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Old 31-10-2012, 09:18   #31
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Re: How Many Bilge Pumps ?

Originally Posted by denverd0n View Post
...........Much better to assess your own needs and wants, rather than to assume that whatever the manufacturer provided will be adequate.
I strongly agree with this wise caution. The manufacurer of my vessel had a bilge pump effluent just above the waterline amidships and when I was in a rolly anchorage I would "take a sip" of a few ounces of water at each roll into the bilge hose and soon to activate the pump cycling. I added a small vented loop to solve the original plan.

Take care and joy, Aythya crew
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Old 31-10-2012, 10:44   #32
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Re: How Many Bilge Pumps ?

Hi everybody,

We have several pumps aboard as follow:
  • 1 Hand pump at the helm station in the cockpit.
  • 1 hand pump at the bottom of the companionway (sharing the outlet with the one in the cockpit trhough a 3-way valve).
  • 1 12 volts electrical centrifugal pump with "manual-auto" modes.
  • 1 24 volts electrical diaphgram pump equiped with a 10 feet hose to "vacuum" where found necessary.
  • 1 engine pump in paralell with the primary cooling water pump (very efficient, the most powerful aboard by far).
Alternatively we can also use (with some emergency adaptation of course):
  • 2 shower drainage pumps (electrical), can be used directly as soon as the flood reach the heigth of the showers receivers...
  • 2 hand pumps (lavac Henderson) for the toilets, once the intake is diverted in the boat.
  • At last, the engine seawater cooling pump but with caution as already said in previous post.
Ultimate backup: 3 buckets...but everybody knows that the most effective pump is a friegthen man with a bucket !

To be honest, I do not rely on these pumps to save the boat from a real serious all, the only way is to stop the flooding (while the pumps are delaying the critical moment...) and then the pumps will ease and speedup the drying.

None of the pumps we have aboard are able to compensate a real leak and I would be a fool to rely on them, or to believe they can.

The larger pump you can install the better.

A proper survey of the potentialy leaking points and the wood cones (sorry I do not know the english maritime word for this object) at the proper diameter to plug the valves inlets, being tied to each valves, a repair solution for the propeller shaft, some plywood panels and other epoxy material can help a lot...not to mention the use of sail or canvas outside the hull to cover the leaking area of course.

Fair winds
Eric - S/Y Azawakh
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Old 31-10-2012, 11:28   #33
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Originally Posted by denverd0n
I wouldn't bet on that. I've seen things installed by manufacturers that made the boat LESS safe than if they had just done nothing at all! And, of course, the manufacturer cannot really know what situations any particular owner might take the boat into.

Much better to assess your own needs and wants, rather than to assume that whatever the manufacturer provided will be adequate.
Agree with this 100 percent......
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Old 31-10-2012, 12:16   #34
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Re: How Many Bilge Pumps ?

Love those old SABB diesels. Sorry to see them become a bit of history along with the MD series Volvo diesels. Hand cranked the MD2b for 10 years when the Dynamotor mount bolts broke off in the block. Always started first crank every time though never had to start in temps colder than 70 degrees.
Peter O.
'Ae'a Pearson 35
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Old 31-10-2012, 12:27   #35
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Re: How Many Bilge Pumps ?

How Many Bilge Pumps ?
just one more than you currently have.....
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard

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Old 25-11-2012, 07:59   #36
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Re: How many bilge pumps ?

Originally Posted by DeepFrz View Post
Except the Bounty lost engine and generator power. Hence it lost the power to de-water the ship.
I last read that the engine was flooded out. Water was comming in at close to 700 GPM according to the Coast Guard. It would have taken a mighty pump to keep up.
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Old 25-11-2012, 08:10   #37
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Re: How Many Bilge Pumps ?

