Ferrocement canal boats.
jim smith
canal craft? Is it because it isnt strong enough? Jim
Mike Stevens
news:3A5776FA...@which.net...
> This may be a silly question but why isnt ferro cement used to build
> canal craft? Is it because it isnt strong enough? Jim
It has been. There were some working boats (butties IIRC) at one stage,
one of which was at the National Waterways Museum when I was there nearly 5
years ago. But it was in a pretty poor state and IIRC the accompanying
blurb indicated that their shortcoming was that they weren't very robust.
And there used to be a ferrocement pleasure boat moored just below Cowley
lock. I'm bit sure whether it's still around.
--
Mike Stevens, nb Felis Catus II
No man is an island. So is Man.
Off-list replies, please, to michael...@which.net
Web site http://www.mike-stevens.co.uk/
David Long
Stevens <mike...@which.net> writes
>jim smith <james....@which.net> wrote in message
>news:3A5776FA...@which.net...
>> This may be a silly question but why isnt ferro cement used to build
>> canal craft? Is it because it isnt strong enough? Jim
>
>It has been. There were some working boats (butties IIRC) at one stage,
>one of which was at the National Waterways Museum when I was there nearly 5
>years ago. But it was in a pretty poor state and IIRC the accompanying
>blurb indicated that their shortcoming was that they weren't very robust.
>And there used to be a ferrocement pleasure boat moored just below Cowley
>lock. I'm bit sure whether it's still around.
>
site of one of the Fiddlers Ferry locks from the Sankey, I'm a bit of an
expert on concrete barges. Eventually they'll appear on our website...
keep tuned in top this station for news.
There are WW2 examples used as mooring bases on the Thames at
Westminster.
Rumours as to their robustness are not well founded - some WW1 examples
are still afloat too.
--
David Long
Sankey Canal Restoration Society
http://www.scars.org.uk/
Updated November 2000 - New: *Illustrated* Edition of Newsletter
jim smith
David Long wrote:
--
112 Rochdale Road
Greetland
HALIFAX
HX4 8HR
ENGLAND U.K.
Philip Dumelow
> canal craft? Is it because it isnt strong enough? Jim
It's not silly, the answer you suggest is along the right lines. A concrete
mix can easily be designed to withstand the compressive forces likely to be
encountered by a boat, however concrete's strength in tension is only about
one tenth of its compressive strength. So to avoid a massively thick section
(hull) to resist tensile cracking the structure (boat) would have to be
designed to include steel reinforcement bars (rebars) which carry the
tensile stresses - hence reinforced concrete or ferroconcrete as it used to
be known.
Generalising, most tensile stress is experienced close to the surface of a
body, thus rebars are secured so that once the concrete has been poured into
the mould, there will be about 50mm between the surface and the rebar. This
distance - known as *cover* provides protection for the steel rebar from the
elements.
This is fine for reinforced concrete used in fixed structures (eg bridges),
where movement can be accommodated by specific joints between the elements
of the structure as it is built. The individual elements are, within small
tolerances, rigid. Sooner or later the stresses to which a moving narrowboat
is subjected - particularly the loading of a working boat (or when your
father in law decides at Factory Junction that he doesn't like Telford's
route & wants to make his own - sorry Ken!) - would cause these tolerances
to be exceeded, resulting in surface tensile cracks. It would then be a
matter of time before the crack propagated to the rebar allowing water /
oxygen to the steel. Result: lumps of your concrete hull pinging off into
the cut under the expansive force of the ensuing rust (to witness this
process check out just about any multistorey carpark built in the '60s,
though in these cases moronic design, cruddy workmanship & appallingly lax
inspections created the conditions which allowed rusting to take place).
The need to include rebar could be overcome by using mass unreinforced
concrete in a thick hull section. I've seen a concrete butty at either
Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
inches thick & it was formed into 2 or 3 compartments by stiffening
bulkheads. I believe it was broad beam.
A 70 ft narrowboat built like this would weigh about 43 tonnes - more than
twice the equivalent in steel. Furthermore, the increased hull thickness
would decrease the hold volume by about 30%: this effect would reduced in
broader beams.
An alternative to using rebar or thick hulls would be to incorporate
stainless steel fibres into the concrete mix, a technique used in
tunnelling: however these are expensive & come with their own technical
problems. Likewise, epoxy coated rebar is an expensive solution & durability
couldn't be assumed for this purpose. However, all technical problems can be
overcome, although I suspect that the cost of constructing a one off mould
would be prohibitive.
