Beyond sentiment, however, the Holland's unseemly demise was an historical tragedy. With the ship destroyed and most of the plans used to build it scattered and lost, researchers long believed that the opportunity to study the innovative genius of the submarine and its inventor, John P. Holland, had disappeared forever.

Seventy years later, however, thanks to the patient historical spadework of a devoted amateur historian and the use of 3D digital design tools from IBM and Dassault Systèmes, the Holland has come back to life in virtual reality. The result is a fascinating journey into the emerging field of virtual archaeology and the opportunity for modern researchers and history buffs to walk the digital decks of the Holland for the very first time

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Reconstructing history

The rebirth of the USS Holland dates to 1992 when engineer Gary McCue began looking for a way to train submarine designers in the use of computer-aided design software. Details about most modern subs, owned by the world's navies, are classified. He therefore chose the Holland because whatever data he could find would be in the public domain and because it was small enough to be modelled completely.

Like the boat itself, most of the data used to build the USS Holland had been scattered and lost. Bits and pieces were unearthed in the National Archives in College Park, Md, the Library of Congress, the Paterson (N.J.) Museum in Holland's adopted hometown, and the US Submarine Museum in Groton, Connecticut. Clues also were found in newspaper articles, letters, antique catalogues and the archives of General Dynamics Electric Boat, descendant of the company that built the Holland VI. (The Holland VI was later sold to the US Navy and commissioned as the USS Holland.)

Virtual archaeology

Holland's original blueprints included 90 as-built drawings. But only three survive - in the National Archives - those for general arrangement, piping and the propeller. Beginning with this base, the system was able to create a 3D reference model that established critical profiles, dimensions and relative positions for on-board machinery. By constantly iterating between the 2D historical documents unearthed over time and the slowly emerging 3D models, new information was validated and incorporated.

The CATIA software can take a series of distinct parts and use constraints and relationship modelling to simulate their operation. This was done in constructing a 3D model of the two-cylinder Otto engine used to power the boat while on the surface. The Otto had approximately 160 parts, and McCue was able to reconstruct the entire engine by positioning parts - some drawn from antique Otto catalogues - within the context of the engine model.

Interpart constraints like surface contact, offset and parallelism were used to capture design intent by formalising how parts relate to one another. Faithful modelling and step-by-step assembly-in-context eventually created a system that moved and operated as one, giving us a window back in time to 'watch' one of the first industrial gas engines ever built in simulated operation.

Kinematics - a science that performs analysis by combining time and motion - also was used to better understand how key systems behaved and how the crew operated them. The main hatch is a good example. It was a simple hinged lid with a double-action lever and a compensating spring. Kinematics studies achieved using the design software revealed that Holland designed a lever-action 'dog bone' yoke that doubles as a handle and a locking mechanism, ensuring the hatch is properly sealed and locked. Such a feature - illustrating Holland's devotion even to small details - would have gone unnoticed without kinematics.

Another feature of CATIA is photo realism - the ability to accurately render the effect of lighting on operations. Lighting analysis clearly illustrates how stark the Holland's interior was. Simple globe diffusers used throughout the sub resulted in stark, high-contrast lighting casting long, dense shadows. These shadows would have made it difficult, at best, to read the instruments. The numerous valves used to operate the torpedo tube and dynamite gun, for example, had to be operated in a particular sequence. Photo realism illustrates that performing this complex procedure with the available lighting must have been a dangerous challenge.

In all, 2200 parts (not including rivets or batteries) - have now been modelled in CATIA, allowing detailed examination of most of the boat's major systems. The greatest achievement of rebuilding the submarine in this virtual 3D environment is that now almost all operations and maintenance of the submarine can be simulated in realtime. Users can 'walk through' the ship, experience its operation, and witness first hand the genius of John Holland, the simple schoolteacher from County Clare, Ireland, who helped to change the course of naval history.

For more information contact CNC Design Consultants, 011 786 3515.