TWL: Copper plating
Bob refers to active vs inactive--and I have E mailed a metalurgist to see
what the difference is. My experience was that the marine growth (first
slime, then small barnicles and tube worms etc) grew on the plated prop as
well as on bare metal. I saw no advantage--and had good results with coats
of epoxy and antifouling paint. However I keep my boat in water that is
only about 50% salinity of salt water (a bayou).
As for the wooden ships--there were no modern antifouling paints and teredo
or marine boring worms were a major problem.
The copper acted as an antifoulant and protection from the marine borer's.
^From what I have read the life of many sailing ships was relitatiely short
because of worm infestations. The copper plates or sheets had to be
replaced or patched on a regular basis. Long before Copper, Lead was used
as a sheathing material--and by some accounts lasted up to 9 years before it
had to be replaced. Most ships had only thin sacrificial wood, beded in a
tallow, hair and tar compound to protect them from Teredo worms. Fouling
was handled by frequent scrubbing.
Two recent experiences show how fast growth can occur on modern
vessels--Nordhavn had tube worms several inches long growing on her bottom
after the recent Transatlantic crossing, and a friend of mine took 25 days
to sail from Hawaii to Long Beach just recently--and during that time had
tube worms as long as 2 1/2" grow on the bottom of his boat.
A quote from the National Marine museum of the UK:
"When was copper sheathing introduced into the Royal Navy?
A search for a sheathing that would protect the hull of a ship from the
teredo worm continued for years in the Royal Navy. Species of teredo worm
occur in all seas but they are most prevalent in warmer waters and cause
great damage to wooden ships by boring through all the timbers below the
waterline. Originally the only protection had been a thin layer of plank
laid on a coating of tar and hair but this covering was itself susceptible
to the teredo worm.
Experiments with copper sheathing were first carried out in 1761 when the
frigate Alarm was sheathed with the material prior to a two year voyage to
the West Indies. Although it proved to be successful in keeping the hull
clean there was the problem of corrosion by the galvanic action of the
copper on the iron bolts which secured the main frame and the planking. This
was solved in 1783 when orders went out that copper and zinc bolts should
replace iron bolts and copper sheathing then became general.
Copper sheathing was an important technological innovation as not only did
the copper afford protection against the teredo worm but kept ships
relatively free from weed thus improving their sailing performance. "
There have been a number of medium size vessels built of hull material of
copper nickel alloy which apparently was successful in antifouling property.
Apparently this was welded to steel frames.
The problem for many years has been the cost. Some modern boats were built
with copper sheathing laminated in the glass or expoxied on. Some boats had
copper embeaded in the outer layer of resin. It is my understanding that
there have been major problems getting the copper sheets to adhere well to
fiberglass hulls, so that project has been abandoned. However apparently
the high concentation of metalic copper in epoxy has been partly successful:
slime forms, but is easily scrubed off.
(A lot of the experience depends on the characteristics of the water where
the boat is kept).
Regards,
Bob Austin (Pensacola--where the water used to be so contraminated that
bottom paint was unnecessary--now cleaned up--and we are contaminating it
with copper etc!)
Bob:
Additional information on copper-nickel alloys in the marine environment
and on the vessels that have been constructed of these alloys can be
found at:
There are references to contemporary use of this material for sheathing
or cladding but none that I have found for use of this alloy as a
plating material.
Wesley
weldred@zoo.uvm.edu
Bob Austin wrote:
There have been a number of medium size vessels built of hull material of
copper nickel alloy which apparently was successful in antifouling property.
Apparently this was welded to steel frames.
As a mater of fact, I went back to the sources in my history--and the
article about hulls made of copper nickle are at:
http://marine.copper.org/5-sheathing.html The section by Dale T. Peters.
The relivant quote from his article is:
"The ideal hull material for ships of various sizes and duties has been the
subject of intense study, and a variety of hull materials are being used or
have been evaluated. Copper-nickel as a hull material was first used as
early as 1941 in the construction of Miss Revere, a 13.7 m yacht with a 2mm
thick copper-nickel hull. Copper-nickel as a hull material was first used in
the mid-1960s by a professor at the University of Alabama after he made an
extensive study of a wide variety of possible hull materials for his yacht,
the Asperida. He had been seeking material with the best combination of
corrosion and biofouling resistance. Alloy C71500, 70-30 copper-nickel, was
selected over C70600 90-10 copper-nickel, because the greater strength was
an advantage in his particular design.
