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-   -   Isolated Compartments: A warning (http://www.sailnet.com/forums/sailboat-design-construction/47084-isolated-compartments-warning.html)

Triquetra 09-14-2008 04:07 AM

Isolated Compartments: A warning
 
I bought a Corsair36 trimaran new in 2005 (hull 16) and had it designed as a live-aboard. Being new to boating I assumed that the design was reasonable for it to be seaworthy. (Naive, I know, but they have been around for a while and are raced frequently, and I do not want to get into discussions of seaworthy semantics :rolleyes: .) I had a marine air conditioner installed in an aft compartment which held the water heater and batteries, and had an incident of a hose coming off of my heater and filling the bottom of the compartment. I asked the Corsair dealer about it and why there was no bilge pump in the compartment, and he suggested that a fix to the situation was to drill a 1/2-inch hole in a particular place to permit drainage to the main bilge pump, which I did. I did not realize at that time that there were other aft compartments with similar non-draining situations.

Recently, during hurricane/tropical storm Fay, I spider-webbed my boat at the marina, and frequently checked on her to see that she was holding fine with no problems. I then got the dreaded call from the marina that the stern seemed to be riding low. It took me about 30 minutes to get to the marina, and sure enough it was low. Using a scaffold to get onboard, I found that the boat had water up to my waist and we could not find the source of the water, though we thought the hull might have been breached by flotsam. We used small pumps throughout the night, and by morning, I was able to get her dried out using two 3-inch trash pumps. :(

We found the source of the leak was actually the 1.5-inch pipe that the rudder control rod passed through which was about 10 inches above the waterline. The pipe was short, and only left about a quarter of an inch of area to hold a rubber boot, which was attached with zip-ties instead of hose clamps when I bought her. The boot came off and water splashed into the aft chamber WHICH HAD NO BILGE PUMP OR DRAIN TO THE BILGE. The weight of the water lowered the stern until the pipe reached the waterline and water poured into the boat filling the rear berth which again did not immediately drain to the bilge until it filled with water. By the time the water reached the bilge, it was pouring in through a 1.5-inch pipe while the bilge was trying to pump it out with a 1/2-inch pipe. Additionally the amas (pontoons) had vents without valves, so the aft chamber of both of those also took on water.

The take-home message is to check your boat for non-draining compartments and either get them connected to your bilge or put in additional bilge pumps. Though my boat needs to be pulled out, stripped and refitted, at least this did not happen on the ocean due to following seas, because I would be calling the U.S. Coast Guard rather than renting trash pumps. I am sure that Corsair is not the only manufacturer with problems like this, though I hope that there are not too many others.

(I'm having problems uploading a jpg of the boat, but will do so if I can later.)

sailingdog 09-14-2008 07:19 AM

One reason, a lot of times, compartments are isolated is to prevent the boat from flooding entirely. This is especially true on multihulls. For instance, my boat has two buoyancy tanks in the aft section, under the cockpit, and they have no bilge pumps... but then again, they're designed to be water tight and unless damaged shouldn't need them. The rudder stock on my boat comes up into a stern compartment that is completely isolated from the rest of the boat, and even if that compartment were to completely fill with water, would do little to change the attitude of the boat.

I would be cautious about drilling limber holes through water-tight partitions, since you need to do it properly to prevent the water from causing damage to the bulkhead or frame. If the bulkhead or frame is wood-cored, you really need to seal the hole with epoxy to prevent the wood from being damaged.

camaraderie 09-14-2008 09:11 AM

Triq...sorry to hear of your problems but thanks for the warning.

Triquetra 09-14-2008 09:40 AM

Quote:

Originally Posted by sailingdog (Post 368414)
One reason, a lot of times, compartments are isolated is to prevent the boat from flooding entirely. This is especially true on multihulls. For instance, my boat has two buoyancy tanks in the aft section, under the cockpit, and they have no bilge pumps... but then again, they're designed to be water tight and unless damaged shouldn't need them. The rudder stock on my boat comes up into a stern compartment that is completely isolated from the rest of the boat, and even if that compartment were to completely fill with water, would do little to change the attitude of the boat.

I would be cautious about drilling limber holes through water-tight partitions, since you need to do it properly to prevent the water from causing damage to the bulkhead or frame. If the bulkhead or frame is wood-cored, you really need to seal the hole with epoxy to prevent the wood from being damaged.

SD, You make a really good point. I guess that there are a lot of design variations. I just wish that the aft compartment of my Corsair was isolated.

Thanks Cam.


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