Royal Navy Order of Battle 1861

Bomarsund was taken by landed forces with siege artillery, not reduced by naval bombardment.
My apologies, it was not Bomarsund but Sveaborg I was thinking of. Though Bomarsund involved much more naval firepower than land firepower, and the landed guns consisted of IIRC a couple of 32 pounders.
 
Colorado might make 9 knots under steam alone (really 8.8 kts is the highest I've seen, in a calm sea, more usually 6.4kts, dropping to 2-4kts in a headwind), but she could do 10-13 under sail alone.
AFAICT all the listed speeds for British steam liners are steam alone. Obviously both are going to be faster when they have a tail wind, but it's probably best to compare like for like (i.e. steam speeds for both if we have them).
 
And seeing no casualties. Conversely, at the bombardment of Fort Fisher six Parrotts burst in the course of about an hour's firing and 43 men were killed or wounded.

I'd rather have the Armstrong guns, certainly.

The Parrott was certainly much worse than the Armstrong.

It should be noted the large Dahlgrens also had a serious problem. 40% of the 15" Dahlgrens cracked or burst in service. Three actually catastrophically burst in the turret whilst in action, those of Canonicus, Saugus and Mahopac. The large US guns also had huge problems with premature detonations of shells - ca. 6-8% of shells burst in the barrel. Whilst the Dahlgren often survived, sometimes with cracking, the Parrott had a good chance of catastrophically bursting.

If I was writing wargame rules, and you rolled 2d6 per shot and a 2 was a potential failure I'd have the following effects:

Armstrong: Roll d6. 1-3 = lose one vent piece, no further effects (when three vent pieces lost gun is out of action). 4 = jammed vent piece (10-30 minutes to clear if the tool not on issue, 1 minute if the tool was issued). 5-6 = no effect

Parrott: gun catastrophically bursts

Dahlgren: Roll d6. 1-2 = gun catastrophically bursts. 3-4 = gun cracked (now unusable). 5-6 = slightly damaged (usable but any further failure automatically a catastropic burst)
 
AFAICT all the listed speeds for British steam liners are steam alone. Obviously both are going to be faster when they have a tail wind, but it's probably best to compare like for like (i.e. steam speeds for both if we have them).

I know, I was just pointing out that Colorado was underpowered and ran better under sail than under steam.
 
. Obviously she's not going to stand up against any ship of the line for long,

Talos, you compared only the overall broadside weight, but the broadside is actually separated on the shell gun boardside and shot gun boardside. And "Merrimack"-class superheavies have shell-only boardside.

I agree, that the total "Colorado" weight of salvo is less than any of ships-of-the-line. But in therms of shells, "Colorado" have nearly 50% advantage over the HMS "Conqueror", for example. "Colorado"'s 9-inch Dahlgren guns were heavier than RN's liner's 8-inch shell guns, their shells have more powerfull bursting charge. And, thick planking of liner's hull basically guaranteed, that the American shells would detonate inside the wood, doing maximal structural damage.

So, in slugging match, "Colorado" could actually fight any (any one, of course) of Dunlop's liners on generally even therm. The RN liners have heavier general boardside, but "Colorado" have better shell guns.
 
Talos, you compared only the overall broadside weight, but the broadside is actually separated on the shell gun boardside and shot gun boardside. And "Merrimack"-class superheavies have shell-only boardside.

I agree, that the total "Colorado" weight of salvo is less than any of ships-of-the-line. But in therms of shells, "Colorado" have nearly 50% advantage over the HMS "Conqueror", for example. "Colorado"'s 9-inch Dahlgren guns were heavier than RN's liner's 8-inch shell guns, their shells have more powerfull bursting charge. And, thick planking of liner's hull basically guaranteed, that the American shells would detonate inside the wood, doing maximal structural damage.

So, in slugging match, "Colorado" could actually fight any (any one, of course) of Dunlop's liners on generally even therm. The RN liners have heavier general boardside, but "Colorado" have better shell guns.

I was comparing the broadside weight of the 51-gun frigate Shannon to Colorado, not a liner.
 
I was comparing the broadside weight of the 51-gun frigate Shannon to Colorado, not a liner.

