On Fri, 26 Mar 2010 10:51:31 +0100, "Steve Lusardi"
wrote:

I do not think Microwave heating to eliminate moisture in fiberglass is practical. The oven in a microwave unit is a reflective
cavity. You would have to have a reflective chamber the size of the boat and a several megawatts of RF to be effective. There
would be dead spots and spots of excessive heating, just like in a microwave oven. Even if you would do this, you would still have
to provide a means of absorbing the moisture generated in the chamber's air. (Basic gas laws and equilibrium apply) There are more
practical ways of achieving this. It is important to understand the problem in order to find a solution. No construction material
lasts forever. They each have their disadvantages and advantages and a finite life. The failure mode of all fiber based plastics
are UV driven disintegration and osmosis. Osmosis is the wicking effect all fibers have when exposed to a liquid, which causes
hydraulic delamination at the weakest bond. Although FG is not waterproof, it is not readily permeable either and there is your
dilemma. Once moisture has invaded the material, it is next to impossible to get it all out.Even though fiberglass boat
construction has been around since the 50's, there are not many boats still around that old. The cost of FG hull maintenance is
only exceeded by wood. All other materials have a better TCO (total cost of ownership). I'm sure that statement will generate some
flames, but it is observable and self evident,
Steve.



I'm sure that you are correct regarding the micro-wave method of
drying a hull as in the article, I read, the writer sounded as though
he had discovered sex and was going to start a company to bring his
innovative methods to the multitudes. Certainly he stated that he had
dried his own deck, or parts of his deck, but I never read another
word about his company of anyone else using salvaged micro-wave ovens
to dry boats.

There also was an article, in Practical Boat Owner, about one of the
their staff who had purchased what was apparently one of the first
fiberglass yachts ever built commercial in the U.K.

For whatever reason the owner, or perhaps the surveyor, cut cores out
of the hull and had them tested. The cores tested at 90-something
percent of the calculated original strength of the hull material.

There was no mention of the boat's history or how much time it had
spent in the water, and in England many boats are hauled out for part
of each year, so the testing was hardly a comprehensive study but, as
the magazine wrote, it did show that fiberglass did not deteriorate
greatly with age.

Regarding the cost of wooden boats, there was another article in the
same magazine written by a bloke who was something of a pundit
regarding wooden boats. He had a "Channel Cutter" that had been built
in 1800-something, and after years and years had sold it. Apparently
there was a great hue and cry, he was a traitor to the traditional
boat world, and on and on.. His article was in justification of his
decision. He simply described, in detail, the trials, tribulations,
and costs of owning a wooden boat of great age. It was an eye opener
as the boat had required substantial repairs nearly every year since
he had owned it. Port garboard replaced, four ribs replaced, portions
of the deck relayed, recaulked hull, etc.

What most people don't realize when they see a wooden boat that when
they were built their life was usually expected to be about 10 years
and many of them were only afloat for a few years - read the history
of the tea clippers.

I once knew Chester Carter who's family had built boats on Miscongus
Bay, in Maine for generations. He told me that the conventional Maine
built work boat, oak timbers, cedar planking, fastened with galvanize
boat nails, would last about ten years and then needed refastening and
might last another five or six years after that. He was well aware of
fiberglass construction and didn't think much of it - not because it
was fiberglass but because it was lighter then wood and bounced around
a lot. He used to say things like "well, you should try pulling pots
in one of those things, jumping around like a rabbit".

Cheers,

Bruce

Bruce writes:

For whatever reason the owner, or perhaps the surveyor, cut cores out
of the hull and had them tested. The cores tested at 90-something
percent of the calculated original strength of the hull material.

I find it highly unlikely they could calculate the original strength
with a 10% inaccuracy. The materials used were not characterized that
well and the variation in the lamination process is much bigger. I
have been told by a senior structural engineering consultant that
the uncertainty in fatigue life for the materials we know best--
structural steels -- is roughly 6%. Composites, even aerospace
qualities, are much, much harder to get good data on.

There was no mention of the boat's history or how much time it had
spent in the water, and in England many boats are hauled out for part
of each year, so the testing was hardly a comprehensive study but, as
the magazine wrote, it did show that fiberglass did not deteriorate
greatly with age.

This is pure nonsense. Fiberglass laminates have limited fatigue life as
do all materials.

This boat has lived a pampered life relative to its scantlings.

/Martin
http://hem.bredband.net/b262106/

If you want to make your wood boat last a long time, you must fasten
it with something that won't rust, you must keep it dry inside, but most
of all you must wash it down morning and evening with salt water!
Gordon

course, you have to protect the bottom from the borers also.

