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Old 22-12-2015, 07:39   #1
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Bilge pump dilemma in Cats?

Hello Cruiser Forum members,
I was just looking through a bunch of threads but couldn't really find the answer to my question yet...
I recently received a 45ft Cat, which has 5 seperated compartments in each hull, with a rather low bilge.
Now since there is no bilge pumps in place so far I was wondering on everyones thoughts about how to fit a bilge pump - or 10 seperate pumps for that matter?
I am unsure which one would make sense or just add bilge alarms in every single compartment and have one pump with a long hose?
Happy to hear about experiences from other cat owners....
Thank you all already!
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Old 22-12-2015, 07:58   #2
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Re: Bilge pump dilemma in Cats?

A new build that hasn't hit the water yet???

Pick the lowest area in each hull and install a pump there... It's nice to have some watertight compartments, but 5 separate in each hull seems excessive...

Google limber holes...
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Old 22-12-2015, 08:00   #3
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Re: Bilge pump dilemma in Cats?

Well, they are seperate compartments in terms of the connection is about 20 cm above the bottom of the hull...
The cat was in the water for over 20 years yet, but the beloved previous owner treated her... lets say badly and now is the time to make an effort to take care of her ;-)
Just got new keels fitted and want to make sure she doesn't sink
Even though the carpenters fitting them were rather sure about their job on the keelbolts...
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Old 22-12-2015, 08:18   #4
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Re: Bilge pump dilemma in Cats?

Quote:
Originally Posted by ProjectManaia View Post
Well, they are seperate compartments in terms of the connection is about 20 cm above the bottom of the hull...
The cat was in the water for over 20 years yet, but the beloved previous owner treated her... lets say badly and now is the time to make an effort to take care of her ;-)
Just got new keels fitted and want to make sure she doesn't sink
Even though the carpenters fitting them were rather sure about their job on the keelbolts...
Wow... There's a story behind this one to be sure!

If she's been built this long and has sat in the water... You should know where the water collects... If it does it in 10 separate places, I suggest you have 8 too many...
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Old 22-12-2015, 08:21   #5
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Re: Bilge pump dilemma in Cats?

In each of the engine rooms, which are the most likely place to flood, I have a large bilge pump. Don't place limber holes (or holes for wiring) through the engine compartment below the water line. The engine room is usually sealed from the rest of the boat. If a catastrophic incident causes water ingress to the engine compartment, the area is small enough to make little difference to the stability of the boat.

The other compartments have limber holes leading to the lowest point of the boat. On my cat this is above the keels where I have another large bilge pump. Also, there is a small 6" x 8" recess deeper into the keel area which it too small for a large bilge pump. Also, the water which would be contained in a 6' run of 1 1/8" bilge hose would be sufficient to flood the small space again and cause the pump to cycle repeatedly. In order to prevent water from permanently sitting in this area, I have placed a very small bilge pump in there which is connected by a very short run directly to my shower sump box.

With this set-up, I never have stagnant water sitting in the keels and hopefully the large main bilge pump never has to be used.
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Old 22-12-2015, 08:59   #6
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Re: Bilge pump dilemma in Cats?

I've been thinking of putting a limber hole into my engine compartment, and fitting it with a scupper like what is used on dinghies, so water can only flow into the engine compartment. Perhaps even have a valve on it. What do you think, any downside?
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Old 22-12-2015, 09:07   #7
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Re: Bilge pump dilemma in Cats?

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I've been thinking of putting a limber hole into my engine compartment, and fitting it with a scupper like what is used on dinghies, so water can only flow into the engine compartment. Perhaps even have a valve on it. What do you think, any downside?
If you look at a cat side-on, most engine compartments sit higher in the boat than the keel. Water won't flow INTO the engine compartment
unless you have an awful lot of it.
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Old 22-12-2015, 09:33   #8
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Re: Bilge pump dilemma in Cats?

Quote:
Originally Posted by ProjectManaia View Post
Hello Cruiser Forum members,
I was just looking through a bunch of threads but couldn't really find the answer to my question yet...
I recently received a 45ft Cat, which has 5 seperated compartments in each hull, with a rather low bilge.
Now since there is no bilge pumps in place so far I was wondering on everyones thoughts about how to fit a bilge pump - or 10 seperate pumps for that matter?
I am unsure which one would make sense or just add bilge alarms in every single compartment and have one pump with a long hose?
Happy to hear about experiences from other cat owners....
Thank you all already!
Unless the compartments are watertight "crash" bulkheads, designed to not let water into the rest of the boat if holed, I would recommend drilling limber holes in them to allow water to easily flow to the lowest point in the hull (preferably bilge pump sump).

A separate unsealed sump (with dedicated pump) may be desired in each engine compartment for prop shaft and rudder stuffing box leaks. These should be designed such that a catastrophic leak will over flow the sump and progress to the main sump.

In each main sump, install a small GPH pump to handle incidental leakage. Then install a 1000 GPH of bilge pump (for every 10 feet of hull), split between at least 2 pumps, tied to an emergency hull breach alarm.

