Castlemania Stage Eleven – Building a Cog
The castle needs a lot of materials delivered quickly to keep up with our kingdom’s growth. Since we’re living in 1275, the fastest way to move things is by ship. We built the docks and defenses. Now we need those ships to start bringing in the goods.
The dominant type of merchant ship in Northern Europe from the 13-17th centuries was the cog. Never heard of a cog? Neither had I. It turns out it was quite revolutionary, and its development was necessary to meet the needs of a huge increase in maritime trading- including ours!
The cog is fast and can carry a large cargo on its flat deck. It is broad in beam (width) and has a keel as a backbone to give it great strength.
Cogs are built in the clinker (lapstrake) style. This means the hull’s outer boards overlap each other rather than being edge to edge.
The castle (raised portion) is above the stern and the forecastle is above the bow. The crow’s nest on the single mast is the best spot on the ship to see what is going on all around the ship for great distances.
The same style of ship was used as a warship and was fitted accordingly, but we’ll be concentrating on the merchant ship here.
The cog is just the ship we need to supply the huge amount of material and goods to build our castle and help grow our town.
Since they are so important to our daily well-being, in this stage we’re going to learn one way of making the keel and hull,which will be ready to be finish in future stages.
Keel and Hull Construction Steps
There are many ways in 3DVIA Shape to build the keel and hull. I’ve chosen the basic revolve method in order to use many of the techniques we’ve already learned in previous stages.
This shows the overall construction steps all in one shot. I like to make most models as a series of steps so I can always go back a step and not have to start all over again. I “CTRL +C” and “CTRL +V” each step and keep the steps oriented along one of the axis.
The red arrow shows the direction of overall work. The yellow arrow shows the development of the hull, and the green arrow shows the keel steps. The final step is joining the keel to the hull.
The first step is to draw the centerline profile which I’ll use to revolve the hull. Searching on the internet, I found that cogs of this time (circa 1275) were roughly 100′ long and 40′ or more wide. Since this cog is meant to be used in the rivers of the kingdom, I’ve kept the overall depth of the ship at around 20′ to keep from running aground (hitting and getting stuck on the river bottom or a sand bar). Because we are revolving the profile, this means the beam will be 40′.
With these key dimensions, I can then use the “Arc” tool to draw the ship’s profile. Notice the bottom is not a straight line (red line). The arc gives the keel more strength and provides clearance in shallow waters.
Try to create the bow and stern arcs as one arc that is as close to tangent with the bottom arc as you can. Every arc section will create a surface that requires a color or texture. Textures can be very hard to match up on these shapes. You’ll notice my whole ship is brown to avoid spending a lot of time aligning textures.
Once I have a profile I like, I use the “Offset” tool to create a shape inside the profile. This represents the thickness of the hull. I chose to make this a smooth hull, like a carvel-built ship, in order to keep the complexity reasonable.
To have a hollow hull, I need to remove the horizontal gray section. To do that, I’ll extend the inside hull profile on both ends. The inside of the hull is a curved line (green line), but if I draw a line that is approximately the same (red arrow), I can then draw a parallel line (gold line) that will be close enough.
To draw a line parallel with another, start drawing your line and then move the mouse over the line you want to be parallel with. Then move the mouse back to continue drawing the line, and it will turn blue when your new line is parallel. Here is a good video that explains the process in more detail: How To Draw a Parallel Line.
Make sure to draw this “extension” line on both ends of the hull.
Now I can delete the horizontal gray section and the white section, leaving me with just the hull outline (upper image).
Next I use the “Advanced Push n Pull” tool to revolve the hull profile 180° (lower image). You can see that keeping the profile arcs simple has left very few section lines on the hull.
The top edge of the cog profile is not a straight line. I could have made it curved back when I created the hull profile, but I want to show a clear demonstration of “Boolean” operations. These processes are based on mathematical work originally done by George Boole. Boolean operations allow us to add shapes to each other, determine the intersection lines and then remove any unwanted sections of either or both shapes. It’s sort of like a 3D cookie cutter. To start, we need a shape we can cut through the hull with.
To make my “cookie cutter”, I first draw lines extending horizontally from the points at each end (red arrows). Then I draw a vertical rectangle that is larger than I’ll need. Because the white lines connect the rectangle to the hull, 3DVIA Shape sees everything as one shape. The end of my white lines must pass through the rectangle. This will give me the start and end points for my arc. I delete the ends of the white lines that pass all the way through the rectangle.
