Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 22-12-2015, 17:11   #1
Registered User

Join Date: Aug 2013
Boat: 1987 Island Packet 31
Posts: 37
Help with deciphering soft knocking sound

I am not sure where this post belongs because I'm not sure exactly what the culprit is, so I'm hoping someone here can shed some light.

I am currently on an Island packet sailboat at anchor in an area with strong current and tide shift. I just noticed this evening there is a soft rhythmic knocking coming from somewhere on the boat...I can't pinpoint its location it sound like it's everywhere and nowhere. But it's continuous. Every few seconds it knocks 5 times then stops for a few seconds and starts up again.

I don't know if it's something on the deck( though I have checked all rigging and nothing that looks or sounds like this.) I live aboard my boat so am very attune to her sounds. I don't think it's anything on the engine, though I have heard prop shaft could cause something tho I'm not sure that's it either...maybe anchor chain ( though I doubt it). It almost reminds me of a woodpecker

Maybe a ghost

Any thoughts or if you have ever experienced this ? Much appreciated!
__________________

__________________
challis0124 is offline   Reply With Quote
Old 22-12-2015, 17:31   #2
Registered User
 
exkma367's Avatar

Join Date: Jan 2014
Location: PA
Boat: 68 tartan 34c
Posts: 76
Re: Help with deciphering soft knocking sound

The one that drove us nuts was the wires inside the mast. Next time we had the mast down we ran conduit.
__________________

__________________
exkma367 is offline   Reply With Quote
Old 22-12-2015, 17:33   #3
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2007
Location: Santa Cruz
Boat: Boatless Again
Posts: 4,324
Re: Help with deciphering soft knocking sound

Is the strong current new?? Is your prop turning??
__________________
donradcliffe is offline   Reply With Quote
Old 22-12-2015, 17:48   #4
Registered User

Join Date: Aug 2013
Boat: 1987 Island Packet 31
Posts: 37
Re: Help with deciphering soft knocking sound

This is our second night in this anchorage wit fairly strong current, but this isn't new for us as we've been in strong current for months. Checked prop in all positions w no change in sound. There are strong winds also and still remains constant. It's definitely a mystery
__________________
challis0124 is offline   Reply With Quote
Old 22-12-2015, 17:49   #5
Registered User

Join Date: Aug 2013
Boat: 1987 Island Packet 31
Posts: 37
Re: Help with deciphering soft knocking sound

Checked the mast but doesn't sound like it's in there. Can only hear it from inside the boat outside you can't hear it at all.
__________________
challis0124 is offline   Reply With Quote
Old 22-12-2015, 18:10   #6
Registered User
 
gamayun's Avatar

Join Date: Aug 2013
Location: Oakland, CA
Boat: Freedom 38
Posts: 1,231
Re: Help with deciphering soft knocking sound

Because it's such a consistent sound, I would check all your pumps and motors. Do you have a mechanical fuel pump? I accidentally switched on my diesel heater's fuel pump just before I went to bed a while back. It woke me up in a crazy panic in the middle of the night when the sound got really loud inside the engine compartment right next to my head. A tapping like you're hearing would drive me insane...
__________________
gamayun is offline   Reply With Quote
Old 22-12-2015, 18:11   #7
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,051
Re: Help with deciphering soft knocking sound

The rudder can knock if current is right.
What year and model, have you had the lower part of the rudder shimmed in the shoe?
Try turning the rudder to one way completely to see if it changes the noise, do you have the optional rudder lock? If so engage it with rudder turned.
I'd try turning off the battery switch unless your sure it can't be something like the water pump or something. Just to eliminate possibilities.
If conditions are right, the water can slosh in the tank.
Any chance it's the leak at the prop shaft, dripping water? Deep bilge.


Sent from my iPad Pro using Cruisers Sailing Forum
__________________
a64pilot is offline   Reply With Quote
Old 22-12-2015, 18:37   #8
Moderator
 
JPA Cate's Avatar

Join Date: Nov 2011
Location: aboard, cruising in Australia
Boat: Sayer 46' Solent rig sloop
Posts: 10,682
Re: Help with deciphering soft knocking sound

Your description of the sound makes it seem to me that it is activated by the boat's motion at anchor. I'd check for anything stowed somewhere where it is rocking back and forth. My boat has cupboard doors that can make that kind of sound when we roll, but also tall small diameter bottles tend to bump back and forth.