Some put alarms on incidental leakage bilge pumps, but I don't recommend it. I only want to be alarmed if something unusual is happening, otherwise nuisance alarms end up being disabled. If really anal about incidental bilge pump operation, rather than an alarm I would recommend a bilge pump monitor. For example, the Blue Sea VSM 422 includes excellent battery, tankage, and bilge pump monitoring functions.
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Old 22-12-2015, 10:22   #9
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Re: Bilge pump dilemma in Cats?

If your 5 compartments have only 10 cm deep separators, just hole saw limber holes between them so one pump services one hull, being careful not to do any structural damage. Seal the cuts. Don't compromise the seaworthiness of crash bulkheads by installing limber holes.

A large capacity (1-1/2"-2") manual pump can be made portable to service both hulls. Or simply install a pair, besides your electric pumps.
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Old 22-12-2015, 10:24   #10
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Re: Bilge pump dilemma in Cats?

Our cat has 4 foam filled compartments 2 of them are sealed off. We have zero bilge pumps but can switch over shower sump pumps to suck from the middle of each hull. We have twin float switches that sound if we get more than 3" of water jn our engine compartments.

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Old 22-12-2015, 14:53   #11
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Re: Bilge pump dilemma in Cats?

in large vessels, commercial and USCG certified, they usually have a pick up with strainer plumbed into every compartment with the pick up hose to a common manifold with valves at the manifold to each compartment. the manifold is plumbed into a single common bilge pump, usually electric.
in compartments with through hulls it is usual to put in a bilge high water alarm. or plumb those compartments with through hulls to single bilge pumps and a manifold to all those without through hulls
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Old 22-12-2015, 15:52   #12
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Re: Bilge pump dilemma in Cats?

Keel bolts? On a cat? That would imply ballast, which makes no sense at all. The keels on most cruising cats weight less than water.

We also seem to have mono thinking sneaking in here. Most cats have very few water entry points and the bilges are dusty dry all of the time. In my case I have 6 compartments on each side, 5 of which could be termed crash tanks in the sense that the bulkheads come above the water line. Limber holes would be quite stupid, or at least they would have valves.

The truth is that most cats are designed around the notion that bilges stay dry. In practice it makes more sense to service the occasional spill (hatch left open, hose break) with a portable pump than to flood more than is required. In 25 years of cat ownership, I have never had a sump pump cycle on. If I had enough water to require it there must be hole and the pump won't help (the bulkheads will).
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Old 22-12-2015, 17:35   #13
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Re: Bilge pump dilemma in Cats?

My cat has pipes leading from the higher compartments to the lowest spot above the keel. There are small taps on these so they can be closed off if needed.

At the lowest point, there is a small bilge pump and it sounds an alarm when activated. A little above that is the large capacity pump that in theory will never be activated. There is also a separate pump in the engine compartment.

The issue I am having at present is the length of hose needed to reach the stern where it is high enough to discharge. When the bilge pump stops, water in the hose flows back almost to the trigger point again.
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Old 22-12-2015, 17:54   #14
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Re: Bilge pump dilemma in Cats?

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My cat has pipes leading from the higher compartments to the lowest spot above the keel. There are small taps on these so they can be closed off if needed.

At the lowest point, there is a small bilge pump and it sounds an alarm when activated. A little above that is the large capacity pump that in theory will never be activated. There is also a separate pump in the engine compartment.

The issue I am having at present is the length of hose needed to reach the stern where it is high enough to discharge. When the bilge pump stops, water in the hose flows back almost to the trigger point again.

Lagoon fit non return valves, but in practice they still let the water flow back. Why not run the hose out under the bridgedeck with an anti-syphon loop? After any water flows in the bilge I usually dry it with a sponge anyway. It's good to know immediately if there's a leak, the bilge should be dry, especially in a plastic cat with saildrives. Times I've had to sponge dry the bilge are limited to things like, forgetting to fasten a hatch and taking in some water, or waterheater pressure relief valve letting off water, or maybe some rain water into an engine compartment. Those are the things I want to know about and deal with pretty promptly. We rerouted the standard factory showers to go directly overboard as well, an hours work and $50 of bits.
For the op, any watertight bulkheads should have a hose running from them to the main bilge pump if possible, or seperate bilge pumps for each compartment. Any areas that are just bulkheads with large openings anyway, limber holes are fine. Again, they shouldn't be getting wet on a regular basis anyway.
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Old 22-12-2015, 18:38   #15
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Re: Bilge pump dilemma in Cats?

However you do it, consider the powered diaphragm bilge pumps. They sit wherever you want (not down where they will always be wet), they don't need strainers as anything that can come up the intake hose they will pump, and they don't need check valves as they have 2 duckbill valves built in.

Another thought is the turbine pump which clamps onto the prop shaft if you have room. This gives you a bilge pump with truly monstrous capacity, plus a bilge blower that runs full time whenever the engine is running.
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