Sketchup Hull design tutorial

Discussion in 'Boat Yard Basics' started by omegadef, Jul 18, 2011.

  1. omegadef

    omegadef Baton Rouge, LA

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    Not sure if this should go here, but some people may benefit from it. I'll do freeship at a later date. Let me know if there are any questions


    Sketchup, distributed free by google, is a program that allows you to create 3d drawings of of objects. It's compatible with both metric and SAE units. I'll stick to the SAE, because for me, it's much easier to visualize 1' than 1m. I wont be focusing on function of the design here, just that the method of drawing it, this is not a working hull design, and I am not qualified to design a vessel for anyone else. Also of note, I am completely self taught in this program.

    What you will need:
    Sketchup: http://sketchup.google.com/
    Soapskin bubble plugin: http://www.tensile-structures.de/sb_software.html
    (big link in the center of the page with a .zip extension)

    Similar to how it's done in freeship(which I'm illiterate in), we will draw one half of the hull and duplicate it for the other side(if only it were that easy to build). If at any point in the tutorial you make a mistake, the undo hotkey is ctrl+z(coincidentally the most pressed key combination on my keyboard).

    When you open a new sketchup file, you will be greeted by an extremely chic and unemotional female. Left click her. She will now be outlined in blue, and we can delete her by pressing the delete key on the keyboard.(Alternatively you can rightclick and select to delete, or even hide, which will be covered later in the tutorial.)

    [​IMG]

    First we will select our measuring tape tool and make a guideline for the length of our vessel. First click the horizontal axis of choice(not at the origin), in my case it's the green axis, move the mouse so that the guideline runs parallel to the red axis, and type in the desired length. I will use is "20'" in this case, followed by the enter key. If you can't see the guide line, zoom out until it is in your view, to do this, I roll my mousewheel back. Alternatively, the zoom tool can be used(helpful for laptops).

    [​IMG]

    Now, we will draw in a guideline for the centerline. I will start from the red axis and go 3.5' over, half of my desired beam of 7'.

    [​IMG]

    Now, lets actually draw the transom. Select the line tool(pencil icon) and click the origin followed by the point where the center-guideline intersects the green axis. This will make a line between the two points, but it will probably be hidden by the origin. The next line will start from the green-centerline intersection and veritcally extend upward to the desired transom height, in my case, we'll use the 3.5' again.

    [​IMG]

    Now, we'll select the rectangle tool(looks like a square). Start from the origin and move up to the end of the line we just made. Boom, square.

    [​IMG]

    Now we'll make the chine(obviously variable depending on design). Select your protractor tool. First click the bottom right corner of your square, then click the origin, now place your mouse in the center of the square and type your desired angle(note: this is only the angle on the transom piece), I'll use "25". There will be a guideline at a 25 degree angle from the green axis now.

    [​IMG]

    Now we will draw a line along this guideline to form the outline of our transom. I'll go to the halfway point by placing another guideline 1'9" from the side. I'll now draw a line from the bottom right-hand corner to the intersection of the angle guideline, as in the image.

    [​IMG]

    Now, I'll finish MY(yours can be different) transom by continuing the line from that point up to the top left corner.

    [​IMG]

    We can now delete the bottom left corner of the square, use the select tool and drag it to select the unneeded lines.

    [​IMG]

    Make two lines parallel to the red axis, from the top and bottom right corners, that run the full length of the boat(20').

    [​IMG]

    Now, select the arc tool(half circle) and click the midpoint in the top-centerline we just drew followed by the endpoint, the tip of the bow. Next click the line at the bottom.

    [​IMG]

    Now delete until you're left with this:

    [​IMG]

    We'll need to make two lines, from the chine and the top left corner, parallel to the red axis extending out the length of our vessel.

    [​IMG]

    Now for the fun part, we're going to actually make the curves for the hull. I, perhaps because I know no better make all of my curves tangent to the lines we just made, luckily Sketchup makes this easy for us to do.
    Select the Arc Tool, and start from the chine to the tip of the bow. Now, without clicking, place the mouse on the line we just drew in and move it along until the arc turns light blue, signaling that the curve is tangent to the line. It will have the phrase "Tangent at vertex" as well. The center will fill itself in again, but we can delete it, I left it for some contrast.

    [​IMG]

    For the top line, I'll start my arc from the top right corner of our transom square and end at the bow point, making the arc radius the line we drew previously from the top left corner.

    [​IMG]

    Now we'll clean it up by deleting excess lines.

    [​IMG]

    We are finally going to "skin" the hull. We will start by selecting the three boundary lines for our "skin", the chine curve, the bottom line, and the transom angle line. Hold the control key and click each one to select them, ctrl+shift deselects. Note that the bottom is in two pieces. We then press the Skin button, and are greeted by a sheet.

    [​IMG]

    We are now prompted for the number of segments we want. I try to stay inside of 10 and 25 segments, 10 is more than enough for this skin. After typing the number, hit enter twice.

    [​IMG]

    Hey, it actually resembles something that might float now!
    Repeat for the top section.

    [​IMG]

    Now we just need to duplicate this side and flip it to make the other.
    CTRL+A selects the entire drawing, then ctrl+C copies, and ctrl+v pastes. click to place the hull, the placement is irrelevant for now, but just ensure it doesnt overlap any of the first half of the hull.

    [​IMG]

    Now, right click and select Flip along, then Green direction.

    [​IMG]

    Now use the move tool(4 way arrow) and move the bow point of the new hull to the same point on the old hull.

    [​IMG]
    [​IMG]
    And there we have it. The possibilities are endless, for instance, here's a drawing of the catamaran I am hoping to build.
    [​IMG]
     
  2. firecat1981

    firecat1981 BBA Counselor

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    awsome! a bit confusing at first, but I think I can manage. Where you able to print out your patterns in full size somehow after you transfered them?
     

  3. omegadef

    omegadef Baton Rouge, LA

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    Freeship allows you to print out the plate developments, but they are not full size.

    Easy to loft over to the ply with the developements.

    If you want, I can post the text file I used to import my chine lines into freeship, from there it was minor tweaking until it was as close as I could get it to sketchup.

    Other than for visualization, sketchup isnt needed at all in the process.
     
  4. twitch

    twitch Well-Known Member

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    Will all the panels created in those 2 programs be developable with stitch and glue? If not, how do you know besides trial and error?
     
  5. omegadef

    omegadef Baton Rouge, LA

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    Yes, the free ship panels are made for stitch and glue.


    Sketchup doesnt give a way for you to transfer the 3d panels back to a 2d shape.
     
  6. WhiteDog70810

    WhiteDog70810 Mostly Harmless

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    I spent a lot of quality time with Sketchup and never figured out how to skin in panels. I ended up filling the sides segment by segment. This is much easier. I'd be very interested to see how you import the image to FreeShip. Me and FreeShip never got along even though I've been told it is very user friendly.

    Nate
     
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