What about reducing the basin depth? Since the heat input is the same and the water volume is less, you will reach boiling more quickly, but there is less water to evaporate so, if seawater were completely transparent, productivity per unit deck area would be the same. But deeper layers in fact receive less heat energy than shallower layers, so there is a slight improvement in heating efficiency.
What about using a parabolic trough (either a single curved mirror or multiple flat mirrors approximating a parabolic cross-section), inclined like the cover of the simple still, to concentrate the sun's radiation? The solar energy input is still determined by the area perpendicular to the sun's rays and should therefore be the same. What you are doing is concentrating the energy onto a smaller collection surface area, which is the projected surface of a seawater reservoir (probably tubular) at the focal line of the trough. There will be a more rapid increase in temperature, but the seawater volume targeted would be smaller so I think that in terms of production rate per deck area, there would be no improvement. And the structure would be far more complex and vulnerable to wave action than that of a simple still.
Ultimately, solar desalination at sea is going to be limited by deck area. There's only so much, and you need to work the ship.
If a ship crew is merely improvising solar stills, then there's also probably only a limited supply of glass on board. But in fact, it may be possible to make a still of sorts without a transparent cover. The "vaporizer" would be painted black and thus absorb heat from the sun. It probably will not get hot enough to boil, but the vapor pressure of water increases from 12.8 mm Hg at 15oC to 55.3 at 40oC (okstate.edu). The rising vapor is passed through a tube to a white-painted, and possibly seawater-cooled condenser. It might be helpful to put a sponge-like material inside to increase the available condensation area.
This is similar in concept to the Incan "fog fence"— provide a cool surface for water to condense out of humid air—except we are humidifying the air first by exposing it to seawater under solar heating conditions. However, my concern is that the process will be much less efficient than solar boiling, not only because of the lower working temperature, but also because the airflow will be slow. And any expedients to increase airflow will make it much more complex than a conventional solar still.
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What can be gleaned about desalination methods from the libraries of Grantville? The famous 1911 Encyclopedia Britannica article on "Spirits" quotes Aristotle. However, I found no particulars about the nineteenth century fire-hearths.
On the other hand, the "modern" (pre-RoF) EB has an article on "desalination." It talks about distillation (at normal or reduced pressure), reverse osmosis, electrodialysis, and crystallization. It is plain that distillation is the only one of these methods that would be practical in the near-term for processing seawater on shipboard. Unfortunately, with regard to distillation, the modern EB's emphasis is on large land-based desalination plants. The only exception is its discussion of solar distillation: "The heat of the Sun partially vaporizes salt water under a transparent cover; on the underside of the cover, the vapour condenses and flows into a collecting trough. The principal difficulty in this process is concentrating the energy of the sunlight within a small area."
I expect that books and magazines on "green living" and wilderness survival can be found in Grantville and that these might say something about supplying drinking water. For example, see Halacy, "How to Build a Solar Still" (Mother Earth News, Sept-Oct 1974).
In any event, Grantville has not just supplied the down-timers with new books, it has also given them proof of the efficacy of controlled experiments. Hopefully, they will test various ideas on how to make a still as efficient as possible.
And that is indeed what happens. In the new time line, solar distillation is used in an emergency in 1633 on board a British ship, the Hazard. Jeremy Toot, the ship's apprentice master mate, picked up a copy of A Compilation of Useful Up-timer Knowledge Gleaned from the Encyclopedias and the Mother Earth Booklets in a bookstore in Hamburg, and it described a solar still—which he and his fellows then improved upon (Huff and Goodlett, "A Nerd at Sea", Grantville Gazette 25).
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Food
Fresh meat. On sixteenth-century Spanish ships, passengers took on board chickens, pigs, sheep and goats so that they could be slaughtered as desired to supplement the normal fare (Perez-Mallaina 130). While not part of the standard rations, a ship's crew or officers could buy livestock to be consumed en route. In 1746, a British navy ship sailed with "a goat, sheep, a sow in pig, six and half dozen hens and 13 ducks on board." The hens of course could also supply eggs, and the nanny goat, milk. Cows were also sometimes taken on board (McKay 38).
