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Old 04-03-2018, 08:13   #1
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Proposed human cycle powered watermaker

On extended ocean passages, one needs to carry lots of water, though hopefully you can supplement it and replenish it from rain.

There is a problem of exercise. 3 or 4 weeks at sea, and one's muscle tone is gone. I've been toying with the idea of a human powered watermaker to address both issues.

1: It has been written that a healthy human can produce 1.2 hp briefly, and .1 hp indefinitely. An athlete can maintain .35 for a number of hours (Wikipedia).

2: Watermakers require about 1000 psi to operate

3: Horsepower =( GPM * PSI ) / 1710

Let's say you want to produce 2 gallons of water per day, and of course it takes 1000 psi to push it through a watermaker. To do that in one minute (unrealistic of course) requires 2*1000 / 1710 = 1.7 HP (rounded up).

Lets further say that you want to produce that water at an effort level of only .1 (1/10) horsepower, which you can produce indefinitely. Divide 1.7 HP by .1, and the result is that you should be able to pedal up 2 gallons of fresh water in only 17 minutes. A light brief workout.

You want a vigorous workout at .2+ HP, followed by a nice warm solar shower. Hang your shower full of water up to warm in the sun, and go at it with the watermaker exercise machine, producing 4 or 5 gallons to go into storage. Some goes to the crew's daily use, and some to your "reward" of a fresh water shower.

The beauty of this is that the bicycle you carry for shore transportation could be broken down to be part of the watermaker when on passage. You get your exercise, and at the same time reduce water tankage, offsetting the weight of the bicycle and the watermaker at the same time. On a multihull where weight is critical, this is a winner!

A rowing machine water maker would be better exercise yet, but would call for a bit more ingenuity. If the rowing machine were actually designed to be incorporated into the dinghy as an efficient sliding foot rest rower similar to the oar board.............

H.W.
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Old 04-03-2018, 08:23   #2
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Re: Proposed human cycle powered watermaker

2 gals in 17 minutes is roughly 8 gal an hour or what my water maker produces when I have my genset running.

Seems to me something in your numbers isn't adding up?? There is more to it than just 1000PSI, mine is only 800 PSI BTW, there is also a lift pump, pre filters, etc.

Someone better with numbers and physics can chime in and see where the fault lies, maybe I'm wrong or maybe your missing something..
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Old 04-03-2018, 08:35   #3
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Re: Proposed human cycle powered watermaker

Maybe I'm missing something with the numbers, but to produce 8 gph you have to pump 80 gph considering the membranes I am familiar with. You generally only recover 10% of the flow across the membrane as fresh water.
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Old 04-03-2018, 09:07   #4
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Re: Proposed human cycle powered watermaker

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Originally Posted by SV Bacchus View Post
2 gals in 17 minutes is roughly 8 gal an hour or what my water maker produces when I have my genset running.

Seems to me something in your numbers isn't adding up?? There is more to it than just 1000PSI, mine is only 800 PSI BTW, there is also a lift pump, pre filters, etc.

Someone better with numbers and physics can chime in and see where the fault lies, maybe I'm wrong or maybe your missing something..

The post below reveals what I didn't know........ the 10% water recovery rate. I'm aware of the additional functions, but intentionally left them out. Presumably one fills a reservoir via a pre-filter and hand pump that takes very little power.

There is really nothing wrong with my calculations except starting with the wrong figure on flow. Garbage in Garbage out as the computer guys say.

The proof of course is in the wattage. What is the wattage of your watermaker? Wattage converts directly into horsepower, and from there we can go to manpower.

Help me out with wattage numbers.

One watt = 0.00134102 hp
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Old 04-03-2018, 09:21   #5
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Re: Proposed human cycle powered watermaker

A quick reality check reveals that the Spectra Ventura watermaker is rated at 6.3 GPH @ 9 amps at 12 volts = 108 watts = 0.14483 HP. Link below to their specifications PDF.

https://www.google.com/url?sa=t&rct=...7xT2OqJ4lWEGVU


While that doesn't match my figures, it's not at all out of reason. Let's say we put out that horsepower figure for 20 minutes, the result is about 2 gallons of water. This tells me it's entirely doable and realistic. Google Watts to horsepower and human horsepower, and look at the Spectra PDF.

I was clearly way off.......... Your workout would have to be about 50% more intense and 3 minutes longer.

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Old 04-03-2018, 09:24   #6
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Re: Proposed human cycle powered watermaker

Quote:
Originally Posted by owly View Post
On extended ocean passages, one needs to carry lots of water, though hopefully you can supplement it and replenish it from rain.
Most long cruising routes encounter rain.

