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  I'm Sinking! (Tonyj)
Posted: 6:18:16 pm on 4/27/2016 Modified: Never
 
Hi;
After sailing last week, I opened up the engine access on my MkV in order to close the raw water intake.  Horrors! Inches of water in the engine compartment!  Quickly I checked the bilge.  It was full, water just up to the underside of the floorboards. I turned on the electric bilge pump while one of the crew operated the manual bilge pump. As the bilge began to drain, I began looking for the leak. I discovered two of the four clamps that seal the prop shaft packing gland hose, the hose between the hull and the shaft packing gland, had failed, corroded apart, allowing water into the boat.

Here's what they look like: https://www.dropbox.com/s/mb7m24hlekk0w7c/clamp2.jpg?dl=0

Scary ,hey? The lesson here?  Stainless steel does corrode when
left in salt water, and sometimes it takes a near miss like this one to remind us not to be complacent.

Fortunately a quick trip to the chandlery for new clamps solved the problem. The boat is fine, the skipper's relieved, though shamefaced.

Dryly,
Tony Jeske
MkV #581
FLYING CIRCUS
Silver Gate YC, San Diego    
  Re: I'm Sinking! (doogymon)
Posted: 7:50:35 pm on 4/27/2016 Modified: Never
 
Ahoy there!

Great that you saved a catastrophe.

"Rounds Correct" is a Canadian Navy protocol for strict Compartment Inspections. They used to make you sign off on your findings.

First and last thing I do when onboard. Check that Bilge.

Cheers

Doog
  Re: I'm Sinking! (davidww1)
Posted: 9:56:06 pm on 4/28/2016 Modified: Never
 
Every year, at least one of the yachting mags runs a story similar to yours - big surprise, "stainless" isn't, disaster averted (or not) by a hairs-breadth. But usually some place exotic where the author has to move heaven and earth to get a fix. But don't feel bad about it, because the nature of the cause means the damage always happens out of sight.

By the sound of it, you had a nasty case of crevice corrosion. My understanding is that stainless steel, like aluminum, protects itself from corrosion by forming a self-renewing and resistant surface film. Problem is that part of the film is oxygen, either from the air or from water. After a while, water that's not moving (as in, between a clamp and a rubber hose) becomes depleted of free oxygen, the surface film breaks down and corrosion begins, and because it's in a closed space, you don't see it.

Your only recourse is to check areas like this on a regular schedule.

Problems like crevice corrosion are exacerbated by the amount of dodgy product now on the market. Time was, when you bought marine hose clamps, they were real honest 316 stainless steel. Now you can get "marine" hose clamps made of whatever, from China, Viet Nam or wherever. Read Black Arts' "Bargain Gear", inspired by surveyor Scott Scholer's experiences caveat emptor.

Roger Taylor wrote a very good book 25 years ago called "The Elements of Seamanship" which astonishingly is still in print (see it on Amazon). It includes a description and rationale for a US Navy process similar to the one described by Doog.


David Weatherston
Towser, Toronto
C&C 27 Mk IV

  Re: I'm Sinking! (PaulB)
Posted: 12:46:30 pm on 5/16/2016 Modified: Never
 
And that's also why they recommend not using the perforated style hose clamps on anything below the waterline.

Paul Baker
Sidney, BC
1974 Mk II