In article , Roger Long
wrote:

And people ask me why I am considering steel for an offshore
boat...G

Go with aluminum if you can. No compass problems and you can make
emergency repairs with hand tools and sheet metal screws.

I saw a 60 foot sailboat that had gone ashore on a rocky island and
had it's keel torn off. One side was pushed in three feet for about
half the length. Still, it could have been made watertight and
floated off with about five feet of duct tape. A steel hull, although
stronger according to some measures, would have been in pieces after
that treatment.

No it wouldn't and saying that demonstrates that you don't know the
characteristics of materials. Steel is more ductile than aluminium - it
will deform more before reaching its plastic limit and tearing. It is
also less susceptible to work hardening and notch sensitivity, and
welds can be 100% the strength of the parent material, which is not the
case with al. Steel is also far more resistant to abrasion.

Notwithstanding, I like aluminium for boats myself and if I ever get
the urge, would weigh carefully the first cost vs maintenance issues
WRT steel and aluminium.

PDW

"Peter Wiley" wrote

No it wouldn't and saying that demonstrates that you don't know the
characteristics of materials. Steel is more ductile than aluminium -
it
will deform more before reaching its plastic limit and tearing. It
is
also less susceptible to work hardening and notch sensitivity, and
welds can be 100% the strength of the parent material, which is not
the
case with al. Steel is also far more resistant to abrasion.

True, (except for the first line), but we are talking about the
behavior of an entire structure not a test specimen. The aluminum
hull behaves sort of like a rubber inflatable boat and the steel hull
like a fiberglass one. The glass hull is "stronger" but may be more
likely to puncture in many situations.

The steel hull would have been in pieces not because it is weaker but
because it would have flooded and been rolled around on the rocks full
of water instead of retaining enough buoyancy to get up above the surf
line.
Obviously, anything can happen in any accident but I've seen enough
damaged boats to have great respect for aluminum.

I have enough understanding of the materials characteristics to design
boats like this one:

http://home.maine.rr.com/rlma/WHOIrv.htm

--

Roger Long

Roger Long wrote:
"Peter Wiley" wrote


No it wouldn't and saying that demonstrates that you don't know the
characteristics of materials. Steel is more ductile than aluminium -
it
will deform more before reaching its plastic limit and tearing. It
is
also less susceptible to work hardening and notch sensitivity, and
welds can be 100% the strength of the parent material, which is not
the
case with al. Steel is also far more resistant to abrasion.


True, (except for the first line), but we are talking about the
behavior of an entire structure not a test specimen. The aluminum
hull behaves sort of like a rubber inflatable boat and the steel hull
like a fiberglass one. The glass hull is "stronger" but may be more
likely to puncture in many situations.

The steel hull would have been in pieces not because it is weaker but
because it would have flooded and been rolled around on the rocks full
of water instead of retaining enough buoyancy to get up above the surf
line.
Obviously, anything can happen in any accident but I've seen enough
damaged boats to have great respect for aluminum.

I have enough understanding of the materials characteristics to design
boats like this one:

http://home.maine.rr.com/rlma/WHOIrv.htm

If the organization that owns that boat has confidence in your
designs...that's good enough for me!

In article , Roger Long
wrote:

"Peter Wiley" wrote

No it wouldn't and saying that demonstrates that you don't know the
characteristics of materials. Steel is more ductile than aluminium -
it
will deform more before reaching its plastic limit and tearing. It
is
also less susceptible to work hardening and notch sensitivity, and
welds can be 100% the strength of the parent material, which is not
the
case with al. Steel is also far more resistant to abrasion.

True, (except for the first line), but we are talking about the
behavior of an entire structure not a test specimen. The aluminum
hull behaves sort of like a rubber inflatable boat and the steel hull
like a fiberglass one. The glass hull is "stronger" but may be more
likely to puncture in many situations.

How does this work? The aluminium has a lower elastic limit (amount of
flex before permanent deformation), lower plastic limit (deformation
before rupture) and lower resistance to abrasion than steel does. It is
structurally an inferior material. It compensates somewhat due to its
lighter weight enabling thicker sections to be used, regaining some of
the difference, and in shipbuilding due to its better corrosion
resistance.

The steel hull would have been in pieces not because it is weaker but
because it would have flooded and been rolled around on the rocks full
of water instead of retaining enough buoyancy to get up above the surf
line.

