Any books on small boat design ?

Discussion in 'Sailboats' started by fcfc, Jun 10, 2008.

  1. fcfc
    Joined: Feb 2005
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    fcfc Senior Member

    Design and manufacturing.

    What I call small saiboats are things between dinghy and cruisers, that are essentially trailerable. Some call them cheap cruisers for youngs, others call them dinghy for not so young people.

    I have tried to design, but faced stability, structure and weight issues.
    A heavy marginally stable boat (but still passing RCD category D stability and structure) marginally trailerable is within my reach. But as soon as I add some usability or performance item, things go badly wrong.

    Trailering, loading, unloading loads on hull. Say someone walking on the deck to remove or put the mast, the boat still on the trailer.

    For performance, what to expect from the crew as ballast ?
    Whatabout sailing single handed. It would be stupid not to sail if the full crew is not present.

    The easy cure is to add real ballast. Then you beef up structure to handle all. But at the end, you end up with a boat that's so heavy that 99% of cars can no longer tow it.

    So, are there books or other papers dealing with this kind of sailboats and specific issues ?

    Thanks.
     
  2. Chris Ostlind

    Chris Ostlind Previous Member

    Dave Gerr has written two books which you should read... Boat Strength and The Nature of Boats

    Lars Larsson and Rolf Eliasson have done Principles of Yacht Design

    Skene's Elements of Yacht Design has solid information

    Steve Killing has written Yacht Design Explained

    Beyond these books, you should consider taking a long look at the boats that are already out there in the world and sailing successfully. Talk to people who repair boats to see what they think about certain building techniques and materials. Buy a set of plans from a reputable designer and build your own boat... and then get it out on the water and sail it to see how it handles and how strong it is when being sailed hard.

    Take your drawings and structural calculations to a local boat designer and hire them to look over your work and offer suggestions.

    There are, literally, mountains of information on the Internet regarding the very questions you have asked.

    All these things will give you a good background in the business of establishing a design and the correct structural needs for the boat as intended.

    You can't do too much reading or asking of well thought-out questions.

    Chris
     
  3. fcfc
    Joined: Feb 2005
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    fcfc Senior Member

    I already read "Principle of Yacht Design". It is a very good book. The problem is that it only cover bigger sailboats. The sample used is a 40 ft yacht.

    How can you use what is in that book where there is so much variation in righting moment due to the crew ballast effect ?

    The problem with small boats is there is a very wide gap.

    It can go from this http://www.i550.org/index.php?option=com_content&task=view&id=17&Itemid=39 to http://www.dixdesign.com/inspir19.htm

    One is 800 lbs (350 kg) , the other is 2000 lbs (870 kg). That make a significant difference.
     
  4. Chris Ostlind

    Chris Ostlind Previous Member

    There's a very big gap in bigger boats, as well. If you compare the various types of sailing craft in the 40' range, for example, there are huge differences in gross weight, sail area, ballast needs, etc.

    Many of the issues of small craft design are similar to those of the suggested 40 footer in the Larsson/Eliasson book, you just need to adjust for size and weight of the boat in question.

    Where the bigger boat relies on a weighted keel form to achieve a good deal of its righting moment, the smaller craft will, typically, get most of its RM from crew positioning and form stability.

    If you are really serious about doing this exercise, then you will need to use your intellect and ask lots of questions of those who already work in the field.
    Take what you learn and apply it to a boat of the type you wish to develop. Again, look at the boats in the same size range as that which you would like to create and see how they solve the basic problems at hand.

    There is no complete book drawn answer for many of the issues facing a boat designer. One has to gain the knowledge of all the issues involved and then apply them, as necessary, to the criteria as needed.

    Good luck in your pursuit.
     
  5. Doug Lord

    Doug Lord Guest

    Check out Pierre Gutelles excellent "Design of Sailing Yachts" (ISBN 0 948646 54 3 ). He covers small planing boats on up.
    And for some high performance info,the bible:" High Performance Sailing" by Frank Bethwaite,(ISBN 0-07-005799-0 ) Be aware that he may be about ready to come out with a new edition or entirely new book soon.
    Good Luck!
     
  6. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    "For performance, what to expect from the crew as ballast ?
    Whatabout sailing single handed. It would be stupid not to sail if the full crew is not present.

    The easy cure is to add real ballast. Then you beef up structure to handle all. But at the end, you end up with a boat that's so heavy that 99% of cars can no longer tow it."

    Welcome to the real world mate. boat design from dingys to maxis is both art and engineering, one without the other leaves many blanks in the eyes of the observer.

    Try multihulls if you want stability and performance, The trailer tris are very fast and very manageable, if that is your sort of thing.
     

  7. fcfc
    Joined: Feb 2005
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    fcfc Senior Member

    This is exactly the very opposite of all the engineering background I have ... The beauty of engineering is when it behaves exactly as you have computed.
    But for this, I need models.

    There are bunch of models to find hydrodynamic pressure on a hull, but it is much more harder to find a model of loads when on a trailer (vertical acceleration).

    Again, for pedal boat, you can find curves for power depending of genre, training, duration of effort, etc ... There is also motion sickness indicator.

    But what percentage of people would accept sailing like this, and how long they would enjoy :)D ) it : http://www.microclass.pl/pub/gal/17/242_med.jpg or http://img219.imageshack.us/img219/4233/plobsheim11mai082gx0.jpg
    Not speaking of the acceptance of this http://img223.imageshack.us/img223/6829/plobsheim11mai086px2.jpg

    Generally, that kind of pictures are not shown in sales advertisement for this class of boats.
     
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