Horses for courses: keep concrete for bridges & wood, steel & (yuk!) GRP for
boats. Having said that, I'd be fascinated to know if any boatbuilder has
considered a concrete hull.
Philip G Dumelow
p...@waitrose.com
Mike Stevens
news:J3NV5UAz...@cableinet.co.uk...
> There are WW2 examples used as mooring bases on the Thames at
> Westminster.
Yes, indeed. I believe those particular ones are "leftovers" that were
built for Mulberry Harbour and were surplus to requirements.
David Long
<james....@which.net> writes
>Thats interesting. What about pleasure narrow boats rather than Barges? Jim
>
at Grappenhall on the Bridgewater. It wasn't very pretty.
Concrete boats were built at times of steel shortages during the Wars,
but they weren't that much cheaper to build than steel craft - so once
steel was available again, they stopped making them.
There was a fad of building sprayed-on concrete yachts a while ago, and
I think one-offs are still made by amateurs.
One key factor is the simple fact that the price of the hull is a
relatively small part of the cost of a boat, and people will play safe
(especially with a mind to re-sale values) and go for what is most
acceptable - steel or fibreglass.
HowardAng
the fad that David Long has mentioned, but they have now largely fallen out of
fashion. The main reason has been that once water gets into the steel iterior
mesh it is very difficult to eliminate and usually the first exterior sign of
something wrong is when bits start to fall off!. This is especially worrying in
areas such as the rudder, stern gear etc. and by then it is too late to carry
our any first aid.
As for use as a canal boat, the downsides have already been mentioned. The only
thing in its favour is that it is very easy to repair non-major damage - just
mix up a batch of cement and plaster it on!
Regards
Howard
timleech
wrote:
>
>jim smith <james....@which.net> wrote in message
>news:3A5776FA...@which.net...
>> This may be a silly question but why isnt ferro cement used to build
>> canal craft? Is it because it isnt strong enough? Jim
>
ISTR there were quite a few built in the 1960's, some for use as hire
craft. I think they were rather prone to having holes knocked through
them.
I can't remember what sort of reinforcement was used, if any.
Probably no cheaper to build today than steel hulls, and you will
have potential problems with sealing a superstructure of different
material (steel, timber, or GRP) to the hull. Anyone for a concrete
cabin ? <G>
Cheers
Tim
Tim Leech
Dutton Dry-Dock
timl...@dutondok.u-net.com
Traditional & Modern canal craft repairs
Paul Jerome
"HowardAng" <howa...@aol.com> wrote in message
news:20010107040022...@ng-cu1.aol.com...
We had a member of the sailing club construct his own concrete yacht some
time ago. As a do it yourself project it is probably easier than steel. Mind
you, he was an expert plasterer!
Paul Jerome
Peter Brown
>> canal craft? Is it because it isnt strong enough? Jim
>
>It's not silly, the answer you suggest is along the right lines. A concrete
>mix can easily be designed to withstand the compressive forces likely to be
>encountered by a boat, however concrete's strength in tension is only about
>one tenth of its compressive strength.
My elder daughter lived for a few years with a chemist working for a
concrete company. He devised a concrete ideal for ship decks in that it
was flexible. Unfortunately, when he did a trial, he found it was
soluble in water.
He wasn't much good at steering a narrowboat either.
--
Peter Brown
Martin E Phillips
writes
>Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
>inches thick & it was formed into 2 or 3 compartments by stiffening
>bulkheads. I believe it was broad beam.
There is indeed a concrete widebeam barge outside the NWM at Glos Docks.
There are also a few pictures of large WW1 concrete barges (1000 Te or
more) being built and launched in Hugh Conway's book "The Gloucester &
Sharpness Canal".
Wassail!
--
Martin E Phillips nb Boden, Splatt Bridge
http://www.g4cio.demon.co.uk
Homebrewing, black pudding, boats, morris dancing, ham radio and more!
fofol
>This may be a silly question but why isnt ferro cement used to build
>canal craft? Is it because it isnt strong enough? Jim
Over here in France they were and still are often used as working boats, for
exactly one reason : because they're cheap. But they only have an average life
of ten to fifteen years, so better never buy one used to transformit into a
pleasure boat, trouble will tend to be endless.