"Shannon" have about 55-60% of "Colorado" shell weight, and again, only 8-inch guns vs the "Colorado's" 9-inch. The overall difference in destructive power was, I believe, was about two times in favour of USN frigate.
 
My apologies, it was not Bomarsund but Sveaborg I was thinking of. Though Bomarsund involved much more naval firepower than land firepower, and the landed guns consisted of IIRC a couple of 32 pounders.

Sveaborg was bombarded by ten liner's and nine frigates for two days, and overall effect was limited. Forts and batteries weren't silenced and their fighting power wasn't significantly reduced. Russian total losses were 73 killed and around 300 wounded.
 
Sveaborg was bombarded by ten liner's and nine frigates for two days, and overall effect was limited. Forts and batteries weren't silenced and their fighting power wasn't significantly reduced. Russian total losses were 73 killed and around 300 wounded.
If you'll excuse me, I'll quote from contemporary descriptions of the "limited effect".



...after a little spell, batteries from all directions on shore sent shot and shell out in return, but so many fell short that it was soon reduced to a few guns of long range, and two or three uncomfortably heavy long-range mortars, which sent shot and shell well out to the line if they wished to. But soon our gun-boats went in and began firing at shorter ranges, and this made the fire from the shore little or nothing for the mortar-vessels, and they steadily went on, causing little clouds and occasionally more smoke, which soon began to show itself in good columns of smoke, and fires were established in several places.

About ten we could see we were evidently successful, and that total destruction was only a question of time. At ten a magazine blew up, bringing rounds of cheers from the crews of the large ships swarming on every top and yard like bees. Still went on smoke and fire, followed by flames through roofs and windows. We were running up and down along the line, with the admiral on board, occasionally being able to swear we were under fire by a stray shot dropping near us, and one shell of the big mortar (named 'Whistling Dick', after his Sevastopol brother) bursting a little over us, throwing the fragments on both sides of us, but not one touched us anywhere. One of my greatest pleasures, next to the feeling that I had proved to be right in my ideas about the effect of shelling in this way, was to see the changed visage of the admiral: instead of the anxious, thoughtful face of past weeks - anxious to do all he could, doubtful if any success to warrant the risk could be gained - he was looking bright and cheerful, and expressing surprise at the result. At twelve another small magazine exploded, bringing more cheers; but at 12.15 a tremendous column of smoke, mixed with fragments of all kinds, masses of timber, etc., showed we had found out a large one; but no sooner was the astonishment over and the cheers roaring in different directions, than up went another column and more fragments, and again another and another, with only intervals of seconds, till at least twenty explosions had followed the first in quick succession. Occasionally towards the end a longer interval would make us think it was over, when again masses of building would fly up in all directions, but all near one spot. At last it reached a larger new earthen battery on the top of Gustaff Island, and away went one side of it, guns and all, leaving, instead of bright-green turf, a heap of stones and rubbish. I think it was all on the inner slope of Gustaff, where I have written m. Now nothing is to be seen about there but bare space; and even on the next island, Vargon, the buildings on the point nearest to it are a heap of ruins. I think such an extraordinary explosion never occurred before. There might have been greater single ones. The fort I was under at Bomarsund, from the account of those who saw both, was a more tremendous explosion than the first; but a succession of at least twenty - some say thirty - is the extraordinary part. I think they must have had the magazine formed in cells or compartments of masonry, and that these went in succession, each blowing up its next-door neighbour by smashing the intervening wall, which might have caused the second or two's interval between each.
(some days later)

While clearing, at noon I got a gun-boat from the admiral, and went to the east side of the place as far as I could to look through the islands. The arsenal fire was still raging, and the ruin over the back part of Swarto, as well as Vargon, was complete. The devastation caused by the grand explosion was terrible on Gustafsvard, but my friend the white house had only one shell-mark, and a house beyond it was uninjured; the long house west of it was burnt out at its south end, showing the extreme limit of destruction in that part. In the evening I went in my boat with Creyke to a nice place for looking between the islands from the westward, an island off Helsingfors, with a high rock, but only two thousand yards from all the Helsingfors batteries. On all the batteries men sat quietly looking at us, officers watching us with spy-glasses, but they did not fire. From there we saw that within the limits I have shown dark the destruction is so complete that not even a portion of a house is left, all a blackened, shattered ruin, but the windmill and two wooden houses on the eastern front, which seem to have been charmed. Between the large black building on the west end of Swarto and the church just outside our range, a little cluster of wooden houses stands quite uninjured, affording a striking contrast to the blackened ruins. The space between that black building and the long storehouses in the middle of Swarto is covered with the ruin of smaller stone houses, apparently dwellings.​

