Material and Construction Choices Article

Discussion in 'Boat Design' started by DCockey, Apr 7, 2012.

  1. DCockey
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    DCockey Senior Member

    The April/March 2012 issue of Professional BoatBuilder magazine has a nine and a half page article by Robert Stephens of Stephens, Waring Yacht Design discussing the material and construction method choices they made for a custom 68' (20.7m) sloop. In his introduction Stephens says "Simply put, the designer's goal is to balance many factors in matching construction method and materials to keep the cost per unit low and the performance of the finished product high." He then goes on to discuss in detail the choices made and the rationale for those choices which include:
    • Hull - cold molded wood, inner longitudinal wood strip planking, outer layer of glass/epoxy.
    • Bulkheads -composite with foam core.
    • Keel support structure - wood frames and blocking, composite sheet on top.
    • Deck - plywood skins with foam core.
    • Cockpit - composite with foam core.
    • Pilothouse - carbon fiber/epoxy with foam core.
    Interfaces such as the deck to hull are shown in drawings. Overall it provides insight into an important aspect of design including considerations other than just weight and cost.
     
    Last edited: Apr 7, 2012
  2. gonzo
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    gonzo Senior Member

    Is that 68' or 10.7m?
     
  3. DCockey
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    DCockey Senior Member

    68' / 20.7 m I mistyped the length in meters but have corrected it.
     
  4. Tad
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    Tad Boat Designer

    A continuation of the techniques we pioneered at Hodgdon Yachts in the 1980-90's. Many of these choices have to do with elapsed construction time. The owner generally wants his boat asap, and actually breaking the boat into sub-assemblies can reduce cost as well as get her out the door sooner.

    Below is Scheherazade; cold molded hull and foam cored deck and bulkheads built in Maine, carbon molded deckhouse built in Rhode Island.

    SCHdeckhouse.jpg
     
  5. DCockey
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    DCockey Senior Member

    Elapsed construction time was a major consideration for the boat Stephens discusses. Other reasons I've heard for breaking a project up into sub-assemblies and sub-contracting out them are limited space at the main build location and expertise.

    Did Stephens or Waring have any connection with Hodgdon Yachts? Given how connected the boat design and building community in Maine appears to be it's not surprising that methods developed in one place spread to others.
     
  6. Tad
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    Tad Boat Designer

    Coastal (Boatbuilding) Maine is a small place. Guys move around between yards all the time, technology gets transferred. Plus Sonny Hodgdon set the standard for sharing info with other builders or whoever happened to be interested. A more than "open" shop that raised standards throughout the state........
     
  7. rwatson
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    rwatson Senior Member

    The points in the article about cold moulded timber being much cheaper material than glass is good, but I would be interested to hear how the labour part of the hull build compares.

    Laying planks would seem to be a bit more time consuming than laying fibreglass - but as he says, you don't have to construct the temporary framework for laying the foam and glass on.
     
  8. Tad
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    Tad Boat Designer

    Feeding into the man hours will be how experienced your labour is in the chosen method. Assuming vacuum bagging for both methods, building an air-tight mold can be time consuming for a part that is not "Boat" but is "tool". Normally the first layer of cold-molding is close to air-tight. The glass version only starts to pay when you build another.......


     
  9. DCockey
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    DCockey Senior Member

    Rob Stephens discusses in the introduction to the article that what materials and construction methods make sense are very dependent on both the type of boat and the number to be produced.

    Brooklin Boat Yard which built Isobel, the boat discussed in the article, is very experienced with cold-molded wood-epoxy construction. The inner skin is longitudinal strip planking which goes in place quickly and serves as the "plug" for the rest of the hull.
     
  10. Tad
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    Tad Boat Designer

    Thus they were pre-disposed to save the owner money by using that construction material and method, they already had the tools and experience required. I always tell new build clients that the best way to save money is go to a yard with experience in the material and construction method they want to use. It's surprising how many fall for the "sure we can do that(though we've actually never tried it)" line.
     
  11. rwatson
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    rwatson Senior Member

    Thats very true - and very wise of them to stick to their specialty.

    Likewise, a firm with expertise in steel, aluminium or straight FG would be much more efficient in their own material.

    The true proof of the method would be to get quotes, or better yet, do actual builds of the same boat by 3 or 4 differing 'specialist' boat builders.

    From my point of view, the method looks really great for a one person, with semi skilled help type of construction
     
  12. DCockey
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    DCockey Senior Member


  13. rwatson
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    rwatson Senior Member

    I didnt say it was !

    I said that from my point of view ( me am a one person with semi skilled help ) the method was appealing.
     
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