Regards,
fofol
Rick Ansell
<p...@waitrose.com> wrote:
>
>jim smith <james....@which.net> wrote in message
>news:3A5776FA...@which.net...
>> This may be a silly question but why isnt ferro cement used to build
>> canal craft? Is it because it isnt strong enough? Jim
>
>It's not silly, the answer you suggest is along the right lines.
<snip>
>Generalising, most tensile stress is experienced close to the surface of a
>body, thus rebars are secured so that once the concrete has been poured into
>the mould, there will be about 50mm between the surface and the rebar. This
>distance - known as *cover* provides protection for the steel rebar from the
>elements.
In boat construction it is usual to dispense with the mould and
use multiple layers of weld mesh (or in some cases chicken
wire), usually 8. This is then 'plastered' with a 'stiff' mix of
concrete. The cover is lower than in civil engineering
construction - typically a 30ft yacht will have 18mm of cover.
<snip>
>Horses for courses: keep concrete for bridges & wood, steel & (yuk!) GRP for
>boats. Having said that, I'd be fascinated to know if any boatbuilder has
>considered a concrete hull.
There is a comprehensive article on this form of construction in
this months 'Classic Boat'.
One interesting use is to save wooden boats where the hull is to
far gone to save - it is covered with Weld mesh and turned into
a ferro boat. This 'might' cause clearance problems for inland
craft though!
Rick
--
"I think there is a world market for maybe five computers."
-- Thomas Watson, chairman of IBM, 1943
chil
David Long
five years ago as a restaurant. It was last used to run the Liverpool
papers to the Isle of Man in the 1950's. Their reputation for trouble is
not borne out by the facts.
David Long
<mar...@g4cio.demon.co.uk> writes
>In article <t5fj70d...@gxsn.com>, Philip Dumelow <p...@waitrose.com>
>writes
>>
>>jim smith <james....@which.net> wrote in message
>>news:3A5776FA...@which.net...
>>I've seen a concrete butty at either
>>Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
>>inches thick & it was formed into 2 or 3 compartments by stiffening
>>bulkheads. I believe it was broad beam.
>
>There is indeed a concrete widebeam barge outside the NWM at Glos Docks.
>There are also a few pictures of large WW1 concrete barges (1000 Te or
>more) being built and launched in Hugh Conway's book "The Gloucester &
>Sharpness Canal".
>
>
Fiddlers Ferry ones - I have original photos of them being built and
launched. Nineteen sites saw 62 1000t dumb barges and 12 steam tugs
launched - but most too late for the war. Their names all began Crete-,
with a different topographical feature forming the second part of the
name for the barges (Cretecamp, Cretecove for the Sankey ones), with the
initial letter being particular to each site ("c" for the Sankey). The
tugs' second part was a part of a ship or its fittings (Cretestem, -bow
etc).
Most were built in a single, wooden mould (the monolithic method),
others, including the Sankey ones, were built in pre-cast sections,
bolted together on the slipways.
Roger Davies
>writes
>>
>>jim smith <james....@which.net> wrote in message
>>news:3A5776FA...@which.net...
>>I've seen a concrete butty at either
>>Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
>>inches thick & it was formed into 2 or 3 compartments by stiffening
>>bulkheads. I believe it was broad beam.
>
>There is indeed a concrete widebeam barge outside the NWM at Glos Docks.
>There are also a few pictures of large WW1 concrete barges (1000 Te or
>more) being built and launched in Hugh Conway's book "The Gloucester &
>Sharpness Canal".
Sharpness as bank defences. It seems that they were floated there at
high tide, allowed to settle at low tide, and then a great hole punched
in the side.
They are easy to approach at low tide, just over the wall near the
remains of the swing rail bridge. Watch out for the tide though, it
doesn't hang around there.
- -
Roger Davies
To reply directly, replace nospam with rogdavies
David Long
<ro...@nospam.fsnet.co.uk> writes
>In article <mRfgPJA$zGW6...@g4cio.demon.co.uk>, Martin E Phillips
><mar...@g4cio.demon.co.uk> writes
>>In article <t5fj70d...@gxsn.com>, Philip Dumelow <p...@waitrose.com>
>>writes
>>>
>>>jim smith <james....@which.net> wrote in message
>>>news:3A5776FA...@which.net...
