We'll Call It A Wabash

On several occasions, TFSmith mentions that US ships have been converted to coastal defence vessels by removing the masts and yards; this, apparently, allows them to become much more powerful.

Du Pont flew his flag in the big steam frigate Wabash (46), Cdr. C.R.P. Rodgers; with her masts and yards removed, she had enough reserve buoyancy to mount heavier artillery than her ocean-going peers and carry some extemporized armor, as a so-called “chain-clad.”

This is little more than a fantasy. While the sight of a tall ship may stagger one with the sight of her masts and her sails, they are a relatively small fraction of the weight of the ship itself.

We will use the Wabash as an example as she is the largest of the lot, and thus should be able to provide an effective demonstration of the upper limit of extra buoyancy available.

Firstly, there is the question of how much weight there is to play with. An article in the Daily Telegraph claims that the masts of the HMS Victory support 25 tons each:

http://www.telegraph.co.uk/news/2016/05/10/hms-victory-collapsing-under-own-weight/

This is for a ship with a displacement of 3,500 tons, and capable of 11 knots under sail, with about 58,000 square feet of sail area total.

The Warrior had about 125 tons in total mast weight (with some of the masts being iron), and was capable of 13 knots under sail alone. Her sail area was less, but her longer hullform made her more efficient for the same propulsive force.

The Wabash was a 4,800 ton frigate with three masts, 49,000 square feet sail area total, and a top speed of nine knots in “ideal conditions” (even when assisted by an engine). It would thus be fair to assume that the total weight on all three masts was in the vicinity of 100 tons.

With 100 tons of extra weight, some changes are certainly possible. However, the armouring or up-arming would not be nearly so extensive as TFSmith implies.

First a little background. The Wabash as of the historical Trent affair carried 1 10” pivot gun, 28 9” shell guns and 14 8” shell guns.

In mid-1862 she was upgraded with an extra fourteen 9” guns in place of the 8” guns, which was achieved by taking the 9” guns off the Roanoke and other vessels damaged or wrecked at Hampton Roads (which has not happened TTL)

All Armour

If the entirety of the 100 tons of weight was to be spent on armour, then it is important to work out how much protection would be available.

The Wabash is stated to have chain-cladding, which is not very effective – in real use on the Kearsarge not only was chain cladding a form of protection intended only to prevent dangerous hits on the upright boiler, but it was vulnerable to damage or penetration by 32 pounder shells and was essentially ignored by the 7” Blakeley rifle which hit Kearsarge.

For the purposes of this analysis, we will use the protection granted by a solid iron plate as being the single most weight-effective form of protection at the time. (This is why ironclads would be common for the next several decades and the historical chainclads were limited to Kearsarge.)

Option 1: Protecting the entire side

Under this option, the entire 100 ton mass freed up by the removal of the masts is assigned to iron plating along the sides of the Wabash – with a total volume of about 6.4 cubic metres per side (165 cubic feet per side). With the waterline length of the Wabash being about 300 feet and her freeboard (by calculation based on lithographs) being about 27 feet, then a plate from the waterline to the top of the freeboard would cover roughly 8,100 square feet, and would have a thickness of 0.25 inches (6.4mm) – approximately enough to stop a rifle bullet.

Option 2: A waterline belt

This option focuses the protection into a belt around the waterline, from 2 feet below the waterline to four feet above. This leaves almost the entire side of the ship unprotected, but allows for the belt to be a little more than an inch thick (30 mm) and would let it stop light field guns.

Option 3: Proof against 32 pounder guns

The weakest weapons used on British ships at the time were 32 pounder guns. During the Battle of Saint Charles, the 2.5 inch casemate of the Mound City was penetrated by a hit which went on to strike the boiler.

As this was a short 32, we can consider 2.5 inches of iron to be the minimum required to protect against the long 32 pounder guns on the British ships.

With this constraint, the armour consumes approximately 0.2 cubic feet per square foot, so to armour the waterline of the Wabash would permit an armoured belt a little under three feet high (2 feet 9 inches) – leaving the other 24 feet of her freeboard unprotected.

All guns

The picture is a little better for increasing armament, but not by much. A 9” Dahlgren gun with carriage weighs upwards of five tons, irrespective of ammunition or deck strengthening (or the weight of the extra crew required to serve the gun and their accomodations.) With the Wabash already quite heavily armed (in July 1862 she carried 42 9” guns and 1 10” gun) the extra armament is non-negligible (perhaps ten to eleven 11” Dahlgren guns?) but is not going to make her able to take on battleships – especially if her side is not protected, as the thicker sidewalls of the battleship will make her more durable.

There is also the question of whether it is possible to find more guns to fit. The United States was not overflowing with heavy guns of 8” calibre and above, and indeed to arm Monitor in reality the guns were taken from the Dacotah; with all the US ships that were OTL available to be stripped of their guns either surviving TTL or being sunk nobly by British ships, there should be a gun shortage for OTL new production and OTL forts (let alone up-arming half the fleet and producing as many ironclads as the United States put out in the entire Civil War).

Both together

The Wabash is designed as a screw sailing frigate – she is a mobile vessel, and is as heavily built as most frigates (i.e. less so than a liner). Her strengthening is intended to take the weight of her masts.

To remove the weight of the masts and expect to use the resultant displacement to make her better armed and protected is to ask far too much of the ship – there is simply not enough extra displacement freed up.

Why?

The real reason for this insistence on the glory to be had from chain-cladding is probably that the Wabash was simply not a very good ship for the task the USN now has. Her top speed of nine knots was achieved under both sail and steam, and she is slower than most RN battleships under steam alone; thus, she is ineffectual at commerce raiding. Her draft is deep (23 feet) and so she has the same flaw for which many British ships are castigated (though it does not prevent even their shallowest ships running aground elsewhere in the timeline).

Her total weight of fire on one broadside as built (with 8” guns) is 1,404 lbs of shells, with about 59 lbs of bursting charge. Some powerful British frigates such as the Mersey had over 2,000 lbs of shells with over 110 lbs of bursting charge.

Thus, rather than compare her real statistics with real enemy ships, TFSmith uses the dramatic-sounding removal of the masts as a smokescreen while making the Wabash (and other ships upgraded in this way) as powerful as they need to be for the convenience of the plot. Chaincladding is treated as a form of armouring which makes the ship markedly superior to any British vessels of the same weight class, and the increased armament (of which there are no details) stands as an excuse for why the British have not mustered a large force of their (apparently unused) liners and gunboats and battered their way into an important US port (such as Baltimore, Washington, Philadelphia, Boston or New York).

It is also notable that TFSmith does not do as he often does, which is to loudly claim he is following historical precedent. This is probably because of the actual historical precedent of a US screw frigate being converted into a coastal defence vessel – the Roanoke, a failure of a ship which took a year to convert.

Roanoke was razeed down to her upper deck starting on the 25 of March (with the process of conversion expected to take about three and a half months), and then the guns replaced in their entirety with three turrets each mounting two heavy guns. The production of the armour for the Roanoke turned out to take nearly a year and the resultant vessel leaked about 1.5 feet per day, with an unmanageable roll in a seaway and guns that dismounted themselves in the turret on their first test firing.

For the US to successfully convert Franklin, Wabash and other ships (frigates and sloops) into superior combatants on short notice, without any mentioned mistakes and at blinding speed, seems unlikely in light of the failure of the Roanoke. If there was a simpler way of converting ships which the US knew about, they would have taken that one.