Scantling rules and hull thickness

Discussion in 'Boat Design' started by ADAM87, Apr 5, 2012.

  1. ADAM87
    Joined: Oct 2011
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    ADAM87 Junior Member

    When using scantling rules to determine hull thickness on a cold molded hull, I get an uncommon size that I can't achieve with stock material. So if I use stock material to achieve the next available size up, I'll have a thicker and stronger hull. It seems logical, but is it acceptable/safe, to take the Sn that applies to that hull thickness and solve for stringer size and placement?
  2. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Scantling rules give you only minimum limits. It is expected that you will design and build a boat to exceed those limits by at least a little bit. You are not expected to hit scantling dimensions exactly. Everyone knows that materials come in fairly standard sizes, and to make building easy, you use the best selection of materials, thicknesses and shapes to make the boat easy to build.

  3. tunnels

    tunnels Previous Member

    Which Way And Where ?????

    Not forgetting the way you stack your materials can also have a detramental affect on the strength as well !!
    The placement and oriantation of glass and where and how you use this is quite important to !:D
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If you're using Dave Geer's scantling rules (my assumption) you can move down a fair bit if the planking thickness is an odd size. 10% thinner would be safe, though more information would be necessary, about the design in general. You can also alter frame or structural element spacing to compensate to a degree as well.

    I'll assume (again) this is for your little skiff. I'd recommend a bit more study in regard to building and design practices, before you commit to lines in a software package. Your previous questions, as well as those here suggest you have considerable software skill, but lack the marine engineering side and general practices aspects of the project. You'd be much better off with a set of plans, of which you can cosmetically modify, to make it look as you desire, rather then attempting to develop scantlings for something you don't fully understand yet.
  5. ADAM87
    Joined: Oct 2011
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    ADAM87 Junior Member

    Thanks for the replies.

    Par, your assumption is correct is on both accounts. I was referencing Gerr's rules on this one. And I do not have the marine engineering side that you and many others have, that's why I ask questions. To that subject, I have befriended a few yacht designers, naval engineers, professional engineers, and builders. And I've expended my share of fuel, time in the shop, and bandwidth since deciding to build this boat nearly 2 years ago. But none of them use Gerr's rules, so I posted up here.

    I was in a builders shop this morning going over more design and building practices. While I was there we looked over my 3D model and prints. When I asked him his thoughts on my design, he said "this is as good or better than most kits or plans you could buy. You need to quit over thinking it and build the darn think."

  6. Ike
    Joined: Apr 2006
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    Ike Senior Member

    He's right. Just do it!
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