by Eric Flint
With water ballasting, it is very important to keep the tanks full; any partially full tank of liquid is subject to the "free surface effect"; the liquid sloshes in the direction of the tilt and moves the center of gravity in the "wrong" direction. Likewise, solid ballast, whether sand or cargo, must be kept from shifting.
Fins
You can increase lateral resistance by placing a fin below the main body of the hull. The fin increases the lateral area and simultaneously lowers the center of lateral resistance. This improves resistance to leeway. Unfortunately, fins increase wetted area (thus, skin drag) and draft.
These disadvantages are somewhat muted by use of retractable fins. Seventeenth-century Dutch coasters were equipped with leeboards. These were fins which hung on either side of the boat and could be let down as needed. A centerboard is a retractable fin mounted in a (hopefully) watertight cabinet inside the hull. It could slide up and down (daggerboard, drop keel) or pivot on a bolt at one end (pivot keel). (Gougeon 33-6). The centerboard first appeared in 1774 (ChappelleHASS 166-8), and the pivoted type around 1809 (360), but wasn't really popular until the nineteenth century.
Chapelle says that the centerboard made it possible for a coaster to sail well when light. (ChapelleSSUS 279). He is also of the opinion that "extremely high speed-length ratios became possible only after the centerboard was introduced (412). Simpson's ironclads have two big centerboards (1634: TBW, Chap. 44).
Bilge keels are fins which are mounted at the boundary between the bottom and the sides. When the ship heels, the leeward bilge keel is submerged, and then resists further rolling. However, the submerged keel also increases resistance to forward motion.
Hydrodynamic Lift
If the underwater form of the ship is chosen appropriately, it can behave somewhat like an airplane wing, generating lift as it picks up speed. This lift, in turn, reduces frictional resistance, permitting the ship to travel even faster.
The necessary hydrodynamic structure can be the shape of the ship's hull itself (a "planing hull"), or a fin-like device ("hydrofoil") below the hull.
Unfortunately, this "planing" becomes significant only when the ship reaches very high speeds-an SLR of 2.5. (Teale 7). The only sailing hulls which reach that kind of speed are those with very large sail areas and very low displacement-essentially, high-performance racers. That kind of performance can't be expected from a pure sailing ship carrying substantial cargo or armament. We could nonetheless see it in a military courier ship, or a ship which has auxiliary power.
Hull Protection
Wood was coated with various substances to ward off marine borers (which damaged the ship) and fouling organisms (which slowed it down). Fouling can double or even triple the frictional resistance of a ship. (Baker, Ship Form 30; White 449; Millar 21).
One such coating was a mixture of tallow and sulfur (sometimes also including ground glass)(BakerCV 98). If this were insufficient, the hull could be scraped or singed to remove the nautical nasties. In the late sixteenth century, Sir Richard Hawkins advocated double planking with a layer of hair and tar in-between. The teredo worm won't tunnel through tar. (Millar 21).
Lead sheathing has a confusing history. It was used on Mediterranean hulls, as early as the fourth century B.C., to make the hulls watertight, but of course also afforded some protection from marine parasites. It fell into disuse after the first century A.D. (except for patching), but it made a comeback after the Europeans had their first Close Encounter with Teredo Worms. As early as 1513, Spanish caravels plated their bottoms with one or two tons of lead. (Crisman 261; BakerCV 97). The 480-ton galleon Santa Margarita (lost 1622) had 325 square meters of lead sheathing, less than 1 mm thick, yet weighing 4706 pounds (Malcolm).
Hawkins didn't think much of the idea; the lead was heavy, costly and easily damaged (especially if the ship got grounded). Nonetheless, the British used it on some warships in the mid-seventeenth century. Milled sheet lead, which was thinner and thus lighter than the earlier plates, was patented in 1670. Unfortunately, it was soft, and also tended to cause corrosion of the rudder irons. (GlobalSecurity) Nonetheless, British use continued for another century.
Another concept was sacrificial planking, that is, put a cheap wood over the good wood; Hawkins liked to put elm over tarred oak. The Dutch East Indiaman Mauritius (1601-9) went to the extreme of having sacrificial pine over lead, but that was to protect the lead from rocks. While sacrificial wood conserves the structural strength of the hull, the hull surface still gets fouled.
