multi or round chine

Discussion in 'Boat Design' started by islands50, Apr 16, 2016.

  1. islands50
    Joined: May 2012
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    Location: Port Lavava,TX

    islands50 Junior Member

    Hi folks been awhile since I asked a question so please bare with me. been looking at several different designs of North Sea trawlers, one thing I notice is most of them have a convex bottom, what I mean is shapes that would be very hard to make without some very expensive machinery and much more skill than I possess, I forgot to mention I am thinking steel, I am not interested in a single hard chine, but have been leaning more to the multi chine. can anyone in basic boats for dummies style, explain the pros and cons between the different shapes and or modifying a typical full displacement design to multi chine

    John

    PS I have taken the time to read and look at the members sites where avaible, so I do have good feeling about asking
     
  2. fredrosse
    Joined: Jan 2005
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    Location: Philadelphia PA

    fredrosse USACE Steam

    Displacement Speeds - Number if Chines

    Have a look at the previous thread titled as above.
     
  3. islands50
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    islands50 Junior Member

    Thank you Fred, reading it now, yet I was not worried so much about speed, as the overall effect on stability, and ease of construction, we are looking at what on the 40-60 foot range of about 9-10 knots anyhow
     
  4. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Simplistically, you can minimive wetted surface by using a flat bottom and a single beveled chine. For a steel boat the wide flat bottom makes for some structural problems, so a slight arc in the bottom while maintaining the beveled chines is working toward a compromise.

    A little arithmetic will reveal that a round chine with arc bottom actually has slightly more wetted surface than the bevel chine section does. That is if section area is the same.

    That is not to say that that section is the most ideal for a boat of the size that you contemplate. You will probably want to use several chines in order to avoid some of the more severe structural demands on wide plate areas.
     
  5. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    " 40-60 foot range of about 9-10 knots anyhow"

    For 1/2 to 1/3 the fuel the 60ft would be happier at 7.5K than 10K.

    Just do what most inshore pleasure marine motorists do , talk MPH instead of KPH.

    To ease construction some folks will purchase a made up rolled chine and weld it in.
     
  6. islands50
    Joined: May 2012
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    islands50 Junior Member

    Fred, are you speaking of a kit boat ?? I have looked at them , but not finding the desired profiles, I like your suggestion about having plate rolled, and explored that Idea yet the cost of having it done I could acquire a used roll myself, which brings us back to the multi chine design and construction, and yes I know there are good and bad points gives and takes, you're also correct about the fuel consumption,
     
  7. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A concept to keep in mind is to have the boats interior servicable , as it will need to be maintained.

    Sand blasting to "water white" is the norm for a n interior repaint.

    Be sure to use stringers of flat stock as its easy to see the weld places and gedt them really clean.

    Having the interior bolted in for easy removal will save massive time and headaches.

    Sure the hull paint and epoxy sellers will claim almost unlimited life for their products , but none will give a guarantee.

    Eventually it will be worth the thought/effort you give the project now.

    Rolling hull plate takes lots of time and skills, using a pre-made roll in the chine for better looks is far less daunting.

    Either way the boats look will change , but not the performance.

    Remember the price of steel is almost the same worldwide , the difference is in the price of labor.

    Building a hull and plopping in the engine is no big deal, and might be cheaper to HAVE done than to DIY.

    With the oil patch on hard times a local builder might surprise you, as some will bid almost at cost to keep their skilled folks working.

    Installing a fine interior and multiple systems might be a better DIY project.

    Willing to take a finished hull with a couple of hammocks , and a sea swing across the Gulf?

    Perhaps a Mexican yard might work for you.
     
  8. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    How big of chunks are getting unbolted and removed? Is it modular or do you pretty much do a full disassembly/reassembly?

    How else would stuff be attached? Welds?

    Any pics plans or links?
     
  9. islands50
    Joined: May 2012
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    islands50 Junior Member

    Fred,

    All of your points are valid, and I love the idea of the interior being semi removable, for easy access, and the idea of having a slow shop doing the roll work, we are forgetting transportation costs, from shop to building site, and if it is not rolled correctly the hassle of the back and forth, there again looking at all that we are talking about keeps me going back to the multi chine as you said steel is cheap,
     
  10. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The usual is the shop rolls the chine , you cut and fit it.
     

  11. islands50
    Joined: May 2012
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    islands50 Junior Member

    thank you Fred, I had assumed that and it would
    need patterns for the shop to work with I see your point and agree with you
     
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