USS Constitution Rehabilitation And Restoration

Patrick Otton, Technical Writer
Naval Historical Center Detachment Boston
Bldg 24 M&R B.N.H.P.
Charlestown Navy Yard
Boston, MA 02129 USA
617-242-0752, phone
617-241-5232, fax

Logo of Naval Historical Center, Detachment Boston

On September 26, 1995, Constitution was undocked, three years and one day after initially being brought into drydock for inspection and minor repair. Not only was Constitution repaired for her bicentennial but there was a significant change in the scope of work between the original plan and the final executed package. Restoration became the central focus where major structural hull components were restored. Known as the Strengthening Initiative, this repair is the most significant structural restoration in Constitution's history.

As history can attest, Constitution represents a successful design. Joshua Humphreys, the designer of the Navy's first six frigates, that included Constitution, had two criteria to satisfy, to out gun the next rate ship and to out-sail adversaries. The solution required a never-before-built design.

The successful integration of the two design criteria demanded an innovated technical solution to the problems of strength of materials and hull design. Humphreys understood that optimization of the two criteria became mutually exclusive when building a hull. The fine entry and run required for sailing qualities and the weight of a heavy armament causes particular problems for wooden hull sailing ships. Combining the weight of the guns and the buoyancy curve of a fast sailing hull results in a force that distorts the hull. The distortion known as "hog" is the bending along the length of the keel. It is the same curve that resembles the curve of a hog's back. With minimal buoyancy, the ends of the ship tend to drop down under the weight loads of the guns, while the center midbody, being more buoyant, rises upward. Humphreys recognized the need to stiffen the hull to resist the forces causing hogging.

From historical research, five components were identified to have been part of Constitution's original construction.

  1. Thick Strakes, Restored using laminated white oak planking on gun deck and lower deck. There are two paired runs, (fore and aft), (port and starboard), of deck planking: One pair running along side of the hatches, the other pair running midway between the waterways and hatch strakes. The thick strakes are thicker by two inches, (five and one-half inches total) than the standard deck planking and are bolted and joggled into each other, and joggled over and into the deck beams below by two inches. These deck strakes add longitudinal strength to the hull.
  2. Standard Knees, Restored at the ends of the ship, both at the bow and stern, are long laminated white oak knees fayed at the end of each pair of thick strakes on lower deck. These joggle over two deck beams and are well bolted to the bow and stem with one and one eighth inch bolts. These knees unite the deck thick strakes to the hull.

    Two additional laminated white oak standard knees restored on the centerline, one reaching from the stem to the foremast and the other from the transom to the mizzen mast, joggled over and into each deck beam and well bolted. These additional two knees also strengthen the hull at ends of the ship.

  3. Midship Knees, Restored on lower deck, are laminated white oak knees made as a single composite of the original hanging and standard knee pairs. The knees fay over each beam the diagonal riders come under with the others placed amidships for a total of twelve on each side. The knees are sided thirteen inches, the body reaches the upper edge of gun deck clamp, the arm is six feet long. The knees are bolted with eight bolts each one and one fourth inch diameter. These twelve knees carry the weight of the overhead gun deck cannon distributing the loads to lower deck.
  4. Stanchions, Made of turned white oak copied from the centerline stanchions. On lower deck, two additional tiers were restored, each under an overhead gun deck beam at the midship thick strakes. These stanchions work in conjunction with the midship knees to form a structural unit supporting the overhead cannon.
  5. Diagonal Riders. Made of laminated white oak, 12 x 24 inches in cross section and approximately 34 feet long. Restored in the hold, a total of twelve diagonals, six per side, three sweeping forward, three sweeping aft, with the two midbody ones butted against each other at the keelson. The diagonals are spaced a distance of two beams apart and follow the curve of the hull along the ceiling plank. They are chocked at the keelson and are cut with a bird's mouth into the overhead lower deck beams. Being bolted every two feet through the bottom plank with one and one-eighth inch copper bolts, the diagonal rider becomes the unifying member joining hull sections together, stiffening the hull and resisting the forces which cause hogging.
Throughout the last 200 years as Constitution's purpose and function changed from fighting warship, to training vessel, to receiving ship, to dock side exhibit, so did Constitution's configuration. Also, Constitution's repair(s) did not always retain her original construction. The five structural components were expensive in materials, techniques, and labor to install. As early as 1820, the diagonal riders were not renewed in Constitution's repairs. Those five components were not part of Constitution's structure when drydocked in 1992.

Over the years, age began to show on the hull of Constitution. By 1992 Constitution had developed over 13 inches of hog. Many suggestions had been proposed for stiffening the hull: air bags, steel girders, and space frames. None of these were historically accurate and none were congruent with the fabric of the ship.

In 1993, aware of the structural needs of an aging hull and that Humphreys had already answered these questions, NHC Detachment Boston modeled the five historical structural components. Using a 1:16 scale model of Constitution, a 10% increase in hull stiffness to resist hogging was shown. Just as Humphreys specified in 1794, the Detachment recognized in 1994 the effectiveness of the structural components and successfully extended the dry dock repair activity to include the restoration of those five structural components.

The drydock repair consisted of both rehabilitation, (the repair of deteriorated structure) and restoration, (putting back into Constitution components of her 1812 configuration). To restore the structural components during the 1992 drydock repair was a justified expenditure of labor, techniques, and materials. Due to the limited availability of the required natural timber, glue lamination technology supplied much of the wood shaped to Humphreys' dimensional specifications.

In 1797, while observing the launch of USS United States, Joshua Humphreys wrote to the Secretary of War, that "...without straining or hogging more than one & a quarter inch, as you will see by the enclosed certificate, to my great and unspeakable satisfaction. The firmness of the ship was convincing proof of the utility of the diagonal riders in long ships, "1 Today the same may be said for Constitution. When undocked in September 1995, the hog was measured to be less than two inches. The effectiveness of the structural components is again shown with "convincing proof" and "unspeakable satisfaction".

Given the satisfactory condition of the hull and the successful completion of the repairs, Constitution is being readied to sail in celebration of her bicentennial. On July 21, 1997, for the first time since 1881, Constitution will make passage under her own sail, sailing in Massachusetts Bay under topsails, jibs, and spanker -- her battle configuration. With a Navy crew and under specified weather conditions of winds less than 15 knots and seas less than two feet, Constitution will sail again as a salute to the Nation.

Joshua Humphreys is owed credit for the 200 year story of success of Constitution. It is his innovative design in building a structurally stiff hull that resolved the design criteria of fast speed under sail while carrying heavy armament. The history of this Nation rests on Constitution as a unique example of American technology. Constitution has become a lasting National symbol as a product of Humphreys' design.

1 J. Humphreys' Letter Book, 1797-1800, pg 26, dated May 11, 1797, Historical Society of Pennsylvania .

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