Part 2 – Working With Plans
A little time spent up-front can prevent a lot of headaches down the road. In this installment, we’ll talk a bit about ships’ plans; where to get them, what you’ll be getting, and how to make them useful for building your warship.
Sources of Warship Plans
Here’s some folks that specialize in ships’ plans:
If you happen to be looking for something unique, as well as a great source of books and other materials (although you’re not likely to find anything in 1:144 scale), try:
Also, for U. S. warships, U. S. National Archives can provide complete plan books for most vessels stricken from the U. S. Naval Register.
Expect to pay anywhere from $12.00 to $25.00 per plan set from commercial plan services. Archive material can usually be gotten free of charge – the only catch is that they don’t have research and reproduction services and you have to do the leg-work yourself.
Working With Warship Plans
When your ship’s plans arrive, what you find will look something like this:
Typical Warship Plan Layout
Your plans will have 4 major sections, often all on one sheet. These sections are numbered in Figure 1.:
1. Plan View – This view shows the layout of the ship as if viewed from directly above.
2. Front View – This view shows the ship as viewed from directly in front.
3. Profile View – Usually, only one side profile is given – viewed as seen from directly abeam.
4. Section View – This view represents views “through” the ship, as if sliced with a knife at various points along the length, viewed from either the bow or stern. The section lines show the hull profile at points that correspond to vertical section lines in the Profile View.
In addition, there will be various views and sections of superstructure and other details. In some cases, there may be details showing the “as built” state of the ship as well as modifications made later in its life. Sometimes, additional sheets are used to present these details.
Essentially, what we’re trying to do here is to construct a 3-dimensional object (the ship) from a 2-dimensional reference (the plan). To do this, the major views of the plan will be used in pairs, or even threes (mostly for superstructure pieces). We need to set some absolute reference points in each of the 2-D views, that intersect with at least one of the other views:
- The Water Line represents the horizontal plane, and is distance ‘0’ on the vertical. The Water Line is the one horizontal line on the plan that can be guaranteed always to be straight and level. Vertical measurements on the Profile View, Front View and Section View are taken relative to the Water Line. This also represents the x-axis in a 3-D model.
- The Center Line represents the vertical plane running the length of the ship. Vertical measurements on the Profile View, and horizontal measurements on the Front View and Section View, are taken from the Center Line. This also represents the y-axis in a 3-D model.
- Each rib of the ship represents a plane. These planes are “stacked” at specific heights (or depths) measured from the forward-most point of the ship’s bow. This stack represents the z-axis in a 3-D model.
To illustrate how it all fits together conceptually, Figure 2 has an isometric view of how the major views work together. Elements are color-coded with respect to which of the original plans’ main views they come from. Note the 3-D coordinate system, with section lines intersecting at the water line.
Relatonships between Plan, Profile, & Bow views, with hull sections.
Using this method, any point on the plan can be represented as some distance above or below the Water Line, some distance to Port or Starboard of the Center Line, and some distance aft of the bow.
Preparing Plans For Use
First things first: Make a copy! A copy shop (such as Kinko’s, etc.) can make a photocopy of your plan for about $10.00-$15.00 while you wait. Make a “working” copy, that you can draw on, etc. and stash your original in a safe place!
As noted above, plans are not usually usable for construction as-received. Not only will some work be necessary to convert the plan into a working document, but the plan may have errors! For example, in the case of USS Pittsburgh (CA-72) the plan showed the stern to be tapered and rounded. However, any number of photographs that I found of actual ships of the Baltimore class clearly showed very little taper, and a flat transom with rounded corners! The corrected stern was drawn directly onto the working copy of the plan, and the ship was built like the original. Also, on the Plan View it was noted that the center-to-gunwale distance was not consistent for both sides at all sections – I had to make a design decision to measure from center to one side (I chose Starboard, arbitrarily) and mirror those measurements to the other side to maintain consistency.