>>>I've seen a concrete butty at either
>>>Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
>>>inches thick & it was formed into 2 or 3 compartments by stiffening
>>>bulkheads. I believe it was broad beam.
>>
>>There is indeed a concrete widebeam barge outside the NWM at Glos Docks.
>>There are also a few pictures of large WW1 concrete barges (1000 Te or
>>more) being built and launched in Hugh Conway's book "The Gloucester &
>>Sharpness Canal".
>I seem to remember seeing concrete barges sunk along the river at
>Sharpness as bank defences. It seems that they were floated there at
>high tide, allowed to settle at low tide, and then a great hole punched
>in the side.
They're WW2 stuff. There are dozens of them in the infilled Paloma Dock
and the Statham dead-end of a Mersey cut-off on the Manchester Ship
Canal. After much trouble they managed to get approval to keep one at
Ellesmere Port Museum.
There are also a couple under the MOSTYN on the Dee - along with the
ELMARINE, the first pre-cast barge launched at Fiddlers Ferry - smaller
than the later Admiralty ones.
Martin E Phillips
<Da...@scars.org.uk> writes
>Them's the ones built as part of the same Admiralty programme as the
>Fiddlers Ferry ones - I have original photos of them being built and
>launched. Nineteen sites saw 62 1000t dumb barges and 12 steam tugs
>launched - but most too late for the war. Their names all began Crete-,
>with a different topographical feature forming the second part of the
>name for the barges (Cretecamp, Cretecove for the Sankey ones), with the
>initial letter being particular to each site ("c" for the Sankey). The
>tugs' second part was a part of a ship or its fittings (Cretestem, -bow
>etc).
Yes, two shown in Conway-Jones's book are Creterock and Creteridge.
Apparently there were six built, each 180 ft long and capable of
carrying 1000 Te cargo.
>Most were built in a single, wooden mould (the monolithic method),
>others, including the Sankey ones, were built in pre-cast sections,
>bolted together on the slipways.
Unfortunately there's not enough detail to see whether the Glos ones are
cast in one bit or in sections. The marks that are visible on the hull
could be from shuttering or from joints.
Martin E Phillips
<Da...@scars.org.uk> writes
>They're WW2 stuff. There are dozens of them in the infilled Paloma Dock
>and the Statham dead-end of a Mersey cut-off on the Manchester Ship
>Canal. After much trouble they managed to get approval to keep one at
>Ellesmere Port Museum.
I vaguely remember reading in the local rag, a few years ago before I
became interested in boating, that one of them was refloated. Could it
be the concrete boat outside the WW museum in Glos Docks?
Tony Clayton
> In article <mRfgPJA$zGW6...@g4cio.demon.co.uk>, Martin E Phillips
> <mar...@g4cio.demon.co.uk> writes
> >In article <t5fj70d...@gxsn.com>, Philip Dumelow <p...@waitrose.com>
> >writes
> >>
> >>jim smith <james....@which.net> wrote in message
> >>news:3A5776FA...@which.net...
> >>I've seen a concrete butty at either
> >>Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
> >>inches thick & it was formed into 2 or 3 compartments by stiffening
> >>bulkheads. I believe it was broad beam.
> >
> >There is indeed a concrete widebeam barge outside the NWM at Glos Docks.
> >There are also a few pictures of large WW1 concrete barges (1000 Te or
> >more) being built and launched in Hugh Conway's book "The Gloucester &
> >Sharpness Canal".
> I seem to remember seeing concrete barges sunk along the river at
> Sharpness as bank defences. It seems that they were floated there at
> high tide, allowed to settle at low tide, and then a great hole punched
> in the side.
Some rather large ones can be seen off Arromanches in Normandy.. ;-)
Those had valves to enable them to be sunk in place.
--
Tony Clayton
'Linton', Godalming Wharf
Tony.Cla...@pem.cam.ac.uk Home Page: http://www.tclayton.demon.co.uk
Sent using RISC OS on an Acorn RiscPC600
... Data, data everywhere, and not a byte to eat!
David Long
<mar...@g4cio.demon.co.uk> writes
>In article <dRPwQIA2...@cableinet.co.uk>, David Long
><Da...@scars.org.uk> writes
>>They're WW2 stuff. There are dozens of them in the infilled Paloma Dock
>>and the Statham dead-end of a Mersey cut-off on the Manchester Ship
>>Canal. After much trouble they managed to get approval to keep one at
>>Ellesmere Port Museum.
