better RO water system for cruisers
 

Most RO systems work by pressurizing water against a membrane that
only passes fresh water. Pressurizing and the pumping is done either
electrically or mechanically from the engine. This involves running
the engine. I imagine you could do it by having the prop turn your
alternator as you sail or use a towed generator behind the boat but
the efficiency of turning motion into electricity and then into motion
to produce pressure may be low. I propose to use a variation on the
old hydraulic ram pumps to directly produce pressure from the boats
motion.
HYdraulic ram pumps use the momentum of falling water to force a small
part of the falling water to a higher level than the water falls. In
other words, if your water falls 20', you can pump a very small
portion of it to say 50' higher without any electricity or engine.
Used on a sailboat, the momentum is not produced by falling, but
simply by the boats motion produced by the wind. This directly
produces pressure in a small portion of the water against the RO
membrane. Of course this produces drag but with proper design the
drag can be varied thus enabling the user to produce more fresh water
in a lot of wind.
Havent done th ecalculations yet but it may be reasonable.

On 27 Oct 2004 20:43:14 -0700, (Parallax)
wrote:

in a lot of wind.
Havent done th ecalculations yet but it may be reasonable.

Tell me again why you are hesitant to go long-term cruising again...

With all the clever if untested notions you come up with I would
suggest a 45 footer pilot house.

The pilot house will be the saloon.

The saloon will be the work bench/test bed/micro-foundry. All
socializing will be on deck as you...Captain Frankenstein...build the
perfect labour-saving gadgets for budget-conscious cruising.

The V-berth will hold 500 lbs of tools.

And you and the missus can sleep in the back.

Now, you can't tell me that's not an attractive plan.

R.

On Thu, 28 Oct 2004 00:41:55 -0400, rhys wrote:
The pilot house will be the saloon.

The saloon will be the work bench/test bed/micro-foundry. All
socializing will be on deck as you...Captain Frankenstein...build the
perfect labour-saving gadgets for budget-conscious cruising.

The V-berth will hold 500 lbs of tools.

And you and the missus can sleep in the back.

======================================

Don't laugh, I once saw a 60 footer that was rigged out just about
like that. The welder was in the pilot house and all construction
material too large for the V berths was under a tarp on the foredeck.
Not pretty but very functional.

This might work from an engineering perspective, but from a usability
standpoint it misses the mark. Many cruisers stay for extended periods of
time at an anchorage and would run out of water because they haven't moved.
Not acceptable.

-- Geoff

(Parallax) wrote in
om:

Most RO systems work by pressurizing water against a membrane that
only passes fresh water. Pressurizing and the pumping is done either
electrically or mechanically from the engine. This involves running
the engine. I imagine you could do it by having the prop turn your
alternator as you sail or use a towed generator behind the boat but
the efficiency of turning motion into electricity and then into motion
to produce pressure may be low. I propose to use a variation on the
old hydraulic ram pumps to directly produce pressure from the boats
motion.
HYdraulic ram pumps use the momentum of falling water to force a small
part of the falling water to a higher level than the water falls. In
other words, if your water falls 20', you can pump a very small
portion of it to say 50' higher without any electricity or engine.
Used on a sailboat, the momentum is not produced by falling, but
simply by the boats motion produced by the wind. This directly
produces pressure in a small portion of the water against the RO
membrane. Of course this produces drag but with proper design the
drag can be varied thus enabling the user to produce more fresh water
in a lot of wind.
Havent done th ecalculations yet but it may be reasonable.

rhys wrote in message . ..
On 27 Oct 2004 20:43:14 -0700, (Parallax)
wrote:

in a lot of wind.
Havent done th ecalculations yet but it may be reasonable.

Tell me again why you are hesitant to go long-term cruising again...

With all the clever if untested notions you come up with I would
suggest a 45 footer pilot house.

The pilot house will be the saloon.

The saloon will be the work bench/test bed/micro-foundry. All
socializing will be on deck as you...Captain Frankenstein...build the
perfect labour-saving gadgets for budget-conscious cruising.

The V-berth will hold 500 lbs of tools.

And you and the missus can sleep in the back.

Now, you can't tell me that's not an attractive plan.

R.

That actually crossed my mind a while back. I have a Prazi jewelers
lathe/mill that I considered putting in a Gulfstar 42 and cruising and
just making weird things. However, then I realized that I am really
terrible at making "pretty" things. Everything I make has lots of
duct tape, hose clamps and gouge marks all over.
In real life, I have realized that it pays to pay people who do that
sort of thing so i have two very good machinist/instrument makers.
They look at me like I am crazy when I explain what I want, but I
think they like the challenges. My designer walks away shaking his
head but returns a few days later with a way to do things. My
engineer and physicist joke that they will lock up the electron
microscopes for fear I turn em into "Frankenscopes". It would be
tough to have this sort of great relationship with these people long
distance and working with them is a real joy.

