On Thu, 16 Aug 2007 23:28:04 -0700, dave
wrote:

I recently purchased a 30 odd year old hartley queenslander ferro
cement sloop. I love it and so does my family and friends. Its a funny
old thing, everything works, but all the know alls who own boats built
of other materials look down their noses and all have some anecdotal
story about the woes of ferro construction. It sails beautifully,
motors with ease, is very comfortable.
Could someone who has owned , or does own a ferro share with me their
trials and tribulations.

I don;t own one but have a mate that owns a 50 footer. He used to sail
it to Perth every year and back to Thailand six months later. No
problems with the hull.

The reason that ferocement boats have a bad reputation is because
people used to b build them in their back wards and when it came time
to plaster them would get a bunch of beer and all their mates in. some
of these were pretty horrible. Other people were smart enough to have
a professional plasterer do the job and never have a problem.

They are heavy for their length though and you'll probably find that
you can carry a lot more sail then the fiberglass boats.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)

wrote

They are heavy for their length though and you'll probably find that
you can carry a lot more sail then the fiberglass boats.

But a LOT less than a cored glass boat of the same shape and equal
displacement with the weight saved in the hull carried as ballast. The
glass boat will also be much stronger if some of the weight savings is used
to add material.

I once figured out that a typical ferrocement hull was the material
equivalent of 1/64 of an inch of steel on each side of a 1/2 inch concrete
core. Does that sound like a way to build a boat? Worse the steel, which
should be the tensile material on a thin shell, was on the inside and the
concrete, a material most effective in compression, was on the outside.

Strong as wood, heavy as steel, about sums it up. That doesn't mean you
can't built a good boat out of it, just that it will not be as strong or
well performing as other materials which are not significantly different in
cost when you consider the full investment.

--
Roger Long

On Aug 17, 2:52 am, "Roger Long" wrote:
....
Strong as wood, heavy as steel, about sums it up. That doesn't mean you
can't built a good boat out of it, just that it will not be as strong or
well performing as other materials which are not significantly different in
cost when you consider the full investment.
....

Indeed, particularly with yachts where most of the total cost is in
the fit-out. But that's new builds. From time to time there are some
really good deals on the used market in fero and I know some folks who
have cruised happily in big stone boats that cost them far less than
an equivalent used boat in metal or plastic would have. I am aware of
the many arguments folks make against fero and am not a big fan of it
myself, but some cruisers have been very well served by their cement
craft.

-- Tom.

On Fri, 17 Aug 2007 12:25:38 -0700, "
wrote:

Strong as wood, heavy as steel, about sums it up.

Steel is lighter than wood. of equal strength. Aluminum is lighter
than wood. For the same weight aluminum and steel are equally strong.

On Aug 18, 2:18 pm, (Richard Casady)
wrote:
On Fri, 17 Aug 2007 12:25:38 -0700, "

wrote:
Strong as wood, heavy as steel, about sums it up.

Steel is lighter than wood. of equal strength. Aluminum is lighter
than wood. For the same weight aluminum and steel are equally strong.

I didn't write that. I was quoting Roger. My feeling is that the
word construction is implied in his statement. As built to typical
scantlings wooden boat construction is lighter but weaker than steel
construction. In small craft the difference is very significant
because of minimum practical plate thickness.

-- Tom.

On Sat, 18 Aug 2007 17:45:11 -0700, "
wrote:

As built to typical
scantlings wooden boat construction is lighter but weaker than steel
construction. In small craft the difference is very significant
because of minimum practical plate thickness.

Lots weaker. As I said, steel has a better strength to weight ratio
than wood If you build similar boats, of equal strength, wood will be
heavier not lighter. My experience with 16 foot boats is that wood is
a lot heavier than riveted aluminum. Same with the canoe. No maintance
whatever for fifty years, with the aluminum boats. It is true that
welded construction does require a minimum thickness. Not so riveted,
you get to use all of the weight, instead of unnecessarily strong and
heavy steel. Aluminum is thicker than steel for equal strength, so it
is stiffer, strength to weight ratio being the same as the steel. For
equal strength wood is stiffer than metal, because it is thicker. I
much prefer metal to wood or fiberglass. Light weight, zero maintance
what more could one want? Metal is noisier. Wood is quieter, give or
take the moaning and groaning, which the engine and/or wind will drown
out. In conclusion, welded steel is not optinum for boats under about
fifty feet. Steel tends to warp from the expansion when you weld it,
so you have a minimum thickness and a minimum sized boat, assuming you
want to use the strength of the steel efficiently. At one hundred
feet, you can use 1/4 inch plate. That is much easier to weld than
sheet metal.

Casady

On Aug 18, 5:44 pm, (Richard Casady)
wrote:
....
As I said, steel has a better strength to weight ratio
than wood If you build similar boats, of equal strength, wood will be
heavier not lighter. My experience with 16 foot boats is that wood is
a lot heavier than riveted aluminum. ...

Volumes have been written on matteral's properties. It isn't a simple
subject and I am not a master of it. The properties of complex
structures in a complex environment are very, very difficult to grasp
from first principles. The strength of a structure is only loosely
connected to the strength of it's materials. Thus, comparing a single
property of steel and wood isn't a great guide to that property in a
complete boat.

Cruising boats aren't 16 foot tinnies. Also, you are comparing a
lightly built tin boat with a heavy wood one. Right up until the 70's
racing dingies, rowing shells, unlimited hydroplanes &c. built of wood
were lighter, stiffer and faster than glass, aluminum was not
competitive and steel was never considered. In practice, boats built
as lightly as permissible to any of the classification societies rules
to a given service will be heaviest in steel and then aluminum and
then solid fiberglass and then wood and lightest in cored glass or
exotic fiber. So, while I will not argue that a steel boat couldn't
be made as lightly as a wooden boat for a given service, such a craft
would be revolutionary. In practice, steel boats are heavy but very
durable and wood ones are light and less durable and in that context
Roger's statement seems very reasonable to me.

