Water in the Pacific

[atoll]

Originally Posted by 2big2small

It’s all fair game. People on this forum are rather exceptionally thoughtful so I don’t take offence. Somebody might even point out something I didn’t think off and then I could preventively modify things. I know the setup isn’t ideal but we’re a family of full time liveaboards and need the energy. If our budget were much higher I’d have another boat and a flush solar setup. But you have to play with the cards in your hand, which is always more fun than not playing at all.

Each solar panel is encased in a 40mm thick frame. They don’t flap at all but the supporting SS framework may wiggle with sudden rolls on larger waves. I’ve been pondering whether to replace it with a stronger, absolutely rigid structure or leave it as is as a way to shed energy. It’s hard to foresee which strategy would be the best for whatever future eventualities. Any thoughts on this choice are welcome but it starts to feel like we’re highjacking the thread.

on my catamaran the dodger is 3m x2m built with nidacore panels on an ally frame,the 2x 250w panels sit on top of this the dodger is ridged and does not move at all even in very strong winds we had 60 knots a few months ago.

[a64pilot]

Originally Posted by 2big2small

It’s all fair game. People on this forum are rather exceptionally thoughtful so I don’t take offence. Somebody might even point out something I didn’t think off and then I could preventively modify things. I know the setup isn’t ideal but we’re a family of full time liveaboards and need the energy. If our budget were much higher I’d have another boat and a flush solar setup. But you have to play with the cards in your hand, which is always more fun than not playing at all.



Each solar panel is encased in a 40mm thick frame. They don’t flap at all but the supporting SS framework may wiggle with sudden rolls on larger waves. I’ve been pondering whether to replace it with a stronger, absolutely rigid structure or leave it as is as a way to shed energy. It’s hard to foresee which strategy would be the best for whatever future eventualities. Any thoughts on this choice are welcome but it starts to feel like we’re highjacking the thread.

I have four large panels as well, they are 250 W. Three on top of the Davits above the dinghy of course, and one on the Bimini. Mine is a smaller boat.
Mine flex quite a bit, and in Hurricane winds I don’t believe they would stay, although they have been through two near misses. I think being flexible may make them tolerate more, being rigid may lead to cracking, the forces have to be dissipated somehow.

[Cyrus Safdari]

You can make your own watermaker that uses AC for about half the cost of 12v commercial variety .
This is a 30 gal/hr version run off the Honda generator

https://www.youtube.com/watch?v=ooVk-__QEME

[Jim Cate]

Originally Posted by Caroline Joan

Great thanks, the rain catcher that I have made is 5ft x 8ft - so similar. Like you it wil only come out when it rains. I do however have hose fitting that means I can run it directly to a tank via a 1 micron filter. Already to go, just need some rain to test it. No rain in sight for at least 2 weeks here.

You may find that the 1 micron filter will have enough pressure drop to slow the flow way down, causing the "system" to back up and spill out the collected water. It comes in pretty fast in a downpour!

Jim

[Zigmo]

Originally Posted by john61ct

If the dino juice is burning anyway and with a wm that makes enough gph,

washing the whole boat down with fresh water twice a week if you want,

why not? it's free other than the noise factor.

I wouldn't consider it free. When your water maker is running it's putting a demand for power on you generator or motor during that time which will lower your fuel efficiency.

[Pelagic]

Originally Posted by Zigmo

I wouldn't consider it free. When your water maker is running it's putting a demand for power on you generator or motor during that time which will lower your fuel efficiency.

I think if you were efficiently motor sailing at 1000 Rpm to make 7 knots with that power assist and had a large case alternator on main engine, that put out 150 amps at idle, recharging your house bank.
Then I think the costs would be pretty insignificant if you were running the water maker via an invertor or with its own DC pump.

[john61ct]

Yes sorry, not precisely free.

But then neither is solar power.

The value I put on a watermaker that only needs to run a few hours per week to deliver copious quantities is much higher than the cost of the extra load on my motor.

If I had to listen to it running many hours per day, that would seriously degrade my enjoyment of the whole experience.

[Zigmo]

Originally Posted by Pelagic

I think if you were efficiently motor sailing at 1000 Rpm to make 7 knots with that power assist and had a large case alternator on main engine, that put out 150 amps at idle, recharging your house bank.
Then I think the costs would be pretty insignificant if you were running the water maker via an invertor or with its own DC pump.

A 150 amp alternator operating at full load has an expected diesel engine load would be about 7-8 hp. Source: https://www.zena.net/htdocs/alternators/alt_inf2.shtml

The key is the load variance. You could have a wide variance in fuel efficiency at the same idle depending on the load on the motor. Spinning an alternator is significantly more difficult to spin under a 150amp load vs a 30amp load. I agree in the scheme of things it not much monetarily. But it is measurable. I would estimate an extra gallon of fuel per hour plus a very small amount of extra stress on the system.

[Pelagic]

Originally Posted by Zigmo

A 150 amp alternator operating at full load has an expected diesel engine load would be about 7-8 hp. Source: https://www.zena.net/htdocs/alternators/alt_inf2.shtml

The key is the load variance. You could have a wide variance in fuel efficiency at the same idle depending on the load on the motor. Spinning an alternator is significantly more difficult to spin under a 150amp load vs a 30amp load. I agree in the scheme of things it not much monetarily. But it is measurable. I would estimate an extra gallon of fuel per hour plus a very small amount of extra stress on the system.

Hi Zigmo
Thanks for the link and yes I agree there is an associated cost, but I am not sure if the low RPM way I use it, in conjunction with motorsailing, translates to around an extra 1 gph of real cost and wear??

Also, with a 2,400 liter (634 gallon) diesel capacity, I really don't worry about the alternator load with my cruising needs around Asia.

