CreateBoat Example

Stephen M. Hollister

New Wave Systems, Inc.

www.newavesys.com

This is a beginners tutorial to introduce you the basic functions and features of our ProChine program (also applies to ProBasic and ProSurf). This can be the first tutorial you see before using the program for the first time. We will give you step-by-step instructions that will allow you to try out the program and see what it can do. We assume that you are a little bit familiar with how to use the computer and how Windows programs work in general.

Start by double-clicking the ProChine (or ProBasic or ProSurf) icon on your Windows desktop. You should see the following screen with four blank windows (after the startup information screen has been shown).

Each window will show a different view of the boat: side (back) or profile view, top (or bottom) or plan view, right or section or bodyplan view, and finally the 3D or perspective view. These views sometimes confuse people since the profile view of the boat is called either the front or back view, depending on which direction the bow of the boat on the screen. Also, the plan view is called the “bottom” view (as opposed to the top view) because we like to keep the bow of the boat pointing to the right. (Have you ever noticed that boats only seem to go to the right?) Don’t get too confused by the labels of the views. Part of our view labeling scheme is based on what the general purpose CAD programs use.

The next change I want to make is to eliminate 3 of the 4 view windows. Some people like to see all 4 views of the model at one time, but I like to see just one view, but at maximum size. I did this by clicking on the ‘X’ in 3 of the 4 windows. Then I maximized the remaining window. If I want to see a different view than the one I have on the screen, all I have to do is pick the appropriate button on the toolbar. Speaking of the toolbar, it is shown below and some of the functions are explained.

As you can see, it looks like a standard toolbar with the command or function pull-down menus located at the top. All of the file and print options work like any other Windows program so they will not be discussed here. If you want a brief description of the toolbar functions, just hold the cursor over the toolbar “button” and a label will be displayed.

The most important command on the toolbar is the counter-clockwise arrow, which is the Undo command. Anytime you change the geometry of the boat and wish to undo the change, just pick on this button once. You can go back up to 25 steps and you can show a list of the previous Undo commands using a command in the View list of commands. The ‘H’ buttons with the circular arrows are for hiding and un-hiding geometry on the screen. This is important when your boat gets complicated and you want to temporarily hide portions so that you can see what you are doing. The 4-direction arrow button is selected when you want to move the “edit” points that control the shape of the boat (Move Point). This is the most common command you will use to change the shape of your boat.

Please note that most of the commands in the program are “mode” commands. This means that the command you picked will stay “ON” until you select another command. This means that if you pick the Move Point command, you can continue to move any point on the model until you pick another command. You do not have to first select the geometry or entity before you can edit its shape.

The tool bar buttons that look like (or at least are supposed to look like) a boat’s profile, a boat’s top view, and a boat’s section view are used to change the view of the boat in the current window. The 3D button puts the current view into the 3D perspective view. The 3D button is followed by 4 buttons that will change the view of the boat in the 3D view; either up or down or rotate left or rotate right. If you switched the program’s display to just one window, you will use these buttons to change the current window to display that view.

The ‘K’ buttons are use to display and control the curvature or “K-curve” on the boat’s curves and they are used to magnify the fairness of the hull. You will have to see the special tutorial on fairing and smoothing to find out more about these commands.

However, the toolbar buttons that look like hand-held magnifying glasses are important. The one that looks like a plain magnifying glass is used to “zoom” in on a portion of the window that you are interested in. It works just like many other CAD programs in that you will press the left mouse button and drag a zoom box to define the area you wish to enlarge. The magnifying glass with the line through it is used to reset the view. It will resize the display to maximize the view of the boat in the window. You will need to use this command many times.

OK, let’s get started the easy way by using the CreateBoat command in the program. This command, located in the File set of pull-down commands displays the following dialog box and allows you to define a starting shape for a boat that uses your own principal dimensions. Go ahead and select this command and you should see this input dialog box.

