From a post to DAVIDWEBER.NET forums on 3/3/2013

HMS King Haarahld 896 Redesign

       Bear in mind that all of this is subject to change if I decide to tweak the design. Also, before anyone points out how thin the deck armor is, remember that these ships are very unlikely to be subject to plunging fire, given the very limited ranges at which individually aimed, truck carriage-mounted guns with no or very simple iron sights are likely to obtain hits.

HMS King Haarahld 896 Redesign

Design Displacement:

    11,510 Tons


    Length: 431’ 6”
   Beam: 79’ 1”
   Draft: 22’4”


       4 10”/40 (2 x 2 centerline with shields)
   10 8”/40 (10 x 1 in casemates)    8 4”/45 (8 x 1 with shields)


       2-shaft, triple expansion: 1,215 SDP* (31,000 SHP)


       28.3 knots (24.6 Old Earth knots)
   *SDP = Shaft Dragonpower; 1 dragonpower=25.5 horsepower


       Design: 2,500 tons
   Maximum: 3,600 tons


       3,643/5,294 miles @ 21 knots (18.2 Old Earth knots)
   7,143/10,286 miles @ 12.5 knots (10.9 Old Earth knots)
   10,000/14,400 miles @9 knots (7.8 Old Earth knots)*
   *steaming on one engine


    The main armor belt is 220’ long, 12’ deep, and 6” inches thick, tapering to 2” at the lower end. It extends from the main deck to 5’ below the waterline. The ends of the belt are closed by 5” armored bulkheads, and a secondary belt 2.25” thick extends from the ends of the main belt to bow and stern. The deck is protected by 1.5” armor.

       The 8” guns are mounted in a casemate protected by 6” armor. The 10” guns are protected by open-topped gun shields with 6” faces and 4” side panels. The 4” guns are protected by gun shields with 2” faces and 2” side panels.

       The belt armor is backed by 6” of Charisian teak, reduced from the original 12” following experience with the River-class ironclads in 896.

Gunnery notes:
These are “brown powder” weapons, firing the Charisian equivalent of cocoa powder, which is one reason for the relatively short barrel lengths. Note, however, that even at “only” 40 calibers length, the tubes on the 10” guns are over 33 feet long, far longer than any other artillery piece ever produced on Safehold. The 8” gun tubes are the next best thing to 26’ 8” long and the 4” guns are 15 feet long, or about 66% longer than a muzzle-loading thirty-pounder.

       The 10” guns have a muzzle velocity of approximately 2,200 feet per second (375-pound HE shell) or 2,000 feet per second (508.5-pound AP shell) and can elevate to 15°. At that elevation and muzzle velocity, they have a range of approximately 19,000 yards (they probably aren’t going to hit a maneuvering target at ranges much in excess of 5,000 yards at this time, however). The 10” HE shell carries a bursting charge of 65.26 pounds, while the AP bursting charge is only 19.6 pounds. Hydraulic power is provided for loading. Maximum rate of fire is 2 rounds per minute; sustained rate is 1.5 rounds per minute (1 round every 40 seconds).

       The 8” gun fires a 192-pound HE shell (33.41-pound bursting charge) and a 260-pound AP shell (10-pound bursting charge), with a muzzle velocity of approximately 2,500 feet per second and a maximum elevation of 15°, to an effective maximum range of approximately 15,000 yards (and a roughly 36-second time of flight). The mount is provided with hydraulic power to aid in loading and rate of fire is 3 rds/min maximum, 2-2.5 rds/min sustained with bagged charges.

       The 4”/45 fires a 22-pound HE shell (4.86-lb bursting charge) or a 31-pound AP shell (1.85-lb bursting charge). Muzzle velocity is approximately 2,300 fps, and maximum effective range is about 13,000 yards. Rate of fire is 3 rds/min using bagged charges and 6 rds/min using cased charges (when they become available). They will be converted into 4” QF guns when the new sliding block breeches and fixed rounds become available (probably not in time for the current war), at which time RoF will increase to 10-12 rds/minute. Hydraulic power for loading is not provided.

       All of the King Haarahlds’ guns have been designed with an eye towards converting them to nitrocellulose propellant as soon as it becomes available. At that time propellant charge weights will reduce radically amd muzzle velocities will increase to approximately 2,900 fps for the 10”/40 and around 2,700 fps for the 8”/40. The 4”/45’s muzzle velocity will be approximately 2,800 fps.

       "Oh, bother!" said Pooh, as Piglet came back from the dead.