Ferrocement Boatbuilding
Everett Collier
updated on what's going on (anywhere in the world) in ferro
construction. In the 1960s and early '70s ferro was really going great
especially in New Zealand and the UK. What happened? Also, I
understand that newer and more promising methods involve tiny steel
fibers that are mixed right in with the cement and then laid on a mold,
something like chopped fiber guns do.
Hopefully I'd like to find someone that is knowledgeable in this area
that I can correspond with via e-mail. Any help would be greatly
appreciated.
Many thanks,
Ev Collier
Glenn Ashmore
Everett Collier wrote:
> <snip>
> Also, I understand that newer and more promising methods involve tiny
> steel
> fibers that are mixed right in with the cement and then laid on a mold,
> something like chopped fiber guns do.
I would be very skeptical of steel fiber reinforcement. Even a little
salt laden moisture would eat it away very quickly. While not a fan of
cement boats, I was fascinated by an admixture that was added to the
concrete for my boat shed. It is a very fine gauge chopped glass fiber
that dramatically improved the tensile strength of the slab. 10 pounds per
cubic yard improved the mix to the point that rebar and wire mesh were not
needed. I was wondering at the time if someone had ever tried to use it in
a glass/cement hull.
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.mindspring.com/~gashmore
Graeme Cook
New Zealand yacht designer Richard Hartley did several ferro-cement designs
and many were amateur built. He set up a system whereby the builders
constructed the loom, then Hartley inspected it, and then sent a plastering
team to apply the cement to several boats in one locality. Many boats were
built in the sixties & seventies; few since. There are still quite a few
around.
Wilf O'Kell, a kiwi who also worked in Australia; and Michael Potgeiter, an
Australian; and Bruce Roberts of mail order plans fame, also did many stone
boat designs.
You might like to look at resale values of stone boats, their common name
in Tasmania, versus the resale of comparable glass, wood or steal boats.
You also might like to talk to some insurance companies - some refuse to
cover stone boats, others apply large premiums and excesses.
Finally aluminum producer Comalco did some experimenting in Australia in
the mid-70's with aluminum looms and light weight concrete (some sort of
foaming process. I think). They burried the project around 1977 or 1978 -
possibly after realising the effects of electrolysis.
Haven't heard of the steel fibres technique that you mention - thought he
big problem of keeping moisture out of the steel, and consequent rusting,
would still remain if not be enhanced.
Hope your researching is fruitful.
Graeme
Everett Collier <us01...@ix.netcom.com> wrote in article
<35DAE102...@ix.netcom.com>...
> I am writing a book under contract to McGraw-Hill and am trying to get
> updated on what's going on (anywhere in the world) in ferro
> construction. In the 1960s and early '70s ferro was really going great
> especially in New Zealand and the UK. What happened? Also, I
> understand that newer and more promising methods involve tiny steel
> fibers that are mixed right in with the cement and then laid on a mold,
> something like chopped fiber guns do.
>
LBRTY4US
<gra...@netspace.net.au> writes:
>You also might like to talk to some insurance companies - some refuse to
>cover stone boats, others apply large premiums and excesses.
Are you aware of an outstanding failure record in yachts that justifies their
stance? Perhaps their concern is the issue of damage repairs.
There is much commercial experience with ferroconcrete in barges, and the major
classification societies have a lot of information & lessons-learned, with
issued guidelines for its use, though I've been away from that arena many years
now. While not directly applicable to yachts, I recall that ABS had a manual
for ferroconcrete construction to Class. As they occupied the two floors above
my office, I saw a lot of things there when I would go up to argue with them
about more costly matters.
I, too, wonder where ferrocement yacht construction has/hasn't gone in present
times. In the early '70's, I built a ferrocement hull with the help of two
retired plasterers and a large beer budget, but the boat was a failure for
other reasons and was never completed or launched. Galvanized #2 rod,
hot-dipped 1" x 2" rabbit wire, chicken wire, & very sharp sand. A light
sledge applied to the beam bounced right back at you - this was the only thing
that quelled the jeering neighbors.
There are some general developments one might consider (?):
- there are many other critical applications of concrete over steel wherein
corrosion is a major concern (bridge decks, parking garages in salted climates,
reinforced concrete decks over chlorine-laden swimming pools, etc.), and
various publicized catastrophies over the past couple decades have occurred due
to corrosion. Steel is now almost universally epoxy-coated in such
applications.
- concrete coatings technology has come several light-years as well, including
(but not limited to) solvent-carried compounds which form protective silicates
with the free (unhydrolized) calcium to give imperviousness to water,
infrequently renewed. Spray-on curing compound/sealers are also very helpful,
both for cure and finish. Sonneborne is one leader in this line in the USA.
- concrete additive chemistry has done the same, and the array of
properties-changing chemicals (plasticizers, air-entrainers, cure modifiers,
etc.) available to heavy industry is impressive. WR Grace has enough info on
these things to scare you, though they are not commonly available in small
quantities to the average Joe, and it is unusual to find anyone at your local
'crete plant that has any sophistication about them, except some of the more
common ones. The plasticizers, in particular, add workability while keeping
the water content very low (as little water as possible is essential for final
strength in any concrete), though used alone they reduce working time. Typical
plasticizer will make a 3" slump mix act like 10" (diarrheah), so that it will
flow into all voids.
