Ask Sail: Mystery Leak

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A MYSTERY LEAK ON THE HARD

Q: We have a 2004 31ft Catalina 310 that has an in-mast furling mainsail, and the mast is deck-stepped. Haulout is the first week of October, and by Thanksgiving water in the bilge is already climbing up the sides and back-filling toward the stern where it is manually pumped into a bucket for removal. From shortly after Thanksgiving to March the water is frozen solid and has reached an “alarming” level. The cables running through the mast into the bilge are for the antenna, anemometer, TV scanner and radar. Other owners with the same setup on a 32ft sailboat don’t have this problem with water ingress. What is causing this to happen every year during outside storage?

Kevin Redmond, Plainfield, IL

DON CASEY REPLIES

This is a problem that can only be diagnosed on site, and you will need to wait until the spring thaw. My first suspicion is that one or more of the wires you mention do not have effective drip loops where they enter the mast. A single wire entering the mast will often be sufficient to channel gallons of water into your bilge.

If you rule out openings in the mast as the source, then the leak (or leaks) must be through the deck. If you think you know where the water might be getting in—around the mast step, for example—flood just that area with water from a hose while watching below for a telltale trickle. A very bright light will help. If this confirms your suspicions, you will need to caulk or reconfigure as necessary to stop the water from entering.

If you cannot find the leak by flooding, the one sure-fire method I know is to pressurize the boat and check for escaping air with soapy water—just like checking a tire for a puncture. This requires closing all through-hulls and sealing all hatches and other openings with leaf-bag plastic and/or tape. Also, tape a garbage bag over a vent so it can inflate to confirm positive air pressure. Provide the pressure with a hose from the outlet side of a shop-vac, a leaf blower or an electric air mattress pump sealed through another vent or port. With the pressure source running and the indicator bag inflated, sponge soapy water around all hardware, and over every seam and joint. Anywhere the solution shows growing bubbles, air is leaking out, which likely means water is leaking in. Again, the fix is to clean and bed or caulk as necessary to reestablish a watertight seal.

Got a question for our experts? Send it to sailmail@sailmagazine.com

January  2018

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