The Hatches

The Hatches: Portholes

he side portholes on the two hatch towers are positioned differently. Like everything else about the Hunley's construction, this difference is likely by design.

The side portholes in the forward hatch are set lower than that in the aft hatch, as shown in the two renderings above. This is probably just a function of practicality. The hatch coamings have an oval cross-section, narrower beamwise than lengthwise, obvious in the rendering below at the same scale. To squeeze through the hatch a crewman would have to turn sideways.

Forward hatch, wire frame schematic (old version).

Notice that the figure in the renderings is sitting as high as possible, his shoulders nearly touching the cabin overhead. The wire frame drawing shows that he can look down at a compass or manometer on the bulkhead with relative ease. Placing the portholes low in the forward coaming permitted the commander to sit facing forward and still get a fair view outside. The above renders show incorrectly low forward-looking ports as well. A photo published in The Blue Light in April 2007 shows the forward ports were actually set very high in the tower, as illustrated below.

It's clear from the graphics that the commander could not position himself to look straight out the side and forward ports at the same time. It's likely that the forward ports were placed high to provide the maximum distance view. He may have to have turned his shoulders to look through these ports. The lower ports would have provided an outside view in normal sitting position. However they were used the portholes were located as shown. The key to understanding their utility is the actual interior size of the hatchway, and the inch or two possible error in my drawings is significant here. Photographs cannot provide exact dimensions because of lens and perspective distortions and no reliable official drawings or numbers have been published. A forward hatch mock-up with 19.5x14.5-inch interior dimensions – about two inches wider than my present drawings – demonstrates that an individual with shoulders against the hatch opening could just see out the forward ports. Relaxing some and lowering ones head permits a view to the sides.

The Hatches: Lid

small mechanism that may be a valve, discovered when the aft hatch lid was removed in 2006, prompts some interesting thoughts. This could be emergency equipment added after the second sinking.

Pressure imbalance prevented the hatches from opening and Horace Hunley and the rest of his crew died. The only way to equalize the pressure would be to let water in and air out. This would likely not be a quick operation with a small valve because a large quantity of water would probably need to be admitted. It’s possible even with such a small valve Hunley would not have been able to equalize the pressure.
It is possible the valve wasn’t emergency equipment at all, but in the original design to assist opening the hatch after a normal dive. If the internal air pressure fell below external for any reason, such as loss of air when the ballast tanks were filled, opening the hatch would be difficult after surfacing. A small air valve such as that described could quickly and efficiently equalize the pressure.
At this point we just don’t know enough about the mechanics or the operation of the submarine to choose any of these possibilities with confidence.

The Hatches: Latches

aria Jacobsen described the latching mechanism as a vertical bolt and cross-bar. In mid-2006 the Friends identified metal parts found on the cabin floor under the forward hatch as parts of the latch.

The parts, discovered behind the steering linkage and inter-tank pipe were likely stowed there and appear to resemble the engaged latch in the aft hatch. This strongly implies that Dixon did not have the forward hatch latched at the time the Hunley was lost.
The graphic at right shows my speculative visualization of the latch parts: The part on top, based on an x-ray of the forward hatch lid, is attached to the lid, possibly through a hole in the its center. The vertical bolt has a hook that engages a ring in the lid part and is threaded on its lower end. The flat crossbar has a hole in the center that fits the vertical bolt diameter. A fourth part is purely speculative on my part. I envision a threaded bolt with a handle to cinch the latch closed. The image below shows the latch cinched down in the forward hatch.

For this concept the vertical bolt is hooked on the ring fitting in the lid. The crossbar, aligned athwartships, is simply fit on the end of the vertical bolt and then the cinch-bolt is threaded on tight. The cross-section images of the forward hatch below depict side and front views of the engaged latch.

