ferro-cement

Brien
I had a Fijian ketch , was a little tender for my liking but was my first large yacht and it cost less than half a years salary. I had trouble with the engine mount webs crumbling and re-designed them.
It seems to me that the prices are rising for the ferro boats on the 2nd hand market here(Austrlia) and in the states. Perhaps just following a rising market.


I would prefer ferro to traditional planked wooden vessels, I know of no ferro boats that received hull damage from the sea, both wood and ferro exhibit brittle failure but at least there is some steel in the ferro layup.

A ferro yacht was abandoned here last week after the engine fell off the mounts and punched a small hole in the hull, the delivery crew (owner not aboard) gave up the boat after many hours because the water was slowly rising against the bilge pumps. The tv footage showed her being abandoned not much below her lines. No repair attempted. Now everyone is nodding wisely muttering " Yes of course it was a Ferro..." and another prejudiced nail is driven into the coffin.

If she had had some basic watertight compartmentisation , fulll bulkheads not requiredl just a couple of feet above the flood trimmed waterline, she would have been ok.

I would not be happy designing a ferro hull unless I supervised the building. That supervision is the key to a good ferro boat. But for the areas with cheap cement and abundant cheap labour they are a very cost effective durable long lived construction.

For the rest of you, get a steel hull

 

Mike Johns. It sounds like the Ferro got as mush care in design and construction as the off shore racers. A failure is still a failure. Especially wiht so many people suffering from "short time span of interest" syndrone. ------------------I remember when boat sinkings were scheduled by lack of maintenance by all involved.

 

Mike,

We think along the same lines: engineering is a serious part of our lives, so we think (or try to) lightyears in advance and our main concern is to create something that is rocksolid and safe for passengers and crew.
My problems were related to the boat (ferro) I sailed.

The strength - I cannot do otherwise than agree with you. Although - compared weight to volume and balance of SA / displacement, they score very badly.
Comfort of sailing however, was great. The volume of mass made even sailing over the Biscaya as going over a cushion. ( Save for the one incident that we fell off a wave.) Actually I sailed in a boat that was not fit to do so. I was bereft of any good nautical instruments.
I have to admit that the boat albeit not being able to move faster than her obligatory 5 knots, and her failing machinery, gave me no structural problems.

Nontheless, it wouldn't be my first choice of material, to put it gently......

 

Ferro has a lot to offer in a building material, but it's resale value, difficulty in inspection and repair make the decision a much more difficult one. I've been on a few sail and a single powerboat of ferro construction. It's nice have the comfort of a higher D/L sometimes necessary in the smaller classes of yacht, but it does fair well against steel in this regard, to a point.

As for Trouty, what can you say about someone who makes wild comments then doesn't back them up. You see, Trouty, I know the melting point of steel. More specifically, the type of steel used on the structure in WTC (it was special). I also know the amount of deflection, that occurred at the temperature of burning jet fuel (which wasn't all that was burning) the center support structure, with it's stressed floor slabs lying on top, had to tolerate. I'll match my two engineering degrees to your inadequacies and haven't the need yet for political comment, an arena you will also, likely find yourself underhung.

 

Will you be drinking it before or after admitting ferro is the best there ever was?

 

hello
Im in the process of repairing a 37' ferro with major damage on the starboard
side. I've heard so many conflcting opinions - hard to fix easy to fix etc.
I am wondering if anyone out there has fixed ferro with major damage and
could give me some hints. I understand you beat out the old concrete with
an air impact tool and straighten out all the steel. After that I'm not sure
what to replaster with: ferralite is out there and sounds good, there are
tons of epoxy products that also sound good. Can anyone let me know if
they've had experience and what they've used. thanks

 

Consider the fact that very few people have experience building ferro craft; let alone the repair of it. I have a book: Introduction to the Ferrocement Yacht; by Baugh, Bowen & Kenyon - from Australia. They claim that it shoud not be that difficult to repair Ferrocement.

In this forum is a lot of common sense available, but you need to give your question hands and legs, so to speak and try to give a detailed report of the actual damage; how big the cracked surface is, how deep; is the steel reinforcement damaged too; is the damage through and through or is only the surface cracked.

I will mention some book titles about Ferrocement construction:

Benford, J.R. & Husen, H. - "Practical Ferrocement Boatbuilding" 3rd edition 1972 Internationakl Marine Publishing Company, Camden, Maine 04843 USA

Bingham, B. - "Ferrocement: Design, Techniques, Application" 1974 Cornell Maritime Press Inc. Cambridge, Maryland 21613 USA;

Whitener, J.P. - "Ferrocement Boat Construction" - 1971 - publisher see above.

This is all very old stuff, techniques may have changed and I am certain that there are some people around who know how to set up a structural repair.
For a start, a more detailed damage report would be of interest.



