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Forum Home > General Discussion > fiberglass age vs strength

tropical dreams
Posts: 1

Does anyone out there in "old boat land" know if fiberglass loses strength due to age, and if so , how much or how bad. I have a 1977 MFG Caprice with a deep V hull that is all original and the floors and stringers are still solid. Can this old boat take the kind of pounding that I see newer boats take on a regular basis running in 3' chop in salt water, or will I break it in half? I don't normally pound my boats, however some times you need to outrun a storm or some other emergency. Some say that fiberglass loses flexability with age, and that after about 10 years old, anything can happen. Any experiences, or comments would be appreciated.

April 22, 2011 at 9:35 AM Flag Quote & Reply

Posts: 7

The biggest percentage of older classic fiberglass boats were made using polyester resin with no UV barrier.  This resin basically never stops curing.  It gets hard enough to pull from the mold and is dry to the touch but the process continues till it decomposes.  Sunlight ultraviolet rays speed this aging process and is a big reason for early decomposition.   The glass fibers that are the reinforcement in the resin is not affected by this and by comparsion outlive the resin.  The biggest difference that I have seen in many of the 40 year old boats that we have rebuilt is the amount of sunlight they were exposed to.  This says nothing about the wood reinforcement that is a whole other issue.    As the resin continues to cure it looses its flexability and becomes more brittle.   A boat like our Power Cats that were designed to flex and give when impacted will need to be reworked to put strength back in those areas that are now rigid.  Since these often have the wood replaced as it has also decomposed, when replacing the wood the glass itself is rebuilt when bonding in the wood.  But any area that shows signs of cracking to the point of exposing the glass fibers should have at a minimum a layer of glass cloth with enough resin to fill all the voids layed over. 

Danny Leger


July 15, 2011 at 3:02 PM Flag Quote & Reply

Posts: 39

Great expanation Danny, thanks!  So in effect it's more the poly resin that fails than the fiberglass itself.  I know my Starflite and Frank's PowerCat both showed some minor signs of cracking in stressed areas after making "wake jumps" last season.  Frank has already repaired his, mine is waiting in line for the GT-150 project to be completed.

I wonder if epoxy resin would eliminate this problem in newer boats?

Bottom line - take it easy with the Glassics, heavy pounding is likely to do some damage!?


Mark S

July 21, 2011 at 5:35 AM Flag Quote & Reply

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