The bombardment of Sveaborg did considerable destruction to the targets. Within four hours of opening fire, magazines on both Vagen and Gustavsvard have blown up; fire eventually consumes all the dockyard buildings, workshops and stores on East Svarto, with lesser damage being done elsewhere.


It's true a lot of this was done by mortars instead of direct fire, but then the fortifications at Sveaborg were quite modern and there was a significant Russian fleet present (four ships of the line, etc). It does nobody any good to pretend the above was little damage - Sveaborg was very badly damaged.

They also weren't going after the batteries themselves - they were going after the important materials, and fulfilled their objectives.


Of course, this was all done with smoothbores. We know from engagements of the Civil War that second- and third-system forts were quite vulnerable to rifle fire such as Armstrongs, and that at the range British liners dropped anchor to bombard forts in the Crimea (800 yards or so) they could score hits quite nicely and could collapse the facings when their shells burst inside. The US bombardment mounted at Fort Fisher sufficed to silence it within an hour or so, and the British could easily manage that kind of attack with the forces present on NA&WI station (though they probably wouldn't need to, Fort Fisher was an earthwork fort which was much more resilient to large shells than the masonry of Forts Monroe, the New York forts etc.)
 
It's true a lot of this was done by mortars instead of direct fire, but then the fortifications at Sveaborg were quite modern and there was a significant Russian fleet present (four ships of the line, etc). It does nobody any good to pretend the above was little damage - Sveaborg was very badly damaged.

Actually, there were two comissioned Russian liners here - 120-gun "Rossya" and 74-gun "Iezekil", not counting the frigate "Tsesarevich" and one armed steamer. Others were disarmed recieving ships, row gunvessels, ect. There were no significant naval presense in Sveaborg in 1855; the Allies probably mistakenly assumed so because there WAS significant naval squadron in Sveaborg in 1854 campaing.

The bombardment of Sveaborg did considerable destruction to the targets.

In therms of "damage to the city & port" - yes. In therms of "damage to the fortifications" - no. The most damage to the defense was done by the destruction of auxilary bomb magazines on Gustavsvard, which have only very limited overhead protection. The main magazines were completely intact, and fortress was still completely capable to defend itself.

It does nobody any good to pretend the above was little damage - Sveaborg was very badly damaged.

We were talking about the ability of the fleet to reduce fortresses by bombardment. The Sveaborg wasn't reduced or even temporarely silenced by naval bombardment.

and that at the range British liners dropped anchor to bombard forts in the Crimea (800 yards or so) they could score hits quite nicely and could collapse the facings when their shells burst inside.

Problem is, that on the same distance the RN liners would be perfect targets for the fort's own weaponry. And there were a lot of heavy guns in Fort Monroe, much more than Sveaborg have. By the way, as far as I could recall, the massive 15-inch prototype - "Lincoln's gun" - were around by the end of 1861, as well as 12-inch Dahlgren rifle. So, basically, the Fort Monroe was actually capable of killing even the "Warrior", if the REALLy try to come here.
 
In therms of "damage to the city & port" - yes. In therms of "damage to the fortifications" - no. The most damage to the defense was done by the destruction of auxilary bomb magazines on Gustavsvard, which have only very limited overhead protection. The main magazines were completely intact, and fortress was still completely capable to defend itself.
And they didn't intend to destroy the fortifications.


We were talking about the ability of the fleet to reduce fortresses by bombardment. The Sveaborg wasn't reduced or even temporarely silenced by naval bombardment.
True, I'd gotten mixed up. Though a lot of the damage done to Bomarsund was done by the gunboats, and of course Kinburn was disabled.

Problem is, that on the same distance the RN liners would be perfect targets for the fort's own weaponry.
Depends on the fort. Most of the guns of Fort Monroe are 32 pounders, and that's one of the better armed forts (the south face had twenty-five 32 pounders and not much else, though, which gives her less firepower than a single 51-gun frigate).

