IN MANY WAYS, the propulsive machinery we covered in the October issue was the easy stuff. Most of it is fairly big, but individual items of machinery are not so big that a diver can’t see enough to visualise them.
The hull of a wreck, on the other hand, is obviously the biggest part there could be. It’s usually so big that it is impossible to see it all at a glance, so big that we can picture it only by mentally integrating our view of comparatively small sections.
As with the propulsive machinery, variations in how a ship’s hull is constructed and fitted out can tell us plenty about the original ship.

RUDDER & STEERING
Most ships will have only one rudder, even if they have two or more propeller-shafts. The general exception is where greater manoeuvrability is required.
A ship with multiple propellers may have a rudder immediately behind each one. Ships fitted this way are usually ferries or warships, so this also provides better prospects for survival in battle. (1)
In order of decreasing frequency, wrecks can have a single shaft and single rudder; multiple shafts with a single rudder; or multiple shafts with multiple rudders. Any such combination could be the clue needed to ID a wreck.
I have never seen a single shaft with multiple rudders. I suspect that a naval architect would say that this would not make design sense.
If the rudder has broken off, it could be for any reason from general decay to clearing it to salvage the propeller.
If the rudder-post is badly bent, a possible cause is that the ship went down stern-first and the rudder dragged on the seabed. Such damage is often combined with broken propeller blades.
A rudder turned hard to one side could indicate that the ship was taking avoiding action when it sank, perhaps to avoid a collision, mine or torpedo.
The most common steering mechanism is a quadrant attached to the top of the rudder-post.
An older form of steering that continued to be used on some smaller ships is a tiller-arm. A cable or chain would run round the quadrant, or to the end of the tiller-arm, and along both sides of the deck to the wheelhouse.
Such cables are often completely decayed, but the pulleys and trunking through which they ran may remain. (2)
Hydraulic steering is almost universal on modern ships, and can be found on older ships where it suited the purpose. On larger ships it helps to cope with the force needed to turn the rudder.
On a passenger liner, greasy cables or chains would not be good for the passenger experience. On warships, hydraulic steering was more robust in battle.
A ship may also have auxiliary steering directly coupled to the rudder-post. Such mechanisms sometimes involve a rack & pinion or worm-gear arrangement. (3)

HELM
At the other end of the steering mechanism, in the wheelhouse, will be a helm or steering binnacle. Where the steering works through chains or cables, the helm will in effect be a winch-like mechanism that, via gears and pulleys, pulls the chains across the ship to turn the rudder.
At the top of the helm will be a shaft with the ship’s wheel on it. Among the gears and pulleys there may also be a small steam or hydraulic motor to help turn the winch as the wheel is turned.
With hydraulic steering, a much smaller mechanism could be enclosed in a binnacle. We also sometimes see both mechanisms, where a steering binnacle on a bridge deck works with a full helm engine in a wheelhouse below. (4)
A ship’s steering is specialist machinery that could carry a maker’s plate and serial number and possibly be engraved with the ship’s name. Examine the hub of any wheel, in the wheelhouse or on the auxiliary steering. While in the wheelhouse, other precision devices such as a compass binnacle or telegraph may also carry a maker’s plate. (5)
Old wrecks have often collapsed to deck level or further, and locating the helm or other equipment indicates where the wheelhouse would have been on the wreck. This will usually be just forward of the engine and boilers, but there are exceptions, and it is these that can help identify a wreck.
Even when the engine and boilers are at the stern, the wheelhouse would sometimes have been towards the middle of the ship.
This was common on tankers and purpose-built colliers, where the design tradition began with everything in the middle before the engine got moved to the stern.
A good proportion of small coasters also had the wheelhouse in the middle, with the engine aft.
On liners and warships, the wheelhouse could be even further forward, at the front of a long superstructure.
Among smaller ships, tugs and icebreakers would often have the wheelhouse forward. Such an arrangement is rare on cargo-carrying ships other than Great Lakes steamers.
At the opposite extreme, the wheelhouse might be located above the engine and behind the boiler where deck space was at a premium, such as on very small ships like Clyde puffers,
or some steam trawlers. The man at the helm would have to look forward past the funnel.

WINCHES
Winches serve various purposes: raising the anchor, handling cargo, managing the tow-lines for a tug, and for lines and nets on a trawler. Identifying the purpose of a winch can be synonymous with identifying the purpose of a ship.
For example, a trawl-winch will have a big open drum for winding long trawl cables and nets. On more modern trawlers, this is often mounted across the stern. On older trawlers it would usually be mounted on the main deck forward of the wheelhouse.
If the drum is empty, it’s possible that the nets were out when the ship sank, but that is not always the case.
The Admiralty often used trawlers as general-purpose boats, with no nets on board. (6)
A ship with lots of winches about its holds was built to handle its own cargo. A ship with few winches for the number and size of holds could have been used where dockside cargo-handling was available, such as on a regular route with a regular cargo. (7)
Beneath or behind a winch you will find a drive motor. This will be a small steam engine on older ships, although after WW1 electric motors slowly took over from these.
Pipes will go from the motor to the boiler or cables to the generator.

MASTS
A cargo-winch lifts its load using derricks swung from masts, which could have been steel or wooden. Steel masts are likely to have fallen over, while wooden masts will almost certainly have rotted away.
Nevertheless, look next to, or between, the winches. Wide tubes set in the deck (often leading right down to the keel) will be the mast foundations, or mast-foot.
Steel masts indicate a more recent ship, and steel derricks more recent still. But the converse is not true – wooden masts and derricks were still used long after steel masts appeared.
A mast would usually be a single post straight up on the centre-line of the ship. (8) The most common variation is a goalpost mast, where two either side of the centre-line were cross-linked higher up, like rugby posts. A further variation combined hollow goalpost masts with ventilators, so a ship would have lines of rather tall ventilators along each side, with little bonnets on top.
Other variations include latticed tripod and quadruped masts. (9) These were used not for cargo-handling but to support radio antennae or a radar dish. You typically find these on top of wreck superstructures from the 1950s or later.

HOLDS & CARGO

Identifying a cargo can sometimes be a big help in putting a name to a wreck. Reports of a ship’s loss usually include at least a brief note about what the cargo was, and sometimes great detail. (10)
Even simple and common bulk cargoes such as coal or iron ore can speak volumes. For example, a wreck off north Cornwall with a cargo of coal would likely have departed from south Wales. In the same region, a wreck carrying iron ore would likely have been on route to South Wales, possibly from Spain. But beware reading too much into such evidence; both bulk cargoes could have come from and be going to other locations. (11)
Even a lack of cargo can be informative. Off the East Coast, fleets of colliers would take coal to London and return empty. But again, there are countless other possibilities.
In the hold area, refrigeration machinery indicates that the ship could have been carrying food or ice. Typical machinery resembles the vanes on the back of a domestic fridge but much bigger, often with stacks of gas cylinders nearby. Ships could also have small refrigerated rooms for crew supplies, or larger rooms on passenger liners.
Even when a wreck is well broken up, the hatch-coamings from the holds will often retain some of their distinctive shape, enabling us to count the number of holds and how they are distributed with respect to the engine-room and wheelhouse.
A small wreck with two holds forward of the engine and none aft will most likely be one of the almost standardised coasters, of which there are many wrecks.
A similarly sized wreck with no obvious hold hatch-coamings or only small ones could be a large steam trawler. Check the winches to be sure.

ANCHORS
Anchors can range from the classical Admiralty-pattern, like Popeye’s tattoo, through to the stockless anchors that are almost universal nowadays.
Identifying the anchor type gives an earliest date of manufacture. The book Anchors by Betty Nelson Curryer of the National Maritime Museum covers their evolution from stones tied to a rope through to modern examples. (12)
There are also variations in how anchors are carried. On earlier steamships an anchor-cable (which these days is actually a chain) would be fed through a hawse-hole at deck level. This developed into hawse-pipes, an iron or steel pipe from inboard on the deck to the side of the bow below the deck level.
In both cases, an anchor raised with the anchor-winch could then be lifted onto the deck with a small derrick on the bow. Stockless anchors could be pulled in tight to the hawse-pipe and remain there rather than having to be lifted on deck.
Finally, anchor-locker recesses were built into the hull about the hawse-pipe, so the anchor pulled partly or completely inside the line of the bow when stowed.

GUNS & ARMAMENT

Warships have guns, but in wartime so would many merchant ships.
During WW1, a stern gun was considered a defensive weapon. A merchant ship so equipped could defend itself while running away, but was not considered a warship because the gun was not sited in a position for attacking. So any wreck with just a gun at the stern is likely to be a Great War casualty. (13)
During WW2, such gentlemanly niceties had vanished. A merchant ship armed for self-defence would likely have multiple guns sited fore and aft, with anti-aircraft guns above, often with distinctive steel gun-tubs about the gun-platforms.
Identifying any gun can help narrow down a wreck’s identity. It will usually have a small plate identifying the type with a serial number, possibly in brass.
After years under water with rust and marine growth it can be difficult to measure the bore of a gun accurately. Look nearby for ammunition, which could be easier to measure.
A trawler with guns would probably have been in Admiralty service. Many were used as convoy escorts, anti-submarine patrol vessels, mine-sweepers and harbour-defence vessels.
Even if no guns were fitted, or can be found, there may be other signs of naval use such as depth charges, mine-sweeping generators, paravanes and A-frames that drop over the bow.
Mine-sweeping equipment was fitted to many WW2 wrecks, not only trawlers. Lead ships in convoys would often carry it to protect the ships behind them.

ODDS & ENDS
Countless small items on a wreck can be revealing, especially those buried among debris in the crew- and passenger-accommodation areas. (14)
Crockery and cutlery usually carried the crest of the shipping line and sometimes even the ship’s name. A coin will give a date that the ship must have been wrecked after, and tells us that a crewman had visited the country of the coin and that quite possibly the ship had been there too.
A button could identify the uniform of the crew or a passenger. Other personal effects may identify a manufacturer or even carry the owner’s name.
Navigational instruments such as binoculars, sextants and logs could be similarly identified by manufacturer’s name and serial number.
Find a bathroom or galley and the fittings may identify the manufacturer. Even floor-tiles could still carry an identity on the back (but please don’t wreck a nice tiled floor just to find out).
Floor-tile patterns also follow fashions. A British ship would usually have a black-and-white-checked floor, but other nationalities could have coloured floors with mosaic tiles. Not definitive, but it is another clue. (15)

HULL & DECKS
Early steamships usually had a riveted iron hull with wooden decks over iron ribs. Large parts of the superstructure and internal partitions into cabins would all be wood.
Developments from this were riveted- and then welded-steel hulls, steel decks, steel superstructures and even steel partitions between cabins. Small ships, including warships, could be built with a wooden hull over a steel frame. (16)
The bow and stern can be raised into a forecastle and sterncastle or poop, or flush with the main deck. Such details are often given in records. The stern can be flat across with a transom, or curved and overhanging as a counter-stern or a sharper cruiser-stern. Cruiser-sterns gave better rudder response in an unloaded ship.
At the bow, a straight-down or “plumb” bow is almost universal on merchant ships, while a raked “clipper” bow is more prevalent on yachts and warships. Below the waterline, more modern ships have a bow bulge. (17)
A wreck’s length can be difficult to measure accurately, but on a reasonably intact wreck the beam is easy to measure by laying a line and putting a knot in it. This simple measurement can narrow down possibilities.
Warships tended to be long and thin for better performance. Merchant ships are generally stockier for better cargo-carrying volume. But there are exceptions. Some merchant ships were built narrow to navigate rivers, canals or specific harbours.
One rare variation is the turret ship, where the hull tapers into a main deck considerably narrower than the beam.
Derricks for the boats or lifeboats usually lie about the superstructure. Counting derricks indicates how many boats were carried. Measuring the separation of the derricks gives a rough guide to the size of the boats.
Hull damage provides clues as to how a vessel sank, although subsequent decay can greatly confuse the issue.
A ship with a broken back, but the two parts still adjoining, will have sunk very quickly, possibly as the result of a mine or torpedo explosion. Where the parts are greatly separated, at least one part will have stayed afloat for a while, a clue that may match up with records of the sinking. Analysis of tides can give an estimate of how long it stayed afloat.
A collision victim will either have considerable damage to its own bow, or a relatively cleanly stoved-in vertical slit or cut in the hull. A mine casualty will usually have much more damage forward than aft, and the damage will not be as clean as that from a collision.
I mentioned earlier that rudder and stern damage could indicate a ship sinking stern-first. Similarly, excessive damage to the bow may indicate that it was first to hit the seabed.
Within our usual diving limits, many ships were considerably longer than the depth of the water in which they sank, so the bow or stern could have dragged or rested on the seabed while the other end of the ship stayed above the surface.
Any obvious area of damage to the hull may match up against records of the sinking. In the case of explosion damage, this could match up against U-boat records of a torpedo attack.
Warships are usually easy enough to distinguish, less so what kind of warship it was – cruiser, destroyer or frigate What is the difference between a mine-sweeper and a corvette The distinction can become even more blurred when a hull is refitted. A destroyer could become a frigate, or a corvette be refitted as a mine-sweeper.
Small warships were often built in large numbers, and it can be next to impossible to distinguish a wreck from its siblings.
Much can be gleaned from records before you even board the dive-boat, either through a definitive statement of where a particular warship was lost or by a process of elimination. But records are often wrong and the only distinguishing mark may be serial numbers on fittings.
At the other end of the scale, the enormous guns, thick armour-plate and squat hull of a battleship are a bit of a giveaway, and a battleship’s loss will be thoroughly documented. I have dived mine-sweepers and submarines of uncertain identity, but battleship wrecks have always been well-known.
It’s easy enough to tell a tanker from the networks of pipes and valves on the main deck, where other ships would have hold-coamings. Passenger liners also have a distinctive construction to allow for all the cabins.
One look at a hull with row upon row of portholes is enough to reveal that a wreck was a liner. But then, as with battleships, the locations of most sunken liners are well-documented! (18)