So I am re-reading some Patrick O’Brian randomly, and they are as happens sometimes desperate for rain or a place to get water, to the point where they’re considering drinking nasty vermin filled old rainwater gathered off the sails.
Why not bring a still or stills on board (or even rig them up makeshift from the ship’s pots) and distill saltwater?
Okay, you’ve got maybe 150-200 guys who need, what, at least a quart apiece a day to drink. Then O’Brian points out that the salted preserved meat has to be steeped in fresh water to make it edible.
Would the stills necessary to produce some bare minimum of potable water just be too bulky, or require too much in the way of fuel (coal, I’d guess, or firewood) to justify carrying or rigging them up?
I think the fuel requirements are just too high, especially since they would have to jury rig something up, which would be far less efficient then something the smitty could have made on shore.
The fire issue shouldn’t be neglected. Probably more sailing ships were lost to fire than to enemy action. Wooden boats, tinder dry and covered with tar, are not good places to have the kind of raging fire you’d need to distill a couple of hundred gallons of water per day. However, whalers generally had no difficulties with their trying pots.
As for the fuel issue, it occurs to me that boiling maple syrup would be a reasonable approximation of distilling sea water, and, with an efficient evaporator, it looks like a cord of wood can evaporate about 2000 gallons of water.. However, the cited 240 gallons/hr seems pretty ambitious for non-specialized equipment – in the sugar shack I’ve helped at, that’s pretty much a full day’s boiling.
Now sailors actually need about a gallon/day of water, so a cord of dry, seasoned wood could, theoretically sustain a crew of a Surprise-like vessel for approx. 10 days. So – surprisingly, not a terrible idea for a ship becalmed in the tropics (although I wouldn’t want to be the guy stoking the fire).
During the Australian gold rush people did bring stills to get drinkable water from the salt water in the desert flats. They plugged up and rusted through in a few weeks and took a lot of fuel for a little water. The condensers were available for ships also, but the before mentioned points had to have made them impractical on sailing ships. I do believe that coal fired ships did use a condensor for some of their fresh water use.
Sailors did use frozen sea water when needed. The freezing removes the salt from water. They also used tarps to catch water in an emergency, but they had to come from the stowage department and be new, or the water was full of salt.
I also recall reading how the ship’s drinking water would become rather foul and bad tasting, near the end of a voyage. the wooden casks were not airtight, and all kinds of things would grow in the water. An interesting aside; when canned foods became available 9ca 1840). the British navy embraced them as a way to keep the sailors from contracting scurvey (Vitamine C deficiency). Unfortunately, the state of the art of sealing the cans was rather poor-there are reports that opened cans smelled bad, and the food inside had spoiled. Howver, even if contaminated with botulism, if boiled long enough, the spolied food could be rendered edible 9the heat destroys the botulism toxin). If not cooked, the food would have been deadly-I’m sure many an old time sailor died this way.
Officers had access to wine-would wine last on a dailing ship?
You know, it does not take a lot of ingenuity or material to filter the salt out of seawater. I am surprised that sailors, as resourceful as they were (and still are today) did not attempt it. Cloth filters and hose were plenty enough material to start with…
Interesting, I believe that modern yachtsmen carry solar stills.
Water boils at a substantially lower temperature if it is under a reduced pressure
some jams are cooked in the opposite of a pressure cooker
I would guess that some form of simple vacuum pump with a cooling tower would get water to evaporate substantially faster and more efficiently than boiling it to 100c - agitated water tends to evaporate
Possibly it was not worth the hassle, since a man of war was seriously ‘overcrewed’ to have sufficient sailors and marines to man the guns.
The main problem with a still of any sort is the power required to run it. When boiling water you need to add 2260 kJ to a liter of water to turn it to steam. You can do this in a straight forward manor with a fire or in a complex way by running a vacuum pump creating a low efficiency thermodynamic engine to get the heat from the surrounding air.