If the ship were tied up at a jetty, the animals could be driven up an enclosed gangway. If not, they would have to be slung on board, or, in the case of the smaller animals, hoisted up in a net or carried by hand.
In Nelson's navy, pigs were placed in a sty constructed under the forecastle until 1801 and in the waist afterward. Sheep pens were built between the capstan and the main hatch and if there was a goat, it probably slept with the sheep. Before 1815, poultry (chickens, ducks, geese, turkeys) were kept in moveable coops, placed on deck in the daytime and below at night. Later, the coops were fixtures of the waist. Cattle were tied between the guns, heads facing the ship's side (Macdonald 86ff).
Macdonald (130) has expressed surprise that she found no record of rabbit-raising, even though they are "very efficient converters of food into meat." Perhaps in the new time line …
In keeping livestock, there was a risk that the keeper, the crew, or the officers would become fond of a specimen and turn it into a pampered pet. One such pig got so fat that she couldn't walk, but grunted to have food brought to her (131).
It should be noted that sailors turned adversity into fortune by eating rats ("full as good as rabbits, although not so large”) (Bown 20).
Preserved food. Food can be preserved by drying, cooling, freezing, salting, sugaring, smoking, fermenting, canning, etc. It appears that in the seventeenth-century sailing ships, the foods were preserved mostly by drying (peas) or salting (beef, pork).
The term "preserved" comes with some caveats. The environment below decks was humid and ideal for mold growth. Even the food that hadn't yet putrefied was likely to be hard. If softened, it was with seawater (Bown 20).
In the 1660s, Robert Boyle demonstrated that cooked meat could be preserved in butter for over six months. This was more or less the same concept as the confit of southern France and was later known as "potted meat" (Macdonald 29).
"Portable soups"—essentially what we would call soup mix—were introduced in the eighteenth century. In 1806, the French Navy tested Nicholas Appert's canning methods. He sealed food in airtight glass jars and boiled to kill the bacteria inside. Tin cans, as an alternative to glass jars, were introduced by English entrepreneurs in 1813.
In theory, even in the seventeenth century, it was possible to keep food cold for an extended period. You needed to load ice on board just before you left port and put it in a well-insulated chamber. We know from the experience of Frederick Tudor's nineteenth-century ice trade that ice can be shipped a long distance if it is appropriately stored. Of course, opening up the ice chamber to remove ice, or food if it is already stored with the ice, is going to speed the melting, but still it seems within the realm of possibility (Cooper).
Ultimately, mechanical refrigeration became possible. I believe that shipments of refrigerated meat began in the 1870s. For analysis of the prospects of refrigeration machinery in the new time line, see Huston.
Food Rations. In the Spanish navy, as of 1568, the staple daily food was 1.5 pounds of "biscuit" (galleta), a double-cooked unleavened bread. To eat it, it had to be soaked in water or wine. To this add, four days a week, 150 grams of menestra, a mixture of horse beans and chickpeas and one-third pound of salted fish; two days a week, one pound of salted meat and two ounces of
cheese; and one day, half a pound of salt pork and one-tenth pound of mixed rice and oil. There was also a monthly ration of one liter of oil and somewhat more than a half-liter of vinegar. It is estimated that the caloric content of the daily meal was 3500-4200 calories (some from the wine), with a protein content of 13%. The principal deficiency was the lack of vitamins, because of the failure to include fresh fruits and vegetables (Perez-Mallaina 141-3).
The Dutch mariner's fare was similar: "to feed one hundred men, the ship had to carry for each month at sea; 450 pounds of cheese, five tons (cubic measure) of meat, four tons of herring, one and a quarter ton of butter, five and a half tons of dried peas, two and a half tons of dried beans, [and] half a ton of salt … ." (Babelier).
The earliest data I have for the French navy is from the Ordonnance of 1689; the daily ration was "one and a half pounds of biscuit, a midday meal of bacon, salt beef, fish or cheese, and a supper of dried peas or beans, prepared with oil and vinegar. The fish might be herring or sardines. There was a monthly ration of mustard seed (Spalding 70).
