ferrocement

Does anyone know if it is possible to build a small (<18'> ferrocement sailboats? And could one use insulfoam (expanded polystyrene) instead of wire/rods to put the cement over? The insulfoam would stay as part of the hull/deck.

 

NO. You need the steel for tensile strength.

 

I have replied earlier on a similar thread posted by you where you could find a plain answer why your idea doesn't work.
For obvious reasons, ferrocement is a useless construction material for small boat construction, in particular sailingboats.

 

Please read:

http://www.benford.us/scp/12keelboat.html

for J. Benford's discussion on his 12 foot ferrocement keelboat.

 

I have , instead of concrete, used "fer-a-lite", chopped glass and microballoons mixed with a casting resing to create a tough fiberglass version of cement. have more info if needed. Jim

 

Ferro cement construction turned up around 1850 and a few of those old craft are still afloat. By nature it's not the lightest material available and must have a mesh matrix inside to over come the flexible properties of concrete (believe it or not, the stuff is surprisingly flexible) As a result of these limitations there is a cut off point for the practicality of it's use in smaller craft. This is true of other building materials as well and nothing new. When designing small craft (under 30') all attempts should be made to keep the weight down, this becomes a big hindrance when the hull material selection is much heavier then the others available. I've seen 27' ferro designs, but none smaller and this is understandable.

To answer your questions, yes, you can design and build a 18' ferro cement sailboat. It will be burdened with the hull material, but that could be compensated for with other elements of the design. No, you must use a steel mesh/wire/rod in the matrix. It's the nature of the material and the only engineering solution workable currently.

The foam could be used as a plug (mold) for a "one off" 'glass hull though. This is a common way to produce a hull and well within the grasp of a backyard builder.

If truly interested in ferro as a method, read Jay Benford's book on the subject > Practical Ferro Cement Boatbuilding <. It covers the process and the correct way to build light weight ferro hulls. This book is out of print, but I see it from time to time in the used book sellers found on line. It's not very expensive either. Or you can try him at the Benford Design Group or Tiller Publications. Talk to him, he's a nice guy and will set you straight on the subject.

 

Way back in the 1980's I did a short spell with a ferrocement boat building yard in Inverness, Scotland - 'Concrete Afloat', and we produced 'cement' hulls from 15 to 50 feet. A chicken wire frame coated with a mixture of portland cement powder and chopped glass. The main drawback (in Scottish conditions) was finding a day when it was neither 'p*ss*ng' with rain or baking heat. Overcast conditions were perfect, The main craftsman needed for the job was a time-served plasterer to apply the initial coats. However we never had any complaints from our customers (though perhaps they all sank). Ferrocement is a lovely material for shaping fractionally before fully cured, and I believe has a strength and flexibility equal to both 'plastic' tubs and timber ships. (Mind you I am a confirmed timber man myself).

 

Hi,
I own and sail a 33ft Hartley Queenslander ferro cement yacht in southern New Zealand. The boat "Gandalf" was built in 1970 and is still in wonderful order and has sailed the southern NZ waters for most of her life. she is not a fast boat 7.5-8knots under sail but a very comfortable boat to sail... she is 9 tons deadweight with fuel,water and stores aboard.
People say they are cold or have great problems with condensation!!! well we call 25C a very hot day in this area ...usually our temps are below 20C and sea temp 6--12C . In the cabin hull surfaces are coated with a 3-4mm thick fabric called "front runner" we use a small solid fuel stove for heating when it is very cold or frosty. ferro boats are dry boats ,, no leaks other than sternglands, I have worked steel and aluminium fishing boats in this area that are far colder than ferro...
I have read that ferro hulls are impossible to repair...not so at all... I have known of local ferro yachts that have come to grief and have been "beached" and plastered using " Cempatch" on site between tides and refloated and have sailed again and are still sailing for many many years later.
The only real problems I have seen locally with ferro constructin was with the use of pipe as frames... this has not always been successful as rust sets in, due to the airspace inside the pipe... steel bar frames were ok with no problems .. heavy ...no ferro is not as heavy as steel...there are a great number of ferro yachts and boats in NZ... many amateur built.
All most all boats will sink if you fill them with water

regards,

happy ferro owner

check out http://groups.msn.com/FerroCementYachts