Copper sheathing was introduced in the 1760s and was initially disastrous (the iron parts, such as rudder hinges, disintegrated)(Millar 21; ChapelleSSUS 207ff). By the 1770s, the problem had been solved; bronze or copper fastenings were used. (Dodds 18). Copper sheathing was used in thicknesses which weighed 22-32 ounces per square foot, depending on the ship and the location. HMS Victory had 3500 4' x 14" sheets, weighing almost 13 tons. (Callcut).
Cost was also an issue, at least until after the War of 1812. (ChapelleSSUS 277).
The cost of sheathing the 1890 Edgar, 7350 tons displacement, was 17,000? (Atwood, Warships 145).
The development of copper sheathing encouraged the use of detailed plans, so that the cost of sheathing could be estimated accurately. (ChapelleHASN 21).
De Roche's Moonraker (Karen Bergstralh's story, Grantville Gazette , Volume 9), is copper clad. The timing is a bit vague; Karen told me to assume 1634-35. In 163x OTL, the price of copper in Amsterdam was 60 guilders per 100 pounds (Posthumus).
Copper is gradually corroded by seawater (Brigadier 12). Cathodic protection (that is, the sacrificial use of a more active and hopefully cheaper metal) was introduced in the early nineteenth century… tin, iron and zinc were used to protect copper. (Morgan). Zinc was also used as a sheathing in its own right, but it was even more vulnerable than copper.
Naturally, copper or zinc sheathing can't be used directly with an iron hull (or for that matter with iron nails and fittings), because there would be an electrochemical reaction between them, mediated by the salt water. One trick used in the British navy after 1887 was to use an inner sheathing of teak and an outer one of copper. (Atwood, Warships 143). There was even experimentation with rubber sheathing (Hebert).
Sheathing didn't merely protect the hull from fouling organisms, it also could increase smoothness and thus lower resistance. However, copper-sheathed hulls weren't as smooth as you might expect; "the plates were laid over tarred felt and the fastening nails dented the whole surface in a manner best described as 'quilting.'" (ChappelleSSUS 402).
Rudder and Steering
When the rudder is pivoted to one side, it creates a drag force that acts perpendicularly to the rudder surface. That drag force acts partially to slow the ship down, and also to cause the ship to turn. The ship will also heel over. (Sinisi).
Small ships were steered with a tiller, which is simply a lever connected to a pivotable rudder post, which in turn bears the rudder. The tiller was swung horizontally, clockwise or counter-clockwise. Flint, 1634: The Baltic War, Chap. 31 comments, "Unfortunately, the length of the tiller had to be in direct proportion to the forces required to shift the rudder, and its maximum length was restricted by the width of the ship itself."
On larger, multi-decked ships, the tiller needed to be worked from above. In the seventeenth century, this was done using a rather improbable contrivance known as a whipstaff. The whipstaff was a long pole which reached down through a small slot, which acted as a pivot point, to the level of the tiller, where it fitted into a ring fastened to the end of the tiller. To turn the tiller in one direction, the helmsman had to push the upper end of the whipstaff the other way, and also push downward. (Anderson 156-7). (While Flint says the helmsman stood on the quarter-deck, Anderson said that "the helmsman was still below-deck as a general rule," just not at the tiller level.)
Flint continues, the whipstaff "provided the helmsmen with a powerful mechanical advantage, but meant that the rudder's range of mov
ement was even more sharply restricted. As a result, a large sailing ship… found it impossible to apply more than five or six degrees of rudder." (Cp. Phillips-Birt 155).
Because of the limitation of the rudder angle, to make a sharp course change, the sails had to be trimmed accordingly. (Landstrom 122)
The earliest evidence of a steering wheel is in the English Ossory (1711). Naval historians aren't entirely sure how long the whipstaff survived after that, but there is reason to believe that it was still in use in the mid-eighteenth century (Anderson 169).
The steering wheel is connected by two opposed pulley systems to the tiller. Turn the wheel one way, and one pulley system tightens while the other slackens, moving the tiller in the appropriate direction.