In the Tudor navy, at one point the weekly rations were 7 pounds biscuits, 8 pounds salt beef, three-quarter pounds each stock fish and cheese, and three-eighths of butter. By 1588, there were three salt beef days (totaling 6 pounds), three fish days, and one day on which the sailor was served a pound of bacon and two pints of peas. The calorific value of the diet, including beer, was estimated at 4265-5132 calories. (Childs 87-88). The fish day on Friday was technically a half-ration, but Childs suggests that it was the day that leftovers from earlier in the week were thrown into the stew.
Between 1677 and 1733, the fish was replaced by oatmeal (Macdonald 9). In Nelson's navy, British sailors received just a pound of bread (weevil-enriched hard biscuit) daily. Twice a week they were fed a pound of salt beef, twice again a pound of salt pork, four days a week a half-pint of pease, and three times a week, a pint of oatmeal, two of butter, and four of cheese. However, these were nominal weights, because in purser weights, each pound of most items was required to weigh only fourteen ounces, butter only twelve, and cheese only nine (Pope 151-5). The calorific value is estimated as 4888 but substitutions could change this (Macdonald 177).
There was a list of official substitutes, which included flour, raisins, currants, beef suet, and mutton for the beef and pork; navy beans, chickpeas, and lentils for pease; wheat, pot barley, and molasses for oatmeal; and rice, sugar, and oil for several standards (Macdonald 176). The practical significance was that this was what the Victualling Board would pay for and a captain who bought off the list might get in trouble if caught (and lacking justification of the absence of all official substitutes or an admiral's order) (Macdonald 10). Note that a purchase ordered by the captain would be charged (impressed) against the captain's salary until the captain persuaded the Board that the purchase was appropriate (73).
That said, there were authorized (or tolerated) purchases of lemons, oranges, and various vegetables (notably cabbages, onions, leeks, pumpkins, kale, collard greens, carrots, turnips, and, rarely, potatoes) (36-8).
Officers generally brought additional food purchase at their own expense. This could be fruits and vegetables or even livestock for subsequent slaughter. In theory, crew could bring personal supplies, too, but in practice usually couldn't afford to (Bown 24).
When they could, this created its own problems. On the 28-gun Sibyl in 1780, at the Cape Verde Islands most of the messes (groups of 4-8 crewmen who ate together) bought "three or four pigs, as many goats and half a dozen fowls", leading the captain to order the pigs to be killed first, as the goats made less of a mess (Macdonald 19).
There was no regulation of food and drink served in the British merchant marine until the mid-nineteenth century (Macdonald 12).
On the USS Constitution, the 1813 menu provided about 4,240 calories a day, mostly from fat. Three modern MREs (Meal, Ready-to-Eat) add up to 3,750 calories, 36% from fat (Biesty).
Food quality. Despite Johnson's quips, according to Macdonald (11-12), at least by the 1790s, the food issued in the British navy (as opposed to the merchant marine) was generally good as well as plentiful, and was at least comparable to what unskilled laborers on land were eating.
The British Victualling Board tried to control food quantity and quality. Some food was purchased from outside contractors, with contracts awarded based on competitive bidding, but over time, more and more was produced at the Board's own depots and yards (Macdonald 46, 52). The Board issued instructions with respect to how the food was prepared, packed, transported, issued, and, if need be, condemned. In the case of cheese and butter, if a batch didn't last for six months, the supplier wouldn't be paid for any of it, and the purser had to issue them within three months of receipt (31). Documentation was needed for purchases (and the Board wanted to see originals), and ships made weekly reports of provisions on board (72ff). Inspections were made at certain points in the chain (22, 75ff), and the Board was notoriously concerned about the fate of every penny (49).
The Board had to make some difficult choices. Fresh-baked bread tasted better than biscuit, but wouldn't keep longer than ten days, whereas biscuit lasted for months (Macdonald 16). Suffolk cheese (thrice skimmed of cream) had a long shelf life, but was said to be so hard as to be fit only for making wheels for wheelbarrows, or buttons for jackets. And when old, it was infested with red worms. In 1758, after many complaints, it was replaced with Cheshire or Gloucester cheese. They didn't last for long but were far more palatable (31).
