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kcolborne

RIB - adding bilge pump between hull layers

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I have an Avon 11' center console RIB as a tender for my sailboat.
The RIB has an existing bilge pump that sits at the stern.  It is mounted in a small well shaped into the floor.
It works well, and is definitely better than bailing.

The RIB also has a drain plug at the stern that lets water out that gets between the 2 fiberglass hulls.
If I leave the RIB in the water for an extended vacation, it collects quite a bit of water in between these hulls.
Currently, I can only drain this water after the boat is out of the water on its trailer by pulling the drain plug.

I have a few questions on how to deal with this:
Any suggestions on how to track down how water is getting there?
Has anyone ever successfully modified a RIB to allow a bilge pump to pump this water out?
Any tricks I am not thinking of for another method for emptying this water when the boat is in the water?

 

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1 hour ago, kcolborne said:

Any suggestions on how to track down how water is getting there?

^^this is probably going to be the most effective place to spend your time...  it solves the problem without creating new ones.

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2 hours ago, kcolborne said:

 

Any suggestions on how to track down how water is getting there?
 

 

Kludge together an arrangement to connect a shop vac hose to the drain hole. It doesn't have to be a perfect connection just good enough to maintain some pressure differential. Connect the hose to the exhaust / blow side of the vacuum. Use soapy water to paint the hull inside and out. If bubbles form they point you to at least some of your problem. It's possible that some of the leaks only open up under dynamic forces but since the boat fills with water at rest the vacuum and soapy water should ID your problem

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Is the space between the hulls vented?

Usually, people think that sealing is the best approach but it isn't. During the heat of the day, the air inside expands and will force its way out. In the evening, as it cools and the air contracts, moist air is drawn in, condenses and water accumulates. To prevent this, adequate ventilation is the answer.

To find existing leaks, soap bubbles are a good idea. But be super careful about the amount of pressure you build inside the hull as there's a lot of surface area and you don't want to split things apart. 1/2 psi creates a force of 70 pounds on just one square foot of surface and your RIB has a lot more surface area than that.

 

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I agree with both the air test as well as the problem of blowing the hulls apart. Don't make a full seal connection and then just turn the vacuum on. Instead make a nozzle and leave open something to let air out and put the air into the hole and very carefully throttle the amount of air that's going in or out and you'll hear the vacuum change and you also the see motion and really should do it with someone else so you can regulate it effectively.

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Why not use one of those cheap battery operated air mattress inflators? They usually have adapters for a variety of hole sizes.

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I had the same problem to solve - turned out there were spare holes under the outboard brackets, only thru the outer skin.  The dealer had either mounted a different motor previously or his clowns coundn't set up the drill template properly. Had to remove the motor to find them.

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Not sure if this is a long-term solution (RIB had other problems so I moved on) but I had same problem and just made the pump sit into the outer hull by cutting out the inner hull sump.

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Sail69:
I have to admit, I was considering that option.
I do not believe the leak is very fast.
Then the bilge pump could remove all the water.

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Why not just add an inspection port somewhere out of the way?  Then you could use a sponge or even drop in a portable bilge pump as needed. 

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