market thing, not a real value thing. And yes, FC boats are not trivial to survey, but then wooden boats are hard too. It is easy enough to require the seller to expose the armature in some location specified by a surveyer. This is easily patched back to new condition. My point is, FC is not a bad material to build a boat from. It 's just not popular, and cannot be mass produced because it is a labor heavy process. If anyone would like to know the real story of FC, I suggest you cough up a few pennies for Colin Brookes' "Ferro Cement Boatbuilding" which is offered for sale at http://www.ferroboats.com/ Jeff, I am sure you are very experienced but I'm sorry.. the tens of thousands of successful FC boats over the years, boats that have hauled cargo and people over oceans reliably and safely even when having encountered rocks and reefs, are a testament to FC as a good material to build boats from. It only takes one counterexample to disprove a hypothesis Jeff, and I think I can provide thousands! The general feeling about FC has been manufactured by culture as well as ticked off builders and designers who found they couldn't cut corners on Ferro and survive. FC, once the Darling of materials is now the red headed stepchild, not because it is a bad material, but because folks realized that they couldn't make any money on it. So it is in everyone's very best interests to badmouth the material. And they have succeeded well, so much so that I dont believe many insurers are left in the US whom will even consider liability on FC, no matter WHAT the survey. All bad news for FC owners, but then you can just sail to New Zealand and get insured Good luck hunting!! --T __________________ "Perseverance alone is omnipotent." --Calvin Coolidge Last edited by knome; 08-09-2003 at 11:43.