Ferro-cement yachts?

[Boo2]

One thing I've sometimes wondered about is the life of the armature; it just has to rust, and salt water will get to it somehow...

Aiui, the cement provides an alkaline environment and prevents the armature from rusting.

Boo2

 

[Seajet]

Aiui, the cement provides an alkaline environment and prevents the armature from rusting.

Boo2

Thanks, but I don't think I'll be trusting my money let alone crews' lives on an old example...

 

[vyv_cox]

Aiui, the cement provides an alkaline environment and prevents the armature from rusting.

Boo2

That's a very good point that I had never considered previously. Boiler water is dosed to give a pH of about 10 to control corrosion. Steel corrosion is almost non existent at this value.

 

[rogerthebodger]

That's a very good point that I had never considered previously. Boiler water is dosed to give a pH of about 10 to control corrosion. Steel corrosion is almost non existent at this value.

That is true but my old ferro boat suffered from galvanic corrosion. What was never considered was that if sea water does get to the steel armature it can suffer like mine did due to no anodes connected to the steel armature.

There are also migrating corrosion inhibitors that protect the rebar available now like this

http://www.contechuk.com/concrete-repairs/migrating-corrosion/

 

[penfold]

There's quite a difference between the old concrete lighters and the 70s/80s ferrocement, though.

Pete

I appreciate that but it illustrates how slowly ferro deteriorates, even with no maintenance and being washed by the tide twice a day. The durability of the material is evident, even if the construction details differ.

 

[CAPTAIN FANTASTIC]

Design and construction of a composite material structure is always more difficult. Therefore, a ferro-cement boat has to be designed and constructed correctly. Steel and cement can be designed to complement each other and to provide the correct stiffness and flexibility necessary for a hull.

Catastrophic failures of ferro cement hulls should be impossible due to the steel reinforcement; however, construction techniques will determine integrity. I would not invest my money on a ferro cement boat because of the uncertainty of its construction; unless I was to build it myself.

 

[BrianH]

There used to be a firm building ferro-cement boats on the East Coast.

One model built was the Endurance 35 (Peter Ibold design) that was chosen as 'Boat of the Show' at Earls Court back in the 1970s. It had been bought by a new member of Whitby Yacht Club when I was a member there. He intended to sail it north to Whitby on its maiden voyage.

Construction, if properly done, must ensure that following the finished armature, cement is poured in one session from inside, vibrated through the steel frame and mesh to ensure no voids and finished by a team of expert plasterers to get a smooth, external finish with sufficient layer coverage of the steel to avoid later rust leaching out. The main trouble is that even with professional construction, you're never going to know if the correct procedure has been followed without a destruction test. The Endurance 35 bound for Whitby became exactly that. One nautical mile short of Whitby harbour entrance, on a falling tide, she went aground on the flat scaur rocks to the east of the entrance due to faulty navigation and poor visibility.

This need not have been a problem, she would have re-floated on the flood but the change of tide brought a strong on-shore wind. Pounding on her bilge she soon pulverised that area, started leaking then breaking up and the owner swam and waded ashore, no longer a boat-owner.

I walked out to the wreck a few low tides later, and idly picked up a complete fragment of the topsides, torn away in its entirety from between the steel ribs, both external to internal skins - they flapped open and closed, hinged on the mesh, there was no bonding whatsoever between them, the hardened internal cement surface could be seen on both inner and outer sides. They had clearly been separately applied, from inside and out, instead of the necessary forcing through from inner to outer for no voids to form.

There's nothing wrong with a properly constructed ferro-cement boat, for as they say, it's really a steel boat with cement to keep the water out. But how to know if it was properly constructed?

 

[TQA]

Worth looking at the for sale section on this site http://www.ferroboats.com/

Lots have sold ! Some at fair price too !