As against this the British 110-pounders and 40-pounders can put shell several feet deep into the masonry before bursting.

By the way, as far as I could recall, the massive 15-inch prototype - "Lincoln's gun" - were around by the end of 1861, as well as 12-inch Dahlgren rifle. So, basically, the Fort Monroe was actually capable of killing even the "Warrior", if the REALLy try to come here.
Not really, no. Neither gun was usable, the 12" gun wasn't test fired until 1864 and the 15" gun would require several days to remount because you'd have to build cranes to do it.
Bottom line, neither gun is of any use. But if the 15" was mounted and was fired at Warrior at 800 yards it wouldn't pierce, and certainly wouldn't kill her with one shot (and one shot's all you'd get, it's a trial mount on the beach and has no defences).
 
True, I'd gotten mixed up. Though a lot of the damage done to Bomarsund was done by the gunboats, and of course Kinburn was disabled.

Disabled, yes. But not by ships of the line, but by ironclad floating batteries & gunboats - i.e. coastal forces, which came close enough to took out fortress guns and were protected (by armor in case of batteries, by small size in case of gunboats) from fortress fire.

Depends on the fort. Most of the guns of Fort Monroe are 32 pounders, and that's one of the better armed forts (the south face had twenty-five 32 pounders and not much else, though, which gives her less firepower than a single 51-gun frigate).

Hm, as far as I knew, she have at least old-type Columbiads around. I'll check the resources.

Not really, no. Neither gun was usable, the 12" gun wasn't test fired until 1864 and the 15" gun would require several days to remount because you'd have to build cranes to do it.
Bottom line, neither gun is of any use. But if the 15" was mounted and was fired at Warrior at 800 yards it wouldn't pierce, and certainly wouldn't kill her with one shot (and one shot's all you'd get, it's a trial mount on the beach and has no defences).

Er, as far as I knew, both guns were put on mounts in just a few days after "Virginia's" appearance. This isn't impossible to do so, and frankly, I could not imagine that Royal Navy would try to attack Monroe immediately without any reconnaisance. They suffered pretty much from Russian mines on Baltic to be REALLY cautious about attacking coastal fortresses.

Would 15-inch gun penetrate "Warrior" from 800 yards? No. But it wasn't designed to penetrate; it was designed to shatter and rip off the armor plates through impact shock, actually, by breaking their backing.
 
Hm, as far as I knew, she have at least old-type Columbiads around. I'll check the resources.
Monroe did have some, but my understanding is that they're largely mounted facing east. If they were facing south it doesn't help much, though, as they had time fuzes and may well have not been able to range properly! (they had no fuze length between 3.5 seconds and 7 seconds.)

To the east the fort can engage with maybe 50 guns (a mix of 42 pounders, 32 pounders and shell guns).

Er, as far as I knew, both guns were put on mounts in just a few days after "Virginia's" appearance. This isn't impossible to do so, and frankly, I could not imagine that Royal Navy would try to attack Monroe immediately without any reconnaisance. They suffered pretty much from Russian mines on Baltic to be REALLY cautious about attacking coastal fortresses.

They didn't lose any ships to the mines, and there were no mines around Fort Monroe anyway. You say "very cautious", but they simply used divers to disable them - they essentially invented minesweeping within a few days and swept all the mines they needed to. (The attack on Sveaborg took three days to organize, including soundings, bouying channels, and sweeping for mines; this is not instant but nor is it an especially long time.)



After the appearance of the Virginia, the US dismounted the 12" and remounted the 15", and this took over a month. It's not an easy task because you have to build a crane capable of taking approx. 22 tons weight - I doubt the British would let them do that out there on the beach!

It wasn't until later (1864-5) that a second carriage was provided, historically.


Would 15-inch gun penetrate "Warrior" from 800 yards? No. But it wasn't designed to penetrate; it was designed to shatter and rip off the armor plates through impact shock, actually, by breaking their backing.
But we now know that that doesn't really work as a way of attacking ironclads. It was a false avenue in research. And note that the 800 yard safety radius is based on firing the 15" in British use with a steel shot and more powder than was authorized for the 15" in actual US usage.