Note that the values are filled in already. This is done for two reasons. One, so you can see what an example boat’s values look like and two, so you can pick the OK button and create a sample boat without having to come up with your own values. There are many times you might want to quickly create a test boat so that you can try out some things… like now. So, pick the OK button and you will see the following screen if your current view is the profile view of the boat. This command creates a starting shape of the boat using 3 NURB surfaces: one for the bottom surface below the chine, one for above the chine and one for the deck. Initially, the deck surface is turned off. Initially, there is no transom defined. That can be added later, if needed. This is a considered to be a 3D geometric surface model of the boat.

The first thing I want you to do is to use the toolbar buttons to look at all of the 4 views of the boat.

When you pick the side view toolbar button, you should see this view.

When you pick the top (or bottom) or plan view toolbar button, you should see this view. If you want to be picky, then this is a view of the bottom of the boat and what is drawn is the starboard half of the boat. Note that the program assumes that the boat is symmetrical about the centerline and all you have to do is to design one-half of the boat.

When you pick the right or section view toolbar button, then you will see this view. This may look rather odd, but it is a common sight for boat designers or naval architects. The traditional display of a boat in cross-section or bodyplan view shows the forward sections (in front of amidships) on the right of the centerline and the aft sections (aft of amidships) on the left of the centerline. The reason this is done is to clean up the display of the sections so that the aft sections (stations or frames, if you prefer) do not overlay on top of the forward sections. The bodyplan view takes a little bit of time to get used to, but it does clean up the view. Perhaps not too much for this simple boat, but for complex shapes, it can make a big difference. You can, however, turn this “flip” option off or adjust exactly where along the length of the boat you can flip the sections from the right to the left.

This view is displayed when you pick the “3D” button on the toolbar. The program will display both halves of the hull for viewing. Try using the “Z” rotate buttons and the “Up” and “Dn” buttons to rotate the boat left and right and up and down.

Next, go to the “View” set of pull-down commands and select the Render View-Open Render View command. You should see something like this. You can also use the rotate buttons to change the angle of the boat in this view. Note that you cannot edit the shape of the boat in this view – perhaps in a future version.

[Note that we use the OpenGL render display commands provided with all Windows systems. We have noted that in some systems, this display might look incorrect or extra jagged. If so, then go to the View-Render View-Screen Options dialog box and make sure that the “Nurb Polygon Tolerance” input field is set to 15. If this doesn’t help, then feel free to contact us.]

To leave the Render View of the boat, just pick the ‘X’ in the corner of the window. You can re-display the view at any time using the render command. For the next part of the tutorial, you want to turn off the render display.

If you want to change the color or some other attribute of a surface, all you need to do is to use the “right” mouse button and click on any curve that represents any one of the surfaces. The following surface attribute dialog box will be displayed.

I will not take the time to explain all of these options, but they are used to control the options for the surface you picked. If you pick the “Color” button, you will see a standard Windows color selection dialog box where you can select a standard color or create a unique color yourself. For this tutorial, I picked the bottom surface and changed it to a burgundy-like color.

This is what it looked like after going back to the Render View display. Remember, so far, we have not changed the shape of the boat yet.

Before we go on, pick the ‘X’ for this display and go back to one of the standard views of the boat. We will now define a set of stations, buttocks, and waterlines for the boat. This is done with the PlaneCuts-Initialize Lines command. (Select the PlaneCuts pull-down menu and select the Initialize Lines command.) You should see the following dialog box.

This dialog box allows you to define a set of stations, waterlines, and buttocks that you want to use for the boat. These lines will form a starting set of lines for the boat that you can add to or subtract from. Do not feel that you are stuck with this starting set of lines. Often times, a designer might use a certain set of stations during the design of the boat, but switch to a different set of “frames” for building purposes. You can also add or delete lines from this list at any time.

For those getting a little bit confused, keep in mind that our program uses NURB surface “rows” and “columns” to define the shapes of all surfaces. The columns are kind of like stations and the rows are kind of like diagonals. One of the biggest changes from traditional hand drafting is the use of these NURB surfaces where you control the shape with “rows” and “columns” and NOT stations, waterlines, and buttocks. You can, however, display any of these traditional lines during the editing process. For example, you can see a waterline change shape while you edit a surface row or column, but you cannot directly edit the shape of the waterline itself. The benefit of this technique, however, is that you do not have to make sure that the three views of the boat match up. The NURB surfaces are guaranteed to match up in all three views.

