Boat Modeling 201

Part 1

Being a new and improved method of producing realistic hull models from an existing set of line drawings. This method covers both chined and round bottomed boats and will produce a hull in one third as much time as the method discussed in my first article. A basic understanding of the parts of a line drawing is assumed so it is recommended that you read my first article prior to continuing on with this one.

Method 1, Step 1 - the Table of Offsets

As we learned in the first article, a table of offsets is the tool used to record measurements along various points on a boat's hull. The lines along which these points are measured are illustrated clearly in the line drawing and though a comparison of these lines and the data found in the table it is a fairly simple task to reproduce the individual "stations" which represent the cross sectional shape of the hull at points evenly spaced along the boats length.

For the following example on how to create a cross section at each station refer to the following illustrations 1.1.1 and 1.1.2

Illustration 1.1.1 - A labeled line drawing of the Nymph

Illustration 1.1.2 - The Table of Offsets for the Nymph

For our example we will be reproducing the station numbered two. This was just a random choice but one that will work fine as the process is the same regardless of which one is being done. If you are unfamiliar with the concept I urge you to sketch out the steps I am about to describe on a scrap sheet of paper as you work through them. Don't worry, you needn't take out a ruler just yet, just approximate the distances and label them as I have in the following illustrations so you can verify that you are doing it correctly.

First sketch out the base and centerlines. These are the lines along which everything is going to be measured. If you look at illustration 1.1.1 you will see these lines and their positions clearly illustrated. Refer to illustration 1.1.3 to check your progress so far. You needn't worry about labeling these two lines, just familiarize yourself with them.

Illustration 1.1.3

Illustration 1.1.4

At this point we are going to begin plotting measurements. Working from the bottom up draw a horizontal line at points along the centerline whose values correspond to those found in the "Heights" column of the table of offsets. As you can see, we measured up 8.40 inches from the baseline, then 15.82 inches up, and finally 22.18 from the baseline. These values can be found in the table of offsets next to the sheer, chine 1, and chine 2 rows.

Now following the same process we used in the previous example measure out from the centerline along the horizontal lines. The values for these measurements can be found in the table of offsets in the section called "half-breadths". Be sure at this point that you are plotting the correct values along the correct lines. For example, the bottom line in our example corresponds to chine 2 so all measurements along this line must also correspond to chine 2.

Illustration 1.1.5

Illustration 1.1.6

Now simply connect the points you plotted in the previous two steps. In the illustration at left I have done this in yellow while still showing the other lines so as to make this step as clear as possible as it is probably the single most important step. By this point your drawing roughly approximate the one appearing in illustration 1.1.6.

All I have done for illustration 1.1.7 is erase the centerlines and the horizontal reference lines we used in the construction of the cross sectional shape. As you will notice, the shape found to the right is identical with the second shape back in the right side of the body view in the line drawing.

Illustration 1.1.7

Method 1, Step 2 - the 3D Model

Before I begin one the actual step by step description of the construction process let me preface it by saying that these instructions are written for 3D Studio R3, which is an older dos based version of the now popular 3D Max. While this tool is ancient compared to the windows version it none-the-less can produce some spectacular models. I won't go into the making of the many details found aboard ship as this is beyond the scope of this article but I will talk you through the making of the Nymph step by step. I am afraid this section will be illustration free as 3D Studio does not allow for taking screen shots but I hope this wont be too much of a hindrance.

Before you begin your project, print this out and have it available for easy reference. A calculator should also be kept on hand.

Step 1: To set things up, first click on View>Drawing Aids and set the x, y, and z values to 1 and turn the snap on.

Step 2: Click on Programs>2D Shaper and begin your cross sections the same way you did in the previous example. To aid in accuracy we are going to make the boat one hundred times actual size. We do this by dropping the decimal point and just using the number as it appears. For example, the value 14.03 would just be treated as 1,403. Be sure to verify that the snap is turned on. Press Ctrl Z to center the screen on the 0,0 axis and click on Create>Line to begin.

Step 3 (FP): Position the cursor on the x0 ,y1503 axis and click once to start the cross sectional shape. Keeping the y-axis on 1503, move the mouse to the right until you arrive at the point corresponding to x500 and click. From there move the mouse up and outwards until you find the point labeled x1000, y 1797 and click. Repeat this process and place a mark (click) on the x1000, y 2389 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "FP" and move on to the next step. If you study what we did in this step you will see how we basically followed the same steps I use in the illustrated example above only we used some shortcuts to produce the shape as we worked along. If you understand how and why this works and don't want to actually build the model I recommend skipping ahead to step 12 as the next eight steps will just be duplicating the process with each section. The text will be identical except the numerical values, which will be changed to suit the needs of the station being worked on.

Step 4 (1): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y1161 axis and click once to start the cross sectional shape. Keeping the y-axis on 1161, move the mouse to the right until you arrive at the point corresponding to x663 and click. From there move the mouse up and outwards until you find the point labeled x1204, y 1690 and click. Repeat this process and place a mark (click) on the x1230, y 2293 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "1" and move on to the next step.

Step 5 (2): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y840 axis and click once to start the cross sectional shape. Keeping the y-axis on 840, move the mouse to the right until you arrive at the point corresponding to x833 and click. From there move the mouse up and outwards until you find the point labeled x1404, y 1582 and click. Repeat this process and place a mark (click) on the x1431, y 2218 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "2" and move on to the next step.