To clarify. my Mark Grassier Alternator puts out 140A @ 24v and 70A at idle.
http://markgrasser.com/alts_2.htm

If I have useable wind below 15knts, I am usually motorsailing between anchorages to maintain 7knts

If running the water maker I would be drawing 45 amps so extremely rare that I would be pulling out more than 100amps underway, with engine around 800-1000 RPM, depending on wind.

Basically i am overpowered when mortorsailing!

As the wind picks up in the afternoon, the load on the engine becomes even less so and whatever alternator load is put on the low rpm engine, I view as a bonus to keep it working a bit.

I just wonder if running a 1500rpm or 1800rpm 12kw generator for same purpose of making water, is a more fuel efficient use of a combustion engine..... ?

[a64pilot]

Originally Posted by Pelagic

I just wonder if running a 1500rpm or 1800rpm 12kw generator for same purpose of making water, is a more fuel efficient use of a combustion engine..... ?

No, not even close. I believe and someone can check me but I think 1 gl an hour on a diesel amounts to about 20 hp on average for our size engine.
So likely to cost less than 1/2 gl an hour to run your water maker off of an alternator, and I think that estimate is way high, now this is extra fuel over and above an engine that would be running anyway.

To run a generator to do it, you have all the excess friction of a motor that would not already be running plus all the excess heat it generates when running.
These losses are the same on your propulsion motor, except your running it anyway, so they are there whether your making water or not.
No on an engine that is already running, it’s far more efficient to pull power from an alternator, than it is to crank a generator.
This is only true of course if you running the motor anyway, it’s not true if you crank it to make water, then a generator may well be more efficient, as it’s likely a smaller motor and can also likely make much more power to use for other things.

[Pelagic]

Originally Posted by a64pilot

No, not even close.

Yeah, I knew that! [emoji4]

To me on a small sailboat, a generator is a luxury and if you only have one, a liability.

My Gen was sized to power 3 AirCons, water heater, dive compressor ....all non essential items except for the original AC watermaker

Good water is not a luxury item and I will move to a new place if I don't trust the fecal count of a popular Asian anchorage with a village.

So making large amounts of water underway, is the whole reason behind a DC HP pump

[john61ct]

1 HP per 250W generated seems a real-world ballpark for alternator load calculations at the low end, 200A at 14V and below.

The very large 24V alts seem to be a more efficient, so perhaps that scales down as you increase the kW capacity.

[lizardofoz]

Originally Posted by Caroline Joan

I am going to spend about 2 years in the pacific.

The question is can we sail in pacific for 2 years without a water maker.
I know some islands have next to no water and what they have is not good quality. I'm hoping that we can catch all the water we require from the rain & top up in places like Fiji, Tonga, Samoa, Tahiti where they have more water.

There are just the 2 of us on board our 50ft Beneteau
We have 1000 litres in 3 tanks. Of course we can take extra bottles as well.
I have made a water catcher and filter.
We use as little water as possible, ie have quick solar shower, have water pump turned off and just use manual pump.
We can go at least 2 months and can probably stretch to 3months if we use sea water for washing clothes & dishes and a bit for cooking.

I'm not sure when we travel north to avoid the cyclone season to places like Tuvalu, Kiribiti, Marshall island etc whether its realistic to be able to catch all the rain water we need over a period of 5 months (Nov - March)

I imagine that hundreds of people have been to the pacific without a water maker and smaller water tanks and it should not be an issue being without a water maker, but maybe its a climate change issue?

We will be sailing from Panama and island hoping.

Your help is really appreciated.

Hello Caroline,
Why dont you look at a Rainman portable unit that is either petrol driven or 230VAC driven from a genset as small as a Honda 20i model. Power unit comes in a carry case as does the membranes and can made between 70 and 140LPH depending on which membrane set you buy. Sailing Doodles has one aboard.

https://www.youtube.com/watch?v=S0fYKRo8oE8

I am a agent in Phuket Thailand and use them myself on my charter catamarans. Simple units and easy to use. If you want a ultra special price I can arrange

[Hasbeen]

I cruised the Pacific islands, to the north & east of Oz, knocking up 53,000 miles in 8 years.


I made a foredeck awning mostly so I could leave the forward hatch open in light to moderate rain. It can still be hot when it is raining.


I added a small weight to the aft centre of this, & attached a 3/4" hose there. Most rain gathered there, & was run through the hose to the main water tank, or to 3 of 5 gallon & 2 of 10 gallon jerry cans in a rack under the bridge deck.


I like a lot of showers but never ran short of water.

[lizardofoz]

Each to his own. I have done similar over the years but now prefer to have a watermaker aboard and as I am a marine equipoment supplier all the more reason. As stated I am a Rainman agent for Thailand and added to that the Rocna agent plus some others. I am also the SEA Editor of Noonsite.com — trying to keep up to date with regional rules and changes. The awning and hoses are a great idea and any sensible cruiser should have something like that. Having catamarans for the mast 28 years I have had plenty of water catching space. Issue there up here in Phuket is that we have a dry season and no rain or very little. I have found the Rainman to be the best around for lack off issues and for portability and independance if you go for the petrol driven one

Originally Posted by Hasbeen

I cruised the Pacific islands, to the north & east of Oz, knocking up 53,000 miles in 8 years.


I made a foredeck awning mostly so I could leave the forward hatch open in light to moderate rain. It can still be hot when it is raining.


I added a small weight to the aft centre of this, & attached a 3/4" hose there. Most rain gathered there, & was run through the hose to the main water tank, or to 3 of 5 gallon & 2 of 10 gallon jerry cans in a rack under the bridge deck.


I like a lot of showers but never ran short of water.