- I've never heard of steel fibers in 'crete (how do they last more than a week
during the cure?), but polypropylene "fibermesh" is everywhere now, and adds
great elasticity to monolithic steel/concrete. The "hairy finish" it gives is
readily alleviated by using high-solids curing compound. FWIW, when the 4"
reinforced, radiant-heated slab of my own house badly frost-heaved during
construction, my transit showed it to be curved 4 1/2" in the space of 16'. It
was a 4000 psi mix that had been properly placed at 3-4" slump (the samples
broke at 7200psi). There was not even a hairline crack anywhere. Covered with
insulation board & heated for a month (due to the insulation under the slab,
and at agonizing cost with a jury-rigged water heater & pump in -20F weather),
it settled to within 1/8" of original position, still without so much as a
hairline from the movement or thermal stress. Despite the already high
resiliency of a thin ferrocement hull, I'd put fibermesh in it if I had to
steal it after this experience.
- Sprayable concrete (Gunnite) has likewise come a long way - talk with a
knowledgeable in-ground pool contractor.
Lacking further insight so far, I'd venture that some builders who have thought
through the placement, location & securing of the steel along with application
of the 'crete, may have concluded that a welded steel hull might not comprise
much more effort and total expense. You can fix it, too.
Michael Edelman
only a fraction of the cost of a large boat, the savings of ferrocement just aren't
worth it for most boats- although barges would be economical. As an amateur method,
it requires too much skill.
--
Michael Edelman http://www.mich.com/~mje
Telescope guide: http://www.mich.com/~mje/scope.html
Folding Kayaks: http://www.mich.com/~mje/kayak.html
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Mel Haylock
>
> Hi Everett
>
>
>
> Wilf O'Kell, a kiwi who also worked in Australia; and Michael Potgeiter, an
> Australian; and Bruce Roberts of mail order plans fame, also did many stone
> boat designs.
>
Most of the cement boats I have seen on the water were Sampson Marine
designs. Sampson model names typically begin with a "C", as in "C-spray,
C-witch, etc. I believe most Sampson designs were amature-built. In
spite of the doom and gloom you will hear from many people, there are a
number of well-built, well -maintained ferrocement boats currently on
the ocean. I believe a large part of their bad reputaion stems from the
many uncompleted (abandoned) and quick-built hulls out there.
BTW An excellent book is "Ferrocement Boats" by Bingham.
Mel Haylock
Graeme Cook
The evidence I have is anecdotal, from friends who bought stone boats and
then had to rush around trying to arrange insurance.
Thanks also for a great letter - you have given a technical insight to some
of the issues that I had seen from a lay perspective.
Although I have no real evidence, I suspect the insurance companies'
reserve towards stone boats is due to:
* number of poorly built amateur built vessels,
* dificulty in assessing condition of loom,
* proneness to "jack-hammer" self destruction, and
* difficulty of some repairs.
I sent a more detailed personal response to Everett Collier and, in view of
your comments, will post it when I return to my home computer.
Fair winds
Graeme
odd...@my-dejanews.com
Mel Haylock <Mel_H...@nt.com> wrote:
> Most of the cement boats I have seen on the water were Sampson Marine
> designs. Sampson model names typically begin with a "C", as in "C-spray,
> C-witch, etc. I believe most Sampson designs were amature-built. In
> spite of the doom and gloom you will hear from many people, there are a
> number of well-built, well -maintained ferrocement boats currently on
> the ocean. I believe a large part of their bad reputaion stems from the
> many uncompleted (abandoned) and quick-built hulls out there.
A friend of mine built a 42" Samson ketch, and it is a a fantastic boat, realy
beutiful, and sails nice. He once was in 55 knots wind (meashured on a nearby
lighthouse) with jib and and a very reefed mainsail, was thinking of lowering
the jib, but did not dare to do it, the sail was as hard as the hull..
He used 3 years for the hull, and 9 years for the rest, and is now sailing
around the world...
BTW Jay Benford also has some plans for stone boats...
--
Odd Goderstad, Oslo, Norway
http://www.geocities.com/CapeCanaveral/Hall/4679/boat.html
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Graeme Cook
construction of a strip plank composite hull, or a wood cored glass hull,
depending on which school you subscribe to.
I commend every one to visit with him.
Graeme
Graeme Cook
"...Ev
I have never owned a stone boat although a couple of friends have, and I
was prevented from buting "Analani" by an uncooperative banker. Thus my
views are second hand.
All the boats I have seen being built have used either galvanised "chicken
wire" or galvanised woven square mesh, plus galvaniseed ties onton
galvanised frames and stringers. A few have used stainless tie wire.
I think all have used some sort of water proofing agent in the cement, but
I do not know the details.