In the Baltic War, Admiral Simpson insisted that all of his ships be equipped with steering wheels (actually, a more modern form than the one described above). "The use of a geared quadrant system to shift the rudder not only permitted him to build in a much greater mechanical advantage for the helmsman, but also offered a substantially greater amount of maneuverability… Simpson's ships
… could apply up to eighty degrees of rudder…"
Superstructures
Sixteenth-century warships had fort-like towers, the forecastle and aftcastle, to serve much like the towers of a castle on land. They were essentially infantry platforms, which gave their inhabitants a height advantage for missile and melee combat, and also some shielding from hostile fire. The problem, of course, was that they reduced the ship's speed, weatherliness, and stability. (Although Glete 38 says that they were of rather light construction, and thus not as adverse to stability as their height suggested.)
Raleigh warned against the "high charging" of ships, which "brings them all ill quality." They were phased out over the course of the seventeenth century (ChapelleSSUS 80), but it was a halting process. There was a concern that with most of the crew below deck manning the guns, the enemy could board amidships and trap the crew. Keeping the "castles" meant that the crew would have rallying points for launching counterattacks. (GleteWS, 30). These concerns ebbed, presumably as a result of both the steady increase in firepower and the provision of fighting platforms in the masts.
The three-deck battleship Sovereign of the Seas (1637) was in service until 1696, but at some point the superstructure was cut down because otherwise her draft was so great that in even a light air she couldn't open the lowest leeward gunports. (Langstrom 153).
Even merchant ships had substantial superstructure. Typically, the afterbody had two levels above the main deck, the half deck and the quarterdeck. (BakerCV 29). The poop deck is part of, aft of, or above the quarter deck, depending on the period.
Monohulls vs. Multihulls
The conventional sailing ship has a single hull. However, multihulls-two or more hulls joined together by a deck or struts-can be found in the seventeenth century in both the Indian Ocean and the South Pacific. The catamaran has two hulls, and the trimaran has three.
European experiments with catamaran designs date back at least to 1662.
According to canon (1633, Chap. 4), the timberclads used in the Baltic War campaign are catamarans, with paddle wheels positioned in-between their hulls. While these were steamships, their success will give the catamaran design a certain degree of credibility that it would not have possessed previously.
I intend to discuss the advantages and disadvantages of multihulls, and the problems peculiar to multihulls in a later article.
Shipbuilding
Plans. The first known printed plans for ships appeared in Instrucion Nautica (1587)(BakerSS 8). In 1650, the British Admiralty began requiring the preservation of warship plans but it took until 1675 to achieve compliance (ChapelleHASS 17). Plans weren't used in merchant shipbuilding until the mid-nineteenth century (McGee).
If you "take off the lines" of a ship (usually a captured vessel whose sailing performance impressed you), it means you reverse-engineer a plan for it. This required a specially-fitted dry dock (ChapelleSSUS 38).
Models. The English shipwright Pett is known to have made ship models as early as 1596. Ship models could be made, before the ship was built, for a variety of purposes-to please a customer (a model of the Prince Royal was given to Prince Henry in 1607), to persuade an prospective customer to approve the construction, as a teaching tool for apprentice shipwrights, or as a guide to the actual construction. . Reading multiview ship plans is something of an art, and the models no doubt had a more visceral impact on laymen.
In Britain, the Lords of the Admiralty were aristocrats and civil servants, not shipwrights, and they couldn't read plans. Hence, they demanded models, as well as plans, before engaging a contractor, and Admiralty models from the 1650s have survived. Their standard scale is 1:48, and they show the hull in detail. Decks were sometimes omitted so that the deck beams could be seen. (Anderson 145, 159; King 113; Davis 17; Grimwood 20). The lift model (layers of wood, held together by dowels, showing successive waterlines) appeared at the end of the eighteenth century. (Edwin 266; ChapelleSSUS 150ff).
Lofting. In the mold loft, thin pieces of wood were laid down to show, full size, the curve of the principal pieces of the hull. The purpose of this was to facilitate selection of which timbers to use where, and to guide the cutting of those timbers. Lofting is described in Fernandez' Livro de tracas de carpinataria (1616)(Schwarz) and Sutherland's Shipbuilder's Assistant (1711)(OED), and I suspect lofting predates the use of formal plans.
Cost and Time. The shipyard you pick makes a big difference. In 1669, Dutch cargo ships cost 40% less than English. (Unger 125). By building its own ships at Deptford, the East India Company reduced its costs in 1607 from?45 to?10/ton. (Gardner 29).
