From Cruisersforum.com:
As I said in a prior thread on this subject, 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 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. At some point these salts 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. Its 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 boats 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.
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 youd 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
parts. When they couldnt 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.
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 Washingtons axe (as in thats George Washingtons axe. Its had a few new handles and a few new heads but that is still George Washingtons 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, 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.