On Sat, 27 Mar 2010 10:07:40 +0100, (Martin
Schöön) wrote:

Bruce writes:

For whatever reason the owner, or perhaps the surveyor, cut cores out
of the hull and had them tested. The cores tested at 90-something
percent of the calculated original strength of the hull material.

I find it highly unlikely they could calculate the original strength
with a 10% inaccuracy. The materials used were not characterized that
well and the variation in the lamination process is much bigger. I
have been told by a senior structural engineering consultant that
the uncertainty in fatigue life for the materials we know best--
structural steels -- is roughly 6%. Composites, even aerospace
qualities, are much, much harder to get good data on.

I am not sure whether they had sufficient data to do accurate strength
calculations although I had a book written back in he very early days
of fiberglass boat building by someone who was described as an expert,
that did list tensile strengths for various boat building materials
and certainly there would have been tests made before publishing such
a table.

Having said that, certainly there is a variance in strength of a
fiberglass structure that varies with all kind of things - chemical
makeup of the actual resin used, hardener/catalysis mix, amount of
glass and resin in the structure and so on. I assume that why they
said calculated strength.

There was no mention of the boat's history or how much time it had
spent in the water, and in England many boats are hauled out for part
of each year, so the testing was hardly a comprehensive study but, as
the magazine wrote, it did show that fiberglass did not deteriorate
greatly with age.

This is pure nonsense. Fiberglass laminates have limited fatigue life as
do all materials.

I didn't say that it didn't deteriorate with age, I said it didn't
deteriorate GREATLY with age.

This boat has lived a pampered life relative to its scantlings.

/Martin
http://hem.bredband.net/b262106/
Cheers,

Bruce

Bruce writes:

On Sat, 27 Mar 2010 10:07:40 +0100, (Martin
Schöön) wrote:

Bruce writes:

For whatever reason the owner, or perhaps the surveyor, cut cores out
of the hull and had them tested. The cores tested at 90-something
percent of the calculated original strength of the hull material.

I find it highly unlikely they could calculate the original strength
with a 10% inaccuracy. The materials used were not characterized that
well and the variation in the lamination process is much bigger. I
have been told by a senior structural engineering consultant that
the uncertainty in fatigue life for the materials we know best--
structural steels -- is roughly 6%. Composites, even aerospace
qualities, are much, much harder to get good data on.

I am not sure whether they had sufficient data to do accurate strength
calculations although I had a book written back in he very early days
of fiberglass boat building by someone who was described as an expert,
that did list tensile strengths for various boat building materials
and certainly there would have been tests made before publishing such
a table.

And the accuracy was stated as? All material data I come across
at work is within +/- something. It is hugely important to make sure
material data used for engineering calculations are for the stuff
coming out of production and not from some lab. Material data should
be for relevant ambient conditions, temperature, humidity or whatever
applies for the intended application.

The use of a new family of high strength steels in ship building in
the early 1908s is a grueling case story. Ships and life were lost
because fatigue life in the corrosive real world was so much worse
than in the lab. Earlier steel qualities had not been affected by
environment in the same way.

Having said that, certainly there is a variance in strength of a
fiberglass structure that varies with all kind of things - chemical
makeup of the actual resin used, hardener/catalysis mix, amount of
glass and resin in the structure and so on. I assume that why they
said calculated strength.

And I say that stating that the laminate still had 90 % of its
calculated strength is nonsense since the errors in calculation
and measurements stack up to far more than 10 %.

There was no mention of the boat's history or how much time it had
spent in the water, and in England many boats are hauled out for part
of each year, so the testing was hardly a comprehensive study but, as
the magazine wrote, it did show that fiberglass did not deteriorate
greatly with age.

This is pure nonsense. Fiberglass laminates have limited fatigue life as
do all materials.

I didn't say that it didn't deteriorate with age, I said it didn't
deteriorate GREATLY with age.

Which is what my statement below was all about.

This boat has lived a pampered life relative to its scantlings.

Leave the thing resting in a cool, dry place away from harmful UV
radiation etc and it will last a long time. Hard everyday use
will see it break down in a few years. That is at least what happen
to the boats used for daily transports by the population of the
Gothenburg archipelago. Three years is what they expect glassfibre
boats to last. These are boats designed and built for recreational
use.

/Martin

On Sun, 28 Mar 2010 12:43:51 +0200, (Martin
Schöön) wrote:

Bruce writes:

On Sat, 27 Mar 2010 10:07:40 +0100, (Martin
Schöön) wrote:

Bruce writes:

For whatever reason the owner, or perhaps the surveyor, cut cores out
of the hull and had them tested. The cores tested at 90-something
percent of the calculated original strength of the hull material.

