Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 28-08-2015, 17:18   #1
Registered User

Join Date: Dec 2014
Location: Brisbane, Australia
Boat: Seawind 1000
Posts: 46
Lightbulb Seawind 1000 rudder corrosion

Slipped our Seawind 1000 last week and found considerable rudder corrosion which was not there when slipped 12 months ago.
1. Is this to be expected after 15 years?
2. Just wondering if corrosion could be due to stainless steel boots sicaflexed onto bottom half of keels when slipped previously?
3. If so how does the electrolysis complete the circuit in a glass boat as keel boots are not connected by metal to any other metal or rudder assembly?
4. If so, do boots have to come off or will an anode on rudder shafts solve the problem and it is just the Manly Qld Australia harbour berth water chemicals?
Attached Thumbnails
Click image for larger version

Name:	KeelShoe1-1Aug3015.JPG
Views:	136
Size:	176.4 KB
ID:	108065  
__________________

__________________
phalo is offline   Reply With Quote
Old 28-08-2015, 17:24   #2
Registered User

Join Date: Dec 2014
Location: Brisbane, Australia
Boat: Seawind 1000
Posts: 46
Re: Seawind 1000 rudder corrosion

Here is the main pic of rudder corrosion which did not upload previously
Attached Thumbnails
Click image for larger version

Name:	RudderPost4Aug2015.JPG
Views:	179
Size:	169.2 KB
ID:	108067  
__________________

__________________
phalo is offline   Reply With Quote
Old 28-08-2015, 20:10   #3
Registered User
 
Dulcesuenos's Avatar

Join Date: Dec 2010
Location: Florida Keys, Bahamas Bound
Boat: 38' French Cat
Posts: 2,828
Images: 4
Re: Seawind 1000 rudder corrosion

Looks excessive as to point nmbr 3. Theres almost always an electrical field around your boat. Even not hooked to dock power you should have .8 to.9 volts
Around your boat. We have had some older cats and never seen that much corrosion on the rudder. 2 had hollow stainless tubes current one is solid shafts

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app
__________________
Dulcesuenos is offline   Reply With Quote
Old 28-08-2015, 20:48   #4
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2002 Seawind 1000 (33 ft) Cat
Posts: 840
Re: Seawind 1000 rudder corrosion

I've never seen any corrosion on mine. Twelve year old boat. Have you posted on the scoaa forum to see if any other owners have experienced. My guess is that stray currents in the marina caused this.
__________________
sailjumanji is offline   Reply With Quote
Old 29-08-2015, 15:20   #5
Registered User

Join Date: Jul 2015
Location: Ft. Lauderdale, FL
Boat: various over the years
Posts: 53
Re: Seawind 1000 rudder corrosion

Was the boat connected to shore power?
__________________
ex-12m-guy is offline   Reply With Quote
Old 29-08-2015, 16:58   #6
Registered User

Join Date: Aug 2015
Location: Melbourne
Posts: 9
Re: Seawind 1000 rudder corrosion

I have just joined this forum - to make some suggestions
Have worked in swimming pool industry for many years dealing with stainless steel parts and corrosion.
Stainless steel is only stainless when i has access to oxygen. The oxygen reacts with the metal additives (molybdenum I believe) to create a protective film which prevents further corrosion. If this film is scratched, the protective coating reforms.
Without oxygen, the material can erode. This is sometimes called crevice corrosion. It is particularly prevalent with $304 and lesser grades of stainless steel. #316 does not appear to have this problem.
When we fit round O rings to stainless parts, the narrow space between the O ring and flat stainless steel surface becomes de-oxygenated, causing corrosion where the o ring touches the stainless. The trick here is to use square section O rings.
When the stainless was covered with sikaflex, it may have created a region deficient in oxygen.
I hope this helps
The corrosion occurs within the metal, and does not require stray electrical current or disimilar metals to form. From metallurgical viewpoint, the dissimilar metals may be the protected shiny surface, and the unprotected corroded surface. The corrosion occurs within the metal part, and not to an external component.
__________________
desdestiny is offline   Reply With Quote
Old 29-08-2015, 20:45   #7
Registered User

Join Date: Dec 2011
Posts: 1
Re: Seawind 1000 rudder corrosion

I would like to relate an case where we laid several kilometres of new 316 stainless cable underwater in the waterway at Kawana on the sunshine coast. The cable lasted 6 weeks before dissolving. The subsequent investigation by engineers found that the cause low oxygen levels and high salinity in the water at certain points. These levels were created by poor water movement, basicly the sea water was not flowing in and out with the tide to be changed. It is possible that the water flow at your mooring is not moving enough to clean it.
__________________
Alan52 is offline   Reply With Quote
Old 30-08-2015, 05:21   #8
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,573
Images: 240
Re: Seawind 1000 rudder corrosion

