Movable ballast?

[rwoofer]

Having had to fix a leaking water pump I finally figured out that my two water tanks (same size, one port, one starboard) are connected by the one pipe that the water pump takes a feed off. Since I only have one filling hole in the deck, so I presume the tanks must balance through this one pipe.

Now the question: If both my tanks are half full and I start healing to the wind, does all the water move down to the leeward tank? If it does that means I would the equivalent of 4 or 5 people sitting on the wrong side of the boat!!

Got me thinking...If I was to put a valve on the pipe I could use the water tanks as movable ballast ie. just before the tack, let all the water rush down, close the valve and then tack. That way I would have the 4 or 5 gorillas on the windward rail making me go faster.

Anything wrong with the theory?

Does water somehow magically stay where it is when healing, therefore scuppering the whole idea?

RB

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[Marsupial]

good idea, but I think you will find that it has been done before - someone out there will be able to name the boat I am sure.

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[Twister_Ken]

Perfectly feasible, but you might want to have big bore cross feed and breathers to shift it quickly. And you'll have to declare it if you have a racing rating.

<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>

 

[benjenbav]

Good explanation of this on a video clip in a thread called "while I was surfing". I'm sorry but I don't know how to add that as a link here.
I don't think I could quite manage the budget they had for Mari Cha IV though!

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[Newbieknownowt]

Alubat? Cigale? or summat?

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[Sybarite]

Alubat make the Cigale (aft saloon) and the Levrier (centre saloon). In the 14m versions, they have two 600l tanks behind the saloon back rests and use sea water shifted by an electric motor.

John

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[rwoofer]

Does anyone actually know if the water moves when healing in the current setup?

I was really asking the question out of curiosity and interest. The valve idea only came about because I wanted to stop water flowing to the leeward side, rather than actually wanted to create a movable ballast setup.

Perhaps I shouldn't have used a tongue in cheek title.....

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[Mudplugger]

Answer is yes!, had a twin tank system on Atlanta 28, as you have to have a breather pipe with solid tanks, could hear water switching sides on each tack. ended up, putting a gate valve in the cross feed pipe that was closed when at sea. Regards Tony W

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[Twister_Ken]

Yep,

Swan I sailed on used to gurgle for minutes after a tack

<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>

 

[bedouin]

It almost certainly does!

I once knew someone who wanted to replace his water tanks, so fitted twin flexible tanks, one under each bunk in the saloon; then screwed the lids back on the lockers.

First time he filled the tanks and got the boat heeled, the pressure forced the tops off the lockers [smile}

Water definitely moved between the two tanks in that case and I'm sure it's the same in your case.

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[BobE]

Dunno About Water. But I sailed across Biscay in a Twister ( 2 up) ( No super dooper teak decks either) permanently on stbd tack. The owner had fitted twin diesel tanks with an SU fuel pump to tranfer from stbd tank to port...Turned out there was a leak in the port tank.. The pump had a non return valve in it and as we rolled across Biscay eventually we pumped the fuel out of both the top of the tank and the breather... Owner asleep complained of headache and my watch lasted about 7 hours until I realised that I was, when sitting to leeward, in a pool of fuel.. So dragged complaining owner on deck and he recovered quite quickly from breathing the fumes for the last few hours.. Mind you it was a shakedown cruise and he went onto the Azores 'n back with out any serious problems..
Anyway to sum up the liquid sure changed side in this case.
Cheers Bob E...

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[BlueSkyNick]

Richard, Unsurprisingly we have an identical set up, probably less capacity though, so I am interested in the serious part of your thread.

You may get some more specific feedback via the MOA board.

<hr width=100% size=1>WANTED - For House and Boat Maintenance - A large supply of round tuits.

 

[rhinorhino]

The Sundeer range use this feature. Try the setsail website and the Dashew's book "Offshore Cruising" for lots of details.
Hope this helps.



<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by rhinorhino on 23/10/2004 10:59 (server time).</FONT></P>

 

[peterb]

In stability terms it's known as "free liquid surface", and is a considerable destabilising factor. Stopping the flow between tanks will give you a noticeably stiffer boat.

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