Oh, come ON. That boat (SG) is ballasted to a displacement of 14400
lbs. The steel version is ballasted to a displacement of 14400 lbs.
Both versions have all inside ballast. The keel shoes are 1" thick
plate in both cases. The chine bars are 3/4" thick rod. The frames are
2 1/2" by 1/4" flat bar. Can you explain to me how this ballast
mysteriously changes between a steel hull and an aluminium hull? How
the aluminium hull managed to keep water out that a steel hull would
have allowed in?

Why would a 4mm thick steel hull plate be ruptured, allowing water
ingress, when a 6mm aluminium plate hull kept the water out?

This argument has no credibility.

BTW, I have a full set of blueprints for a Colvin Witch hull so I do
know how they're built.

Obviously, anything can happen in any accident but I've seen enough
damaged boats to have great respect for aluminum.

I have enough understanding of the materials characteristics to design
boats like this one:

http://home.maine.rr.com/rlma/WHOIrv.htm

Nice boat. I have 2 30', 6 tonne alum boats, 4 jet barges and a number
of other small craft. However I also have steel vessels up to 6500
tonnes. Any impact that an aluminium boat will withstand, a steel boat
will also withstand, and likely with considerably less structural
deformation.

PDW

Oh, I see why we are having this conversation.

I wasn't talking about Sara Gamp. There doesn't appear to have been
much pounding in that case. A steel boat would have done fine as well
and probably would have experience less deformation and damage. If
you want to experience minimum deformation and damage from typical
impacts, steel is stronger. However, if you really beat on a boat in
extremis, the energy absorption and yielding of an aluminum structure
may leave you with something deformed and battered but mostly
watertight in a situation where the steel hull would have ruptured.
The strength and resistance of the steel concentrates the impact.
It's the rubber boat vs fiberglass dinghy thing except that the
aluminum doesn't spring back.

I'll admit that it's difficult to justify in typical engineering terms
and, yeah, I'm talking about examples I'm familiar with that are
anecdotal and without the controls of having a nearly identical steel
hull go ashore at the same time. Professionally, it's not defensible
to claim that an aluminum hull is more survivable but, hey, this is a
newsgroup. The point is that aluminum is certainly an excellent
choice for a long distance cruiser that is careful about the
electrical system (and those pennies). If you were faced with getting
a really badly damaged hull, patched, jury rigged, and back to safety,
you might be glad that it was aluminum. If you make a habit of
banging into things though, your boat will end up carrying more
permanent dents if it is aluminum than if it is steel.

I've seen enough steel hulls broken to be pretty sure that the boat I
was referring to was more watertight than a steel hull of similar size
and weight would have been after that treatment. When I saw it, it
was about 150 feet back from the normal high tide line on a rocky
island.

--

Roger Long



"Peter Wiley" wrote

Oh, come ON. That boat (SG) is ballasted to a displacement of 14400
lbs. The steel version is ballasted to a displacement of 14400 lbs.
Both versions have all inside ballast. The keel shoes are 1" thick
plate in both cases. The chine bars are 3/4" thick rod. The frames
are
2 1/2" by 1/4" flat bar. Can you explain to me how this ballast
mysteriously changes between a steel hull and an aluminium hull? How
the aluminium hull managed to keep water out that a steel hull would
have allowed in?

Why would a 4mm thick steel hull plate be ruptured, allowing water
ingress, when a 6mm aluminium plate hull kept the water out?

"Peter Wiley" wrote

Nice boat.

Thanks.

I have 2 30', 6 tonne alum boats, 4 jet barges and a number
of other small craft. However I also have steel vessels up to 6500
tonnes.

How did you end up with all those boats?

--

Roger Long

On Thu, 10 Nov 2005 17:08:29 +0000, Peter Wiley
wrote:



Notwithstanding, I like aluminium for boats myself and if I ever get
the urge, would weigh carefully the first cost vs maintenance issues
WRT steel and aluminium.

If I recall, Ted Brewer wrote an article on this very subject (and he
should know). Overall, he saw it as about a 50/50 situation as
regarding ease of building (easier with Al, but trickier to weld),
strength vs. weight, cost of materials, corrosion and electrolysis,
etc.

If you go into it understanding the materials fully, it's pretty
straightforward. One point, however, to note is that while the vast
majority of under 60 foot/under 19 metre yachts are built in various
types of fibreglass, the majority of high-latitude boats are in metal,
and a strong minority of passagemakers are also in metal.