Greetings and welcome aboard the CF, desdestiny, & Alan.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 30-08-2015, 06:17   #9
Registered User

Join Date: Dec 2014
Location: Brisbane, Australia
Boat: Seawind 1000
Posts: 46
Re: Seawind 1000 rudder corrosion

Only connected to shore power once a week for an hour at most
__________________
phalo is offline   Reply With Quote
Old 30-08-2015, 06:24   #10
Registered User

Join Date: Dec 2014
Location: Brisbane, Australia
Boat: Seawind 1000
Posts: 46
Re: Seawind 1000 rudder corrosion

Yes I take your point thanks Desdestiny and Alan 52 as have had a bit to do with stainless steel hot water tanks, but doesn't explain the rudder stock corrosion in the pic, which I meant to post first
__________________
phalo is offline   Reply With Quote
Old 30-08-2015, 16:14   #11
Registered User

Join Date: Jul 2015
Location: Ft. Lauderdale, FL
Boat: various over the years
Posts: 53
Re: Seawind 1000 rudder corrosion

The corrosion could be a "green wire" problem, even if you are
plugged into shore power for only a short period. The problem can
be in the dock wiring or aboard another boat in the marina.

A defective battery charger aboard your boat can also cause problems.

Does the boat have a galvanic isolater in the ground (green) shore power
circuit?

Is the rudder stock (or support bearing or steering gear) bonded to the general boat grounding system (usually the engine block + prop shaft.)

The various comments regarding a possible lack of oxygen supply to the rudder stock also have merit. Is there sufficient water flow over the metal, or is the corroded portion of the rudder stock sealed off from water flow by a plastic fairing washer or equivalent?
__________________
ex-12m-guy is offline   Reply With Quote
Old 30-08-2015, 20:04   #12
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2002 Seawind 1000 (33 ft) Cat
Posts: 840
Re: Seawind 1000 rudder corrosion

Quote:
Originally Posted by ex-12m-guy View Post
The corrosion could be a "green wire" problem, even if you are
plugged into shore power for only a short period. The problem can
be in the dock wiring or aboard another boat in the marina.

A defective battery charger aboard your boat can also cause problems.

Does the boat have a galvanic isolater in the ground (green) shore power
circuit?

Is the rudder stock (or support bearing or steering gear) bonded to the general boat grounding system (usually the engine block + prop shaft.)

The various comments regarding a possible lack of oxygen supply to the rudder stock also have merit. Is there sufficient water flow over the metal, or is the corroded portion of the rudder stock sealed off from water flow by a plastic fairing washer or equivalent?
Just to provide some info, as I have the same model boat. Not sure if Phalo has a shore power system. I do, with a galvanic isolator, and have not experienced any problems. The rudder shafts are fully exposed, but not bonded to anything. The boat has dual outboard motors, and normally left pulled up clear of the water. The only other metal exposed to water in my boat is the air conditioner.
__________________
sailjumanji is offline   Reply With Quote
Old 31-08-2015, 06:12   #13
Registered User

Join Date: Dec 2014
Location: Brisbane, Australia
Boat: Seawind 1000
Posts: 46
Re: Seawind 1000 rudder corrosion

You might be onto something there Ex-12m-Guy as the berth adjacent to us has changed boats and has shore power connected all the time.

One of our outboards just touches the water when raised and shows considerable corrosion for a one year old outboard.

Sailjumani has clarified the shore power issue and our boat is not set up for shore power and is only connected by extension cord to vacuum or run a laptop. Batteries are charged by two 130W Kyocera panels and the outboards. Not sure if relevant but the 15 year old Kyocera panels were replaced under warranty a year ago and they (and outboards) are the only DC generators.
Do I understand correctly corrosion is linked with DC power only?
Don't know the scoaa forum but will look into it
She does leave the marina every week for 3 or 4 days sailing which would give flow over rudder and keels.

So it's starting to look like a marina berth issue and will have to find what the power is connected to in next berth but not sure what i can do about it unless i can save them from the same corrosion problem
__________________

__________________
phalo is offline   Reply With Quote
Reply

Tags
corrosion, rudder, Seawind, wind

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
For Sale: Dramatic price reduction Seawind 1000 33' cat girouxkj Classifieds Archive 2 14-06-2012 09:11
For Sale: Key Largo Seawind 1000 1/6th Ownership girouxkj Classifieds Archive 0 12-02-2012 13:23
For Sale or Trade: Seawind 1000 - FSBO girouxkj Classifieds Archive 5 29-09-2011 12:17
Seawind 1000 Oven Bricky Multihull Sailboats 7 30-04-2010 17:39



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:58.


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.