Substituting food of inferior quality definitely occurred in all navies. For example, in Spain, there was an instance in 1566 of a steward mixing two jugs of water with one of vinegar and characterizing the mixture as three jugs of wine. In Britain there were cases of collusion between Victualling Board clerks and contractors, and between contractors and pursers, to supply food in quantity or quality inferior to what was supposedly supplied (Macdonald 49). But there were cases of adulteration and mislabeling on land, too; bakers who used alum to disguise the texture and flavor of bread made from inferior flour (16).
Even without fraud, food wholesome when delivered would deteriorate under shipboard conditions. In the case of biscuit, there is a case of 41,440 pounds of bread powdering, over the course of ten weeks, to produce 2,420 pounds of dust. Also, the sailors involuntarily shared their provisions with rats and insects, and frequently these vermin got to the table first.
Provisioning En Route. The typical pattern was that the food options narrowed the longer one was at sea. There were three ways of producing food between ports. First, livestock could produce milk (usually from goats, not cows) and progeny.
Secondly, the crew could fish when their duties and sea conditions permitted. Fishing lines were among the items in Antonio Gonzalez' sea chest in 1571 (Perez-Mallainas 150). In Nelson's navy, all ships were supplied with fishing tackle. Angling was not the only fishing technique practiced; I have found references to trawling. The sickbay had first dibs on what was caught (Macdonald). It was also possible to catch seabirds (30).
Finally, there is the possibility of cultivating a vegetable garden on board. This was in fact attempted by the Dutch, but proved impracticable because of waves (and sea spray) coming over the bulwarks (Torck 24 n54, Carpenter 23, Bown 39).
It might still be possible, however. First, the garden should be in portable containers that can be taken below if the sea is roughening. Second, a waterproof tarpaulin should be on hand to cover the containers quickly if there's no time to take them below. Third, there should be some way to secure them so they don't get washed overboard.
A step up from that would be a Wardian case. This was essentially a glass terrarium used to bring home foreign plants from overseas. It was used to ship tea plants from China to India and Brazilian rubber plants from Kew Gardens to Ceylon and Malaya (Wikipedia). Wardian cases have been used to transplant small mature plants, immature plants, and even seeds permitted to germinate en route.
The Wardian
case is waterproof, and will let in sunlight, but trap heat—the "greenhouse effect." A typical case was 40 inches long, 24 inches wide, with a base 10 inches deep and sloping sides 20 inches high. The sloping sides, that meet to form the roof, were movable to provide access to the interior. In each end, near the top, there is a small circular hole, covered with mesh, to provide ventilation. On the inside, these holes are covered by a small box, open at the top, to catch sea spray. (Macmillan 475) While the size mentioned is portable, a large ship might be able to justify one big enough so as to be a fixed installation, if the deck space in question can be sacrificed.
This can be taken a step further by including a heat reservoir inside or in thermal communication with the case—essentially a "thermal flywheel"—black-painted material with a high heat capacity, such as water (preferred), stone, brick, and concrete. This would keep the plants warm even after the sun went down, but would increase the weight of the device.
But would the garden be worth the space and cost? It is not likely that you could grow enough to meet the daily needs of the crew. It might be advantageous, however, for growing medicinal herbs.
Provisioning on station. The British navy ultimately developed a complex set of practices for keeping blockading or patrolling warships provisioned. Obviously, sending the warship home was not desirable. Rather, victualling yards were established abroad, merchant ships were hired for transport use, and purchases were made from local merchants at the nearest friendly or neutral port. Ships sometimes traded provisions, too. Of course, if a ship were sent home for repairs or to carry messages, it likely would be expected to return with fresh food (Macdonald 59ff, 72).
Cooking. On the Mary Rose (sunk 1545), food was cooked "in two large cauldrons supported on iron bars over a fire box." The cauldrons were made of a copper alloy, and were of 360 and 600 liters capacity. There were also small metal and ceramic cooking pots (Watson).
Grantville Gazette, Volume 64 Page 15