This assumes it hits, and with one gun firing once it's not especially likely! In any case, assuming she does hit it does a small amount of damage (at most disabling one gun) and then it's silenced.


Disabled, yes. But not by ships of the line, but by ironclad floating batteries & gunboats - i.e. coastal forces, which came close enough to took out fortress guns and were protected (by armor in case of batteries, by small size in case of gunboats) from fortress fire.

By both, actually. At Kinburn there was an outer line of bombarding ships of the line and an inner line of ironclads.
Other bombardments were conducted by ships of the line where possible, but the gunboats were mainly employed because they were shallow enough to actually get into the Sea of Azov (where a lot of the good targets were). We know from Sevastopol that it was quite hard to disable ships of the line with fortress guns, and the main problem was doing damage back to the forts.

In 1861-2 many of the steam liners have some Armstrong guns and so that problem has gone away. An Armstrong shell from a heavy gun will penetrate 2-3 feet deep into the six foot masonry of the Union forts before detonating, and will derange the structure.
 
Colorado might make 9 knots under steam alone (really 8.8 kts is the highest I've seen, in a calm sea, more usually 6.4kts, dropping to 2-4kts in a headwind), but she could do 10-13 under sail alone.

Colorado's broadside was not outgunned by the 51-gun frigates like Shannon though, which have 15 x 8"/65cwt guns and 10 32-pdr/56cwt guns per side, and a single of the mighty 68-pdrs on pivot. The 51-gun frigate's main deck armament is essentially the same size gun as Colorado's spar deck. Straight up broadside weight is higher by a few hundred pounds (~1,167 to Colorado's 1,424), but the main deck armament is heavier-hitting and longer-ranged. Obviously she's not going to stand up against any ship of the line for long, but her firepower is comfortably higher than the 51-gun frigates. Now Walker's 32, 26, etc gun "Big Frigates" with their 10-inch broadsides, that's the interesting matchup.

Colorado had, in 1861, 14x 8", 7x 9" and 2x 10" in broadside = 1,419 lbs throw weight and 46.5 lbs of bursting charge

However, the 8" were handy and could fire once a minute. The 9" about 1 per 2 mins and the 10" once per three, so firepower per minute in action was:

14x 8" = 721 lbs/ min and 31.5 lbs powder exploding
3.5x 9" = 252 lbs/min and 10.5 lbs powder
2x 10" = 64.7 lbs/ mins and 2 lbs powder

= 1,038 lbs/ min and 44 lbs powder

After landing the 8" and carrying 9" (with a loss of speed and stability) the broadside per minute is:

23x 9" = 11.5 shells/ min= 828 lbs/ min and 28.75 lbs powder
add chasers:
1x 11" = 1 shell/ 5 mins = 27.6 lbs/min and 1.2 lbs powder
1x 150 pdr Parrott = 1 shell/ 5 mins = 25.8 lbs/min and ? lbs powder (ca. .6 lbs?)

= 881.4 lbs/min and ca. 30-31 lbs/min

A 51 like Shannon in 1861 had:

Gun deck: 15x 8" 65 cwt per side
Upper deck: 10x 32 pdrs 56 cwt per side
Spar: 1x 68 pdr 95 cwt

= 1,408 lbs throw weight, and 47.25 lbs of bursting charge

and from early '62 Shannon had:

Gun deck: 15x 8" 65 cwt per side
Upper deck: 4x 40 pdr and 2x 110 pdr Armstrongs
Spar 1x 110 pdr pivot

= 1,510 lbs throw weight, and 67.75 lbs of bursting charge

Unlike the US frigate, all the Shannon's guns can fire 1 rd/min and perhaps more (the lighter Armstrongs can get upto 2 rds/mins).

Ca. 1863 the Shannon, reduced to a 35, but out twice the weight of fire per minute of the overladen Colorado, and around April '62 about 50% more.

The problem is the 8" gun is about as heavy as a gun can get whilst maintaining around 1 rd/min. Dahlgren's 9" guns are not much more effective at close range, as the extra mass of the shell has been put into thickening the shell body to allow it to penetrate 30" of oak at 1,000 yds intact and then burst. This was Dahlgrens theory.

