Ferro-Cement hull building?

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Sparky00

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First, I know I am opening a can of worms here and going down this rabbit hole, but I want to ask this question on Ferro-Cement boat building. Has anyone used it lately, and if so have you gotten away from using steel rebar and thought about using Rock Rebar / Basalt rebar instead, or even fiberglass rebar? Before you explode with a bunch of hate and words of Oh what a piece of $#$#% it is or anything else there, hear me out and think with some logic first and foremost. I am not writing this out of fun to stir up an angry mob of haters and nay sayers, I am just throwing an idea out there and asking the question of “Has anyone done this and if so how did you get away from the main issue of steel rebar?” If you look at cement in general, it does a wonderful job of protection from the elements, used in many areas of construction, to include bridges and damns, dikes and more. Used in corrosive environments like saltwater... So why is it ok for a bridge which holds up tons of weight, or a damn which holds back a lot of water, but not a hull?
I have had a Samson ferro-cement sailboat once. The biggest issue was the rust bleeding. There was even a 6 inch crack under the waterline that was inspected by a marine inspector and no issue of integrity. Yes it was a heavy beast and yes it did not roll as much as the fiberglass boats in the mooring, especially when a gator freighter slipped by. But again the question is “Does anyone use Ferro-Cement?” And If so have you considered alternatives when using without steel rebar? Thank you and I hope the rabbit hole was not too deep...
 
Greetings,
Welcome aboard. I remember there was a flurry of ferro-cement boats being built back in the 70's. Seemed almost every yard had at least one hull in progress with varying amounts of rust collecting under the build. Unlike FRP one could build a hull oneself and many WERE built.



Interesting questions you raise but I really can't help you at all. Not being critical but I know nothing about the material.
 
Welcome aboard, Sparky, and what, pray tell, does the term "gator freighter" refer to?

It's been 35 years since I parted ways with an amazing ferro-cement ketch, after putting thousands of offshore miles on her. Your question was whether anyone on the TF gone a-building in cement recently. My answer is, not me, and nor would I, despite my confidence in the cement boat I had. The reasons are several, but they lead to the same bottom-line: the market for cement boats is vanishingly thin. It may not equal "zero," but the market measurement value is so close to zero that it might as well be.

Put it this way: if I knew firsthand the build quality, I would own a cement boat and go anywhere with it. But, if or when the time came to sell, I would expect to wait forever for a buyer and to get next to nothing for it. No one builds or buys a boat expecting value appreciation, but I am probably not alone in thinking that I should at least recover some of my equity upon sale.

That said, I have never heard of "rock Rebar / Basalt rebar," or the "fiberglass rebar" that you mention, and so I hope to learn something from this thread. My old ketch was built with steel rebar and a mesh armature, and discrete little spots of rust were staining the hull surface the last time I saw her.

As to why bridge pilings, dams etc. are built with cement and steel rebar with less anxiety than boats, I believe it has to do with all the complex dynamic loads placed on a hull underway at sea. Bridge pilings are engineered to resist predictable loads from compression or sheer.
 
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Any steel in a ferro-cement hull needs to be coated with epoxy. Like they do in bridges now. Cement allows moisture to the steel, even without cracks. The ferro-cement hulls I've seen scrapped had little of their steel and wire left.

I live on the coast and many of the older cement bridges from before epoxy use have rusted rebar bursting out.
Does fiberglass rod have the same strength as rebar? I doubt it. Ask an engineer.

I've built boats in wood, steel, aluminum, and fiberglass. IMO the easiest would be steel. Wood is cheaper if you can find the right lumber. But takes much more time.
Fiberglass takes several people for a decent sized boat.
You couldn't give me a ferro-cement hull unless it had a Detroit Diesel. And then I'd pull the engine and sink the hull. It would make a good mooring buoy anchor.
 
If you replace the steel rebar with fiberglass rebar and mesh, then further replace the cement with a thermoplastic resin like polyester or epoxy, then you have a pretty good hull material.

I think the ferrocement craze died with the realization that since the hull material is <10% of the cost of a boat, reducing its cost to zero doesn't affect the build cost by much, while affecting the resale value by nearly 100%.
 
Steel may compare favorably with ferro. You'd still be buying,
welding and coating the ferro rods, then buying the cement.
 
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The tensile strength of fibre rebar is 20% higher in comparison with a steel bar. The material bonding force of fibre reinforcement is considerably stronger compared to steel; this explains better operational endurance of FRP rebar.

Basalt Fiber contributes to reduction in concrete coverage by 25 – 30%, and its weights 4.5 times less than steel fiber This means you'll need less manpower to lift and place the material during construction.