>
>I vaguely remember reading in the local rag, a few years ago before I
>became interested in boating, that one of them was refloated. Could it
>be the concrete boat outside the WW museum in Glos Docks?
>
dug out of the bank, where they were supporting part of the Stuarts
glass factory, and taken to Gloucester.
There are enough of the WW2 barges around for them to be readily
available for preservation.
Philip Dumelow
Rick Ansell <ri...@globalnet.co.uk> wrote in message
news:6h2h5tcqv9n1htamk...@4ax.com...
> On Sun, 7 Jan 2001 01:54:26 -0000, "Philip Dumelow"
> <p...@waitrose.com> wrote:
>
> >
> >jim smith <james....@which.net> wrote in message
> >news:3A5776FA...@which.net...
> >> This may be a silly question but why isnt ferro cement used to build
> >> canal craft? Is it because it isnt strong enough? Jim
> >
> >It's not silly, the answer you suggest is along the right lines.
>
> <snip>
>
> >Generalising, most tensile stress is experienced close to the surface of
a
> >body, thus rebars are secured so that once the concrete has been poured
into
> >the mould, there will be about 50mm between the surface and the rebar.
This
> >distance - known as *cover* provides protection for the steel rebar from
the
> >elements.
>
> In boat construction it is usual to dispense with the mould and
> use multiple layers of weld mesh (or in some cases chicken
> wire), usually 8. This is then 'plastered' with a 'stiff' mix of
> concrete. The cover is lower than in civil engineering
> construction - typically a 30ft yacht will have 18mm of cover.
The more I think about it, the more I like the idea of trying out stainless
steel fibres for reinforcement. It would be interesting to use them in a
Self Compacting Concrete mix (which is not in common use in UK but very
popular in SE Asia). There could be segregation problems with such large
specific gravity differences in such a fluid mix. If the opportunity arose
in the next few months, I wouldn't mind running a small trial in one of our
labs.
Philip
--
Philip G Dumelow
p...@waitrose.com
Ian and Jo Jeremiah
Martin E Phillips <mar...@g4cio.demon.co.uk> wrote:
> In article <dRPwQIA2...@cableinet.co.uk>, David Long
> <Da...@scars.org.uk> writes
> >They're WW2 stuff. There are dozens of them in the infilled Paloma Dock
> >and the Statham dead-end of a Mersey cut-off on the Manchester Ship
> >Canal. After much trouble they managed to get approval to keep one at
> >Ellesmere Port Museum.
> I vaguely remember reading in the local rag, a few years ago before I
> became interested in boating, that one of them was refloated. Could it
> be the concrete boat outside the WW museum in Glos Docks?
> Wassail!
I seem to remember that the one at Gloucester was salvaged from the banks
of the Severn estuary, down by Purton.
I think I have an account of its recovery somewhere, I'll see if I can
find it!
Ian J
--
___ _|______________________:_ __________________________
\___|___Glas y Dorlan________|____ /
|________________________________/ / Ian Jeremiah
http://www.argonet.co.uk/users/ianandjo iana...@argonet.co.uk
Martin E Phillips
writes
>The more I think about it, the more I like the idea of trying out stainless
>steel fibres for reinforcement. It would be interesting to use them in a
>Self Compacting Concrete mix (which is not in common use in UK but very
>popular in SE Asia). There could be segregation problems with such large
>specific gravity differences in such a fluid mix. If the opportunity arose
>in the next few months, I wouldn't mind running a small trial in one of our
>labs.
The fibres could be in the form of a wool (like a giant, boat-shaped
scrubby) to prevent separation.
Martin E Phillips
<Da...@scars.org.uk> writes
>That could have been the concrete narrow boats at Stourport. They were
>dug out of the bank, where they were supporting part of the Stuarts
>glass factory, and taken to Gloucester.
I don't think so. The one I'm thinking of was definitely dug out from
Purton.
Neil Arlidge
news:4E436UAg...@g4cio.demon.co.uk...
> I don't think so. The one I'm thinking of was definitely dug out from
> Purton.
During our 1994 Purton concrete barge wander, you could definitely see the
spot where it was recovered from, not so obvious last year thought.
