Why Ferro Boats Have A Bad Reputation

Ooops, sorry about my wrong terminology!
Agreed totally that you do need a very high steel to cement ratio to give it strength - so much so, that if building new today, it is worthwhile investing in some more steel, and building the whole hull from steel one time.

The boat that was written off here after coming ashore had been well constructed in South Africa by a mason who 'knew his stuff' alright - she was a lovely boat. I had a survey job on her after she had been salvaged, and I was quite amazed / horrified at the beating she had taken. Yes, she probably could have been repaired, but it would have been a very big job - most of one side would have had to be renewed, and there were cracks on the opposite side as well.
In addition, the Owner / Builder didnt have the time or inclination to tackle this, after having spent 5 or 6 years building her 15 years before in South Africa. And even though she was virtually offered to anyone who would take her (for the salvage cost of the equipment), there were no takers.

Coincidentally, the single chine ply epoxy boat that came ashore on the same beach was also built in RSA - she is a 37' Robert Tucker design with a deep fin keel (bolted on) and a cantilevered spade rudder (no skeg). The rudder stock broke and she sustained a couple of holes in the hull, but other than that it was not an awful lot of work to get her back in commission again.
 
When I restored my wooden boat in Totnes a few yrs ago there was a yacht hull that had been converted and was used for fishing under sail. When you rapped the hull with your knuckle it literally rang like a bell. She was concrete and just hearing the way the hull rang totally changed my opinion of this method of construction (if done properly). I think like others that the large number of poorly executed homebuilds has unfairly given them a bad reputation. Mike
 
This has turned out to be a very interesting thread, which was my intention all along.
Thanks to all for the input.
I'll be taking close-up pics of my hull when I get there.

Cheers!
 
hm, the concrete itself is not the structural material - it is the STEEL inside that gives the strength and the aim is to make a structure that is predominatly in compression. Now, under compression, steel is not bad - until a certain point where the steel kinks over. But surrounded by a bunch of concrete this point is delayed massively, and strength dramatically enhanced.

My personal view is that steel reinforced concrete (or more correctly concrete restrained steel mesh) is not an ideal choice of material for a boat - the potential strength is vast but then so is the weight. Steel or aluminium gives easily the strength needed such that the hull won't fail, together with better integration of bulkheads, less weight, and easier (visible and accessible) verification of hull condition.
 
I was sitting off a sandy beach on the south coast a few years ago when a ferro boat ran ashore (on purpose) and two guys set about beating a hole in the hull, cleaning it up and "priming it" and then making it good! they were back to sea on the next tide. the day before yesterday a large FC boat was lifted in the yard and the bottom cleaned and antifouled and the topsides painted! it was back in the water in about two hours all togeather! so it would seem that FC hulls are not too demanding when it comes to Maintenence and repairs. Isnt there a reef in NZ where many boats have run aground and the FC hulls last the longest before break up? do I remember correctly, a post appertaining to this?
 
The cement IS VERY MUCH part of the structure, as is the steel. It is BOTH that combine with the relative merits to produce a sound hull.

NB! Concrete is not used in the construction of ferro-cement boats, as this contains agregate. (SR) Cement, sand and water is all that is used.

Ferro-cement is, in fact, less dense than glassfibre.

The thickness of a ferro hull is typically less than 1". And 3/4" & 1/2" are not uncommon.

The weight of a ferro boat is fairly similar to a traditional frame-built wooden boat of the same size.

Steel and Aluminium are acceptable for boat construction, but both require a lot more skill to produce a good boat than FC construction. Quicker though.

Steel corrodes by rusting. The steel in a Ferro Hull is encased in cement, and so does not rust. I have seen this for myself.
 
In the process of repairing a 1970's Hartley 48ft

[ QUOTE ]

The steel in a Ferro Hull is encased in cement, and so does not rust


[/ QUOTE ]

In theory yes , in practice due to small cracks in the concrete No. This is either due to cracking during curing or by small dings during use allowing water (seawater) to get into the reinforcing and cause corrosion either by rusting (oxidiation) or as in my case by having no anodes on the structure which allowed cathodic corrosion.

I have several areas where the steel reinforcing has corroded away without rusting. I have an area approx 1m x 1.5m where the reinforcing has disappeared I know this is not by oxidiation (rust) as the volume of the reinforcing increases by a factor of about 11 dur to rusting which would crack the concrete and causing rust bleed. In my case no rust bleed just reinforcing disappearing.