	The image at left shows the hatch slightly ajar when the latch is not engaged. The hatch is still fairly watertight because of the weight of the lid, but the seal is not tightly compressed.
These paragraphs presented one concept. Since the Friends have released no photos of the latches nor provided any substantive descriptions there are many other possibilities. For example, there may not be a separate cinch-bolt. The crossbar hole may be threaded and the crossbar turned tight to engage the latch, similar to the concept shown in the earlier paragraphs below.
Chapman's painting includes a detailed view of the inside of aft hatch (right). What is probably the lid deadlight is visible on the forward (hinge) side and something like part of a latch or a handle on the lid edge. Nothing is visible in the center where the ring fitting is clearly shown in the forward hatch x-ray.
I won't speculate about this except to address another question. I believe that the Hunley's pilot would have always wanted to use the hatch view ports while the boat was running of the surface. Since a latch similar to that described above could not be engaged and permit viewing, there may have been a small, less positive latch used to simply keep the hatch from opening accidentally. Too small to be cinched down, it would not provide complete water-tightness, but would prevent the hatch opening, for example, from violent rolling.
The following paragraphs discuss earlier concepts for the latch mechanism. The scientists are uncertain even today whether the forward and aft latches are the same. The location and number of ports forward and aft shows a clear difference in purpose. The forward ports are situated for viewing, consistent with Dixon's navigation responsibility. The aft ports appear to be only for providing light. Since the portholes and usages of the hatches are different the latches might be different too. Having settled on a hinged, rotating latch after the Smithsonian lecture (see the animation below), I returned to Brian Hick's description of a hook and brace and came up with this new interpretation.

Unlatched hatch

Latch turned 90 degrees to seal hatch

The graphic of the aft hatch at left shows the hook attached at the center of the cover, as described by Brian. The brace is set lengthwise, and since the hatchway is longer than it is wide, serves as a handle to dog the hatch closed on its sealing gasket. The lid may weigh 150 pounds and probably closed itself. The latch and crossbar could have served as a handle to help push the hatch open. In the graphic at right, the cross bar is turned 90° to lock the hatch closed by bracing it against the bottom sides. The mechanism in the center of the hatchway now prevents any access.
Applying this interpretation to the forward hatch, the vertical bar visible in the photos would not be attached to the overhead, but only stored there. The L-shape might actually represent the hook, slightly different from what I've illustrated above. Details of the mechanization conflict with Chapman, since the painting shows nothing in the center of the hatch cover, but something that might be a ring closer to the hinge.
Discussions in 2006 with Kim Johnson, and reports from the Friends of possible latch rods on the cabin floor, I re-evaluated my interpretation of the bar visible in the photos. See the commander's station pop-up for another possibility.

The following paragraphs discuss even earlier concepts for the latch mechanism.

Drawing copyright 2002 Kevin Wilcomb, used with permission

Kevin Wilcomb, who provided this drawing illustrating some of his thoughts about the latching mechanism, offers the interesting theory that whatever made the hole in the forward tower knocked the latch bar loose as well.

Some details disagree with the meager data but Kevin's drawing presents several good discussion points.
o Firstly, there seems to be room in for an observer to use the portholes even with the latch engaged. Maria stated this is not possible, based I believe on the aft hatch where the latch is engaged. This must mean either that the vertical bar engages not at the forward end, but actually slants within the tower, engaging at the top or even further aft. Alternatively, the crossbar might fit in sideways or might run fore and aft to brace the latch bar.
o Kevin depicts a small ring on the hatch lid to engage the latch. A feature on the aft hatch lid in Chapman's painting might be such a ring.
o Lastly, Kevin presents a smaller mechanism (arrow) that appears to be a better design, raising the question why such an apparently bulky latch was used.

At the 2002 Smithsonian lecture, Maria Jacobsen identified a vertical bar visible in photos of the forward bulkhead as part of the forward latch. The graphic illustrates my early speculation about how it might have worked.

The bar is about a foot and a half long, almost touching the compass shelf at its lower end, and could to be hinged at the cabin ceiling. The L-shape would allow it to swing up into the hatch to engage the lid. At least one photo of the aft section shows what might be the bottom of the latch bar rotated into the hatch tower in latched position.
The drawings below show my speculation about the mechanism. An "ideal" design consistent with the archaeologist description is on the left. When the vertical bar swings up, it engages a lip on the lid. The bar is locked in place by dropping the cross bar (seen end on) into receptacles on each side of the coaming. An alternative fore-aft brace is shown in dotted lines.

Ideal mechanism

More likely apparatus

The drawing on the right accounts for the apparent length of the vertical bar, which exceeds the height of the hatch tower. Only the location of the hatch-cover part of the mechanism differs. The operation is identical. This is the more likely mechanism of the two pictured.

(See the captain's station pop-up for an alternative interpretation of this feature.)

E-mail me with comments