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Default Fiberglass loss of strength

The following is an excerpt from a discussion on a forum regarding the
Oday 37 and then turned into a discussion on fiberglass, I believe
that the author is a boat designer or works in the field of water
vessels....or has a very specific and informed opinion....or,,,

And since I posted articles perviously that are related I though this
was worthy,,,,



(Much of this was cloned from a response to a similar discussion, so I

aplogize if it does not precisely match your question and may be a bit

I would not think that well- designed and constructed fiberglass has a
life span per se. Neither properly designed and constructed concrete
nor fiberglass truly breaks down or loses strength on their own. They
require other causes. The key here is the term 'well- designed and
constructed'. Boats like the Oday 37 were not all that well engineered
and constructed to begin with, using lots of resin rich laminate with
large proportions of non-directional materials (mat)in the laminate
(more on that later) and 1979 was in the heart of the period that was
worst for blisters and other resin issues.

In the case of fiberglass loss of strength can result from one or more
of the following,

-The surface resins will UV degrade.
-Prolonged saturation with water will affect the byproducts formed in
the hardening process turning some into acids. These acids can break
down the bond between the glass reinforcing and the resin.
-Fiberglass is prone to fatigue in areas repetitively loaded and
unloaded at the point where it is repetitively deflected. High load
concentration areas such as at bulkheads, hull/deck joints and keel
joints are particularly prone.
-Salts suspended in water will move through some of the larger
capillaries within the matrix. Salts have larger molecules than water.
At some point these salts cannot move further and are deposited as the
water keeps moving toward an area with lower moisture content. Once
dried these salt turn into a crystalline form and exert great pressure
on the adjacent matrix.
-Poor construction techniques with poorly handled cloth, poorly mixed
or over accelerated resins, and poor resin to fiber ratios were very
typical in early fiberglass boats. These weaker areas can be actually
subjected to higher stresses that result from much heavier boats. It’s
not all that unusual to see small spider cracking and/or small
fractures in early glass boats.
-Of course beyond the simple fiberglass degradation there is core
deterioration, and the deterioration of such things as the plywood
bulkheads and flats that form a part of the boat’s structure.

Earlier boats had heavier hulls for a lot of reasons beyond the myth
that designers did not know how strong fiberglass was. Designers knew
exactly how strong fiberglass was. The US government had spent a
fortune studying and developing fiberglass technology during WWII and
by the early 1950’s designers had easy access to the design
characteristics of fiberglass. (Alberg, for example, was working for
the US Government designing composite items when he designed the
Triton and Alberg 35) The reason that these hulls on the early boats
were as thick as they were had more to do with the early approach to
the design of fiberglass boats. Early designers and builders had hoped
to use fiberglass as a monocoque structure with a minimal amount of
(if any) framing to take up interior space.

On its own, fiberglass laminate does not develop much stiffness and it
is very dense. If you simply try to create stiffness in fiberglass it
takes a lot of thickness. Early fiberglass boat designers tried to
simply use the skin for stiffness with wide spread supports from
bulkheads and bunk flats. This lead to incredibly heavy boats and
boats that were comparably flexible. (In early designs that were built
in both wood and fiberglass, the wooden boats typically weighed the
same but were stiffer, stronger, and had higher ballast ratios)

Fiberglass hates to be flexed. Fiberglass is a highly fatigue prone
material and over time it looses strength through flexing cycles. A
flexible boat may have plenty of reserve strength when new but over
time through flexure fiberglass loses this reserve. There are really
several things that determine the strength of the hull itself. In
simple terms it is the strength of the unsupported hull panel (by
'panel' I mean the area of the hull or deck between supporting
structures) itself, the size of the unsupported panel, the connections
to supporting structures and the strength of the supporting
structures. These early boats had huge panel sizes compared to those
seen as appropriate today.

This fatigue issue is not a minor one. In a study performed by the
marine insurance industry looking at claims on older boats and doing
destructive testing on actual portions of older hulls, it was found
that many of these earlier boats have suffered a significant loss of
ductility and impact resistance. This problem is especially prevalent
in heavier uncored boats constructed even as late as the 1980's before
internal structural framing systems became the norm. Boats built
during the early years of boat building tended to use a lot more resin
accelerators than are used today. They also would bulk up the matrix
with resin rich laminations (approaching 50/50 ratios rather than the
idea 30/70) non-directional fabrics (mat or chopped glass) in order to
achieve a desired hull thickness. Resin rich laminates and
non-directional materials have been shown to reduce impact resistance
and to increase the tendency towards fatigue. The absence of internal
framing means that there is greater flexure in these older boats and
that this flexure increases fatigue further. Apparently, there are an
increasing number of marine insurance underwriters refusing to insure
older boats because of these issues.