Anyway, just pick the OK button to accept the default lines for the default boat. [The default boat and lines make it easy to play around with the program.] Next, select the PlaneCuts-Display Lines-All Lines ON command to show the lines on the boat. For the profile view, you should see the following.

You can switch to the other views to see the lines in those views. The green lines are the waterlines, the red are the stations, and the blue are the buttocks.

To see this traditional lines view of the boat, select the View-Lines View command. Note that at any time, you can print the current view using the File-Print command. The default is to scale the view to maximize its display on your printer. You can also control the scale factor of the output and plot all the way up to full size.

Before I start to edit the shape of the boat, I’m going to turn off the automatic display of the lines (PlaneCuts-Display Lines-All Lines OFF command) and display one of the 3 standard views of the hull. For this example, I will use the profile view of the boat.

To begin editing the shape, you need to select the Move Point button on the toolbar. This is the button showing the four arrows pointing in different directions. I call this the “rough” shaping part of the design process. This is not the time yet for detailed shaping and fairing or smoothing.

Once the Move Point command has been selected, you can select and drag any edit point on the boat. An edit point is defined by a little square located at the intersections of all curves (rows and columns) on the surface. Notice that each surface of the hull is defined with only two rows (the top surface has the sheer and chine rows and the bottom surface has the chine and profile or fairbody rows). Also note that each surface is made up of only three columns (one at the bow, one at amidships and one at the transom). For the NURB surfaces that are used to define these surfaces, the rows and columns that define their shapes can be moved into any position you want. However, it is best if you try to follow some basic rules and terminology. For example, we call the curves that go along the length of the boat the “rows” and the curves that go vertically the “columns”. These definitions help us explain how to use the program. In addition, it is best if you try to use the fewest rows and columns as possible (this makes it easier to smooth or fair the hull) and try to keep a relatively even spacing of the rows and columns (this avoids unwanted wiggles or bumps in the surface).

The CreateBoat command creates a boat with the desired principal dimensions using the fewest rows and columns as possible. The initial shape of the boat is very simple, but the expectation is that you will be adding in more rows and columns to create your desired shape. (There is another tutorial that goes into detail about the whole hull design, shaping, and fairing process.)

OK, where were we? Oh yes, Move Point. Once this command is selected, you can proceed to grab and drag any point on the model. (Remember the Undo command if you make any mistakes!) In the example below, I grabbed the amidships sheer edit point and moved it much higher. Keep in mind that these are NURB surfaces and that any change in shape in one direction affects the shape in all directions. This means that the 3D model remains complete and exact.

Note that if you move an edit point on the chine curve (common to both surfaces) then both of the surfaces move together and do not split apart. Of course (!) you say? Well, you might be surprised to find that many (most?) CAD programs can’t move both surfaces at the same time!?! Our program sets up a geometric relationship between the two surfaces so that if you move a common point on both surfaces, then both surfaces move at the same time. Also, remember that you do not have to “select” any geometry (like in many CAD programs) before you can edit its shape. Once you select the Move Point command, you can proceed to (and continue to) move any edit point on the model.

Once you move a point on the hull, try looking at the hull in all views, including the Render View, as shown below.

The Render View should reinforce the concept that the NURB surfaces are true 3D surfaces that completely define the shape of the hull. All you have to do is to shape and fair the hull surface.

I won’t go into the whole shape designing process here since it is covered in detail in another tutorial. I will just say that the process involves two phases: one is the rough fairing portion that uses the Move Point command and the commands to add additional rows and columns in the boat. The second phase involves using the curvature curves (K-curves) to do the final fairing or smoothing of the boat.

Before I continue, I want to Undo the change to the sheer curve that I just made.

What I do want to show here, however, is the process of adding another chine to the boat. (I hope you didn’t wait until this point to find out that you are not stuck with the single chine that CreateBoat gives you.) The first thing you should do is to display the “Right” or section or bodyplan view of the boat on the screen.

