I would not think that fiberglass has a life span per se. Neither concrete nor fiberglass truly breaks down or loses strength on their own. They require other causes. 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 resin 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. (see discussion on older boats below)
-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.
In a study performed by the marine insurance
industry looking at claims on older boats and doing destructive testing on older hull
materials, 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 accelerators than we use 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 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 degradation that I have not thought of 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 minor electronics
, a bit or 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 an auxiliary, but even buying
everything used the boat was worth a lot less than the cost of the “new-used” parts
. When they couldn’t afford the slip fees
, the Rainbow was disposed of. She now graces a landfill and the cast iron keel
for scrap for more than they could sell the whole boat for.
Wooden boats represent the difference between a maintainable construction method versus a low maintenance
. 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”.)
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, a potential buyer 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.”