Crackling hull?

Rob_Webb

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Anyone else experience crackling/popping sound from their hull? Sounds like a big bowl of rice crispies continually popping away - only audible from inside and seems to come and go at different times but most evident at night. Hull = cedar core glassed over. Apparently a well-known phenomenon here in NZ but no-one has given me credible answer - most stupid so far was prawns nibbling away at growth on the hull! Any (more sensible) offers? Never notice it in UK but maybe I was too busy fending off money-grabbing harbour masters.
 

Rick

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I've heard it lots in the Whitsundays, and the locals tell me it's sealife feeding on the grass on the hull .... maybe most stupid, but it's widely held it seems ... :)
 

William_H

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Here on Swan River the noise is common and i believe is prawns and crustaceans. One prawn called the snapper prawn has one giant nipper which he can snap to make a shock wave to stun prey on a minute level. I think that is the crackling noise. Certainly not nibbling on the hull. could be wrong though. regards will
 
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Anonymous

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Yes, I used to hear that on my parents' GRP boat, exactly as you describe. The sound appears to be coming from the hull material itself, not something outside - the crackles seem to contain higher frequency components than you'd imagine you'd get by sound transmission through the water. Sorry, I don't know what the cause was but they did have an osmosis problem /forums/images/graemlins/frown.gif
 

pelissima

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Yes we have it as well.
If it is creatures feeding, then the first month, after a fresh antifouling, should pass in complete silence. But if we do have that sound, then it might be we discovered the sound of delamination...Did we invent the absolute osmosis startup signals?
 

jerryat

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Don't worry, as the others say, it is the local sealife dining out, not your hull delaminating or the cheerful sound of exploding osmosis blisters!!

We seldom hear it in this country, but heard it many times in the Med. On the first occasion, I was so alarmed that I turned out all the lower lockers, convinced that there was an electrical short circuit going on. THEN, my chuckling neighbour told me the facts!!
 

Robin

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It is quite common here too and Lulworth Cove used to be a favourite spot for it, we also hear it quite often when anchored in several places around S Britanny. The most often heard explanation is that it is the local shellfish population, though which branch of them or what they are doing exactly and whether they are doing it on the hull or the seabed is another question.
 

Sean

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I've also heard this a lot in the Med - been told it's urchins feeding, but it could be lots of things, I s'pose. Water is a very good conductor of sound, being virtually incompressible, and I should think that your boat makes a great resonant chamber...
 

alahol2

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We've only ever heard it in Portland Harbour, anchored in the NE corner. First time is very disconcerting. Only seems to happen at night. Love to know what precisely are making the noise but there must be hundreds, if not thousands, of the things.
 

Rob_Webb

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That\'s it!

Well done BrendanS, Snapping Shrimp is exactly what it sounds like! At last a credible explanation - in the last 24hrs a couple of more reliable sources here in NZ have cited the same cause. But you'd be amazed at the range of alternative answers and how few people genuinely knew the cause!

Cheers
Rob
 

BrendanS

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Re: That\'s it!

There are (a very few) times when it's useful to have a biology background, and not to dismiss aquatic life as the source of background noise <g> Go on, give us some of the range of answers so we can have a laugh.

V pleased we got to the bottom <groan> of your question.

PS love questions like this, so if anyone has got anymore? The answer to Rob's was his excellent description of the rice crispies popping, which immediately rang bells.
 

Swagman

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Re: That\'s it!

Well I knew it was not osmosis based as had experienced same on a past aluminium hulled yacht (even louder in fact) - and having lived in Oz for 17 years also heard it 24 hours after antifouling - so it was unlikely to be 'hull nibbling' either!

But nice to have it confirmed at long last..................
 

machurley22

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Puzzle for Brendan

Happy to oblige Brendan. I know the answer to this one so if you're stumped just say.

Spent the 2003 season on a swinging mooring and shortly after arriving noticed a regular chirping sound. After switching off all electricals (few as they are) disconnecting the battery, hauling the mooring chain tight and considering various even more fanciful theories, I asked the moorings owner.

"Oh, you mean "sea crickets"" he said, and this is indeed a very accurate description of the noise. What do you think it was? Perhaps this is too easy but it was my first season afloat.

Dave
 
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