Observations On CSS H. L. Hunley, A Milestone

English: apparently cropped from image found o...

Image via Wikipedia

Indiana Jen has posted an interesting update on the preservation and restoration of the Confederate submarine CSS Hunley. Interestingly, Hunley is still going to be kept under (fresh) water. The use of water as a preservative against corrosion may seem strange to some, but oxygen is necessary to the corrosive process, so it makes sense.

One interesting aspect of its design is its counter-balanced dive planes, so designed as to make them easier to rotate. They were placed fore and aft. This design might have been a factor in its sinking which many consider to have been due to a loss of depth control. Placing one set of planes forward instead of amidships meant that the angle of the boat was more difficult to control than if one set were placed amidships and dedicated to depth changing. Consider too that the two sets of planes had to be operated manually by different men and somehow coordinated and you begin to understand how formidable that task must have been because the angle of a submerged vessel is inherently unstable.

CSS Hunley

The Hunley, by AN HONORABLE GERMAN via Flickr

Modern sub designers struggled with this concept as well. WW II subs and prior had the planes both fore and aft like the Hunley’s, but requirements changed with the advent of the bulbous hydrodynamic shape of the true submersibles made possible by nuclear power. Placing the planes forward on that shape of hull was awkward and made them more vulnerable to damage while maneuvering alongside a pier, but more importantly it interfered with the increasing size and sensitivity of sonar arrays. Designers continued to flirt with forward-placed planes but eventually settled on the midships location, i.e., on the “sail”.

Thus, the sail planes, being near the center of gravity of the boat, can be operated solely to make small adjustments for depth maneuvering while the stern planes are used to adjust the angle of the boat for large depth changes. The penalty for this was a loss of effectiveness by the sail planes at shallow depths (periscope depth) and slower speeds because they were closer to the surface of the water. However, the change proved acceptable because advances in sonar tracking and torpedo-homing technology made operations at periscope depth less necessary.

The Hunley was as much a milestone for engineering itself as it is for war and, I submit, it demonstrates how war itself, abhorrent as it is, promotes technology and economic development. We have come a long way since then. Submarine design is especially apt as a model for technology because as a system it combines all the aspects of engineering, science and physics that I can think of, including:

fluid dynamics
electrical power
chemical batteries
electronics
sonar (active and passive)
metallurgy
explosives
radar
radio, including satellite communications
gps
inertial guidance (both weapons and ship)
rocket design
hydraulics
atmosphere control (oxygen, CO2)
nuclear radiation
nuclear fusion warheads
sound isolation of equipment
sanitation management in a pressure environment
food preservation
psychology (isolation, stress, women)

One final thought about this: keeping technology secret is pretty much futile in the long run, although we have to try. One visit to Wikipedia is instructive in showing the breadth, depth, and ubiquity of information in the digital age.  It diffuses like salt in the ocean.

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About Jim Wheeler

U. S. Naval Academy, BS, Engineering, 1959; Naval line officer and submariner, 1959 -1981, Commander, USN; The George Washington U., MSA, Management Eng.; Aerospace Engineer, 1981-1999; Resident Gadfly, 1999 - present. Political affiliation: Independent, tending progressive as the GOP recedes from its Eisenhower roots.
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3 Responses to Observations On CSS H. L. Hunley, A Milestone

  1. PiedType says:

    Such an interesting article, Jim. Thanks. I didn’t know all that stuff the location of the dive planes. I’ve been fascinated by submarines since I was a little girl (never missed “The Silent Service” on TV). Totally in awe of the men who first dared to crew the Hunley and other early subs. (You guys who served more recently are also pretty cool!).

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  2. Thanks for taking this story and running with it. The Hunley is such a fascinating piece of maritime history.

    Like

  3. ansonburlingame says:

    to all,

    I visited the Hunley Museum in Charleston several years ago. A site (sight) to behold and consider how those men dared the unthinkable in war.

    I have never heard that the Hunley went down because of loss of depth control. I always thought the “bomb” was too close to the ship when it exploded.

    But I did serve on a WWII diesel boat (with bow planes not sail planes). Bow planes were on the “front” (bow) of the Trumpetfish, not located near midships on the sail. I also know that depth control at periscope depth on that diesel submarine was MUCH EASIER than on any later “nucs” with sail planes. Lots of hydrodynamic reasons for that problem.

    Moving the planes to the sail had nothing to do with nuclear power. Recall, Nautilus and Seawolf, our first two “nucs” had bow planes as well.

    It was the advances in SONAR that drove the planes “aft” away from the very sensitive hydrophones located in the new “bulbous bow” mentioned by Jim.

    As for nuclear power creating less need for nucs to operate shallow, I also disagree to some extent. Many are the nights and days spent at periscope depth in the North Atlantic (with 30 foot seas) trying to get a navigational fix or radio broadcast while not “broaching” (breaking the surface of the water with the sail or even the whole ship). Not fun at all.

    Anson

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