For this example, I want to add a horizontal chine step to the boat. This can be done with just a few commands. The first one is the Surf-Add Row/Col-Add Row/Col Knuckle command. This command allows you to add a chine “row” to the hull in one step. What it will actually do is to split a surface into two surfaces at your picked point.

After you select this command, position the cursor on the amidships column (station, if you want), just below the chine and click the left mouse button. You should see something like this above. The program has split the bottom surface into two portions at the newly inserted row.

The next step is to merge the forward end of the new chine step row with the forward end of the original chine. This is done with the Edit-Merge Pnt To Pnt command. When you pick this command, it will display the following on the status line:

“Pick the point to merge”

Pick the forward-most edit point on the new chine row.

The next message will be:

“Pick the merge to point”

Pick the forward-most edit point on the old chine row. Now the two points are tied together and you can use the Move Point command to move them both at the same time. The points will stay merged together unless you specifically un-merge them.

Since I want to have a perfectly horizontal chine step, I want to move the inside chine edit points to have the same height or ‘Z’ value as their associated outside chine points. There is a quick way to do this with the Edit-Match Pnt-Z Match command. This command allows you to set the first picked edit point to the same ‘Z’ value as the second picked point. The picture above shows the result of using this command on the middle and aft inner chine edit points.

Adding a new chine takes only a minute or two. The Render View above shows the result of adding a horizontal step into the boat. Of course, I really needed to talk about creating the proper shape and width of the step, but this tutorial is getting to be long enough. In real life, one would probably spend quite a bit of time on the hull shape before adding the inside chine step. It is much easier to shape the hull without the inside chine than with the inside chine.

As you design the boat, you might want to see a grid that defines the original principal dimensions that you entered in the CreateBoat dialog box. We call these the “target” values since those are the numbers you entered, but the program allows you to change the shape to any size that you want. This is done by setting a value in the Options-Display Options dialog box, as shown below.

To draw the principal dimensions on each view, change the Grid Display menu to “Pdims” for principal dimensions. After you pick the OK button, you will see something like what is shown below.

The green line is the target waterline. Of course, you don’t know where it will float, but many designers like to see where they “hope” it will float. If you want to change any of these target dimensions, you can do so in the File-Design Data dialog box.

At any time during the design process, you can calculate the hydrostatics, stability and resistance of the boat. This will allow you change the shape of the boat early in the design process to make sure that the target weight or displacement of the boat matches the desired waterline location.

The hydrostatics are calculated using the defined (PlaneCut) stations, so you must make sure that there are “enough” stations (10-25) defined along the length of the boat. Also, the program does not require you to close off all portions of the hull with surfaces. For example, this boat does not have a deck or a transom. The program will, however, close off the deck when creating the stations to use for the calculations. Since this is not an exact process (the program may have to make some educated guesses), then you must check to see if the stations that will be used for the calculations look OK. This is done with the Calcs-Hydro-Draw Stations command. When you pick this command, you will see the stations that will be used for the hydrostatics calculations drawn in purple, as shown below.

You can rotate the boat and zoom in to make sure that these stations look correct and are located from the front of the boat all the way to the transom. Remember that the calculations are done using these stations, so, if they look good and they cover the full length of the hull, then you know the calculations will be accurate. (Note that our calculation routines have been developed over 25+ years and have been tested on boats of all sizes and shapes.)

After you check out the stations and they look OK, select the Calc-Hydro-Hydro Input+Calc command to display the Hydrostatics Input dialog screen shown below.

I won’t explain all of the options since our goal is to show you just a little bit about how the program works. There are four different ways to do the calculation. The first is to enter a draft (distance from the baseline at amidships) and a trim angle. The second is to enter a draft and LCG (longitudinal center of gravity). The third is to enter a displacement and trim angle. The fourth is to enter a displacement and LCG. In the early stages of design, most designers use the target draft and a trim of zero and that is what is filled in here in the dialog box. Later in the design process, after you have put together a detailed weight and center of gravity study, you will probably enter the displacement, LCG, and VCG values and see where the program says the boat will float.

Just for the sake of the example, use the existing input values and just pick the OK button. You should see something like what is shown below (a partial listing of the results).