I find it highly unlikely they could calculate the original strength
with a 10% inaccuracy. The materials used were not characterized that
well and the variation in the lamination process is much bigger. I
have been told by a senior structural engineering consultant that
the uncertainty in fatigue life for the materials we know best--
structural steels -- is roughly 6%. Composites, even aerospace
qualities, are much, much harder to get good data on.

I am not sure whether they had sufficient data to do accurate strength
calculations although I had a book written back in he very early days
of fiberglass boat building by someone who was described as an expert,
that did list tensile strengths for various boat building materials
and certainly there would have been tests made before publishing such
a table.

And the accuracy was stated as? All material data I come across
at work is within +/- something. It is hugely important to make sure
material data used for engineering calculations are for the stuff
coming out of production and not from some lab. Material data should
be for relevant ambient conditions, temperature, humidity or whatever
applies for the intended application.

It is?
Here is a section of a specification sheet: "The standard requirements
for ASTM A516 physical and chemical characteristics are given in the
tables below."

Mechanical Properties:


A516 Grade 60 A 516 Grade 65 A16 Grade 70
Tensile Strength (ksi) 60-80 65-85 70-90
Tensile Strength (MPa) 415-550 450-585 485-620
Yield Strength (ksi) 32 35 38
Yield Strength (MPa) 220 240 260
Elongation in 200mm (%) 21 19 17
Elongation in 50mm (%) 25 23 21
Max Thickness (mm) 205 205 205


The supplier is Oakley Steel,
" a specialist steel supplier focusing in boiler and chrome moly steel
plates. We stock pressure vessel quality plate in ASME and ASTM grades
principally for use in the oil and gas industry."

Hard to find a mention any tolerance, any +/-.

The use of a new family of high strength steels in ship building in
the early 1908s is a grueling case story. Ships and life were lost
because fatigue life in the corrosive real world was so much worse
than in the lab. Earlier steel qualities had not been affected by
environment in the same way.

This is news"

Nearly all uses of new materials,or use of materials in a new way, has
resulted in failure. Not always catastrophic failure but some problem.
The first iron bridges were built with cast iron - they fell down. The
de Havilland Comet, the first commercial jet airliner, used to explode
in flight. Pressurization caused the fuselage to flex, the aluminum
cracked and the side blew out.

I have sent quite a number of coupons for testing and processed quite
a few materials certificates, furnished by steel makers, and I have
never seen a tolerance, never; "Tensile strength 50,000 psi +/- 10%".
Every materials certificate or test coupon has listed only the results
of the test as "tensile strength 50,000 psi" without a tolerance.



Having said that, certainly there is a variance in strength of a
fiberglass structure that varies with all kind of things - chemical
makeup of the actual resin used, hardener/catalysis mix, amount of
glass and resin in the structure and so on. I assume that why they
said calculated strength.

And I say that stating that the laminate still had 90 % of its
calculated strength is nonsense since the errors in calculation
and measurements stack up to far more than 10 %.

There was no mention of the boat's history or how much time it had
spent in the water, and in England many boats are hauled out for part
of each year, so the testing was hardly a comprehensive study but, as
the magazine wrote, it did show that fiberglass did not deteriorate
greatly with age.

This is pure nonsense. Fiberglass laminates have limited fatigue life as
do all materials.

I didn't say that it didn't deteriorate with age, I said it didn't
deteriorate GREATLY with age.

Which is what my statement below was all about.

This boat has lived a pampered life relative to its scantlings.

Leave the thing resting in a cool, dry place away from harmful UV
radiation etc and it will last a long time. Hard everyday use
will see it break down in a few years. That is at least what happen
to the boats used for daily transports by the population of the
Gothenburg archipelago. Three years is what they expect glassfibre
boats to last. These are boats designed and built for recreational
use.

/Martin
Cheers,

Bruce

On Fri, 26 Mar 2010 10:51:31 +0100, "Steve Lusardi"
wrote:

All other materials have a better TCO (total cost of ownership). I'm sure that statement will generate some
flames, but it is observable and self evident

So which is cheapest, steel or aluminum ?

We are seeing a lot of steel sailboats from Europe with semi-hard
chines down here in the Caribbean. Some are showing rust streaks but
most seem to be holding up fairly well.