Basalt rebar is 3 times stronger than steel rebar (the strength of basalt reinforcement is about 800–1100 MPA, while steel reinforcement has a strength of 225-365 MPA).
 
Greetings,

Mr. S. Sounds like you're well along with the technical aspects. Are you considering a sailboat or a motor cruiser style hull?
 
The reality is that ferro cement has such a bad reputation now that any resale value would be extremely poor. So IMO it doesn’t make it a good choice no matter what reinforcing rod is used.
 
If I were going to consider it, I would look into a motorboat for commercial usage. Not a fishing vessel, not just pleasure, but possible transport. I have some ideas and I am just looking into all aspects. I know that the resale part would be extremely low, unless you could prove and provide the quality assurance needed. Also in the commercial usage I was looking into day charters to and from small islands where a shallow draft and tough hull would be necessary due to the coral reefs and rocky beaches. Again just looking, I have had a Ferro sailboat year ago and have seen the rust issues and know that if the rebar corrodes out you are left with rubble....
 
Greetings,
Mr. S. Not too sure BUT I'm guessing construction specs for commercial vessels will be far more stringent than for pleasure craft. Can you even license a cement boat?
 
We were the caretakers of an excellent build quality ferro boat from the late 70's. Ours had monel for the armature and I believe the grid was stainless. We owned her for 9 years and traveled the inside with her every summer. The boat never had a rust stain nor did she have a crack or any spalling. She was 50' and tipped the travel lift scale at 68000 lbs. The lines were a typical seiner hull and she was very economical to run ( thank you John Deere).
The Admiral was always suspicious of the hull, but the previous owner(builder) ran her between the PNW and Socal a few times and spent 20 summers going to BC and Alaska. The builder had built her with 1100g of tankage integral to the hull and as such she always had a diesel smell that drove me nuts. I would still own her today if she had been anything but ferro. Insurance was very hard to get and the comments about resale value are spot on.
I got lucky and sold her to someone who loved her looks and comfort but wasn't worried about the ferro. To the O.P, fiberglass rebar definitely solves one of the issues of ferro. Very few of the old ferro boats were built correctly.. mine had cured in a steam tent for 27 days to cure the hull.
 

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Ferro- cement is not an approved hull material for an inspected vessel, which would limit you to only carrying 6 paying customers.

If I were going to build a ferro-cement hull, I would also consider galvanized rebar and galvanized mesh for the armature.

Ted
 
Lepke said:
Any steel in a ferro-cement hull needs to be coated with epoxy. Like they do in bridges now. Cement allows moisture to the steel, even without cracks. The ferro-cement hulls I've seen scrapped had little of their steel and wire left.

I live on the coast and many of the older cement bridges from before epoxy use have rusted rebar bursting out.
Does fiberglass rod have the same strength as rebar? I doubt it. Ask an engineer.

I've built boats in wood, steel, aluminum, and fiberglass. IMO the easiest would be steel. Wood is cheaper if you can find the right lumber. But takes much more time.
Fiberglass takes several people for a decent sized boat.
You couldn't give me a ferro-cement hull unless it had a Detroit Diesel. And then I'd pull the engine and sink the hull. It would make a good mooring buoy anchor.
Click to expand...

Any steel in a ferro-cement hull needs to be coated with epoxy, that's new to me!
I have worked in hydraulic engineering all my life but have never seen anything like this.
If we were processing rebar, and it had just come out of the factory, we were not allowed to use it because the steel was blank.
The steel had to rust before it could be used.
The reason for this is, concrete adheres poorly to bare steel, so a large part of the effectiveness of the reinforcement is lost.
The cement neutralizes the rust present.
The problem of rusting the reinforcement lies in the coverage of the reinforcement, the layer of concrete on the reinforcement.
Normally in a sweet environment it is 3 to 4 centimeters, in a salty environment 4 centimeters, nowadays 7 centimeters is used.
These thicknesses are obviously not feasible for a ship.
As a substitute for reinforcing iron, there are steel fibres and synthetic fibres, but these are not suitable for structural purposes.
Another form of cement that used to be widely used in shipbuilding was to provide the steel drinking water tanks with a cement layer, cement tar.

I hope it is readable by the translation.

Mvg,

Pascal.
 
I spent a season in a marina next to a beautiful 40 something foot ketch. I knew it was home built but was truly shocked when the owner told me it was ferro. I thought it was glass. He bought it from the guy who built it, didn't say how much he paid but I'd bet it wasn't a lot. I've seen a few other ferro boats, they all looked pretty bad.
I've built boats for a living, and can say that the bare hull is only around 10-20% of the total cost. Ferro is probably the cheapest hull material but it's the interior and systems that cost the money. You don't save much building in ferro, and what you do save will likely cost you 10x on resale value.
 
I have known of 2 well built and strong ferro cement boats...they are both still going strong after 50 plus years. The little I do know of them I got from my neighbour at our marina that still has one that he built himself. He's currently repainting it and the only thing he would do different from what I know is to use stainless mesh that wasn't available then he did use stainless rebar though. Good Luck.
 
If you have to try

In building a cement hull today, you would use epoxy bar, wire and add calcium nitrite to the mix which prevents corrosion. You could also treat the finished hull with silicates which you see being used on the floors of the large box stores like Home Depot to densify the finish. use of the fero cement hull was popular in WWII to reduce the use of steel in basic barges.
But really can’t think of any advantages over other materials.
 
The 55 ft Ketch "Limershin" is Ferro and most people think she is FRP. Boat looks new by the way !! Launched her in 1970 along with a 55 ft Trawler, lost track of her a few years back but she was holding up as well. Do not think it best to build in Ferro unless you want a ship like they built in WW2. 50 some odd years of being a designer have been fun and to build in Ferro boat I can say it was most interesting. Stephen Seaton
 
Stephen Seaton said:
50 some odd years of being a designer have been fun and to build in Ferro boat I can say it was most interesting. Stephen Seaton
Click to expand...
I have admired your work for a long time.
 
A guy in the Orlando, Florida area, built a ferro-cement sailboat in his back yard back in the 70's and early 80's. He finished the boat around 1980 and moved it from the back yard. You could see the boat from a major road so it was sorta well known and the newspaper had a report when the boat was moved.

I have always wondered how well did the boat held up, where it went, and where is it today....

Saw a power boat in Ireland that I think was ferro cement. We were only in the marina for a few days and never saw anyone on board to ask.

Later,
Dan
 
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They were very good for immigrant Viet Namese fishermen back in the 70's - cheap, functional and easy to build. The Texas coast was where I saw most of them. Go steel, so much better and easier and acceptable to the general public.
 
If you want to build a boat and don't want to do it in fiberglass or steel/alum, then I'd say the cold-molded (wood strip/epoxy) way to go would be much better. More accepted. Certainly better resale than cement, although not as good as FG. Easy to work with wood, although all that epoxy seems like a nightmare to deal with. In either case, you're talking about a lot of manhours. Might be better off just picking up a sorry project boat and stripping it naked.
 
It used to be pretty popular. Both commercially made and do-it-yourself. Don't see many anymore.

If they were built right and taken care of they were an OK option. The problem nowadays is that once you own one, you will own it forever. No resale market.

pete
 
Guy must have been a neat freak.
 
A couple comments about the craigslist boat, not that anyone asked..

You can usually tell a live aboard boat in one or two pictures. More set up for living and not for sailing. This boat hasn't gone anywhere in a long time.

The cane hanging on the wall in one of the cabins pretty much tells it all.

I recently sold my 36 foot Albin. Part of the deal was that I pretty much walked away from it in usable condition. I didn't remove anything except my toolbox and towels. I'm not sure how the new owner feels about this now though.. Anyway I bought a basically abandoned 25 foot SeaRay where every nook and cranny was jammed with "stuff". trust me, it was a lot of "stuff". Can you imagine the pile of stuff a new owner would pull off this 75 footer?

I'm sure some of our members know exactly how big a 75 foot boat is. Personally, I can't even imagine 75 feet, it is beyond my comprehension.

I don't think ferro cement is really any heavier than a steel boat of the same size but maybe it is, anyway can you imagine what that boat weighs?

Hell of a good price though. Maybe I should buy it..

pete
 
Pete Meisinger said:
A couple comments about the craigslist boat, not that anyone asked..

You can usually tell a live aboard boat in one or two pictures. More set up for living and not for sailing. This boat hasn't gone anywhere in a long time.

The cane hanging on the wall in one of the cabins pretty much tells it all.

I recently sold my 36 foot Albin. Part of the deal was that I pretty much walked away from it in usable condition. I didn't remove anything except my toolbox and towels. I'm not sure how the new owner feels about this now though.. Anyway I bought a basically abandoned 25 foot SeaRay where every nook and cranny was jammed with "stuff". trust me, it was a lot of "stuff". Can you imagine the pile of stuff a new owner would pull off this 75 footer?

I'm sure some of our members know exactly how big a 75 foot boat is. Personally, I can't even imagine 75 feet, it is beyond my comprehension.

I don't think ferro cement is really any heavier than a steel boat of the same size but maybe it is, anyway can you imagine what that boat weighs?

Hell of a good price though. Maybe I should buy it..

pete
Click to expand...
The ad lists it as 32 GT, not overweight for that length, IMO.
 
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