Here is the informative American Civil War Society of the United Kingdom's description of the Laird Ram timeline.
Link:
acws.co.uk
The Laird rams drew 15'.
Relief shown by hachures. Depths shown by soundings. Oriented with north toward the upper left. Includes "Tide Scale at Smithville." Available also through the Library of Congress Web site as a raster image. LC copy imperfect: Discoloration and staining on bottom of all sheets. Torn along edges...
www.loc.gov
This historic tide map of the mouth of the Cape Fear River is indicative of the challenges the Lairds would have faced " …cruising up & down …" the coast.
The bar at entrance of the Savannah River was 12'.
View attachment 549646
Charleston Harbor
The natural depth of the entrance to Charleston Harbor was 12' at high tide.
The channels were dredged to 17' before the war. Silting up during the war meant that the channels were shallower.
10'6" was the draft of a Monitor (+/-).
The waters the eastern seaboard off the Carolinas are known as the "graveyard of the Atlantic for good reason. Not only are there days long violent storms, the shoreline is constantly changing.
At high tide the channel between Dafuskie & Hilton Head Islands adjacent to the mouth of the Savannah River only leaves a narrow beach on both sides of the channel. At low tide, it looks like the ocean has all bit disappeared. It is possible to walk & wade across between the islands.
What, you may ask would a ram unable to enter a harbor except at spring tide, if that, get resupplied, refit & refurbished? As we know the CSS Virginia could not threaten Washington because of her 21' draft. The Lairds would have had similar problems. Where would the Lairds have gone during hurricane season… Havana?
Distance between cape Cod & Florida Keys (+/-) 1,500 miles. Combined radius of control Laird Rams (+/-) 4 miles.
Like all raiders, the Lairds would have been dependent on captured coal. Speed comes at a price, in this case tons of coal. City Class gunboats burnt a ton of coal/hour.
Metallurgy of the day meant that after cruising for several days or weeks, engine overhauls were mandatory. Where were the Laird's going to lay up for extended periods of time doing periodic maintenance?
Just what two vessels commanding (+/-) a four mile circle along 1,500 miles of coastline without a base could possibly accomplish escapes me. It would have taken every breath the crew took just to keep the Laird's seaworthy.