Most boats can carry enough water for several months.

Quote:
There is a problem of exercise. 3 or 4 weeks at sea, and one's muscle tone is gone. I've been toying with the idea of a human powered watermaker to address both issues.

1: It has been written that a healthy human can produce 1.2 hp briefly, and .1 hp indefinitely. An athlete can maintain .35 for a number of hours (Wikipedia).

2: Watermakers require about 1000 psi to operate
Perhaps you can feed the sweat dripping to the watermaker, and possibly urine. Of course all the pedaling means you need to drink more. Less salty water needs less pressure.
Quote:
3: Horsepower =( GPM * PSI ) / 1710

Let's say you want to produce 2 gallons of water per day, and of course it takes 1000 psi to push it through a watermaker. To do that in one minute (unrealistic of course) requires 2*1000 / 1710 = 1.7 HP (rounded up).
I don't know how your calculation works. but you should consider how much water the hand pump water makers make, and you might get 2-3x that with good effort.

Quote:
crew's daily use, and some to your "reward" of a fresh water shower.
You would be better off filtering the shower drain (after you first scrub maybe) and reusing that in the shower if you want a lot of shower.

The best shower is outside in a squall.
Quote:
The beauty of this is that the bicycle you carry for shore transportation could be broken down to be part of the watermaker when on passage. You get your exercise, and at the same time reduce water tankage, offsetting the weight of the bicycle and the watermaker at the same time. On a multihull where weight is critical, this is a winner!
Which multihull? 15 gallons of water is enough for virtually any cruising route.
Quote:
A rowing machine water maker would be better exercise yet, but would call for a bit more ingenuity. If the rowing machine were actually designed to be incorporated into the dinghy as an efficient sliding foot rest rower similar to the oar board.............
H.W.
Why don't you instead make pedaling power the boat, and/or dingy? This is much more useful, but if you make a pedal watermaker be sure to share your results.
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Old 04-03-2018, 09:34   #7
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Re: Proposed human cycle powered watermaker

Interesting. Do you have any concepts or drawings yet as far as how it would look/work?
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Old 04-03-2018, 10:14   #8
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Re: Proposed human cycle powered watermaker

The folks who successfully break the rules, first have to learn them.

Ask yourself, Has this ever been done before? Have similar peddle-power devices been built before? If not, why? If so, and they have failed to take hold, why?

Peddle power is nothing new. Committing large amounts of space on a boat to something that might be used once a day...not so popular. Engineering aside.

And don't forget, one human exerting maximum power for 1/2 hour or so, will require hydration and calories. More stuff to carry. And then, there will always be significant friction and conversion losses in taking slow rotary motion and trying to convert it to high PSI systems. Shoot for 10:1 losses.

Other than that...There's usually a reason things are done the way they are done. Sometimes, not so good a reason. Other times...Just do it.
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Old 04-03-2018, 10:22   #9
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Re: Proposed human cycle powered watermaker

Quote:
Originally Posted by boat_alexandra View Post
Most long cruising routes encounter rain.

Most boats can carry enough water for several months.


Perhaps you can feed the sweat dripping to the watermaker, and possibly urine. Of course all the pedaling means you need to drink more. Less salty water needs less pressure.

I don't know how your calculation works. but you should consider how much water the hand pump water makers make, and you might get 2-3x that with good effort.


You would be better off filtering the shower drain (after you first scrub maybe) and reusing that in the shower if you want a lot of shower.

The best shower is outside in a squall.

Which multihull? 15 gallons of water is enough for virtually any cruising route.


Why don't you instead make pedaling power the boat, and/or dingy? This is much more useful, but if you make a pedal watermaker be sure to share your results.

All that you say is valid........... but misses the point altogether, which is that one can kill two birds with one stone here. You need exercise, and you need water. Nothing feels as useless as working out on something that has no function other than burning energy. Gym equipment seems to be the norm. I've never used exercise equipment for the above reason. I hike, bicycle, walk, split wood, stack hay, etc.