I’ll draw the cutting shape on this rectangle, and since I want to be able to see the hull while I’m drawing the arc to cut with, I’ve applied a transparent color to the rectangle.
This video is a helpful way to visualize the process: How To Use Boolean Operations.
3DVIA Shape applies a little bit of perspective view all the time. This means I cannot get a true side view, so I get as close as I can by moving my view. Using the section lines (green ellipses), I can gauge when I am close to horizontal.
Now I can draw the arc from one white end point to the other, and then pull down to the amount of curve I want (red arrow). I also need to draw the two black vertical lines so I have a closed shape to cut with.
This is the fun part! Using the “Push n Pull” tool, I pull my cutting shape all the way through the hull (red ellipse). You can see the black lines that show the intersection of the two shapes.
Now I just delete all the bits and pieces of geometry I don’t need, including the cut off pieces of the hull (red arrow). Remember to keep the curved surface that is the actual cut line. Change the color to the hull color so you know it is part of the hull. If you’ve already deleted it, then use “CTRL +Z” as many times as it takes to bring it back.
The hull should now be complete.
Now I’ll build the keel. In real shipbuilding, the keel would be laid as the first piece you would start construction with, but I need the hull profile and thickness first to be able to build the keel and then join it to the hull.
First I “CTRL +C” and “CTRL +V” the hull profile. Now I use the “Offset” tool to create my keel thickness OUTSIDE of the hull profile (red ellipse). I can do this by eye or I can draw a line of specific length and pull the offset line to the outer end of the line (green ellipse).
For this model I want the keel to penetrate the hull, so there aren’t any gaps when they are joined. I also don’t want the keel to go all the way through the hull.
Now I have the hull outer profile and the keel outer profile. Next, I draw a line that will determine how far the keel penetrates into the hull (green ellipse).
Next I delete the hull outer thickness, but leave the vertical line. Now I can use the “Offset” tool to create a profile that matches the inner end of the vertical line.
I’ll follow the same steps I did with the hull to extend both ends of the keel inside profile. I’ll also add a small reference line (red ellipse, left image) before deleting the gray horizontal and white shapes.
Now I’ll use the “Deform” tool to add a reference point to the end of the keel profile (red arrow, right image) and then rotate it 90° (green arrow, right image) so it is vertical, like the center of the hull.
To add thickness to the keel and keep the profile in the center, I’ll use the “Push n Pull” tool to add the same amount of thickness to each side, one side at a time (red ellipse, left image).
To create the correct point to join the keel to the hull, I’ll use the previously created reference line (red arrow, right image) to draw across the inside face of the keel and then the two crossing lines (green arrows). Where those two lines meet is the joining point.
Joining the Keel and Hull
Now I’m going to join the light gray hull with the dark gray keel. First I draw a reference line connecting the outside of the hull with the inside (red ellipse, left image). Then, on the keel, I use “CTRL +C”, “CTRL +V” and hit the space bar so I can select the center point I just created (red arrow, center image). I can now move the keel until it snaps to the center of the hull reference line (red arrow, right image).
The joining process leaves the white reference line which will show up every time I use the model in 3DVIA Shape. Deleting the first half is easy (yellow ellipse, left image), but half of the line is inside the keel. I can delete this by drawing an “access panel” (red ellipse, left image). Once I delete the “panel” I can easily delete the other half of the line (red ellipse, center image). To replace the panel I just have to draw along one edge of the open hole and it will fill back in (red ellipse, right image). Then I delete the panel lines, and I’m all set.
The How To Fill a Hole video shows how to fill other kinds of holes.
Now the hull and keel have been joined, and you can see there aren’t any gaps and that the keel does not intrude inside the hull.
All we need now is the rest of the ship, but I think we’ll save that until later.
It worked! We built the docks, and the ships have come, bringing all the good things we need to survive and thrive as a castle and town.
Another way of making the hull in 3DVIA Shape is to use the Freeform Deform tool. You can see the results are much smoother and more like the actual ship. There are no construction lines down the length of the hull, which makes adding textures much easier too (green ellipse, upper image).
It also does not have a keel yet (red arrows, upper image), which would require more construction.
Making a Freeform Deform type of model takes more construction steps to get the final results, but it also gives you more control of the key dimensions. Perhaps another time we’ll explore this method in more detail.
The investment of time and money to build the docks and defensive positions has really started to pay off now! Delivered materials are starting to pile up on the dock.
Now we’ll need more wagons and carts to move all of those goods to where they are needed. In the next stage, we’ll use some of that timber to build what we need.
Links to previous Castlemania Stages: