A Brief & Concise History
of Medieval Shipping (abridged):
Medieval ships of northern Europe were Clinker built, i.e., hull first with overlapping planking. The ocean going ships were of three main types: Keels, Hulks and Cogs.
Keels (or Ceols):
These were the descendants of the Scandinavian tradition of shipbuilding, with the familiar lines of the Viking longboats:
Keels were open decked with a single mast and square rigging. They were generally small (up to 100 tuns), and had a extremely shallow draft which made them very suitable for coastal, estuary or river work, as well as for raiding. They seem to have had an unsavoury reputation for piracy right into the Middle Ages. They were the most common sea vessels in Anglo-Saxon times.
Hulks (or Hulcs):
These were derived from the Low Countries and French tradition of shipbuilding. They had a characteristic crescent shape (only lowest strakes shown):
They were reverse clinker built, apparently to reduce drag on the bows. They were decked, sometimes with a castle structure added at front or back. They were mostly single masted and square rigged, but larger ships could have a square mainsail with a small square foresail. They were larger (up to 500 tuns) and were the most common merchant vessel in the early Medieval period. When rudders changed from side to stern fitted (around 1250 AD) the banana shaped stern proved troublesome to fit. After a brief experiment with hybrid shapes, the design was overtaken in popularity by the Cog.
This design is associated with Germanic and Danish traditions, but there is some speculation that it may have ancestry in the Roman ships of northern waters.
It has much straighter lines, with a integral sterncastle and sometimes a forecastle. It was usually single masted (square rigged) and sometimes had a lateen (triangular) rigged mizzen (stern) mast. It was commonly built up to 500 tuns, a few Royal Great Cogs were built up to 1000 tuns and one flagship, the Grace Dieu, took the design to its technical limit of 1,400 tuns. They dominated late Medieval shipping until a merging of northern and southern European shipbuilding techniques in the 15th Century produced an entirely new breed of ships.
The clinker building of northern ships had problems when scaled up to great warships. The overlapping planks are held together by clenching nails, and on very large ships the shear pressure could deform these nails. The Grace Dieu was triple thickness clinker built and proved to be extravagant in its use of iron: account rolls show that 17 tons of nails were ordered for her construction. (It might be significant that her eventual demise was due to being struck by lightning and burnt while laid up on the mud flats of the River Hamble. Her remains are still visible at low spring tides.)
Medieval ships were measured not by their displacement, but by the number of wine barrels (tuns) which they could carry as cargo. Sail area was reduced by reefing; taking a tuck in the sail using short cords or ties known as reef points. Sea trials with Viking replica ships show that the square rigged sails could sail at about 55o from the wind direction, adding a second sail makes changing tack smoother and more reliable, and lessens the chance that the ship might be "taken aback" (go in reverse).
Anchors were in use from the earliest times, as were a log-and-line for estimating speed; measurements which were timed by a one minute hourglass. Magnetised compass needles were in use from the 12th century, although obtaining strong lodestones to remagnetise the needles seems to have been a problem (they had to be imported from Elba). Quadrants and astrolabes were not yet in use. Portable sundials were common and are accurate to within a quarter of an hour if used at the correct latitude, texts describing these seem to be widely available from the 14th Century on.
Sounding leads were used for taking depth readings, they also had a waxed cavity on the bottom for obtaining samples of the sea bottom. Experienced sailors were said to be very adept at recognising the different types of gravel along the English Channel; the "ragged bean pebbles" near the Lizard were very bad news. Masts were fitted with crows-nests for look-outs, and not just for fighting; there is roughly a gain of an extra nautical mile of visibility for every 5 metres of elevation above deck. From the deck the horizon is about 5 nautical miles away. The pole star was important if you had the good luck to be sailing with a clear sky at night.
Fighting at Sea:
The first phase of fighting was an archery battle as the ships closed on each other. An attacker would then try to position his forecastle against the side of another ship and prevent its escape with the use of grappling irons. Stones, pointed bars and sometimes quicklime would be thrown down onto the opponent, and the advantage of height was crucial. The final phase was to board the ship and overpower the enemy in melee. Invariably the objective was to capture a ship rather than sink it. Trumpets were used for signalling in sea battles.
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