There are probably other forms of hull degradation that I have not
mentioned but I think that the real end of the life of a boat is going
to be economic. In other words the cost to maintain and repair an old
boat will get to be far beyond what it is worth in the marketplace. I
would guess this was the end of more wooden boats than rot. I can give
you a bit of an example from land structures. When I was doing my
thesis in college, I came across a government statistic, which if I
remember it correctly suggested that in the years between 1948 and
1973 more houses had been built in America than in all of history
before that time. In another study these houses were estimated to have
a useful life span of 35 years or so. As an architect today I see a
lot of thirty five year old houses that need new bathrooms, kitchens,
heating systems, modern insulation, floor finishes, etc. But beyond
the physical problems of these houses, tastes have changes so that
today these houses in perfect shape still has proportionately small
market value. With such a small market value it often does not make
sense from a resale point of view to rebuild and these houses are
therefore often sold for little more than land value. At some level,
this drives me crazy, since we are tearing down perfectly solid
structures that 35 years ago was perfectly adequate for the people who
built it, but today does not meet the “modern” standards.

The same thing happens in boats. You may find a boat that has a
perfectly sound hull. Perhaps it needs sails, standing and running
rigging, a bit of galley updating, some modern electronics, a bit of
rewiring, new plumbing, upholstery, a little deck core work, an engine
rebuild, or for the big spender, replacement.

Pretty soon you can buy a much newer boat with all relatively new gear
for less than you’d have in the old girl. Its not hard for an old boat
to suddenly be worth more as salvage than as a boat. A couple years
ago a couple friends of mine were given a Rainbow in reasonable shape.
She just needed sails and they wanted a newer auxiliary, but even
buying everything used the boat was worth a lot less than the cost of
the “new” parts. When they couldn’t afford the slip fees, the Rainbow
was disposed of. She now graces a landfill and the cast iron keel was
sold for scrap for more than they could sell the whole boat for.

Then there is the issue of maintainable vs. durable/low maintenance
design concepts. Wooden boats for example represent the difference
between a maintainable construction method versus a low maintenance/
durable method. A wooden boat can be rebuilt for a nearly infinite
period of time until it becomes a sailing equivalent of ‘George
Washington’s axe’ (as in “that’s George Washington’s axe. It’s had a
few new handles and a few new heads but that is still George
Washington’s axe”.) The main structure of a fiberglass hull is
reasonably durable and low maintenance but once it has begun to lose
strength, there is nothing that you can do.

The best deals on older used boats are the ones that someone has
lovingly retored, upgraded, and maintained. Over the years they have
poured lots of money and lavished lots of time into maintaining the
boat in reasonably up to date condition. No matter how much they have
spent the boat will never be worth anything near what they have in it
because there is a real ceiling to how much an older boat will ever be
worth and they will often have several times that ceiling invested.

And finally if you buy an old fiberglass boat, paint the bilges white.
It does nothing for the boat, but if you ever have to sell the boat,
then someone may look in your bilge and say “Lets buy her because any
man that would love a boat so much that he went through the trouble to
paint the bilge white must have enjoyed this boat and taken great care
of her no matter what her age.”

As to the Oday 37 CC. These were mediocre boats in the true sense of
the word. They were not the best sailors but not the worst. They were
not the fastest boats but not the worst, they were not the best built
boats but not the worst. You get the idea. One think that I really
dislike about these boats is there center cockpit layout. When you
compare the center cockpit version to the aft cockpit version of these
boats, it is easy to understand why these are the poster child for why
center cockpits make very little sense on a boat under 40 feet.

Good Luck,
  #2   Report Post  
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Default Fiberglass loss of strength

You were saying before you got cut off ? ( I have a grp boat but also a
45 year old cape roofed/termitey 2 story w/termitey joists and oak
floors up stairs, cbs and terrazo otherwise)

de java dave

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