Farragut himself poured scorn on the 9", believing the lighter 8" to be far superior. Unlike Dahlgren his concern was the ships in combat, and what was needed was rapid and effective fire, capable of damaging enemy vessels at ca. 500 yds. The heavier 9" actually reduced the volume of fire and hence effect on target, for a slight increase in effective range. The explosive power delivered with all 9" was only ca. 2/3rds that with 8" on board.

However, Dilandu was arguing the Colorado could stand toe-to-toe with a ship of the line. The weakest battleship in the RN was Sans Pareil (70), with a broadside of 34x 32 pdrs, 4x 8" shell and 4x 68 pdrs = 1,634 lbs and 56.25 lbs of explosive power. She's roughly got double the firepower of Colorado, thicker armour and similar speed (SP was slow). Dunlop's other battleship is the St. George with a broadside of 2,052 lbs and 69.75 lbs of explosive power. She's about 2.5:1.
 
Would 15-inch gun penetrate "Warrior" from 800 yards? No. But it wasn't designed to penetrate; it was designed to shatter and rip off the armor plates through impact shock, actually, by breaking their backing.

No, they were designed to penetrate. When they didn't penetrate Dahlgren etc. invented a new theory and justify their continuance.
 
Colorado had, in 1861, 14x 8", 7x 9" and 2x 10" in broadside = 1,419 lbs throw weight and 46.5 lbs of bursting charge


However, the 8" were handy and could fire once a minute. The 9" about 1 per 2 mins and the 10" once per three, so firepower per minute in action was:


14x 8" = 721 lbs/ min and 31.5 lbs powder exploding

3.5x 9" = 252 lbs/min and 10.5 lbs powder

2x 10" = 64.7 lbs/ mins and 2 lbs powder


= 1,038 lbs/ min and 44 lbs powder


After landing the 8" and carrying 9" (with a loss of speed and stability) the broadside per minute is:


23x 9" = 11.5 shells/ min= 828 lbs/ min and 28.75 lbs powder

add chasers:

1x 11" = 1 shell/ 5 mins = 27.6 lbs/min and 1.2 lbs powder

1x 150 pdr Parrott = 1 shell/ 5 mins = 25.8 lbs/min and ? lbs powder (ca. .6 lbs?)


= 881.4 lbs/min and ca. 30-31 lbs/min


A 51 like Shannon in 1861 had:


Gun deck: 15x 8" 65 cwt per side

Upper deck: 10x 32 pdrs 56 cwt per side

Spar: 1x 68 pdr 95 cwt


= 1,408 lbs throw weight, and 47.25 lbs of bursting charge


and from early '62 Shannon had:


Gun deck: 15x 8" 65 cwt per side

Upper deck: 4x 40 pdr and 2x 110 pdr Armstrongs

Spar 1x 110 pdr pivot


= 1,510 lbs throw weight, and 67.75 lbs of bursting charge


Unlike the US frigate, all the Shannon's guns can fire 1 rd/min and perhaps more (the lighter Armstrongs can get upto 2 rds/mins).


Ca. 1863 the Shannon, reduced to a 35, but out twice the weight of fire per minute of the overladen Colorado, and around April '62 about 50% more.


The problem is the 8" gun is about as heavy as a gun can get whilst maintaining around 1 rd/min. Dahlgren's 9" guns are not much more effective at close range, as the extra mass of the shell has been put into thickening the shell body to allow it to penetrate 30" of oak at 1,000 yds intact and then burst. This was Dahlgrens theory.


Farragut himself poured scorn on the 9", believing the lighter 8" to be far superior. Unlike Dahlgren his concern was the ships in combat, and what was needed was rapid and effective fire, capable of damaging enemy vessels at ca. 500 yds. The heavier 9" actually reduced the volume of fire and hence effect on target, for a slight increase in effective range. The explosive power delivered with all 9" was only ca. 2/3rds that with 8" on board.


However, Dilandu was arguing the Colorado could stand toe-to-toe with a ship of the line. The weakest battleship in the RN was Sans Pareil (70), with a broadside of 34x 32 pdrs, 4x 8" shell and 4x 68 pdrs = 1,634 lbs and 56.25 lbs of explosive power. She's roughly got double the firepower of Colorado, thicker armour and similar speed (SP was slow). Dunlop's other battleship is the St. George with a broadside of 2,052 lbs and 69.75 lbs of explosive power. She's about 2.5:1.





