How long lasts Fiberglass?

Discussion in 'Materials' started by Vega, Apr 26, 2006.

  1. Vega
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    Vega Senior Member

    I have asked myself many times if the high resale price of some 20-year-old sail boats, from reputable builders, were justifiable. I mean their hulls would still maintain their original integrity, or has time collected his bill?

    Some interesting answers on this Research Project, by Prof. Paul H. Miller's

    (it looks that time is not the main problem, but use. That's interseting and a little bit surprising, at least for me)


    From "Stiffness Reduction of Marine Composites"
    by Prof. Paul H. Miller's

    "During the summer of 1999 some on-the-water testing was performed in San Francisco Bay using two J/24's supplied by OCSC. One was a 1981-vintage boat that saw very few hours of use (about 50 hours/year) prior to the testing. The other was a 1984 boat that averaged over 800 hours/year of sailing, for a total of more than 11,000 total sailing hours at the time of testing! The goal of the comparison testing was to see if a difference in stiffness could be measured, indicating the amount of fatigue. The methods used to check these included static measurements at the dock (discussed above) and underway dynamic strain readings.
    .................................................................................................
    The dockside "string tests" indicated the 1981 boat was about 15% less stiff in global longitudinal bending than a brand-new boat, and the heavily used 1984 boat was 52% less stiff than a new boat.
    The panel flexural stiffness measured during sailing indicated the lightly-used boat was 4% less stiff than a new boat and the heavily-used boat was 18% less stiff than when new.
    ......................................................................................................
    the crew that sailed both boats were asked to immediately comment on the two boats' conditions. Universally they felt the newer (more used) boat felt "softer"."
    ........................................................................................................
    The “service-life” of recreational craft is difficult to predict. Designers should realize that some vessels may experience 10^8 significant wave loading cycles. As most composite fatigue data only carries to 10^6 cycles this requires a higher safety margin. "

    http://web.usna.navy.mil/~phmiller/J-24fatigue/j-24fatigue.html
     
  2. Guillermo
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    Guillermo Ingeniero Naval

    Well, fatigue usually is a secondary issue against resin hydrolysis and other GRP problems for an old boat, from my point of view. But imagining a perfect laminate with no other harms, yes, fatigue is more important than age.
     
  3. Roly
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    Roly Senior Member

    Good stuff vega!
     
  4. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    That's why you can have an "almost new" Soling for almost nothing :)
    After a few years they are to soft to compete.
     
  5. Ike
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    Ike Senior Member

    It really depends on the laminate. The Navy made gigs for their ships during WWII out of fiberglass. The laminate was about twice as thick as it needed to be because back then no one really knew how strong and durable fiberglass would be. Some of those boats are still being used over 60 years later.

    So the answer to your question, how long the fiberglass last? No one knows. I imagine thousands of years from now archeologists will dig up old land fills and find completely intact fiberglass boats, hot tubs, shower enclosures and who knows what else.

    That is, unless there really is a polyestermite. LOL
     
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  6. DGreenwood
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    DGreenwood Senior Member

    Cyclic loading is one of the aspects of
    GRP that has not been tested enough. From what I have seen it doesn't look like it stands up to it very well.
    Then along comes a boat like Nigel Irens', Formul Tag. AKA ENZA later in life. After years of racing and charter work it was lengthened by Peter Blake and co. and blasted around the world---breaking the record.
    Now there is definitely a difference longevity wise in Epoxy carbon as opposed to your standard Poly e-glass mix. But anyone who has been around ocean racers has seen the effects of long term strain has on a hull.
     
  7. Guillermo
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    Guillermo Ingeniero Naval

    That's one of the problems I see with GRP (and the like) boats: They do not rot or oxidize, as the wooden and iron ones do, if they are abandoned in the beaches after their working life or when wrecked/sunken. When in the end of working life situations, authorities enforce expensive enviromental-friendly destroying systems in the developed countries, not always or happily complied with by every boat owner :rolleyes: , and I believe this is worst in no developed ones. And, for sure, many wrecks and sunken boats simply end in the bottom of the sea or the coasts.
    Resin in GRP may decay trough a process of hydrolysis, but this produce acids, glicols, etc, as well as fibers, etc., going into the enviroment. But I'm deviating from the thread's purpose.....Has this matter been treated before in these forums?
     
  8. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I think GRP has been recycled as garden/outdoor furniture.
    But it's a problem, all those old boats lying around.
     
  9. FAST FRED
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    FAST FRED Senior Member

    Its really simple.
    If the laminate was constriucted heavy enough to NEVER FLEX (about 400% over the minimum structural loading) the boat will basically last "forever".

    This is the scantling Required by the USCG for inspected vessels (in other words bigger than 6 passengers). Fire retardant resin is also required.

    So if it dont flex it wont break.

    EZ

    FAST FRED
     
  10. Wellydeckhand

    Wellydeckhand Previous Member

    What if the fiberglass is mix with kelvar, or cabon composite will it be the same? Will it be more durable and rigid...... be a good resale boat?
     
  11. Roly
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    Roly Senior Member

    Then again, if certain structures don't flex the weakest junction will fail,especially with shock loading.Just how has Lindsay Lords scantling rules stacked up longterm?
     
  12. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    Lindsey Lords rules, more developed by MacNaughton, for glass sheated strip planking seems to work fine.
    Carbon is better than glass when it comes to "fatigue", but it's expensive and not so easy to work with. Wood is excellent, it's cheap and easy to work also :)
     
  13. longliner45
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    longliner45 Senior Member

    fiberglass does rot ,it depends on the conditions it is maintained in mostly at joints, but it dose rot,
     
  14. Milan
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    Milan Senior Member

    Well, from the boats which I saw, my gut feeling is that heavily built solid fiberglass boats from the sixties are still oftenly structurally more sound then a lot of the newer 5-6 years old lightly built boats. Many sandwich boats suffer delaminations which can cause a real problems, especially in colder climates if water finds its way through the cracks in de skin in to the foam and then freeze and expand during the winter …

    Also, solid, thick, fiberglass laminate, even if bitten by the time (in the form of osmosis for example), still has enough "meat" left to be easily repaired. Layer or two of glass cloth and epoxy add another 20 years of life.

    Milan
     

  15. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I once met three Germans in a Swan 65 in Lofoten (we where 5 Norwegians in a Swedish Vega, 25 feet long). They had just made a large hole in the side of a car ferry, probably 9mm steel. The bow of the Swan had just a few scratches in the gel coat. I think that was a boat from 1970 or so.
     
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