The Hunley's Rudder

The Hunley's Rudder
... how did it work?

W	riting about the Hunley 40 years later, William Alexander described a small horizontal wheel atop the forward ballast tank bulkhead and control lines high on each side of the cabin passing outside the hull on each side of the rudder.

His lines attached to a lever at the top of the rudder, turning it in response to the wheel. This mechanism is seen in the historical drawings linked from my main Hunley page. Alexander may have remembered one of the earlier subs, because the Hunley has a very different mechanism., a tiller attached to a single control rod on the cabin floor. Excavation of the aft ballast tank revealed a single centerline tube or rod high in the tank, exiting just above the rudder. The rest of the external mechanism is missing, but this is consistent with the Chapman illustrations, which show a single control rod in the same place. The sketch below is Mike Christy's idea of how the mechanism shown by Chapman might work. Mike has also constructed a miniature proof-of-concept model.
Drawing courtesy of Mike Christy
In 1976 Joseph Leary designed and Fred Frese built a full-sized working reconstruction of the Revolutionary War submarine Turtle as a U.S. Bicentennial project. Their Turtle in an exhibit . Photos of the Turtle reconstruction at the Connecticut River Museum provided by Tim Smalley show a strikingly similar rudder control system. There are few differences between the Turtle rudder interpreted by Joe Leary and the Hunley rudder envisioned by Mike Christy. The Turtle control is offset from the centerline and operates the rudder from one side. Based on the Chapman art, Mike has split the final control rod on either side of the rudder in a symmetrical arrangement. The number and characteristics of the linkage elements are the same. After carefully studying the Chapman material myself, I can't fault Mike's construction. I've had some difficulty accepting the ball-joint required because of its susceptibility to fouling in a seawater environment, but my concerns may be unfounded.

Looking for a simple ball-joint alternative, I came up with this solution using two machined nuts. The conical inner form on the nut faces permits a high degree of lateral and vertical rotation while limiting slippage. A number of similar arrangements would work as well.

One of many possible mechanisms.

These two figures show the rudder mechanism in operation on my recon-
struction.

The rudder animation below is from a movie by Mike McMillan.

Left rudder.

Animation copyright Mike McMillan

Follow the link below for speculation about the interior controls. The remaining excavation of the Hunley cabin and ballast tank promises to reveal the interior steering arrangement. A small part of the exterior control remains on the rudder under the heavy concretion, but because of the highly eroded condition of the Hunley's stern we may never know the details of the external linkages with certainty.

E-mail me with comments

How was the Hunley controlled?