Step 6 (3): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y684 axis and click once to start the cross sectional shape. Keeping the y-axis on 684, move the mouse to the right until you arrive at the point corresponding to x955 and click. From there move the mouse up and outwards until you find the point labeled x1547, y 1502 and click. Repeat this process and place a mark (click) on the x1572, y 2172 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "3" and move on to the next step.

Step 7 (4): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y612 axis and click once to start the cross sectional shape. Keeping the y-axis on 612, move the mouse to the right until you arrive at the point corresponding to x1000 and click. From there move the mouse up and outwards until you find the point labeled x1600, y 1462 and click. Repeat this process and place a mark (click) on the x1625, y 2142 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "4" and move on to the next step.

Step 8 (5): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y634 axis and click once to start the cross sectional shape. Keeping the y-axis on 634, move the mouse to the right until you arrive at the point corresponding to x950 and click. From there move the mouse up and outwards until you find the point labeled x1541, y 1473 and click. Repeat this process and place a mark (click) on the x1570, y 2136 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "5" and move on to the next step.

Step 9 (6): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y780 axis and click once to start the cross sectional shape. Keeping the y-axis on 780, move the mouse to the right until you arrive at the point corresponding to x825 and click. From there move the mouse up and outwards until you find the point labeled x1394, y 1530 and click. Repeat this process and place a mark (click) on the x1428, y 2182 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "6" and move on to the next step.

Step 10 (7): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y1009 axis and click once to start the cross sectional shape. Keeping the y-axis on 1009, move the mouse to the right until you arrive at the point corresponding to x651 and click. From there move the mouse up and outwards until you find the point labeled x1188, y 1615 and click. Repeat this process and place a mark (click) on the x1229, y 2272 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "7" and move on to the next step.

Step 11 (AP): Delete the previous station and start again from the x0, y0 coordinate. Remember to press Ctrl Z to center the coordinate as well as zoom in to the correct level. Position the cursor on the x0 ,y1214 axis and click once to start the cross sectional shape. Keeping the y-axis on 1214, move the mouse to the right until you arrive at the point corresponding to x500 and click. From there move the mouse up and outwards until you find the point labeled x1000, y 1702 and click. Repeat this process and place a mark (click) on the x1000, y 2384 coordinate. From there, move the mouse left, leaving the y position the same but returning the x to 0. Click here and then drop the line down to your starting point, clicking to close the polygon. Save this shape as "AP" and move on to the next step.

Step 12: Now that you have created and saved each of the various stations it's time to starting forming something resembling a boat. For this step you will need a calculator so if you are actually producing the boat rather then just reading over these instructions I recommend getting one now. Click on Programs>3D Lofter. Then click on Path>3D Scale. It is important to know at this point that the boat is exactly eight feet long and that the various stations are spaced one foot apart. It doesn't say this in the line drawing but I know it's true as I am the one who created the boat in the first place. If you are working from a drawing that is lacking information use a known distance as a reference point and scale everything from that. You also need to know that translated to our scale of one hundred times actual size and working in inches the length is 9,600 and the station spacing is 1,200. The default length of the path is 100 inches and this needs to be scaled up to our boat length so this step will cover how to do that. First shrink the path to 96% of the original size. By this point we have a 96 inch patch which needs to grow by one hundred times. To do this, scale it up by 400%, then 400% again, then 250%, then 250% again. If you were working in 1000 times actual size this would have to be scaled up another 400% and then another 250% again.

Step 13: Click Path>Steps and change this value to 7 as the two end steps aren't counted.

Step 14: Click on Shapes>Pick and click on the top most point on the path. If it is off the screen then press Ctrl Z to bring it down to size. Click on Shapes>Get>Disk and pick "FP" from the file list you are presented with. Once you have done this move down to the next step on path and repeat the process only using "1" instead of "FP". This is done until all the steps on the path are filled.

Step 15: Click on Object>Make and press ok. This will produce an extremely accurate half hull model of the boat in the 3D Editor.

Step 16: Click on Programs>3D Editor and press Ctrl Z in each window to bring the boat into view. At this point you may want to add some lights and render it to see how all of your hard work has paid off so far. You will certainly notice that only half of the boat will be present and that the whole thing will be a solid block. If you refer to illustration 1.2.1 you will see which edges need to be cut away in order to hollow out the boat. These edges are plainly marked in blue. To clip away an edge click on Modify>Edge>Delete. Be sure to save often so that is you mess up it wont ruin all of your work.

Illustration 1.2.1

Step 17: Using the line drawing as a guide move the lower vertexes in the bow and stern inward until they both have the desired slant.

Step 18: Click on Modify>Odject>Mirror and then zoom in as close as you can to the centerline in the top view. Making sure that your snap is turned on, click on the half hull and move it until your x coordinate read 0. Single click to place the hull.

Step 19: Click on Surface>Material>Choose and pick copper or blue metal. Click on Surface>Material>Assign>Object and then click on each half of the model pressing ok when prompted.

Viola! All done! All you have to do is render it and enjoy! Please download my Nymph here and check yours against it to see how well you did. And that sum's up part one of Modeling 201. Part two will cover more complex topics such as round bottomed boats, sharp and rounded bows, attached surfaces such as decks as well as a few hints on how to make masts and a few other details. I will also go into detail on how to use a drafting program to aid in the modeling process. I highly recommend reading and understanding this section as part two wont have the same by the hand approach to describing the processes and I'm afraid that a new modeler wont be able to follow very well without a working understanding of the basics.