The pause, bump, bump, bump, bump, bump and repeating doesn't sound right for internal halyards or for any of the kinds of pumps we have, but who knows? You are familiar with all your pump sounds? Lots of things sometimes bump the boat, but not that regularly. 'Tis a puzzlement.

Ann
__________________
Ann, with Jim, aboard US s/v Insatiable II, in Oz, very long term cruisers
JPA Cate is offline   Reply With Quote
Old 22-12-2015, 20:06   #9
Registered User

Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 609
Re: Help with deciphering soft knocking sound

Oh man. That's gonna be a special kind of satisfaction when you figure this one out.

Be a pal and let us know what you find.
__________________
chris95040 is offline   Reply With Quote
Old 22-12-2015, 20:27   #10
Registered User
 
gamayun's Avatar

Join Date: Aug 2013
Location: Oakland, CA
Boat: Freedom 38
Posts: 1,231
Re: Help with deciphering soft knocking sound

OH! Is your computer on? Maybe the fan is going bad....
__________________
gamayun is offline   Reply With Quote
Old 23-12-2015, 04:19   #11
Registered User

Join Date: Jun 2015
Posts: 315
Re: Help with deciphering soft knocking sound

Spent a couple hours one night trying to find a knocking noise.
Somebody had moved a bilge pump handle, when the boat would rock the handle would roll and hit the hull. Sounded like it was comming from every direction. Drove me nuts!
Could be anything, start at one end and work you way to the other.
My search started on deck looking overboard around the waterline for something floating. Handle turned out to be behind the stove in the galley rolling back and forth on the counter completely out of sight....
__________________
Siberianhusky is offline   Reply With Quote
Old 23-12-2015, 06:44   #12
Registered User

Join Date: May 2015
Location: Florida
Boat: Jeanneau 44i SO
Posts: 139
Re: Help with deciphering soft knocking sound

Also had this on an Island Packet and it took a while to find as it sounded like it was something in the aft cabin. Turns out it was the spare propane tank rocking against the inside of it's storage locker.
__________________
l2ridehd is offline   Reply With Quote
Old 23-12-2015, 07:00   #13
Registered User
 
Privilege's Avatar

Join Date: Oct 2009
Location: Bermuda
Boat: Privilege 435
Posts: 362
Images: 12
Re: Help with deciphering soft knocking sound

I recon'....because your anchor is out you don't have the normal pile of chain in your chain locker. The remaining chain running from the deck to the bottom of the anchor locker is swinging rhythmically and tapping on what's left of the chain pile or the locker wall.
__________________
Privilege is offline   Reply With Quote
Old 23-12-2015, 07:17   #14
CF Adviser
Moderator Emeritus
 
Hud3's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Virginia
Boat: Island Packet 380, now sold
Posts: 8,929
Images: 49
Re: Help with deciphering soft knocking sound

I was anchored in a strong current once, and it turned the boat around so that the small, wind-generated waves slapped the stern under the overhang. It made a soft knocking noise.
__________________
Hud
Hud3 is offline   Reply With Quote
Old 23-12-2015, 07:21   #15
Registered User
 
Reach's Avatar

Join Date: Jul 2008
Location: Bahamas
Boat: Manta 40
Posts: 118
Re: Help with deciphering soft knocking sound

Quote:
Originally Posted by Ann T. Cate View Post
Your description of the sound makes it seem to me that it is activated by the boat's motion at anchor. I'd check for anything stowed somewhere where it is rocking back and forth. My boat has cupboard doors that can make that kind of sound when we roll, but also tall small diameter bottles tend to bump back and forth.

Ann
Quote:
Originally Posted by l2ridehd View Post
Also had this on an Island Packet and it took a while to find as it sounded like it was something in the aft cabin. Turns out it was the spare propane tank rocking against the inside of it's storage locker.
From your description I'd lean towards these ideas above. It sounds like something round with a short roll/bump frequency at anchor. I've heard similar soft thumps with a mag flashlight rolling for example.

Good luck finding the culprit!
__________________

__________________
~Michele
www.svreach.com
Reach is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tapping, Knocking Sound from bottom of Hull Pacific Anchoring & Mooring 17 09-06-2013 15:36
Deciphering yachtworld codes Sand crab Multihull Sailboats 3 28-12-2012 03:12
Perkins 4-107 - Loud Knocking seafarer74 Engines and Propulsion Systems 3 09-08-2009 20:55
Help deciphering prop marking Orion Jim Propellers & Drive Systems 2 22-03-2009 05:05



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:19.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.