There are actually over 35 different values that are calculated and displayed. You can even output many different sectional area data values that you can import into a spreadsheet for further analysis. You might notice a number of calculated values that are unfamiliar, like “Moment to Trim One Inch”. Since we are doing the calculations, we figured that we should provide as many values as possible, even if they are useful for only a few designers.

Also note that if you enter a heel angle, the program will first do the calculation in the upright condition and then use the calculated displacement and LCB to determine where the boat will float when it is heeled over. In other words, the program will heel the boat to the desired angle and then automatically sink and trim the boat to find the balance condition that matches the upright condition displacement and LCB.

The program also provides four different types of resistance calculations, but you have to enter a target speed or velocity. One type of resistance is for canoes and kayaks (Kaper), one is for sailboats (Delft), one is for planning powerboats in the pre-planing condition (DispMode), and one is for large ships (Holtrop). Keep in mind that these are “empirical” calculations whose results may not be perfectly accurate, since they are trying to determine a very complicated result. They are actually better at comparing boat ‘A’ with boat ‘B’ (a relative comparison), rather determining the exact resistance of the boat. Also note that these resistance calculations are based on the values of the boat at the current hydrostatic balance condition, using calculated values like the waterline length, displacement, wetted surface and half angle of entrance of the waterline.

After looking at the hydrostatics values, you can select another hull view toolbar button to change the view.

The next big area of the program to investigate is plate development or layout. For many, the ability to plot or cut full-size the frames and plates is the main reason for using this program. If you don’t know too much about plate development and layout, I would suggest that you read our other article on this subject. It talks about the difference between developable, expandable, and buildable. Many hulls may not be perfectly developable, but they are buildable.

This program gives you two ways to create and check for developable surfaces. One way, familiar to many, is to use “ruling lines” that connect two curves, such as a chine curve and a sheer curve. The ruling line method is described in another one of our tutorials and will not be discussed here. Here, we will look at the process of unwrapping or developing a surface and do some checks to see how close a surface is to being perfectly developable.

The program will try to unwrap or flatten any surface. All you have to do is to select the Develop-Develop Plate command and pick along any row or column of any surface (don’t pick along a common edge between two surfaces). Even if the surface has a lot of twist or double curvature, the program will try to flatten it out. The program uses a finite element type of calculation to flatten the plate and determine the stretch or strain in the plate. This is a very sophisticated calculation and is not just a simple triangulation-type of layout.

There are some surfaces that have too much double curvature and the layout will fail. If this happens, it means that the surface has too much curvature to unwrap and you will have to break down the surface into smaller pieces. If you are using our full-capability ProSurf program, then there are commands to attach curves to surfaces to define the sub-portions of the surface that you want to develop (butt and seam lines for ships). You would then create sub-surface patches on top of the larger, doubly curved surface that you could develop.

OK, back to the example. Pick a row or column point on the top surface of the boat. You will see the following dialog box with many input fields that are all filled in with default values.

Again, I won’t go into details about all of the fields, but you can see that there are many options. Just leave the default values and pick the OK button to see what you get. You should see the results box below.

The program uses a search technique to find the solution to the flattening problem. The default condition is to make sure that the 2D perimeter of the pattern matches the 3D perimeter of the 3D surface. The box also gives you some idea about the amount of stretch in the middle of the plate. After you pick the OK button, you should see something like what is shown below.

This shows the 2D pattern of the top plate marked with all of the defined station locations. Remember that some designers will change from defining stations to defining frames (using PlaneCuts) during the later stages of design so that these markings will show frame locations rather than station locations. The pattern is rotated to minimize the amount of paper that would be used when the pattern is cut out.

This view of the pattern can be printed or plotted out at a scale factor, plotted out full size, or output to various types of file formats to either bring to another location for plotting or for CNC cutting.

To plot at a scale factor or at full size, you need to go to the Options-Mod/Doc Definitions dialog box, as shown below.