This can now with the moden epoxies be solved using the techneque as used on wooden boats with the "west system"

I have also found a product used in the repair of reinforced concrete bridges and other structures that will coat the steel with a corrosion protection coating by migrating through the porious concrete and surounding the steel bars.

I have not used this yet but have seen several structures done this way and it looks sound

I plan to use this migrating corrosion inhibiter then seal inside and outside with west type epoxy following the replacement of the corroded reinforcing.

I will then weld anode connection studs to the mesh as is done for steel boats. There two technequics should protect from both kinds of corrosion.

[ QUOTE ]

Steel and Aluminium are acceptable for boat construction, but both require a lot more skill to produce a good boat than FC construction. Quicker though.



[/ QUOTE ]

Depends on your method of construction. If round bilge more skill is required for steel or aluminium but for hard /multi / strip chine I dont think alot more skill is required. The skills requires is welding for steel / aluminium and good plastering skills for ferro construction.
 
Sounds like you've got some very serious structural problems there, inherent from the build. IMHO scrap the hull :-(

But on the other hand, FC construction lends itself to creative repair techniques :-)
 
Plan is :-

New steel yacht to cruse Indian Ocean OZ, south east asia and Pacific Islands when retired and put ferro in KZN yacht club as base then sell house, busness. other goods and property, invest results to provide income to go crusing in next 2-3 years
 
[ QUOTE ]
But on the other hand, FC construction lends itself to creative repair techniques :-)

[/ QUOTE ]

A mate of mine repaired his FC hull and included the ashes of a late pontoon neighbour in the patch. /forums/images/graemlins/laugh.gif
 
Re:- the repair done by the guys I mentioned above (Their reinforcing mesh had erroded away due to "electrolitic action") was made by replacing the steel mesh to a slightly larger area and then rendering with a quick drying Ferro cement. the inside was a little lumpy as it seemed to have to be a little thicker than the original hull but the outside was a fair finish which they said they would "epoxy fill" smooth at some later date!
 
[ QUOTE ]

The steel in a Ferro Hull is encased in cement, and so does not rust


[/ QUOTE ]

As an hartitect and therefore not qualified to venture an opinion on such matters without my tame structural engineer to hand, I also insisted/expected (rule of thumb) on at least 25mm of concrete cover over the steel reinforcement. I guess this probably has a lot more to do with frost/freezing protection and spalling prevention, but I am surprised to hear how thin FC hulls can be. Didn't realise that. But of course, concrete contains aggregate, which these hulls don't. Nevertheless . .
 
The cement mix is generally 1 part cement 1.5 parts dryed graded sand amd 0.5 part water which makes a very stromg mix
My hull is average 25 mm thk but the deck can be 20mm thick to keep weight down.

Covering over rebar is 3 mm approx.

Don't get much frost in the tropics


As an architect do you know of Cortec who do repair products for concrete structures and do you have any comments.

info http://www.cortecvci.com/index2.php
 
Cortec?
Unfortunately not. a) They seem pretty American and my experience is UK-based b) Never was much into this kind of deeply structural hoopla (know my limitations and recognise the expertise of other professionals) c) Haven't practised architecture, as such, in anger, for about 15 years.
However, they cite SBD on their website (although no link), who are part of Weber(+Broutin) and who were one of our regular (marketing) clients (before we sold up and sailed!).
Gawd knows if any of this makes any sense or is in any way helpful, which it probably isn't.
 
I've got an Endurance built by Windboats, and a lovely thing she is too. Strong and seaworthy, although at present a bit of a nightmare as we're trying to finish an epoxy/coppercoat/repaint topsides job that we started in August expecting to take 6 weeks /forums/images/graemlins/crazy.gif However once it's done she'll be nearly ready for the grand move aboard in March.
Incidently, before we found her we looked very seriously at the boat now owned by CodStewart. We thought she was absolutely brilliant, but sadly since our plans at the time involved bringing her back to Europe, the wonderful burocracy put paid to that. /forums/images/graemlins/mad.gif
Glad she found a good home!
 
That's nice to hear. Folks down in Mexico think she's a good boat, too. She deserves to spread her wings and go for a good old voyage.
I'll make that dream come true for her.
/forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
 
You must log in or register to reply here.

Other threads that may be of interest

Y
The Seafarer 700 and NASA clipper sounders saga
Replies
10
Views
432
Dellquay13
Dellquay13

Share this page

Top