Watermaker on fast Multihulls

[waterman46]

Oh geez, I'm glad I read this thread. And to think this old monohull sailor was considering switching to the dark side, now they tell me they can't make water!

P.S. I also heard they can flip right over and stay that way. What is the sailing world coming to.

[Jim Cate]

Unless in the long range record setting game, why is this a big deal? Cruisers (who are, after all the main users of watermakers) seldom attain these fabulous speeds for long periods, unbroken by either lesser speeds or being at anchor long enough to run the w/m for a few hours. And even the most weight conscious multihullers surely carry enough water for a day or two's usage... don't they?

Seems a non-problem to me...

Jim

[toolbar]

Thanks for the great feedback!

There have been two contradicting statements regarding the affected parts, so what will break down, if air-bubbles get into the water-maker system? The membrane (relatively cheap to replace) or the pump (expensive)?

Paul

[a64pilot]

I know that cavitating almost any positive displacement high pressure pump will ruin it pretty quickly, that is why for instance your Diesel engine has a low pressure pump, to ensure the injection pump never cavitates.
I am postulating that large pressure variations, pulsation if you will, will destroy the membranes.
I get that from my Watermaker manual that cautions many times to not turn on the system with the pressure already turned up, that the sudden pressure will damage them, that you must start at the lowest pressure and slowly increase it.

[2big2small]

On my mono with regular thruhull a bit after the mast I get into trouble above 5 knots and have stopped making water while underway altogether, except when motoring slowly in a dead calm. Like people pointed out, it’s a non-issue most of the time and not worth time and effort to improve for a cruiser like me.

[out42]

Originally Posted by waterman46

Oh geez, I'm glad I read this thread. And to think this old monohull sailor was considering switching to the dark side, now they tell me they can't make water!

P.S. I also heard they can flip right over and stay that way. What is the sailing world coming to.

Don't worry, Waterman, most men find it more difficult to make water as they get older.........

[Four Coconuts]

Take a look at the Spectra Cape Horn Xtreme fed by a retractable snorkel thruhull intake. Relatively light, you can run one or two pumps depending on what you have for solar power and no electronics to break.

[Four Coconuts]

Actually, looking around I don’t know if you can buy them anymore. The best you might do is a scoop style thruhull.

[waterman46]

Monohuller me, apologizing for posting again in multihull thread, but I did have a few thoughts on the interesting and useful posts here on watermaker intake issues. Air intake can also be a problem for monohulls if intakes located forward and going upwind in rough seas.

Many posts suggest using the watermaker only at anchor. Not a good option for many, I think. If wind is light and you will be motoring, you probably want to activate the watermaker and fridge at that time, to take advantage of the large almost free source of electrical power from the alternator. And some folks may not want to use the watermaker at all, when anchored in a confined situation with questionable water quality.

[Bean Counter]

MAybe something like an air purge valve connected to the top of the raw water filter or strainer. There different types of air purge valves on google which may also work.
Never done it myself so just a thought.

https://pentairaes.com/air-purge-valve.html

[a64pilot]

Originally Posted by Dave_S

If drawing air would be a problem.

You could run the intake through a settling tank or separator or swirl pot where the raw water feed with any air bubbles seperated and the water maker drew it's supply from the bottom of the tank and air was bled of the top of the tank. It would only need to be full while the maker was running and only a couple of liters anyway.

This is the best answer I think, it doesn’t have to be any more complex than a 5 Gl bucket that has an airtight lid, airtight so that a lower water level should cause a vacuum which will pull water into the bucket, but have an opening so that you initially fill it and then close off the opening.
Graduate level, you could even put a float switch in it so that if the level ever got low, the float switch would turn off the Watermaker.

[nwdiver]

Run water into a bucket use that water for the water maker, simple solutions are best.....

[Bean Counter]

Originally Posted by nwdiver

Run water into a bucket use that water for the water maker, simple solutions are best.....

Need a second pump to get it into the bucket and it needs to be same flow rate as the WM pump - not simple at all unless you want to sit and watch it.

[nwdiver]

Originally Posted by Bean Counter

Need a second pump to get it into the bucket and it needs to be same flow rate as the WM pump - not simple at all unless you want to sit and watch it.

It seem the volume talked about is for a small dc driven water maker, I would bucket the water from over the side as required, KISS, why add an extra pump......

A have a friend with a 55 ft custom cutter, has one below water through hull the poop out, all others at or above the water line, to make water (only on anchor), he buckets 20 gal SW into a tank on deck runs the 110 volt 40gal/hr system off the gen set fill as needed then puts it away......it seem very simple to me....

[clockwork orange]

I personally have nothing to offer other than what has already been pointed out, that the big record breaking tris and also the many much smaller racing boats crossing oceans simply must have this problem solved and its not just multies that are travelling at significant speed. This may be a question to ask on a more race oriented forum where you may encounter folks who have actually raced fast boats with a need for making water. Macif just circumnavigated at an average speed of over 27 knots, I would guess he had to make water.