Certain key lines need to be extended to different views of the plan. One prime example is the section lines – they need to be extended to the Plan View, if they aren’t there already. Make sure that the Plan View has lines at the extreme bow and stern, perpendicular to the Center Line (make sure that the Center Line is on the Plan View as well!) Measure the distance of each section line (in the Profile View) from the bow of the ship. Draw a line through the Plan View at this same distance from the bow, and repeat for each section.
You will have to decide what rib spacing to use. It would be ideal if the plan’s sections lined up perfectly with your desired spacing, but this is unlikely to be the case (Murphy’s Law is always in effect!). However, it is a good idea to make use of existing sections wherever possible, to use as patterns for cutting ribs. Decide what spacing you want to use, make as much use of existing sections as is practical, and draw vertical lines on the Profile View to represent these rib locations. Transfer these lines to the Plan View as well.
If you’re lucky, and your design rib locations fall on the plan’s hull sections, you can copy and/or trace individual section outlines from the Section View. For USS Pittsburgh (CA-72), I chose 1″ rib spacing. The rationale behind this choice was that, since the original ship carried little armor I was limited to a belt thickness of 1/16″, and I’d like to be able to compensate for this weakness in any way I could. At the time I was working on the design, several messages in the Big Gun e-mail relay suggested that glancing shots can rip a big hole, until they strike a rib. The idea here was to accept that I was not going to stop a direct shot, but could minimize the effect of a glancing one. Whether or not this is valid, I don’t know yet – the ship hasn’t seen combat as of this writing.
In several cases, I had to figure out the profiles of 4-5 ribs that fell between the plan’s sections. This required interpolation between the sections. With 1″ spacing, I had to create patterns for 56 ribs! Fortunately, I was able to come up with a method using my computer and my favorite illustration program, CorelDRAW!
As described above, the origin (point 0,0) of the stacked section planes falls at the intersection of the Water Line and the Center Line. DRAW! was set up with 0,0 near the center of the page, and horizontal and vertical guidelines running through this point. After looking at a few hull profiles on the Section Plan, I noticed that each one could be represented with reasonable accuracy using two segments per side. For example, some profiles could be represented with 2 curved lines, others with one curved and one straight, and others with two straight segments. A typical hull section curve could be defined as an end point (x = 0, somewhere on the Center Line), a convex curve, a point where the curve changed direction, a concave curve, and another end point (at the gunwale). I could plot the end points of the segments, then use DRAW!’s Bezier tool to “tweak” the curves. Then, when I was satisfied, I could copy a mirror image to the other side of the Center Line. Each section was placed onto its own layer, so I could turn them on or off individually, for printing and viewing.
The existing sections were drawn first. When I was happy with them, the in-between sections were calculated. This turned out to be rather simple, if time-consuming. If I needed 4 ribs between plan sections, I’d display the existing sections, then plot 4 points between the segment end-points and “connect-the-dots”. Intermediate sections could be easily tweaked so that both segment end-points as well as curves create a smooth interpolation of the sections that needed interpolation between those of the original plan.
After a while of this, I made another interesting observation: The points at which the section segments intersected, and the curves changed direction, traced their own curve! Once this became apparent, I was able to go back and tweak segment intersection points to match this curve, and get some real precision to my sections! The result can be seen, not only on the ship itself, but in the following illustration:
Baltimore-Class Heavy Cruiser Hull Sections.
Once the sections were completed, it was a simple (but again, fairly time-consuming) task to turn on one layer at a time for printing, and print each one to a laser printer. Center Line and Water Line were also turned on, to provide frames of reference when the ribs were later assembled to the keel (I used a keel rather than a baseboard, since the hull is fairly rounded).
This method resulted in a frame that was extremely light-weight, yet incredibly strong. Once the ribs were attached to the keel, cap rails installed, and the whole works epoxied together, the whole assembly had such a strong “feel” to it that I was almost tempted to try to stand on it! Also, the compound curve of the hull, where the sides are curving in toward the bow on the z-axis, while simultanteously tracing a “wine-glass” shape on the x-y plane, came out extremely well (ironically, this precision created certain problems when it came time to skin the hull, which will be covered in a later article).