Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 08-06-2015, 05:44   #1
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,333
Scooping Freshwater

I just read in a "Things I Wished I Knew Before Starting Sailing" book on interest. It was that to extend your fresh water supply you can scoop fresh water off the top of the ocean after a rain because the seawater is denser so the fresh water floats on top.

Guess it is something to consider when you have been in the life raft a few weeks, but overall I now remember why I stopped reading sailing books!

BUT JUST IN CASE - has anyone tried this (just curious really)
__________________

__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is online now   Reply With Quote
Old 08-06-2015, 05:52   #2
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 12,391
Re: Scooping Freshwater

Never even heard of it before, much less tried it. I think it would take a hell of a rain and a very, very calm sea for that to have a chance of working.

I have read that ships used to take on fresh water off the coast of Florida where fresh water springs discharged off shore There are still a number of springs on land that discharge millions of gallons of fresh water per day but since the aquifer has been pumped down I only know a couple that discharge into the ocean.
__________________

__________________
The water is always bluer on the other side of the ocean.
skipmac is offline   Reply With Quote
Old 08-06-2015, 06:03   #3
Senior Cruiser
 
Kenomac's Avatar

Cruisers Forum Supporter

Join Date: Jan 2012
Location: Somewhere in the Adriatic Sea
Boat: Oyster 53 Cutter
Posts: 8,517
Re: Scooping Freshwater

I doesn't seem possible, the rain would agitate the the surface mixing the two solutions. Like you said, I'd have to be pretty thirsty in a life raft and delirious to try it. Sounds like something for "Myth Busters."

While we're on the fresh water topic, do you have plans to add a watermaker before you head out cruising full time?
__________________
Kenomac is offline   Reply With Quote
Old 08-06-2015, 15:30   #4
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,333
Re: Scooping Freshwater

Quote:
Originally Posted by skipmac View Post
Never even heard of it before, much less tried it.
But I read it in a book, it must be right!
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is online now   Reply With Quote
Old 08-06-2015, 15:38   #5
Marine service provider
 
newhaul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 4,057
Re: Scooping Freshwater

Quote:
Originally Posted by sailorboy1 View Post
But I read it in a book, it must be right!
Not necessarily true was it on the internet if so it has to be true they don't lie on there
__________________
newhaul is online now   Reply With Quote
Old 08-06-2015, 15:41   #6
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Scooping Freshwater

I think I need a bigger scoop…

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 08-06-2015, 16:50   #7
Senior Cruiser
 
roverhi's Avatar

Cruisers Forum Supporter

Join Date: Aug 2005
Location: Kona, Hawaii, Carlsbad, CA
Boat: 1969 Pearson 35 #108 & 1976 Sabre 28
Posts: 6,006
Send a message via Yahoo to roverhi
Re: Scooping Freshwater

Unless it was a real downpour can't see there being enough freshwater layer to scoop. Would need 6" or more of rain in a very short period of time and flat seas for a layer to remain stable.
__________________
Peter O.
'Ae'a Pearson 35
roverhi is online now   Reply With Quote
Old 08-06-2015, 16:55   #8
Registered User

Join Date: Oct 2014
Boat: Shopping
Posts: 426
Re: Scooping Freshwater

Quote:
Originally Posted by roverhi View Post
Unless it was a real downpour can't see there being enough freshwater layer to scoop. Would need 6" or more of rain in a very short period of time and flat seas for a layer to remain stable.
And a 6" rain event is inconsistent with calm seas, and if you're in a 6" rain event, just open your mouth, don't need a scoop.

Busted, I think.
__________________
Cottontop is offline   Reply With Quote
Old 19-06-2015, 16:02   #9
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,333
Re: Scooping Freshwater

I'm still reading that book (I read it at the proper place for it's wisdom). Today I came to another item where he once again mentioned the scooping fresh water thing.

So that's twice in a book, must be doubly right
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is online now   Reply With Quote
Old 19-06-2015, 17:02   #10
Marine Service Provider

Join Date: May 2011
Location: PDX
Boat: Gulfstar 50
Posts: 896
Re: Scooping Freshwater

Quote:
Originally Posted by Kenomac View Post
I doesn't seem possible, the rain would agitate the the surface mixing the two solutions. Like you said, I'd have to be pretty thirsty in a life raft and delirious to try it. Sounds like something for "Myth Busters."

While we're on the fresh water topic, do you have plans to add a watermaker before you head out cruising full time?

Sounds like something to keep in mind for life raft survival. The mixing could be minimal and with scooping you need only pull off the top fraction of an inch. Also, you do not need pure fresh water in a survival situation, just water with the PSU (salinity) down enough not to kill you or destroy your kidneys. (water intake needs to be less salty than your urine so that you can rid yourself of the excess salt too)

In terms of mixing we do modeling of the Columbia River where I work and see the salt wedge come 20 plus miles up the river with minimal mixing. Of course the fresh water flows out over the ocean for many miles.

Take a look here: Daily Forecasts | Center for Coastal Margin Observation & Prediction

If nothing else you might be able to place a cloth on the surface and soak up some water in a rain.

desperate measures for sure....

Click on the transects to see the salt wedge cross sections along the channel to see the minimal mixing..

Here: http://www.stccmop.org/datamart/virt...&slice=channel
__________________
evm1024 is offline   Reply With Quote
Old 19-06-2015, 17:12   #11
One of Those
 
Canibul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Location: Turks and Caicos Islands
Boat: Catalac 12M
Posts: 3,209
Re: Scooping Freshwater

Interesting. Says here we can survive on a 2:1 mix of fresh to sea water, and live happily on 10:1, if I understand it.

How Much Seawater Can You Safely Drink? - survival | Ask MetaFilter

Could certainly stretch limited supplies, knowing this. Maybe throw one of these in the ditch bag
Amazon.com : Instant Ocean SeaTest Hydrometer : Aquarium Hydrometers : Pet Supplies

Could have a little sundown mixing ceremony.
__________________

__________________
Expat life in the Devil's Triangle:
http://2gringos.blogspot.com/
Canibul is offline   Reply With Quote
Reply

Tags
water

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
connecting multiple tanks to freshwater system (+) vacendak Plumbing Systems and Fixtures 12 14-01-2009 13:10
converting MD 17C to freshwater cooling delmag Engines and Propulsion Systems 6 15-12-2008 17:36
Engine anodes after freshwater conversion Dr. C. Engines and Propulsion Systems 2 03-11-2008 19:55
2005 Silverton 38 Sport Bridge- 100% freshwater Woodsong Classifieds Archive 8 18-09-2008 08:40
Freshwater pump: how much oomph? Geoff S. Plumbing Systems and Fixtures 13 02-11-2006 20:00



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:25.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.