On Thu, 28 Oct 2004 06:33:48 -0400, Wayne.B
wrote:

Don't laugh, I once saw a 60 footer that was rigged out just about
like that. The welder was in the pilot house and all construction
material too large for the V berths was under a tarp on the foredeck.
Not pretty but very functional.

Except for the raised CG, I would imagine. Actually, that layout has
some appeal. November's Cruising World has an 83 foot pilothouse
cruiser that just sleeps four, because the owner is realistic about
how many crew he's ever going to have and because he's rich enough to
have a skipper and mate as permanent employees. The workshop is to
drool over, I swear.

Although I would likely design something in the 40-45 foot range for
myself (if I won a lottery, say), I find the idea of a larger
work/cargo space and a more compact saloon appealing. "Cozy" is safer,
too.

R.

On 28 Oct 2004 07:11:20 -0700, (Parallax)
wrote:

However, then I realized that I am really
terrible at making "pretty" things. Everything I make has lots of
duct tape, hose clamps and gouge marks all over.

Same here, although I managed some nicely symmetrical woodworking on
deck this year G

I think you can justify a nice workspace if your cruising plans
include providing a small business service on board. People who do
sail repairs are always popular in remote anchorages, and converting
the V-berth to a sewing room makes a lot of sense.

A machine shop, albeit a small one, is doable on board, with the
biggest obstacle likely power, not space.

I believe there is one cruising dentist who pays for his continuing
travels by tooth care for both cruisers AND locals. He apparently has
the full dental chair bolted in his gutted V-berth!

Now, that's a type of genius, although you'd have to be very careful
about stowage. I have no idea what he does for X-rays.

R.

You *might* get 1 or two PSI from the ram action. You need about 3000!

Actually you only need 800 PSI which is still way past what a ram pump can
produce. There is a tow behind RO watermaker called the Waterlog that uses
a small mechanical pump powered by a propellor. Though JAX claims them to
be mythical I met two cruisers in the BVI who used them all the way from
Gibralter and were very happy with their performance.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"joe_sailor" wrote in message
...
You *might* get 1 or two PSI from the ram action. You need about 3000!

On Thu, 28 Oct 2004 22:00:46 -0400, "Glenn Ashmore"
wrote:

There is a tow behind RO watermaker called the Waterlog that uses
a small mechanical pump powered by a propellor. Though JAX claims them to
be mythical I met two cruisers in the BVI who used them all the way from
Gibralter and were very happy with their performance.

============================

72 gpd:

http://www.watermakers.ws/

On Fri, 29 Oct 2004 02:39:55 -0400, Wayne.B
wrote:

On Thu, 28 Oct 2004 22:00:46 -0400, "Glenn Ashmore"
wrote:

There is a tow behind RO watermaker called the Waterlog that uses
a small mechanical pump powered by a propellor. Though JAX claims them to
be mythical I met two cruisers in the BVI who used them all the way from
Gibralter and were very happy with their performance.

============================

72 gpd:

http://www.watermakers.ws/

50 gpd = $2 grand....

Brian W

"Glenn Ashmore" wrote in message
news:7vhgd.80763$hj.25297@fed1read07...
Actually you only need 800 PSI

You can certainly do it with far less than that. A home RO unit runs off the
water line pressure, which is usually less then 75 PSI.

which is still way past what a ram pump can produce.

There are always ways to convert a flow of water and one pressure to a
lesser flow at higher pressure. You might have better output running a
solar still, however.

There is a tow behind RO watermaker called the Waterlog that uses
a small mechanical pump powered by a propellor.

There are a lot of instances of a towed electrical generator. It certainly
would not be conceptionally difficult to convert it into a water pump. I
can picture a small prop on a steel cable that runs up to a gear box on the
transom rail. Enough gear ratio can turn the spinning cable into sufficient
torque to generate just about any PSI you wanted.

I would think that you would be better off to just generate electricity and
then run the standard electric pump. Perhaps not as efficient, but much more
versatile.

Rod

"rmcinnis" wrote in message
...

Actually you only need 800 PSI

You can certainly do it with far less than that. A home RO unit runs off
the
water line pressure, which is usually less then 75 PSI.


Osmotic pressure is directly related to the concentration of salts in the
water. Tap water has a maximum concentration of 200 PPM salt so that the
pressure is about 10 PSI. Seawater OTOH at 36,000PPM salt and 68F has an
osmotic pressure of about 376 PSI. That is just enough pressure to STOP the
osmosis of salt into the low concentrate side. To REVERSE the osmosis
requires more pressure. Generally double or about 750 to 800 PSI.

(When you build your own watermaker you learn a lot of normally useless
stuff. :-) )

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com