Anyone familiar with the book 'Boat Strength' by Dave Gerr

Discussion in 'Sailboats' started by EAP, Sep 5, 2006.

  1. EAP
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    EAP Junior Member

    I'm looking for any validation, whether good or bad, of the designing method described in the book "Boat Strength", by Dave Gerr. Is there anyone familiar with this book and/or had experience building to these rules??
     
  2. Alik
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    Alik Senior Member

    Try ISO12215. Much better, even simplified methods in Annex.
     
  3. Crag Cay
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    Crag Cay Senior Member

    What sort of boat do you want to engineer? Will you be going for RCD certification?

    I'm afraid my answer comes in several parts. Firstly, I have run metal boat designs through it that I have already built and there has been close correlation. All these boats have been in service for some years without problem, so that is a positive. My colleague has also done the same with the wood strip epoxy boats he has designed and built and again found nothing amiss (typo on page 158 excepted - in formula 11-3, the Sn number should be raised to the power of .37) In addition Dave Gerr has used his rules for a number of boats, in various materials, and they have all proved satisfactory in service as well.

    All the examples I have quoted have been conventional designs, well within the parameters of the rules as stipulated in the book.

    My only reservations would be; it's a very prescriptive rule. You have to accept the underlying premise and follow the prescribed structure. If it coincides well with your needs, viz a vis layout, frame clearances, etc then good. Other rules are better at letting you explore more variables which may make finding a solution to some design headache's more straightforward.

    Also the procedures are in narrative form, rather than flow chart or even PC based. You have to make sure you don't miss a step.

    Finally, proof of RCD compliance is possible by:
    * compliance with harmonised standard ISO 12215
    * using other published scantling determination methods — eg classification society rules.
    * direct calculation using basic engineering principles.
    * trials and/or testing — eg a drop test.
    * documented empirical knowledge derived from a satisfactory service history.
    * comparison with a similar boat with a service history known to be satisfactory.

    I don't know if the Gerr Rules would count under 'using other published scantling determination methods' or, if he has designed a similar craft to yours, whether you could seek to argue 'comparison with a similar boat with a service history known to be satisfactory'. Obviously the size of your intended vessel and the intended Design category, would have a bearing on it's possible acceptance.

    ******
    Gerr's Book: 20 GBPs - - - - Wolfson Unit's Hullscant Software: 1000 GBP's +
     
    Last edited: Sep 5, 2006
  4. EAP
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    EAP Junior Member

    In Answer To Your Question I Am Designing A Replica Of The Old Sandbaggers Of Late Nineteenth Cent. My Aim Is To Incorporate New Technology Into An Classic Design. I Believe My Parameters Are 'conventional' Enough (d/l Falls Within Gerr's Requirements), And I'd Say Frp Thicknesses I've Derived From The Formulas Seem Adequate To My Experiences With Vessels This Size. Thanks For Your Input
     
  5. Scott Carter
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    Scott Carter Senior Member

    Hi EAP -
    I've dogeared my copy of Boat Strength in a short 4 months of owning it. It is, in my inexperienced experience (ahem...4 months) of designing boats generally conservative enough to not feel the need to hedge in a safety factor on significant scantlings. From a reader perspective, the graphs accompanying each formula have saved me many calculator key strokes on rough estimating sizes. I like the book, and it's helped me build (on going) a very seaworthy yet not over built 74' schooner by any standards. Hope this helps.
    Scott
     
  6. westlawn5554X
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    westlawn5554X STUDENT

    The book is an eye opener... It is after all the rcommended book that also the westlawn text book... like it or not if you like boat you should purchase it... OR collect it.
     
  7. MikeJohns
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    MikeJohns Senior Member

    The steel scantlings are workboat scantlings, and seem to comply with ABS steel for boats under 90 meters.

    You'll find ABS racing/ cruising steel framing scantlings to be generally lighter than Gerr's.

    Can't comment on the other constructions but I think RaggiThor was expressing some concern a while back, presumably on cold moulded. Suggest you message him.
     

  8. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I think I was forwarding some conserns from MacNaughton.
    Later I bought "tentative rules" from DNV, and I think the logic is quite simmilar as in Gerr's book, just more detailed.
    I don't know much about steel :)
     
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