I don't mean to dis metal boats, many of them are great. I've got an
aluminum RIB that I'm very fond of. Riveted aluminum can be very
light and I know a guy who built a catamaran of cor-ten steel with an
ingenious space frame system that was reasonably light. On the other
hand, I remember a lovely evening in Apia Samoa when I shared dinner
and a couple of jugs of wine with three world cruisers who had voyaged
there on their steel boats. We got to talking horror stories and they
each had one to tell about putting a finger or dropping a hammer
through a bit of the hull or deck on their own boats. Localized
corrosion can be a real problem for steel boats and thin plates will
make it worse. Steel boats are always rusting and thick ones last
longer too. A riveted thin skinned aluminum boat with an electrical
system that was in the water full time is almost certain to have major
electrolysis problems. So, I'd advise caution when you attempt to
make a steel boat as light as a wooden one. Scantlings take into
account mistakes other folks have made for you...

-- Tom.

"Richard Casady" wrote:

Strong as wood, heavy as steel, about sums it up.

Steel is lighter than wood. of equal strength. Aluminum is lighter
than wood. For the same weight aluminum and steel are equally strong.

Compared to an Airex cored hull with epoxy and knitted glass skins, all of
the above are a joke.

Lew

On Sat, 18 Aug 2007 20:19:58 -0700, "Lew Hodgett"
wrote:


"Richard Casady" wrote:

Strong as wood, heavy as steel, about sums it up.

Steel is lighter than wood. of equal strength. Aluminum is lighter
than wood. For the same weight aluminum and steel are equally strong.

Compared to an Airex cored hull with epoxy and knitted glass skins, all of
the above are a joke.

The very best plastic may be stronger. I think if Boeing is using it
that says something.
Be interesting to see a table comparing the S/N for various materials.
I know the latest fiberglass [and other plastic] is a lot better than
it used to be.
Been my experience that the older fiberglass boats are heavier than a
comparable aluminum boat. In any case, I got a 22 foot aluminum boat,
in the usual good shape, for two grand, instead. I laughed all the way
to the bank. If the available steal had been a plastic boat I might
well have bought that. It is well known that you can build a decent
boat from any of the popular materials. That is why they are popular,
after all. The family has a plastic boat that has been in use for
fifty years. It is pretty heavy. A turbocraft, first of the jet boats,
SN 10. It finally got painted after forty years. On the other hand,
the local aluminum boats of that vintage are still doing fine with the
original bare metal. We have a couple of neighbors with 1940's
fiberglass sailboats. The material was not well understood, they used
too much, and the boats are way heavy. They are, however, still in
good shape. Something called Rebels, they are among the earliest of
the production glass boats. Plastic [not necessarily glass], _is_
lighter than aluminum if it is done right, the aircraft industry is
proving that. As for glass, it is heavier than graphite or kevlar, and
you can get those materials in boats. Titanium is lighter than
aluminum, for that matter. Ever hear of the Russian Alfa class subs?
Titanium. They didn't build many of them. Where you really want the
lightest construction is in canoes that are destined to be portaged.
Early fiberglass canoes were way heavier than aluminum, and the
wooden ones were heavy. While metal and wood haven't changed, the
plastic is a lot better than it used to be.

Casady

"Richard Casady" wrote:


The very best plastic may be stronger. I think if Boeing is using it
that says something.
Be interesting to see a table comparing the S/N for various materials.
I know the latest fiberglass [and other plastic] is a lot better than
it used to be.
Been my experience that the older fiberglass boats are heavier than a
comparable aluminum boat.
snip

Most existing "fiberglass" boats are polyester resin with woven roving and
mat.

Woven roving is coarse compared to knitted material and requires the mat to
retain the polyester resin.

About the best glass/resin ratio you can expect is 35%Glass/65%resin which
produces a heavy laminate.

Polyester is also more brittle than epoxy resin.

Polyester is also NOT an adhesive which is why you see holes thru the
plywood used for bulkheads with the glass going thru the hole. It provided a
mechanical means of bonding.

OTOH, epoxy is an adhesive, can take advantage of knitted glass which means
much higher glass content with less resin required.

A 50%glass/50%resin ratio is easy to obtain with hand layup techniques,
vacuum bagging can achieve even higher glass/resin ratios.

The result is a much lighter as well as stronger laminate.

Add Airex foam as a core material to the mix and it is a whole new ball
game.

You could build a dynamite hull for a 15'-20' boat using 1/2" thick Airex
foam core(6.3lbs/ft^3), and 3 layers of 17OZ double bias(+/-45degree) glass.

Translation:

3 layers of 17 Oz with a 50/50 G\R ratio= (17*3)*2=102 Oz for each laminate
skin or 204 Oz/sq yard for both skins.

The Airex: (1/2)(6.3*16*36*36)/1728 = 14.2 Oz/sq yard for 1/2" Airex.

204 + 14.2 = 216 Oz/Sq Yard = 216/9 = 24.0 Oz/Sq Ft = 1.5 Lbs/Sq ft.

Pick a metal, you will need at least 1/4" plate to provide equalivant
strength which means a lot more weight.

BTW, add a layer of 17OZ glass, say 6"-8" wide along the keelson for a wear
strip, and you are good to go.

The only problem with epoxy is that it has no UV resistance so a coat of
paint is required.

Lew