Belt and braces. I have one electric set low in the bilge that does the bulk of routine pumping. Mounted slightly above that is a much bigger electric with its own switch that never runs unless I switch it on manually or the first one has failed. Then I have a small manual in the cockpit near the helm that goes to the deepest part of the bilge and is useful to keep an eye on how much water is coming in (count the strokes). Then I have a big whale manual that takes a 1.5" hose mounted down below where I can stand up and pump hard for long periods of time, if I had to. That one requires me to hook up the hose from the bilge, which is normally stored nearby under a floorboard. Not sure I would want a valve that would allow the engine to pump the bilge as the possibility of clogging is very high, and I might need the engine to move me more than I need the pumping at that point. For example, if anywhere near shore I am going to try to put her aground somewhere before I allow her to sink.
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Old 25-11-2012, 08:57   #38
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Re: How Many Bilge Pumps ?

something nobody seems ot have mentioned yet - Whatever electric bilge pump you have, make sure that you have an IDENTICAL spare. That way if it fails you can just plug in the spare using the same bracket with the same connections which ought to even have the same color wires. Ditto for the float switch or whatever kind of switch you have.

I had an unfortunate bilge pump experience about 250 miles offshore when it quit working. No hole in the boat but heavy seas and rain and a lot of water finding its way into the boat and needing to be pumped out again. the bilge pump quit altogether and we ended up hooking up a spare pump and some hose to the galley sink. It worked but what a pain! Remounting a pump while in 20 ft. seas is way harder than you think it will be. I now have the identical pump ready to be plugged right in. For good measure, I put another bilge pump mounted under the settee with a foot hose down to the bilge.

I think you are far more likely to have a pump simply fail than to have a hole in the boat. Be ready for both of course, but don't forget the more common problem of a bad pump or switch while preparing for the worst case scenario
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Old 25-11-2012, 12:16   #39
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Re: How many bilge pumps ?

Originally Posted by Nicholson58 View Post
I last read that the engine was flooded out. Water was comming in at close to 700 GPM according to the Coast Guard. It would have taken a mighty pump to keep up.
A diesel engine will operate underwater provided it has proper inlet air ducting from a higher location. (and suitable plumbing for breathers)

A pump direct-driven from the engine (with NO reliance on electricity, implying NOT electrically clutched) would handle such an inflow easily, and given a wooden ship of the size of the Bounty replica such an inflow is eminently likely.

So there seems to me there would have to be extenuating circumstances for the engine to have "flooded out"

As to the quoted inflow, and whether it should have been manageable:

The calculations look something like this, using US units in deference to the Bounty's presumed flag:

Assume a head of twenty feet (very generous)
Take the weight of a gallon of water as 8.3 lbs
700 GPM equates to 5,810 pounds of water per minute

Pumping this to a height of twenty feet requires
5,810 * 20 or 116,200 foot pounds per minute

33,000 foot pound per minute equates to 1 horsepower

Hence such a flow would represent a hydraulic power of 116,200 /33,000 or 3.5 horsepower

Obviously there is an efficiency factor to be applied to this, but it would certainly be well over 50%, so we're looking VERY conservatively at 7 hp.

I'm not sure this qualifies as a 'mighty pump', in the context of a large planked ocean-going ship with so many souls on board.

7000 gpm would be eminently doable, let alone 700.

In fact, as Evans S posted, it seems the main pump was a small mains powered electrical unit (which seems woefully misguided) further compromised by the piping being undersized even in relation to the pump, let alone the size of the ship.

If it had been working, and the inlets were not choked, it would have nevertheless almost certainly have handled 700gpm
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Old 25-11-2012, 13:02   #40
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Electrical supply: long term availability vs short term

It's perhaps a bit of a red herring argument to claim that engine driven pumps rely on electricity, because you (supposedly) can't start a modern diesel without it.

It's not asking a lot of human intelligence to start the engine immediately any significant leak is detected. The engine will not go underwater within seconds; if it does, no pump is going to save the situation.

Once running, a properly installed diesel will continue to run until the fuel runs out, regardless of electrical supply or water ingress. This could buy you a LOT of time, and you might need a lot of time to make good a major leak. Or you might need enough time to get to a beach.

Electrical bilge pumps large enough to rival an engine driven pump will flatten any realistic battery bank in short order. So, in such circumstances, they ALSO rely on the diesel engine running, to put charge back into the batteries.

Electrical power (if needed in bulk) relies on diesel power, but not vice versa.

It's worth also noting that the rated GPM for centrifugal electric pumps is not achieved in practice, so not generally comparable with an engine driven pump of the same nominal capacity.

Electric bilge pumps are (in my view) a convenience feature, like electric windows in a car, not a piece of bona fide safety equipment.

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bilge, bilge pump

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