Tuesday, February 11, 2020

Cleaning the USS Monitor's big guns: Special coring drill will soon remove harmful salts, sediment inside Dahlgrens

One of the guns that will be bored. Below, a barrel view. (The Mariners' Museum and Park)

Research on another famous Union vessel is aiding USS Monitor conservators who will soon clean the insides of two Dahlgren guns that pounded the CSS Virginia during the Battle of Hampton Roads.

Later this month and in early March, a custom-made machine and a spade bit will remove concretion from inside the guns, which were housed in the vessel’s revolving turret during the March 1862 clash.

The drilling project is considered an important step in preserving them.

(Civil War Picket photo)
For nearly two decades, the 16,000-pound Dahlgrens have sat in treatment tanks (right) at The Mariners’ Museum and Park in Newport News, Va. Harmful sediments on the outside have been removed, making engraved inscriptions quite visible.

“By boring the guns, we will finally have the ability to remove trapped ocean salts from the interiors of these massive artifacts; which sets the stage for us to dry and put the guns on display,” said Will Hoffman, the museum’s director of conservation, in a statement. “Due to the size of the guns, no one has done this procedure at this scale, so we’ve had to develop new equipment to make it happen.”

The Monitor’s turret was raised off Cape Hatteras, N.C., in 2002. Numerous artifacts have been found in the years since as it, too, is stripped of concretion with electrochemical treatments and handheld tools.

Officials said there is a small chance some artifacts may be found during the drilling of the XI-inch (diameter) shell guns.

“Originally, that hollow cavity was filled with loose sand, sediment, coal and other debris from the sea floor,” conservator Erik Farrell told the Picket. Those have been removed, leaving stubborn concretion.

The turret after its 2002 recovery (The Mariners' Museum and Park)
The barrels have between 1" and 3" thickness of concretion covering them all the way down the bore and forward to the muzzle.

"So there is a hollow cavity down the middle of the bore all the way back, which is great, because we can tell they're not loaded as a result," said Farrell. "The axis of travel for the drill must exactly match the center line of the gun bore, so the gun (will be) mounted on a support system."

The Dahlgrens have been treated in their own tanks. “By 2018, the exterior of the guns had been cleaned of ocean deposits, but the bores of the gun are still full of marine materials which cannot be accessed by hand tools,” the museum says. The bores are 11 feet long.

Erik Farrell and Will Hoffman examine Kearsarge gun (U.S. Navy)
In 2018, Farrell and others traveled to a Naval History and Heritage Command facility to look at a similar Dahlgren -- one used by the USS Kearsarge, the sloop of war famous for sinking the Confederate raider CSS Alabama off Cherbourg, France in 1864.

They were able to measure the interior of the gun and learned both the Monitor and Kearsarge barrels -- which were made at the same foundry – were built to a specific Board of Ordnance pattern. The measurements will help crews know exactly how far down to drill without causing damage.

The guns will be drilled one at a time and it will take about a day per gun. The current timetable is February 25 and March 3, but those dates are subject to change.

An inscription on a USS Monitor Dahlgren (The Mariners' Museum and Park)


  1. This is great news! When does the museum think that the Dahlgrens and the Turret will finally be conserved? What are their plans for displaying the pieces of artillery?

  2. Can't wait to see what they find

  3. As Mr Spock would say...”Fascinating.”

    Two factors which may have significantly affected the outcome of the battle between the CSS Virginia and The ISS Monitor.

    On the Confederate side - The South has some special shells cast for its Blakey 9 inch rifled cannon aboard The Virginia. The shells were cast iron with a steel cap - designed to penetrate deeply and damage the boilers and magazines on steam powered wooden ships. They also would have been likely to penetrate the 8 inch armor (made of 1 inch plates bolted together) of the Monitor’s Armor.

    With regards to The Monitor - due to safety concerns with its Cannon (both were 111” Dahlgren Smoothbores) the guns were fired with half charges (15 lbs) vice full charges (30lbs) of powder. Had they been fired at full charges - the battle would have likely ended as soon as The Monitor scored hits on The Virginia’s Armored Casemate - as the extra velocity would have made the projectiles far more destructive.

    Needless to say - The Battle was a major turning point in the History of Naval Warfare. The Monitor -in particular- presaged many of the advancements that were to come ie a small battery of large caliber guns - mounted in a rotating turret- and an emphasis on maneuverability.

    The Virginia - was better designed for its role of destroying wooden ships - as it carried more weapons - even though they were of smaller caliber - they were still capable of destroying wooden ships. Significantly- the sloped armor of The Virginia’s Casemate - made its thinner, lower quality armor plate more effective as it was inclined - approximate 45 degrees. Whether The Confederates were specifically award of this effect is unknown. The ship’s casemate was also slathered in a liberal coating of hog fat - meant to help “Yankee Cannonballs slide off more easily.” It’s efficacy was unknown - but it did make sure the ship drew a large number of flies until it got up to speed - as they were of course attracted to the grease.

    One other major problem with The Virginia - was her maneuverability - or rather the lack of it. The USS Merrimack - from which the CSS Virginia was built - had problematic engines before the conversion. When The North abandoned the Gosport Naval Shipyard (predecessor to the Norfolk Naval Shipyard) - it razed as much of the yard as possible - and sank The Merrimack in dry-dock after setting her upper works alight. The immersion of the engines in water did nothing to improve then.

    When rumors concerning the Virginia’s imminent Launching - many in the North were terrified at the prospect of fighting the Confederate Leviathan. After the first days battle, The Secretary of War, Staunton, was concerned The Merrimack would sail up The Potomac and ...”Launch a Cannonball through his (office) window.”

    He needn’t have been concerned. (1) The Merrimack drew to much water to sail the Potomac, (2) its numerous low and open gun ports me at it wasn’t very seaworthy and (3) The ship was a pig when it came to maneuverability. At full speed - it took over 20 minutes to come about.

  4. See my later post, please, for the answer on that.