You have Colorado’s armament reversed, she had 14 x 9” and 7 x 8” per side, not vice-versa… Dahlgren actually hated the broadside 8”/63s on the Wabashes, he considered them antiquated wastes of space. His preferred spar deck armament was a half dozen XI-inch pivots (in addition to the fore and aft pivots) since he was a proponent of long-ranged accurate fire instead of regular broadsides. More on this later.



Please cite your sources on two minutes per IX-inch shell. That sounds more like sustained, aimed fire rather than max speed. In the experimental voyage of the sloop Plymouth armed with IX-inch and a XI-inch Dahlgren gun in the 1850s, the well-trained crew managed five rounds from an IX-inch Dahlgren on a Marsilly carriage (the exact same arrangement as Colorado’s IX-inch guns) in 2 minutes and 39 seconds, which equals 40 seconds a shot if the gun was loaded at the start of the timer. That compares well with the well-trained HMS Excellent crews, which managed 43 seconds average per shot from 11 rounds out of a 32-pdr and 46 seconds for the same out of an 8” gun. Obviously, none of those numbers mean anything in real world except that the IX-inch gun is mechanically not that much slower loading in practice. A well-trained crew with two men moving the shell would work just fine. Both American and British manuals of the era supported an average broadside number of about 75 seconds (this is quoted by Spencer Tucker in his ‘Arming the Fleet’, along with the firing rates. I’ve seen the 75 second figure in the 1866 US Navy Ordnance Manual but haven’t found the British manual he’s referencing yet).



I am not in the slightest bit surprised Farragut would prefer faster-firing guns closer in. He was a product of the old Navy, even sailing on the famous USS Essex under Captain “Carronade ‘em all” Porter in the War of 1812. What Phoebe and Cherub did to Essex, utterly demolishing the American ship, is exactly what Dahlgren intended the Wabashes to do to European frigates, engaging them at 1000+ yards where most of their armament would be ineffective short of the 68-pdrs (and where a IX-inch Dahlgren will still easily penetrate the side of a frigate and possibly a liner). The fact that Farragut didn’t understand that just means he wasn’t infallible.



I wasn’t bringing up the liners in my initial post, I was responding to a specific comment you made re: Colorado vs 51-gun frigates and correcting several things you said. Those ships were the specific ships the Wabashes were designed to outclass and your skew on the numbers is muddling the facts. If the American frigate has a competent captain on board and even semi-decent gunners, then she’ll fight the way she was designed, not like it’s still the War of 1812 and they’re still using short range, high-ROF broadsides. But even close-in, they had a good firepower advantage over /that particular/ class of British warship.
 
What Phoebe and Cherub did to Essex, utterly demolishing the American ship, is exactly what Dahlgren intended the Wabashes to do to European frigates, engaging them at 1000+ yards where most of their armament would be ineffective short of the 68-pdrs (and where a IX-inch Dahlgren will still easily penetrate the side of a frigate and possibly a liner).
Unfortunately by 1861 the average RN frigate is getting some rifles in and hence has been upgraded.

It's not correct to say a IX inch Dahlgren would "still easily penetrate" the side of a frigate and possibly a liner, because it looks like the penetration of a liner can't really be predicted from that gun. Liners are planked to 30" or even 36", while the Colorado was planked to 24", meaning a long 32 pounder will penetrate the Colorado at 1000 yards with shot, but not with shell, and the 8" will nearly penetrate with shell; however, the liner will only be penetrated by the 64 pounder with shot (and nearly by the 42 pounder if the liner's only planked to 30".)
The 64 pounder's penetration is achieved with shot while burning 16 lbs of powder. Since the IX Dahlgren only had a 10 lbs powder charge approved (smaller charge, heavier projectile, hence lower speed and lower penetration) it seems it would not be able to penetrate a liner's sidewalls with shot let alone with shell. The IX Dahlgren is actually burning less powder than the 42 pounder.

The penetration of the 10" old shell gun with 10 lbs of powder was about 24" oak when firing shell. Based on that and the powder load of the IX inch, we can say penetration of an enemy heavy frigate would be "possible but marginal" - a liner, however, is right out.
 
