Watermaker on fast Multihulls

[toolbar]

Hi,

I am thinking about adding a watermaker to my Farrier F-32 RX Trimaran. Weight shouldn't be a problem (on average the boat might weight less, as I don't have carry excess water).

However I remember reading somewhere, that most
(all?) watermakers don't like to operate at higher boat speeds.

Does anyone have experience with this? What are the practical limits?

Paul

[a64pilot]

Speed I’m sure is irrelevant as long as you make certain that at higher speeds that your not introducing any air, the pump and I believe the membrane don’t like air, as in I believe it will ruin them.
In your case I believe I’d want a forward facing scoop for the thru hull. Of course when your not using the water maker the thru hull should be closed.
Give Tellie (Spectra) a call if your considering a DC one or Rich Boren (Cruise RO) if you want an AC machine, both of course have their distinct advantages and in my opinion are very dissimilar products, like your fast tri and my slow full keel are.

My advice is go for a bigger one than you think you will need, cause once you have one, you’ll use more water than you do now, cause you can.

[SV DestinyAscen]

If the massive trimarans foiling speed records can, don't see why you can't.

Nothing a thruhull scoop or hose w/ weighted intake won't fix.

[thinwater]

Originally Posted by toolbar

Hi,

I am thinking about adding a watermaker to my Farrier F-32 RX Trimaran. Weight shouldn't be a problem (on average the boat might weight less, as I don't have carry excess water).

However I remember reading somewhere, that most
(all?) watermakers don't like to operate at higher boat speeds.

Does anyone have experience with this? What are the practical limits?

Paul

Don't. Even my 9000 pound PDQ catamaran would get air in the AC intake (lowest point of bilge) when going hard. All you need is a few bubbles going under the hull as you smash waves. It's not the speed, it's the ventilation under the hull, which you do get (I currently have an F-24 also).

I'm sure you could make water while ghosting at less than 5 knots mid-ocean, the only time you would need to underway. Otherwise, you'll be happier waiting until the hook is down. High pressure pumps hate air bubbles.

[senormechanico]

We have never had a problem making water with our Spectra while deep reaching with chute at around 12 - 13 knots.
The boat was on plane on the Strait of Georgia.

[thinwater]

Originally Posted by senormechanico

We have never had a problem making water with our Spectra while deep reaching with chute at around 12 - 13 knots.
The boat was on plane on the Strait of Georgia.

I wonder if up wind would be different. I never thought it was the speed, more the matter of air getting under the hulls when smashing.

My real thought is that there is generally no need to make water when you are really going upwind. Just wait until you slow down. Thus, there is no important conflict.

[senormechanico]

I agree with that.
We were getting near our destination (Desolation Sound) and wanted to arrive with a full tank.
With about 3 hours to go and making around 8 gph, our 26 gallon tank would be full by arrival.
When traveling, we carry only a few gallons to keep weight down, as the tank is in the bow.

[SV DestinyAscen]

Originally Posted by thinwater

Don't. Even my 9000 pound PDQ catamaran would get air in the AC intake (lowest point of bilge) when going hard. All you need is a few bubbles going under the hull as you smash waves. It's not the speed, it's the ventilation under the hull, which you do get (I currently have an F-24 also).

I'm sure you could make water while ghosting at less than 5 knots mid-ocean, the only time you would need to underway. Otherwise, you'll be happier waiting until the hook is down. High pressure pumps hate air bubbles.

Where's the thruhull located? The F-24 has got to be one of the most exciting boats to sail

[thinwater]

Originally Posted by SV DestinyAscen

Where's the thruhull located? The F-24 has got to be one of the most exciting boats to sail

On the PDQ it was just in front of the keel.

I down sized to the F-24 because I wanted something quick and fun. I was not disappointed. I liken it to a sports car vs. Winnebago. And the PDQ was a damn fast RV (numerous speed mods).

[senormechanico]

My Spectra is in the bilge midships. Dedicated thruhull is also miships slightly offset and ahead of centerboard, slightly less than 1 foot below waterline.

[44'cruisingcat]

Good thing about a fast multihull is that you get to the anchorages nice and early and can do your water making there.

[senormechanico]

Around here, sometimes that is why we make it on the fly.

[contrail]

Mine is aft, right next to the engine intake, just inboard of the bottom of the port hull.

[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.

[out42]

Having had a 31-1D, I cannot imagine how a watermaker would survive the aeration. I also suspect the settling tank (which would be the only successful method to my mind) would have to be quite big and have interior baffles given the speeds you will reach.
It is after all a planing hull.
Maybe a scoop at the transom might work but it would still need a separator/settling tank. Have you asked the watermaker manufacturer about high speed fitments? Lots of power cruisers must face the same problem so they are likely to have a menu of suggestions.