Neil Arlidge - nb Earnest, ex nb Beatty
Follow the travels of TNC in hireboats, Beatty and Earnest. 1969 - Present,
at - http://www.tuesdaynightclub.co.uk
See Earnest being built at - http://www.nbearnest.co.uk
Roger Davies
<can...@tclayton.demon.co.uk> writes
>In message <khtUdrBL...@rogdavies.fsnet.co.uk> Roger Davies wrote:
>
>> In article <mRfgPJA$zGW6...@g4cio.demon.co.uk>, Martin E Phillips
>> <mar...@g4cio.demon.co.uk> writes
>> >In article <t5fj70d...@gxsn.com>, Philip Dumelow <p...@waitrose.com>
>> >writes
>> >>
>> >>jim smith <james....@which.net> wrote in message
>> >>news:3A5776FA...@which.net...
>> >>I've seen a concrete butty at either
>> >>Ellesmere Port or Gloucester Docks museums: as I recall the hull was about 8
>> >>inches thick & it was formed into 2 or 3 compartments by stiffening
>> >>bulkheads. I believe it was broad beam.
>> >
>> >There is indeed a concrete widebeam barge outside the NWM at Glos Docks.
>> >There are also a few pictures of large WW1 concrete barges (1000 Te or
>> >more) being built and launched in Hugh Conway's book "The Gloucester &
>> >Sharpness Canal".
>> I seem to remember seeing concrete barges sunk along the river at
>> Sharpness as bank defences. It seems that they were floated there at
>> high tide, allowed to settle at low tide, and then a great hole punched
>> in the side.
>
>Some rather large ones can be seen off Arromanches in Normandy.. ;-)
>
>Those had valves to enable them to be sunk in place.
>
maybe?
David Long
<mar...@g4cio.demon.co.uk> writes
>In article <PumEPKAT...@cableinet.co.uk>, David Long
><Da...@scars.org.uk> writes
>>That could have been the concrete narrow boats at Stourport. They were
>>dug out of the bank, where they were supporting part of the Stuarts
>>glass factory, and taken to Gloucester.
>
>I don't think so. The one I'm thinking of was definitely dug out from
>Purton.
>
are afloat elsewhere - and the Ellesmere Port Boat Museum had a hell of
a job getting the local council to let them moor one there.
Ian and Jo Jeremiah
Martin E Phillips <mar...@g4cio.demon.co.uk> wrote:
> In article <PumEPKAT...@cableinet.co.uk>, David Long
> <Da...@scars.org.uk> writes
> >That could have been the concrete narrow boats at Stourport. They were
> >dug out of the bank, where they were supporting part of the Stuarts
> >glass factory, and taken to Gloucester.
> I don't think so. The one I'm thinking of was definitely dug out from
> Purton.
There is a concrete barge _and_ a concrete narrow boat at Gloucester!
Paul Jerome
"Tony Clayton" <can...@tclayton.demon.co.uk> wrote in message
news:20010107....@tclayton.demon.co.uk...
>
> Some rather large ones can be seen off Arromanches in Normandy.. ;-)
>
> Those had valves to enable them to be sunk in place.
>
> --
> Tony Clayton
> 'Linton', Godalming Wharf
> Tony.Cla...@pem.cam.ac.uk Home Page:
http://www.tclayton.demon.co.uk
> Sent using RISC OS on an Acorn RiscPC600
> ... Data, data everywhere, and not a byte to eat!
A couple never got there. One is a navigation hazard when sailing out of
Langston Harbour. Part of the Portsmouth to Arundel canal to keep us on
topic.
BTW the museum at Arromanches is worth seeing.
Paul Jerome
David Long
<paul....@nospam.cwcom.net> writes
>
>"Tony Clayton" <can...@tclayton.demon.co.uk> wrote in message
>news:20010107....@tclayton.demon.co.uk...
>>
>> Some rather large ones can be seen off Arromanches in Normandy.. ;-)
>>
>> Those had valves to enable them to be sunk in place.
>>
Churchill when at the Admiralty - so it's not surprising the idea
reappeared as the WW2 Mulberry Harbours. Churchill also had the idea in
WW1 of extending Heligoland with precast concrete structures to act as a
base for invading Germany from the North.
>
>BTW the museum at Arromanches is worth seeing.
>
It is - we visited when it first opened.