Tackling Titanic's Double Bottom (Patreon)

As you've probably seen, I have started to work on the double bottom structure. However, there's only so much that can be done with the double bottom until some details are worked out. Specifically, the layout of lightening holes in the bottom floors as well as intercostals.

The double bottom consisted not just of the steel plates making up the bottom of the ship and the tank top but also its internal structural members. These included frames acting as the ribs of the bottom, which are actually called "floors", and intercostals running fore and aft forming girders between the floors. It was to the floors that the hull plating was riveted.

The floors consisted of single large plates of steel, and almost all of them had lightening holes, holes cut in the plates to lighten the structure but also to allow movement of water as the double bottom was divided into tanks for uses like ballast and boiler water. The tanks were divided at the watertight bulkheads as well as in other places, and usually 4 tanks across with inboard tanks either side of the keel and wing tanks along the bilge. There were also many smaller "limber holes".

There's nothing particularly unique about Titanic's double bottom in the general sense. The general ideas and elements that went into it were standard for ships and still are today. Sadly the layout of lightening holes for the Olympic Class is only shown on plans for a few floors/frames, and there are glimpses in construction photos that seem to indicate a general pattern for how the holes were places. So before I can make all the bottom floors, I must figure out the pattern of lightening holes.

The patterns don't need to be exact, as that's not 100% possible. Many lightening hole locations will always be a mystery. But with the material we have I can at least guess where most are and fill in the gaps based on what's most likely.

To plan out the layout of those holes, I'm roughly blocking out the structure of the bottom, as seen in the images above and below. I'm also plotting the layout of the structure in general, so there are 3 main things being plotted out:

- Frames - Green

- Intercostals - Blue

- Lightening Holes - Pink

NOTE: The bottom blockout is a work-in-progress and many lightening and limber holes are not yet planned out. Most of the intercostals would also have holes.

I'll probably be working on this and the double bottom and tank top for a fair bit, so expect to see more on this later as I grind through the work. While some may see the double bottom as pointless to make, I think it's valuable to have this structure figured out and done. There were numerous manholes granting access, meaning this is another potentially explorable part of the ship, it's helpful for visualizing Titanic's structure, it's something I've wanted to do for a long time, and ultimately it's part of the process of building not just a base for the Alpha but a base for that base.

Once this is all done and the tank top plating is laid down, that's when the real fun begins. Unless you think the double bottom is fun, then the real fun is happening now.