Cairncross, C. "Ferrocement Yacht Construction"- 1973, Adlard Coles, London 1973

 

Another hint: there is a product called "Furan Resin Mortar Grout"No 21 c
made by the Sauereisen Inc. Company, 160 Gamma Drive, Pittsburgh PA 15238;
Google and you will find! It is a modified mortar, specifically suited for ferro-cement repairs.

 

ferro repair

thanks for the quick consideration and reply

Im repairing a 37ft endurance. It fell over on its side where
it sat in the rain for 30 days. When it was picked up the bow pulpit snapped off exposing 1/4 bar with 2 or more layers 1/2 inch square mesh on each side of the 1/4 bar. The hole in the bow is approx 1 ft. in diam. All over most starboard side are many small cracks that you can't see through and 3-5 larger cracks perhaps 1/8 to 1/4 inch wide extending from the deck to the keel. There is a hole in two areas on the side approx. 2 in in diam. that you can put your finger through. The corner where the deck meets the hull is dented in at one spot about 2-5 in. There is an indentation where I suspect most of the weight of the fall impacted the hull. This is about 1.5ft. in diam. Any steel 1/4 bar thats exposed has surface rust. The mesh looks as though it is galvanized. Both seem in relatively good shape. I 'm certain I can weld to the bar.

IN addition to my concerns about what to mortor with I'm a bit concerned about getting the lines right during repair given there is such a large area that has to be repaired.

Any input would be much appreciated. thanks

 

Ai, that is a very considerable damage. Let's see if other guys chime in - contact this Sauereisen Company for further advise. Can you post some pictures? The galvanised mesh is correct - that is always used as a reinforcemnt layer, mostly two or three and rods as kind of frames and stringers. You can weld to it but make sure that it cannot rust any further. Main concern are the small haircracks. If there are so many, the basic structure might have left - personally I would grind them open and repair those haircracks with epoxy mixed with silica - the larger damages I would ask for advise - there are specific epoxy's used for fastening steel bolts / anchors into concrete. I have repaired once an engine-mounting in a ferrocement hull with that specific material. I believe the repair is still holding and the engine vibrates a lot - so the connection might have some strength

 

If you get a grinder with a diamond-dust blade used for cutting tile and cement board you can explore all cracks and widen them to allow the penetration of sufficient patching material. Make sure any powdery concrete is completely removed before patching.

I have restored and repaired many different types of materials. Because a boat hull is convex on the outside and concave on the inside, there is a risk of poorly anchored patches popping out to the outside. The way to prevent this is to have a patch which has surfaces on the inside and outside which are larger than the crack or whole being patched. This approach creates a double-ended plug that cannot be easily dislodged. You might actually grind excess concrete to make a shallow indentation around cracks and holes to assure a .5 cm outer and inner plug thickness.
Think of the finished plug's crossection like an I beam crossection.

I would suggest a mixture of a good marine epoxy, fine sand that has been rinsed with water, dried and well cleaned with acetone, and chopped fiber glass (a bit of carbon fiber wouldn't hurt) which must be completely saturated with thinned epoxy (no air bubbles) before being mixed into the epoxy and silica. This should create a grindable surface to make the surface fair. When mixing the hardener don't mix it too hot or you won't have time to patch inside and out, or else use two people to work the material in and out at the same time.

Before putting the patches in, you might consider painting all hole and crack areas which are to be patched with thinned epoxy to get penetration in the pores of the ferro-cement.

Lots of luck.

 

Thats a genuine, helpful, and nice post, JC.
Refreshing in these parts.
Mike

 

I come from a famous family of ferro cement boat builders in NZ.
We built probably 40 odd yachts of my fathers and my designs and would have been responsible for plastering over 100 craft in the 1970-80s.
Ferro is one of the easiest materials to fix but unfortunately, this is more to do with how good the yacht was built in the first place. Generally you are right to say that you can pound the fractured cement out with a hammer and dolly but care must be taken to not continue the vibration and fracturing of the material further. In saying this, we had best results by cutting the damaged area out and then sand blasting a knit area back into the good hull and reinforcement area so that you can get a tappered joint back onto the replaced steel and mesh.
There is nothing wrong with re plastering with the sand and cement mix but there are multitude tricks as to sand grit, ratio's and pozzolan aditives etc.
The biggest trick is to simply grout (thick plain cement and water) the old edges as you plaster the new coat.
Because the mixture is so strong of 2 parts sand to one part cement, this must be cotinually water cured for 28 days. I used to race these yachts and in fact won a single handed race from New Zealand to Australia.

 

Jonsailor, I believe your advise might be of great importance to bilgeboy since the techniques you are familiar with are unknown to the most of us.
Therefore a more explicit explanation might be necessary.

Jonathan, a diamond disc makes very smooth cuts, and that is just what not is needed - the rougher the surface, the better the repair will hold.