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  #1  
Old 06-02-2006, 01:14 PM
Huerta88 Huerta88 is offline
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Old Sailing Ships Running Out Of Water: Why Not Distill It?

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?
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  #2  
Old 06-02-2006, 01:18 PM
gazpacho gazpacho is offline
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I would say that fuel is your biggest problem.
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  #3  
Old 06-02-2006, 01:19 PM
kanicbird kanicbird is offline
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Quote:
r require too much in the way of fuel (coal, I'd guess, or firewood)
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.
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  #4  
Old 06-02-2006, 01:48 PM
Finagle Finagle is offline
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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).
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Old 06-02-2006, 01:49 PM
Harmonious Discord Harmonious Discord is offline
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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.
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  #6  
Old 06-02-2006, 01:55 PM
Harmonious Discord Harmonious Discord is offline
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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.
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Old 06-02-2006, 02:04 PM
Finagle Finagle is offline
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Well, apparently some sailing vessels did have distilling devices. There's a mention of one in this description of Cook's Resolution.

Why they weren't standard issue is anyone's guess. Probably due to the expense and the notorious stinginess of the British Admirality.
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  #8  
Old 06-02-2006, 02:08 PM
ralph124c ralph124c is offline
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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?
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  #9  
Old 06-02-2006, 07:05 PM
Bosda Di'Chi of Tricor Bosda Di'Chi of Tricor is offline
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Why not burn the empty water barrels for fuel?
After all, ships carried a Cooper (barrelmaker) in those days.
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  #10  
Old 06-02-2006, 08:17 PM
Huerta88 Huerta88 is offline
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Quote:
Originally Posted by Bosda Di'Chi of Tricor
Why not burn the empty water barrels for fuel?
After all, ships carried a Cooper (barrelmaker) in those days.
I think they needed the water barrels to refill.

However, they were forever using the empty beef and pork casks for target practice. Maybe they could have been used for fuel.
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  #11  
Old 06-02-2006, 09:24 PM
Ficer67 Ficer67 is offline
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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...
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  #12  
Old 06-02-2006, 09:30 PM
astro astro is offline
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Originally Posted by Ficer67
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...
If the salt is in solution (as in seawater) how is a cloth filter gong to "filter" it out?
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  #13  
Old 06-03-2006, 02:09 AM
Enola Straight Enola Straight is offline
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Originally Posted by astro
If the salt is in solution (as in seawater) how is a cloth filter gong to "filter" it out?
If the filtering membrane is fine enough...as in passing only certain molecules of a certain size, one can use reverse osmosis desalinization.
http://www.lenntech.com/desalination-RO-modules.htm
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  #14  
Old 06-03-2006, 04:22 AM
Shalmanese Shalmanese is offline
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Quote:
Originally Posted by Enola Straight
If the filtering membrane is fine enough...as in passing only certain molecules of a certain size, one can use reverse osmosis desalinization.
http://www.lenntech.com/desalination-RO-modules.htm
Thats not a cloth or hose and outside the technology of the time.
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  #15  
Old 06-03-2006, 05:12 AM
FRDE FRDE is offline
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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.
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  #16  
Old 06-03-2006, 09:18 AM
gazpacho gazpacho is offline
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Quote:
Originally Posted by FRDE
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.
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  #17  
Old 06-03-2006, 09:51 AM
FRDE FRDE is offline
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Plenty of power - paddle wheels could be dropped from lower gunports

A suction pipe half way up the mast would be a simple funnel

It could be as simple as keeping a black sail turned to the sun
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