The Transportation Costs Addendum (1632. org) provides costs/ton for ships of various periods. In 163x, a 40-gun warship might cost 6000 pounds (Langstrom 149).
Ridler (62) suggests that for mid-nineteenth century warships, the number of man-days work required to build it and equip it for sea can be estimated by the formula 0.4*B^ 3*L/100, and the cost in dollars by multiplying the number of days by four. The cost breakdown, he says, is 72% hull, 5.4% spars, 4.6% sails, 4.8% rigging, 2.5% boats, 3.5% gun carriages, 0.5% outfits and sea stores, and 2.2% furniture. But Laing (54) says that as you increase the length/breadth ratio, while keeping capacity constant, the cost of construction increases.
Revenue. A merchant ship might reasonably hope to recover its cost in two trading voyages (Millar 3). Long-distance traders of course would need to carry more valuable cargoes for this to be the case.
Lifespan. Rot was the main enemy of the wooden ship, but of course navigational hazards, storms and hostile vessels also took their toll. On the Lisbon-Goa route, about one-sixth of the ships were lost, in either passage (Brigadier 14). The typical lifespan for a merchantman was 5-20 years, but some ships were flimsily built in the expectation that they would be used for just a few high profit, high risk voyages. Warships had a longer life, but required expensive rebuilds (at least half the original cost) every decade or so. (ChappelleHASN 47).
Up-Time Knowledge
In terms of books, the public and school libraries don't have much (see Addendum). But the "Four Musketeers," the teenage wargamers, were able to assemble "two tall piles" of books on naval history. In particular, we know Eddie Cantrell has "Chapelle's books on American sailing ship designs." And that "Chapelle's books had been pounced upon by the Swedish shipwrights as if Eddie had been Galahad, returning to King Arthur with Holy Grail in hand," and used to design a new sloop-of-war (1633, Chaps. 4, 28). EB11 "Shipbuilding" describes basic stability calculations.
Practical knowledge is important, but hard to find in a town that is over two hundred miles from the nearest ocean. Fortunately, we have John Chandler Simpson, a Naval Academy graduate with a bachelor's degree in engineering, and combat experience in Vietnam. Who was able to look at Eddie's plans for a riverine ironclad, and immediately realize that the displacement estimate wa
s way too low, and that the ship would have twice the draft Eddie hoped for. (Weber, "In the Navy," Ring of Fire).
We also have Jack Clements, a retired Coast Guard boat pilot) who owns a large power boat (Century 3200), and Louie Tillman, a thirty year Navy veteran with another (Cris Craft). (1633, Chap. 35). Then there's Ernie Trelli, who served with the Navy in the Gulf War (Grid), but hasn't yet appeared in a story.
While there aren't many "old salts" in Grantville, the new USE navy is going to need physicists, engineers and mathematicians to reconstruct the sciences of aerodynamics and hydrodynamics, and to modernize construction methods and materials, and there at least we have a respectable pool of talent.
Experimentation
Even if some engineers or physicists have basic texts on aerodynamics and hydrodynamics, there are going to be a lot of gaps in their knowledge. Those gaps will need to be filled by experimentation, at first with models and then with full-scale ships.
Early hydrodynamic experiments included towing wooden blocks (Christian Huygens and collaborators, 1668), simple geometric solids (Samuel Fortrey, 1675; Fredrik Chapman, 1775, 1794), planks cut to the waterlines of actual ships (Henry Sheeres and Anthony Dean, 1685; Pieter van Zwijndregt, 1750s), models constructed by joining circular sections to facilitate changes in shape (Bird, 1750s), and finally three-dimensional ship models (William Shipley, 1758-63).
There were several pitfalls. The first was ensuring that the models were towed at a constant speed, and accurately timing their performance. Another problem was avoiding blockage. Finally, for ship model studies to bear any relevance to the real world, they must be scaled properly. Usually, the scaling is chosen so the model accurately duplicates real-world wavemaking resistance, and the frictional resistances for ship versus model are determined by calculation.
In the 1820s, the British went so far as to invite competitive designs and assemble the resulting full-scale ships into experimental squadrons which underwent sailing trials. However, the competition rules didn't prohibit "tuning-up," and that limited what could be learned. (ChapelleHASN 369).