 

[fishermantwo]

This is timely, here's a few random links:

http://www.ferroboats.com/
http://www.boatdesign.net/forums/boat-design/pictures-my-ferro-boat-advice-sought-15838.html
http://www.cruisersforum.com/forums/f47/cement-boats-4128.html
http://members.shaw.ca/petersfreeman/sports/sailing/sailing.htm

I've just bought a ferro hulled boat in Greece, she's a Hartley RORC 32, on the small side for ferro hull, she weighs about 8 tons. Mine was professionally built in 1978, has had a total refit that was completed in 2007 & for what I paid I couldn't come anywhere near a boat of the same standard of equipment & fitout in fibreglass. You'll have to accept that insurance will be difficult to obtain, FC virtually impossible so effectively you need to be prepared & able to self insure your own boat. On the test sail before I bought mine I didn't have a clue what to expect of the sailing ability of an 8 ton 32 footer but was pleasantly surprised, she will not win races but will I think make a good cruiser & liveaboard. The last of the links above includes the tale of a guy who sailed a Hartley RORC 32 weighing in at 20,000lbs (9 tons) around the world non-stop in a then world record time, so they can sail, even the little ones...

View attachment 31514

Lovely boats. My mate has the 38 foot Hartley RORC and it also sails really well. Trouble is no one seems to be aware that these boats are ferro. I have seen yachts up on the slips and passers by refuse to believe they are ferro. In my home port ferro vessels outnumber fibreglass! They range from a 50 foot staysail schooner down to a 30 foot motor boat, 3 of the boats are motor boats, one a game boat and one is a fishing trawler. The fishing trawler has rust streaks and looks like a ferro boat but the others don't.
Helsal, the floating footpath even won a Sydney to Hobart race!

 

[Sybarite]

Ferro-cement boats are made with cement, not concrete.

The 'Ferro' in ferro cement is important - it overcomes the brittleness of the cement. Cement is good in compression; steel good in tension. The two work in tandem to produce a solid hull.

Ferro is very tough - certainly not 'vulnerable' to impact failure. I'd much rather be in trouble in a ferro boat than a grp one.

Buying is cheap and selling is always difficult. There are too many 'bad' examples around that de-value the 'good' ones.

Insurance can be obtained through Yachtmaster Insurance in suffolk.


As for advice in buying one? Seek out one built in the 70's / early 80's - as this is when ferrocement boatbuilding was in it's heyday - and there was plenty of experience around. Also, if it's lasted this long - then you can be sure the hull itself is sound.


Here's an interesting thought - Ferrocement is less dense than GRP...

Two advantages :

Easy to repair in case of damage
It's a material that actually gets better as it gets older.

However, for many reasons I wouldn't ever envisage one. It's difficult enough to sell a 'standard' boat these days without goung out on a limb.

 

[fluffc]

Concrete is a mix of cement and aggregate(inert granular material). I've no idea what mix is was used for ferro-cement boats but would be very surprised if it was 100% cement - the heat of hydration would be enormous and would cause a lot of cracking when it cooled down.

The mix for FC boats contains no agregate - it is a strong cement/sand mix.

 

[TiggerToo]

Here is a pretty example:

http://www.jryachts.com/boat-details?boatid=187812

 

[vas]

The mix for FC boats contains no agregate - it is a strong cement/sand mix.

no offence, but this statement is slightly contradictory, as sand IS an agreggate as far as concrete is concerned.

No idea on ferro boats, but as an engineer, have seen LOTS of concrete frames of buildings by the sea in extremely sorry state after as little as a decade.
I find it difficult to accept that the pH due to cement will be enough to avoid rusting of the armature.
Yes concrete becomes stronger as it ages (trying to open two windows on my '57 vintage home concrete walls was a nightmare!) but stressing/flexing/bumping will inevitably create cracks that will get the steel frame going...

cheers

V.

 

[Bobobolinsky]

One thing I've sometimes wondered about is the life of the armature; it just has to rust, and salt water will get to it somehow...

A lot depends on how well the hull has been painted. Steel reinforcing is protected by the cement. In seawater immersion or atmosphere, the cement slowly changes to a less protective state (Chloridation) Eventually the steel corrodes and spalls the cement, blowing it off and exposing more steel to corrosion. Initially a ferro cement hull will show signs of cracking with rusty dribbles. If that is obvious, run for the hills.

If a good impervious paint coating is applied, though I have seen hulls with epoxy coating and bi-directional cloth, a good chlor rubber (Swimming pool paint)coating will slow or totally prevent the changes in the cement.

There are some examples of Roman and Post Roman concrete, still standing today as well as Renaissance domes.