Eric Flint: Grantville Gazette.Volume 22

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 movement 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…"