This led directly to a series of engineering studies by the International
Copper Research Association (INCRA - now the International Copper
Association), the International Nickel Company and the Copper Development
Association Inc. and the construction in 1971 of Copper Mariner (Figure 1),
a 20.4 m commercial shrimp trawler with a copper-nickel hull. The primary
objective was to determine whether the inherent resistance of alloy C70600
to biofouling and corrosion would generate sufficient fuel and maintenance
savings to justify the cost premium for the copper-nickel hull.
Copper Mariner has been described elsewhere (2) and will not be elaborated
on here. This trawler has a 6 mm thick alloy C70600 hull welded to steel
framing. Copper Mariner demonstrated a return on investment in the range of
12.9 to 16.7 percent after taxes for shrimp trawler operations off the coast
of Nicaragua. These figures are based on measured fuel and maintenance
savings and estimates of the increased earnings potential of this boat due
to additional days of availability when compared to the sister steel hulled
boats.
The corrosion rate of the hull was less than the 0.00125 mm/yr reported for
long-term exposure of C70600(3). Interestingly, hull plate thickness
measurements after 52 months of service showed no differences in metal loss
in the heat affected zone areas of the hull where re-solution of the
precipitated iron had taken place compared to the hot-rolled plate with iron
precipitated. The majority of the hull had a dark-colored corrosion product
film; the heat affected zones were a light golden color. The speed of Copper
Mariner is in the 4-10 knot range.
The copper-nickel hull of Copper Mariner is very resistant to fouling
(Figure 3). Comparison with the steel hull of the sister ship just prior to
its third cleaning after 18 months of service, is striking (Figure 2).
Copper Mariner was 20 years old this year*. She is still in service, and at
last word from the Minister of the National Fishing Industry in Nicaragua,
the copper-nickel hull has never required maintenance. Inspection of the
hull at drydockings for propeller and shafting maintenance have shown no
noteworthy signs of general or pitting corrosion. Four similar boats with
4.8 mm- thick C70600 alloy hulls were built in the early 1970s for service
in Sri Lanka.
A number of very successful copper-nickel hull ships have been constructed
using a composite material of 90-10 copper-nickel alloy clad on to steel. A
second shrimp trawler, Copper Mariner II, was built in 1976 with 8 mm, 25%
C70600 alloy clad steel hull plate. This hull demonstrated fabricability and
weldability using clad material and welding techniques described by Prager
et. al.(4). More recently, the Italian Ministry of the Interior purchased
several fire boats for the port at Naples and other locations. These boats
have hulls made from 2 mm of 90-10 copper-nickel clad on 6 mm of steel with
a length of 22.56 m and a displacement of 72 tonnes. These copper-nickel
hulls assure maximum availability of the fire boats by eliminating the need
for hull maintenance of any kind.
Two clad-metal-hull pilot boats were constructed in 1987 for the Board of
Navigation in Finland. These two boats were planned as a comparison between
austenitic stainless steel and 90-10 copper-nickel for use in the Baltic Sea
where ice is a major problem. Both boats are reported to be performing well.
Two boats of note have been constructed in Japan. Although we have no
details, we were informed of a yacht, the Akitsushima, built by the Furukama
Electric Co., Ltd., with a 4-mm-thick copper-nickel sheath welded to the
steel hull. In 1989, this boat was reported to have crossed the Pacific
Ocean to Victoria, British Columbia, Canada. The NKK Corporation has
reported the construction of an experimental ship, Cupro, with a
copper-nickel clad steel hull. These Japanese ships are of great interest
and we would be most interested in knowing about their performance and
construction details. A summary of vessels constructed to date with
copper-nickel hulls is presented in Table 1. The concept has attracted
considerable attention for smaller commercial craft, but a ship of length
greater than 25 m has not been built."
Bob Austin
----- Original Message -----
From: "Wesley Eldred" weldred@zoo.uvm.edu
To: "Bob Austin" thataway4@cox.net
Cc: "1trawler world" trawler-world-list@samurai.com
Sent: Friday, June 14, 2002 7:34 AM
Subject: Re: TWL: Copper plating
Bob:
Additional information on copper-nickel alloys in the marine environment
and on the vessels that have been constructed of these alloys can be
found at:
There are references to contemporary use of this material for sheathing
or cladding but none that I have found for use of this alloy as a
plating material.
Wesley
weldred@zoo.uvm.edu
Bob Austin wrote:
There have been a number of medium size vessels built of hull material
of
copper nickel alloy which apparently was successful in antifouling
property.
Apparently this was welded to steel frames.