On Mon, 29 Mar 2010 17:15:54 -0400, Wayne.B
wrote:

On Fri, 26 Mar 2010 10:51:31 +0100, "Steve Lusardi"
wrote:

All other materials have a better TCO (total cost of ownership). I'm sure that statement will generate some
flames, but it is observable and self evident

So which is cheapest, steel or aluminum ?

We are seeing a lot of steel sailboats from Europe with semi-hard
chines down here in the Caribbean. Some are showing rust streaks but
most seem to be holding up fairly well.

It depends a lot on how the vessel is built.

A steel boat that used stainless everywhere there is chafe or wear -
rail cap, all exposed bolt or pin holes bushed, stainless cleats and
fairleads, any dissimilar metals insulated, no wood, teak decks,
cockpit combings, etc., the electrical system totally insulated from
the hull and an alert captain or crew that catches every scratch that
appears will certainly not require much, if any, major maintenance for
very long periods.

On the other hand I know a chap that has a French built aluminum
sloop. Electrical system insulated from the hull, anything that is in
the water is either aluminum or some alloy that doesn't react with
aluminum strongly. To the best of my knowledge the only major
maintenance he has done in probably 20 years is to overhaul the main
engine.

You often see French built boats that are unpainted aluminum, except
for the anti-fouling. They appear to have few problems.

And finally you see the home built boats, built by amateurs, that seem
to rust away in 10 years or sometimes less.

I believe that you are a power boat man so have a look at Seahorse
Yachts, the Diesel Ducks, I did a bit of work on one when it came
through Thailand on its way to the U.S. Beautiful work.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Bruce writes:

On Sun, 28 Mar 2010 12:43:51 +0200, (Martin
Schöön) wrote:

snip

And the accuracy was stated as? All material data I come across
at work is within +/- something. It is hugely important to make sure
material data used for engineering calculations are for the stuff
coming out of production and not from some lab. Material data should
be for relevant ambient conditions, temperature, humidity or whatever
applies for the intended application.

It is?
Here is a section of a specification sheet: "The standard requirements
for ASTM A516 physical and chemical characteristics are given in the
tables below."

Mechanical Properties:


A516 Grade 60 A 516 Grade 65 A16 Grade 70
Tensile Strength (ksi) 60-80 65-85 70-90
Tensile Strength (MPa) 415-550 450-585 485-620
Yield Strength (ksi) 32 35 38
Yield Strength (MPa) 220 240 260
Elongation in 200mm (%) 21 19 17
Elongation in 50mm (%) 25 23 21
Max Thickness (mm) 205 205 205


The supplier is Oakley Steel,
" a specialist steel supplier focusing in boiler and chrome moly steel
plates. We stock pressure vessel quality plate in ASME and ASTM grades
principally for use in the oil and gas industry."

Hard to find a mention any tolerance, any +/-.

No, in your example I find that right away for tensile strength. If
you find it hard to get the information it is either because you use
the wrong suppliers or because you are not important to them.

Having written that I think I have to point out that published
data sheets seldom are really helpful because the tolerances found
there are cooked up by the sales department... you have to go to the
next level in most cases.

snip

I have sent quite a number of coupons for testing and processed quite
a few materials certificates, furnished by steel makers, and I have
never seen a tolerance, never; "Tensile strength 50,000 psi +/- 10%".
Every materials certificate or test coupon has listed only the results
of the test as "tensile strength 50,000 psi" without a tolerance.

If I got such an answer I would start looking for another tester.
Someone who knows and acknowledges that test equipment and test
procedures have limited accuracy. Several samples should be tested
since all manufacturing processes have variations.

Trying to insert some boating content:
The other day I revisited a report on the structural modelling of a
racing yacht. One chapter is dedicated to material testing. They
manufactured laminate samples and had them tested at a test institute
to get data for the modelling. The data they got came with a mean
value and a standard deviation number. The standard deviation
for the material parameters of those carbon pre-preg laminates were
roughly 3%. (You see were my skepticism regarding that 90% figure
comes from.)

Back to my rant:
It is *very* important to realize that real world materials and
production are subjected to random variations and modern engineering
must acknowledge that and take it into account. "If you haven't
done a proper yield analysis you aren't done." Yield in this case
is not yield as in yield strength, but you realized that for sure.

http://en.wikipedia.org/wiki/Six_sigma
http://en.wikipedia.org/wiki/Cpk_Index
http://en.wikipedia.org/wiki/Statist...rocess_control
http://en.wikipedia.org/wiki/Design_of_experiments

http://en.wikipedia.org/wiki/W._Edwards_Deming

/Martin (sorry for the late reply, it has been busy times. I have
been studying the impact of mechanical tolerances on a proposed
design, among other things.)