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post #55 of Old 02-03-2013
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Re: Life Span of a Boat

Thank you for the kind words. There are three studies that I have have quoted over the years that you may be referring to.

The first was a US Navy document produced in the early 1950's which was intended establish design guidelines for F.G. Reinforced composites. I have a copy of that in my file and have quoted from that study on occasion, and make the point that this study existed and were widely circulated. Carl Alberg more likely than had been working with those standards when he designed the Triton. Charlie Wittholz told me that he worked with those standards at Rhodes and Alden in the 1950's.

The second is a marine insurance study which looked at the strength of fiberglass over time, and with one section particularly focused on early f.g boats. That 10 or 12 year old study was available on line but was not available the last time that I looked for it. This study was significant in comparing actual sections of older boats to what might have been expected simply from an identical new section with the same level of fiber and resin.

The third study was part of a series of Naval Academy student projects exploring the new sail training boats. That study looked at the failure modes of fiberglass in an impact situation. The lessons of that study is very interesting in terms understanding the behavior of glass reinforced plastics.


Originally Posted by RichH View Post
Nice write up Jeff.
Some time ago you had made reference to USN studies of FRG hulls vs. long term fatigue endurance. Ive misplaced that URL reference ... any 'reminders' where to locate?

The ultimate problem for fiberglass, like any other 'plastic', is that its not a long term stable material if constantly stressed. The very definition of 'plastic' means that the material is subject to long term deformation, called 'creep'. In addition, the glass fibers used to strengthen are really not a 'true' solid but a visco-elastic 'hybrid liquid' with long term 'easy' deformation - an example would be: take a sheet of glass and 'lean' it against a wall at a large angle for several years and that glass plate after several years will be found to be 'bent' ... all by itself, due to the material quality called 'creep'.

So after a few hundred years, your prized boat will probably be approaching the shape of a 'large puddle' on the ground, simply through the action of gravity and the nature of 'plastic' and not a true 'elastic'. "Creepy", huh? ;-)

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