In addition the outsides of my friends boats have been coated below the
waterline with a rubberised or epoxy compound.
All the boats periodically have spots of rust appearing on the topsides,
and they routinely touch up with rust killer and an epoxy waterproofing.
I am not sure if these rust spots are simply common rust at imperfections
in the galvanising in the loom, or if it is the result of electrolysis
action in the metal. Both the zinc in the galvanising and the iron/steel
in the mesh are quite low on the nobility table and thereby prone to
electrolysis attack if moist and there is any stray micro-currents around.
The big danger is that the strength of ferro-cement comes from the
interaction of the loom and the cement and the loom is permanently burried
deep inside the plaster. It is thereby impossible to inspect the loom
directly, and one cannot be sure if insidious corrosion over time has
robbed the hull of its strength.
The second major problem with ferro-cement comes from the effect of severe
repetitious hammering on the hull. I think I can illustrate this effect by
saying that if you belt a piece of concrete with a hammer then the hammer
bounces off, but if you apply a jack hammer then the concrete crumbles
quickly.
If a stone boat hits a reef hard then it basically bounces off possibly
leaving an "egg-shell" fracture which can be easily repaired. However, if
it remains on the reef, bouncing up and down with the sea, then it very
quickly "jack hammers" itself to pieces. Its initial strength is much
stronger than other materials (except steel) but the dissintegration rate
is frighteningly fast - much faster even than wood.
"Analani" was designed and extremely well built by Wilf O'Kell as a
showboat when he moved his operations from New Zealand to the larger market
of Australia. When I looked at her she was five or six years old and in
as-new condition. She was a 40ft, heavily rigged ketch. About twelve
months later she hit a coral reef near Thursday Island, Northern Australia,
and was a total wreck within 30 minutes. Subsequent diving showed that the
cement plaster had been shaken from the loom over that section of the hull
that was in repeated contact with the coral.
Some concrete boat design books are:
Samson, J and Wellon, G, "How to buils a Ferro-Cement Boat" (Samson Marine
Design Enterprises, BC, Canada, 1968)
Hartley, R, "Ferro-Cement Boat Building" (Broughton HousePrinting, New
Zealand, 1972)
Jackson, GW, and Sutherland, WM, "Concrete Boatbuilding" (George Allen &
Unwin, London, 1969)
All these books were published when ferro-cement was regarded as a new
wonder product, and before its shortcomings were becoming obvious.
Also, all the publications emphasised the cheapness of ferro-cement. They
overlook the value of the builders labour (assumed zero value !!), and they
ignore the fact that for a blue water craft the cost of the hull rarely
exceeds 15 - 20% of the cost of the finished vessel. Fit-out, machinery,
rig, sails and electronics cost the same irrespective of the hull, and a
low cost hull does not make a big difference to the cost of the completed
boat. But its resale value can vary very materially. A false economy.
Stick with your research.
Graeme "
LBRTY4US
<gra...@netspace.net.au> writes:
>Sorry LBTY4US
>
>The evidence I have is anecdotal, from friends who bought stone boats and
>then had to rush around trying to arrange insurance.
>
>Thanks also for a great letter - you have given a technical insight to some
>of the issues that I had seen from a lay perspective.
I do not merit these words. I am a former sophisticated marine industry
professional and have my own sailboat experience, including a very
over-protected singlehand crossing with all my powerful industry resources of
the time watching over me, and plenty of more recent time in a small yacht with
very young children, but I do not know *diddly-squat* about competent hands-on
construction of yachts - this is why I read this conference. I try to bring my
other related knowledge to the discussion in a suggestive capacity, to the
extent that big-ship knowledge may relate to boatpeople (for the two seldom
communicate as professions) and your anecdotal and hands-on knowledge is likely
more valuable and insightful in many areas than mine and my few humble boat
dabblings to date. Were it a welded steel ship with shell expansion dwgs, this
might be reversed. Think of me like a trained builder and operator of tall
skyscrapers responsibly wielding investors' millions, trying to learn how to
build a small house alone & frugally with one's own money and hands that will
survive the same hurricane with different materials & methods (though I did the
latter with my house).
Beyond this, I am still wondering how one effectively repairs a ferrocement
yacht hull - seem like a nightmare to me (restoring integrity of the matrix),
and damaged ferroconcrete barges have been scrapped for this very reason,
though they were not built like yachts. I though this might bear on the
underwriting question.
In the anecdotal department, the most important use of concrete (not cement -
that is the ingredient of it that comes in the sack) at sea is to effect
interim repairs to cracked or wasted *steel hulls*. :-)
I though your comments about galvanic action were insightful, since concrete is
very hygroscopic and a good electrical conductor no matter what you coat it
with, though it is unclear to me if/whether the zinc ions will migrate through
the 'crete or what actual experience has been. This might strenghten the case
for epoxy coating of the loom for the determined ferroconcrete builder.
Regarding the lesson of pounding destruction in a stranding, without further
insight and given the properties of the material sections, one might speculate
whether anything less than framed steel would fare better, no?