This example shows that the program will use the defined scale factor and the defined scale factor is one inch equals one foot. If you want to plot full size, then you need to change the document units to feet. Then, the scale factor will be one foot equals one foot. WARNING! Always use the File-Print Preview command to see if and how the program will break the drawing into pieces (pagination) for drawing. If you get the scale factor wrong, then the program might want to plot out a thousand pages! The program “asks” Windows about the printer or plotter that is attached to the system and what size of paper it is using. Then, the program figures out how many pages are required to plot the drawing at the selected scale factor. Note that the default print or plot size is to use whatever scale factor will fit the entire drawing on your paper (one sheet).

For output to a file, you need to use one of the options in the File-Data File Output submenu. The most common one is to use the 2D DXF file output. Most CNC cutting systems can read these files. If you are interested in doing this, then contact the place that will be doing the cutting (or plotting) and see what software they have and what transfer geometry file formats they accept.

To output to a 2D DXF file, first, make sure that the 2D pattern is shown in the current view window. Next, select the File-Data File Output-DXF File Output command to see the dialog box shown above. Now, make sure that the top field is set to “2D View Output” rather than the 3D output option. This will guarantee that the program will output the 2D view shown in the current view window. Once you select the OK button, Windows will display a file output dialog box that you can use to name the file and select the destination folder.

Well, we flattened this plate, but how do we know if it is developable or buildable? We can use the Surf-K_Patch-Kpat All command to turn on the display of the Gaussian curvature. If you select this command and redraw the screen, you will see the following.

The dark blue indicates a Gaussian curvature of zero, which means that that portion of the hull is perfectly developable. (Gaussian curvature is a way of calculating how much double curvature a surface has.) If the Gaussian curvature is zero, it means that the surface has at least one direction that is flat at that point. As the colors change to light blue, to green to yellow, and then to red, the amount of double curvature increases. We have found that a boat is buildable if the colors remain in the dark blue, light blue or light green regions. This means that (within reason) you can twist or torture(?) the plate material to fit. Please don’t hold us to this criteria, since everything depend on the type of material, its thickness, and its dimensions. We usually tell people that if there is any question at all, build a small model to see if everything will fit. This is especially important if you CNC cut out both the frames and the plates. You may wish to leave extra scrap material along one of the edges of the plate. (See our other article that goes into more detail about this developable vs. buildable question.)

Note that this picture isn’t filled in completely. This is because the Gaussian curvature calculation is done for each pixel of the boat and we wanted to make sure it is reasonably fast. If you want to see what it would look like filled in completely, then select the Surf-K_Patch-Kpat Options to see the dialog box below.

Change the Row and Col Densities to 1 and select the OK button. You may have to use the View-ReDraw View command to see what is shown below.

As you can see, it looks better, but takes longer to draw. Note that the top plate is almost perfectly developable, but there is a good amount of double curvature in the front end of the bottom plate. If you are trying to create a developable boat, then you would have to change the shape of the bottom surface and recheck with the Gaussian curvature display. Since the Gaussian curvature cannot be dynamically redrawn as you are dragging points on the surface, then you may want to look into our “ruling line” method for creating developable surfaces. That technique allows you to dynamically see the amount of twist in the surface while you are dragging or moving the edit points. (See the other ruling line tutorial.)

If you use the develop plate command on the step surface, this is what you will see.

If you looked at the Gaussian curvature of this surface, you would see that it was developable and this pattern should be accurate.

This is the result of developing the bottom surface.

It can be done, but you wouldn’t want to use the results, since it requires a lot of stretching. Just because the program can flatten the 3D surface into a 2D pattern doesn’t mean that you want to use the result. [I can, however think of one exception. Perhaps you are trying to cut out some very stretchy material that you want to use to protect the bottom of the hull.] In any case, we have to leave it up to you to decide when to use a particular 2D pattern.

Before I end this example, I want to make sure you know that the program created a deck surface in the CreateBoat process. It was a simple straight across surface and it was turned off. If you select the Surf-Draw All Surfaces command and turn on the Render View, you should see something like what you see below.

Thank you for going through this tutorial. Hopefully, it hasn’t been too long (or too short) or boring. There are other tutorials and articles that can continue on from here. Feel free to contact us if you have any questions or comments.