Drafting cross sections and ahead/rear views?

Discussion in 'Boatbuilding' started by ChesapeakeBay1, May 9, 2014.

  1. ChesapeakeBay1
    Joined: May 2014
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    Location: VA-BEACH

    ChesapeakeBay1 New Member

    Hello
    For the past few months I have been teaching myself to draft plans for boats. I have figured out views from the side above and simple hall shapes and have turned it to a science, But I have not been able to figure out drawing/calculating the shape of curved cross sections/ahead astern view. It has proved very frustrating. I have searched the internet thoughly and no one seems to draw their plans any more. Most people buy kits or plans witch seems to take the fun away. Most are using CAD programs, I would not like sitting in front of a computer I am not good at using them, nor do I wish to spend the money, it seems to take the difficulty that makes drafting fun for me away. Does any one draw their own plans anymore!? If you do please tell me how you do it i'd be much obliged.
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Drawing on a computer is the same thing as drawing freehand, just slower. Yep, I said it and a hail storm will soon erupt, but generally it takes (me at least) longer to generate concepts and a rough GA on the machine than by hand. Now, with this said, where the machine comes in handy is several fold. First is the math, which is calculated on the fly in the machine, so no more center of masses calculation, which is a tedious affair by hand, plus the other assorted difficulties, like running a full stability curve through 180 degrees for example. Where the machine really shines is in reproduction, regurgitation and correcting changes or errors. A hand drawn plan with the need to move some masses around, to make things balance properly, requires lots of erasing, cussing and recalculation. The machine speeds this up tremendously. Next is the reproduction aspect. Having had to regenerate drawings previously by hand, the machine easily spits out as many copies as you need. Lastly, I'm in the middle of a new build. Previously, I would have lofted the lines, station molds and a few other details by hand, say the rudder, appendages, bow profile, etc., but now, with a large printer, I can print full size templates, saving all the hand drawn bother and time, lots of time. I printed the station molds for this build in about a half hour. If I'd hand drawn it, this time would have been many hours.

    To your question, yes, we still "draw" things by hand, though the hand is working with different tools. Instead of a T square, curves and architectural scale, we use a keyboard, mouse and other "devices", but the same work is preformed.

    Drawing profiles and internal views are just simple 2 and 3D dimensional drafting, regardless of the method employed. Below is one of my "Framing Guide" drawings, which is designed to show where things live in relation to each other. I find this type of drawing more beneficial then a pretty picture of a bulkhead, without any idea what's in it, behind it, attached to it, fillet locations, fastener spacing, etc.

    Drawing these shapes is exactly the same as drawing a station mold, just with more detail. You may be better served by looking up isometric and/or direct projection drawing. Simply put, if you want a bulkhead view, looking aft lets say, you erect a perpendicular at the location of the bulkhead (on the profile), wherever this might be and pick up the ordinates from the plan and sectional views, to plot the other views. With these dimensions in hand you add what you need, like the planking thickness, viewed on edge of course, and other build details.
     

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  3. ChesapeakeBay1
    Joined: May 2014
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    ChesapeakeBay1 New Member

    Thank you PAR
    I guess I have to start looking into computer programs. Do you have any that you would recommend? Can you use any hull shape you want with these? Can I put the plans I have Already drafted into it?
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You select the hull shapes, not the software and these are defined by the goals (SOR) of the the design's parameters. You really can't ham hand this type of design work, unless you just pan of experimenting with small boats and failure isn't something you're too worried about.

    It might be easier to find out what you know or need to know. How's your hydrodynamics understanding? The same should be asked of general engineering principles and maybe a splash of physics, just to keep you grounded? Simply put, if you don't have a fairly firm grasp on the the fundamentals and principles, you're just making pretty boat shaped pictures. For example how have you determined where your newly drawn boat will float?
     

  5. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    Welcome to the forum and to the wonderful world of three D drafting. Rather than try to tell you how to do this in the limited space here, I suggest you go find a copy of Skene's Elements Of Yacht Design by Kinney.Look for an eighth edition. This book hasn't been updated since the eighties but if you want to learn to draw hulls the old fashioned way then this is the book. You should be able to pick up a used one on Amazon, or maybe even at a Used Book Store. It covers the drafting of lines very well. You need to learn how to use offsets, that is, the values of a single point on a hull, in three dimensions. Every point on a boat has a dimension longitudinally (fore and aft), transversely (side to aside) and vertically above an pre-defined baseline. Once you learn how to determine these points and put them into a table then you will be able to draw lines such as waterlines, buttocks, stations and diagonals in the three views.

    I hope that makes sense.

    Anyway once you learn the basic elements, then you can move on to doing it on computer with one of the free programs. I use Delftship. The program previous to that was Freeship and can still be downloaded from some web sites but is no longer supported except by enthusiasts who use it. Try the Freeship Yahoo group at https://groups.yahoo.com/neo/groups/Freeship_HTandT_Group/info

    As for on line learning how the lines are drawn look here http://paulbudzik.com/current-projects/Enterprise Scratch/ShipForm.pdf. This deals with ships but the basics of drawing lines are the same.
     
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