The Europeans and the South Africans make some lovely...and
fast...boats in steel and aluminum, and they are not as widely
appreciated in North America as is GRP, etc. But if it was good enough
for Moitessier...

R.

rhys wrote:
On Thu, 10 Nov 2005 17:08:29 +0000, Peter Wiley
wrote:



Notwithstanding, I like aluminium for boats myself and if I ever get
the urge, would weigh carefully the first cost vs maintenance issues
WRT steel and aluminium.


If I recall, Ted Brewer wrote an article on this very subject (and he
should know). Overall, he saw it as about a 50/50 situation as
regarding ease of building (easier with Al, but trickier to weld),
strength vs. weight, cost of materials, corrosion and electrolysis,
etc.

If you go into it understanding the materials fully, it's pretty
straightforward. One point, however, to note is that while the vast
majority of under 60 foot/under 19 metre yachts are built in various
types of fibreglass, the majority of high-latitude boats are in metal,
and a strong minority of passagemakers are also in metal.

The Europeans and the South Africans make some lovely...and
fast...boats in steel and aluminum, and they are not as widely
appreciated in North America as is GRP, etc. But if it was good enough
for Moitessier...

R.
I think that generally steel boats are best above a certain size. But
they are too inefficient or heavy below that threshold. Once you are up
into the steel size range, all the other annoying things about steel
boats become bearable.

I just discovered that the steel boat that I Captain has areas 50%
corroded due to stray current over the past three years. That just
doesn't happen in fiberglass and happens faster in aluminum.

Welding new plates on is a bigger job than grinding out blisters and no
boat ever sank from blisters!

Gaz

On Thu, 10 Nov 2005 19:09:35 GMT, Gary wrote:

Welding new plates on is a bigger job than grinding out blisters and no
boat ever sank from blisters!

Agreed. I am looking at steel, aluminum AND fibreglass for
ocean-capable cruisers in the 40-45 foot range. I am seeing decent
examples of each, with a few observations:

The aluminum boats are very touchy about galvanism, and dent easiest.
However, they tend to sail very nicely, but command a premium in price
and, I expect, attention from the owner to keep them free from
electrical issues. To build them is easiest; to weld them is tougher.

The steel boats have a huge variability in fit, finish and general
construction. A lot of homebuilts are utter crap, particularly those
ubiquitous Roberts designs; on the other hand, I have seen that about
1 in 10 are as good or better than any production boat of similar
dimensions. The break point of steel in term of "too heavy" is around
40 feet for a cruiser, but you can get a "leisurely" sailer that is
pretty bulletproof in that range if you are willing to wield a
chipping hammer and stay on top of the paint schedule.

The fibreglass production boats of today are generally insufficient in
design and strength for offshore. They have too much freeboard and not
enough beef where it counts. There are exceptions, of course, but if
you can find and live with designs 25 years or so old (and the boat
isn't a wreck or needs immediate repowering and refurbishment), you
can find some nice deals.

In sum, I am finding a pilothouse cutter and/or ketch that can sail
semi-decently in any material is difficult, but not impossible. You
won't find "names" in these category, however, because the vast
majority of recreational sailors stop at coastal or perhaps Caribbean
sailing grounds. That's fine: they have scads of choices, particularly
lately as the charter fleets are cycling out middle-aged boats because
there's reduced mooring due to hurricanes, etc.

But a three cabin, two head Beneteau is a long way from what I want to
cross the Pacific with.

R.

On Fri, 11 Nov 2005 01:33:03 -0500, rhys wrote:

The break point of steel in term of "too heavy" is around 40 feet for a
cruiser, but you can get a "leisurely" sailer that is pretty bulletproof
in that range if you are willing to wield a chipping hammer and stay on
top of the paint schedule.

I would contest this slightly, I have a 31' steel boat that weighs in at
(allegedly - I never checked) 6,5 tonnes, which is not really any more
than a similar sized cruiser of other materials. There are certainly much
heavier wooden and plastic boats out there..

My hull is mostly 3mm I think, multi-chine with plenty of framing and
after 20 years and 2 atlantic crossings the external plates are not
significantly buckled except in a couple of places under the waterline
where I think the hard stuff has been in contact.

In your comment, you seem to be implying that a cruiser and a leisureley
sailor would be different things? If so then maybe a steel yacht under 40'
would be too leisurely for you, but I find fast boats are uncomfortable
and noisy when I'm trying to sleep.

--
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