Design Life

Discussion in 'Boat Design' started by issac82, Aug 27, 2009.

  1. issac82
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    issac82 Junior Member

    What is the design life of GRP boats.How can we estimate its design life?
     
  2. Fanie
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    Fanie Fanie

    Hello Issac82,

    GRP lives forever. Someone else may tell you otherwise but in my experience it will outlive you. The GRP should be protected from sun (UV) though or else the resin will disintigrate over time. If it is protected in my opinion there is no limit.
     
  3. amateur mariner
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    amateur mariner Junior Member

    Still how to predict the design life??
     
  4. CDK
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    CDK retired engineer

    Like Fanie wrote, without UV protection by gelcoat or paint, the lifespan is short. I've seen repairs done 5 years ago where the glass is already above the surface. On the other hand there are well built boats from the 70's in good condition.
    As a general rule, the parts that are installed/attached determine the lifespan of a boat. Stern drives in seawater: 15 years, in inland waterways 25 years. Stern drives without service: less than 5 years.

    Another point is that long after the 1th owner has discarded his boat because it has lost its gloss, the 3rd or 4th owner may still be happy with it once the scratches have been repaired and the hull was painted over.
     
  5. bntii
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    bntii Senior Member

    I am happily sailing about in one of the Bounty II series yawls- 53 years and going strong.

    There is another exhaustive thread on this subject around here somewhere...
    If I could summarize the thoughts in one sentence: If the material yields beyond a critical amount in each cycle, the design life will be limited to a finite number of cycles.

    The engineers will no doubt weigh in ..
     
  6. joz
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    joz Senior Member

    I read an article from Professional Boatbuilder to which they are starting to recycle old GRP boats that are 40 yrs old to which you place your old boat in this machine and it destroys the boat to which the fibreglass can be re used in the production of a new GRP boat (powder form), plus it seperates all items whilst it breaking the boat which is quite interesting.
     
  7. Willallison
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    Willallison Senior Member

    Same simple answer as I gave in another thread... "Depends"
     
  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    Way back in my motorbike days it was common knowledge that the fiberglass helmets we used back then softened with use and had to be changed every couple of years. I don't know why, body heat, moisture, poor material, whatever ... I wonder if it was the resin used and if some boats hade the same problem.
     
  9. amateur mariner
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    amateur mariner Junior Member

    Can somebody quote a reference about it?
     
  10. amateur mariner
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    amateur mariner Junior Member

    Somebody quote some reference of the statements already mentioned.If there is any mathematical formula published mention it over here.Waiting for answers
     
  11. Fanie
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    Fanie Fanie

    There is no formula, only estimates.

    To make an estimate valid you have to supply all the conditions.
     
  12. RHP
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    RHP Senior Member

    Joz do you have a link to that PB article I looked on their website and couldnt find it - I would be really interested to read it.

    Thanks
    Richard
     
  13. joz
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    joz Senior Member

    RHP

    I'll try to find that edition for you give me a week or so.
     
  14. RHP
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    RHP Senior Member

    Many thanks.
     

  15. Willallison
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    Willallison Senior Member

    Amateur Mariner, there is almost certainly a great deal of information about the duty cycles / design life of GRP, though much of it would be proprietory. The problem is that there are so many variables that impact on the results of such testing that they are all but worthless to the bulk of the designing / building community. Get five people to laminate a given part and you will get laminates with 5 different sets of properties. Hell - get one person to laminate the same part 5 times and the same will be true!
    Different resins, fibres, core materials, laminating procedures, temperatures, curing times and conditions, humidity, mixing times... the list goes on and on...
     
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