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It's also worth nothing that the plan "pick your engagement range" only works if you can control the engagement range. But the Colorado's top speed wasn't high enough to let her outpace a RN heavy frigate in a straight line race, and that means she can't turn away to hold the range open and must remain effectively still firing as the heavy frigate approaches.

Assuming that the ideal engagement range for the Colorado vs. a Liffey class is 1,000 yards, and that the Liffey class can satisfactorily engage at 500 yards, then the time it would take for the Liffey to close that intervening 500 yards at 11.5 knots is a little over a minute. Colorado gets one or maybe two effective broadsides before the Liffey turns and presents her own at effective range.

If Colorado turns to keep the range open, she fails to do so and wastes some of her broadside time. She could theoretically keep alternating between sailing away at full speed and turning to present her broadside, but that wouldn't buy more than a few additional broadsides (at the generous most) owing to the time taken to do a 180 with ships of the time - essentially each broadside (turn out of the line, fire, go back into the stern chase) would have to take less than twelve seconds for it to give an extra three broadsides...


Now, if the Colorado's machinery had been the better (i.e. more powerful) of the two she could get off that 1,000 yard broadside and then sail away to open the range again, and repeat that until victory happened. Instead it's the Liffey which can control the engagement range, and the Liffey also has plenty of additional advantages from better gun crews to (depending on ship) possibly some RBL guns to the Moorsom director, to say nothing of how in any realistic matchup the Liffey-class has probably brought along friends...
 
Looking specifically at Fort Monroe, and how the RN would actually attack it, there's a simple approach to follow - effectively a three-step plan. (n.b. this assumes HMS Terror is left at Bermuda.)


Step one: Take Fort Calhoun (which has no back and is pretty much open to the south), and move heavy rifles and big shell guns onto it.
Step two: Bombard the southern casement of Fort Monroe with the rifles. This should quite rapidly render the south casemate of Fort Monroe essentially impotent.
Step three: With the south face reduced, sail heavy ships into the channel and take the water battery in the rear arc. This battery has no reverse defences and as such is vulnerable from the rear.

The fort is now essentially indefensible.



This is actually one of the stronger forts in the Union, mind.


Fort Delaware has about the firepower of a super-frigate (22 8" and 5 10") to split between five faces; Fort Washington was not very strong; the New York defences are a little better but their south-facing firepower is about 86 guns split between 32 pounders (and a few smaller guns) and 8" shell guns - the firepower of a couple of small liners or three big frigates.
If Warrior was present, she could demolish the forts for almost literally no damage, none of the guns can come even close to penetrating her. (The same is true of Fort Monroe, though there a single gun does exist which has a theoretical chance of close-range penetration.)


In New England it's worse. Boston has one old condemned (unmounted) gun in the main fort and about 20 guns facing landward at Fort Winthrop - the main defence in a Trent situation might actually be that Mason and Slidell are being held prisoner in one of the Boston forts! Then in Maine and Portsmouth things get a little better, but only by comparison with Boston:

Portland is defended by 12 24 pounders and an 8" mortar.
Portsmouth is defended by 5 32 pounders, 20 24 pounders and four field guns split between two forts that aren't mutually supporting and that can be attacked from any one facing. This would be outgunned by the planned blockade squadron.




The reason all this matters is that none of these are anything like as well protected compared to the British capabilities as were the targets during the Crimea. Sevastopol had 208 guns and could train a little over a third of them on the ships, with the full armament of the forts (Quarantine, Alexander and Constantine) being:


40x 36-prs
66x 26-prs
4x 18-prs
4x 108 pound shell gun
65x 36 pound howitzer
13x 18 pound howitzer
16x 180 pound mortar

The British and French liners were under fire from the defences between 12:30pm and 6:30pm, and the British suffered about 310 casualties (mostly wounded) with the main damage being to the rigging. (French casualties were about 212, and the Russians reported 1100 casualties during the day.)


The main problem the bombardment suffered was a lack of ability to make any serious impression - a problem rectified by the heavy 110 pounder and lighter 40 pounder rifles of the British ships. Certainly the fire of 73 Russian guns for six hours didn't sink any ships!
 
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