I'm looking at several multihulls in the 30' range. I've more or less abandoned the idea of trimarans. A 1500 lb payload is simply not enough for a permanent live aboard voyager..... At least not for me. There are two cats, both modern owner built designs, that are very high on my list. One 28' LOA, and the other 30' LOA (approx). Smaller is better for my purposes, and the 28' cat has lower empty weight and higher payload, smaller rig, and is less boat to maintain. Space in either his huge for my purposes, mostly solo, with perhaps a single crew once in awhile, perhaps two. Looking at tris in my size range, there is more boat to maintain, and less of it is useful space, and the payload is a bit over half. I was looking at extreme measures to keep weight down, but I believe in that anyway.
Normal calculation is half a gallon of water per person per day. A Pacific or Atlantic crossing can easily run 30 days. 15 gallons would be reasonable for one person if nothing went wrong, and you got rain and could collect it efficiently. 20 would be more realistic including a safety margin, and that would be 168 pounds plus the container(s). Let's say 180 pounds. Two people aboard, and you have 360. Considering that fuel, batteries solar and other chargers, charge controllers, bedding, clothing & weather gear">foul weather gear, a dinghy and perhaps a motor, spare materials cordage, parts, blocks, tools, computers, nav gear, pots and pans, and countless other odds and ends contribute to consuming the 1800 lbs or 2600 lbs of payload for the two boats, the amount of payload left for food and water is rapidly reduced. That 360 pounds of water is 360 pounds of something else you can't carry......... perhaps the bicycle(s).
Weight in a multihull is critical...... I'm a pilot and a backpacker, so I'm hyper sensitive to weight. A multihull that is overloaded will pound the bridge deck, I want to basically live on the bridge deck a good share of the time.......

H.W.
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Old 04-03-2018, 10:27   #10
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Re: Proposed human cycle powered watermaker

Solar panels don't need water, they don't sweat or get tired.
Just sayin'...
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Old 04-03-2018, 10:35   #11
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Re: Proposed human cycle powered watermaker

Just adapt the ones designed for manual use
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Old 04-03-2018, 11:51   #12
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Re: Proposed human cycle powered watermaker

" That 360 pounds of water is "
Roughly eight pounds per gallon, that's sixteen pounds of water per day per person. And in hot conditions with exertion, that may need to double. But's let's say 16#, and of course there are at least two people on board to keep proper legal watch. 32# per day now. 360# of water is under a two week supply, not allowing for any delays or breakdown. And it will take up the space of roughly one 55-gallon drum.
Considering most recreational sailboats (over 90%) are 28' OAL or shorter...better to load up on the freeze-dried water, it is way lighter and more compact to stow. (Commonly sold at outfitters in the Adirondacks, honest. In #10 tins.)
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Old 04-03-2018, 12:15   #13
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Re: Proposed human cycle powered watermaker

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Interesting. Do you have any concepts or drawings yet as far as how it would look/work?

I haven't gotten that stage. Interestingly I have a pressure washer with a pump that has about the right capacity to do this direct drive. You could literally put pedals on each side, bolt the pump down and pedal it. It's a home built washer that consumes about 15 HP. A Hotsy 800 pump. It may not be perfect, but it's very very close. I need to do the math. 90 RPM is a comfortable pedaling cadence. I need to look up the displacement and I can't find it at the moment. With dual shafts, it's by far the simplest solution. With quick couplers, it could sit in the cockpit when in use and be stowed away when not. Drawing from a reservoir of prefiltered seawater, and discharging draining into an empty container. The filter and valving for back flushing, etc. would be down below as would the receiving tank.
This isn't rocket science, it's a very simple technology.

With the direct drive system, each installation would be boat specific with the distributed system concept. Pump and pedals would quick attach at the selected location. The supply tank might be permanent, or nothing more than a bucket properly located to feed the pump. The membrane and housing would probably be in a fixed location where it could easily be removed if need be. It's not a unit that would be suited to being purchased off the shelf and simply put to work. My biggest concern is making it salt water friendly. These are a plunger pump rather than a piston pump, which is good. The head is solid brass, and contains the cylinders, reed valves, seals etc. A very simple structure that could be duplicated from solid stainless if necessary, but if I recall correctly the reed valve cages are also brass. Fortunately pumps of this type are also made for harsh chemicals. A little research would be in order. I'm not sure what the life expectancy of brass is in seawater, but it's a damn sight better than steel.



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Old 04-03-2018, 12:16   #14
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Re: Proposed human cycle powered watermaker

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Solar panels don't need water, they don't sweat or get tired.
Just sayin'...

Exercise is a big part of the reason for this......... What do you do to keep in shape on a 3 week passage across the Pacific or Atlantic?
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Old 04-03-2018, 12:17   #15
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Re: Proposed human cycle powered watermaker

Taking a home made watermaker to save 300 odd pounds is dangerous. If it breaks, you have no water and no way to make it.
Even with a watermaker aboard, you will still want a minimum amount of water aboard as emergency rations. So that 300 pounds is still there, plus the bike.
A water maker is great for self sufficiency. Allowing you to not use marinas, or have to transport Jerry jugs. I wouldn't rely on it as your only source of water for a crossing.
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